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Bio- and soft materials


Polymer and hybrid thin films deposited from the vapor phase for functional (bio-devices)

Polymers and organic materials are essential components of functional devices for applications in various technological areas. The possibility to tailor the material properties by molecular design make them attractive functional materials, especially for biological and medical applications. Their synthesis as thin films has significant advantages due to the reduced amount of supply used and faster processing times.


Polymer and organic materials are currently garnering more recognition in thin-film industry that historically has been dominated by inorganic films. Functional polymer thin films (< 100 nm) are typical components of modern devices in a variety of fields, including microelectronics, biotechnology and microfluidics. The need for miniaturization and structuration has boosted the development of advanced thin film growth techniques (e.g. iCVd, oCVD, PECVD, MLD) that can be easily implemented in the manufacturing steps of device production. As free-standing structures, two-dimensional thin films have advantages over bulk materials due to their large surface-to-volume ratios, desirable for applications requiring enhanced surface interactions. Thin films can also be employed as coatings over bulk materials to achieve application-specific properties that are unattainable in the substrate material.

Recent efforts are dedicated to conceive innovative deposition techniques that are versatile platforms for fabrication of a wide range of polymer thin films preserving all the desired chemical functionalities. The retention of the functional groups of polymers is critical to achieve the desired response. Not only, polymer thin films to be successfully integrated into functional devices require a combination of properties: chemical structure, micro- and/or nano- scale topography, porosity, durability, stiffness/elasticity, surface energy, etc. Each of these properties needs to be optimized for the specific application. The control of the film properties requires tuning of the thin film deposition parameters, which in return requires a thorough understanding of the underlying mechanisms of deposition.

The symposium will be dedicated to advanced functional polymer with particular highlights on the correlation between polymer properties and functionality. The focus will be on polymers synthetized by vapor phase deposition that provide ultrathin layers (<100 nm), conformal coverage, with low defect/impurity levels. Contributions on the applicability of polymer deposited from the vapor phase in the field of bio-devices are particularly encouraged.

Hot topics to be covered by the symposium:

Areas of particular interest will include, but not limited to, the following topics:

  • Functional Polymer Thin Films and their application in microfluidics, sensors, biomaterials, pharmaceuticals, healthcare, energy, etc.
  • Innovative Deposition Techniques, which retain the chemical functionality: initiated CVD, oxidative CVD, downstream/pulsed/low power plasma CVD, parylene deposition, Vapor Deposition Polymerization and Molecular Layer Deposition
  • Nanostructured Polymer and Hybrid Thin Films, including hierarchical structures, nanocomposites, multilayers.
  • Rational Design of Polymer Thin Film Properties to achieve the desired functionality, including engineering surface and interfaces properties.
  • Surface Modification/Functionalization approaches



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08:45 Welcome and Introduction to the Symposium    
Biomaterials part I : Anna Maria Coclite
Authors : Sung Gap Im
Affiliations : Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST)

Resume : Three-dimensional in vitro cancer models have emerged as a promising tool for various cancer-related applications. However, the limited availability of the in vitro model capable of adequately recapitulating the active interactions between the cancer cells and the surrounding tumor microenvironment (TME) hampers their use for therapeutic applications. Here, it is demonstrated that the proteins adsorbed on the culture substrate significantly influence the characteristics of the cancer cells, thereby suggesting that the modulation of cell–protein interaction can be a powerful tool to construct an advanced cancer model. A series of polymers are prepared for the precise control of the surface hydrophobicity of the culture plate. Cancer cells cultured on the polymers exhibit distinct morphological transitions ranging from monolayer to spheroids with entirely different characteristics depending on the surface hydrophobicity. The poly (cyclohexyl methacrylate) surface of the highest hydrophobicity tested in this study strongly attracts albumin from the media for enhanced adsorption and induces conformational changes in albumin upon binding, leading to the formation of spheroid with the most enriched tumorigenic properties. It is believed that this finding can provide new insights when selecting the experimental strategy to appropriately mimic the complex interplay between the cancer cells and the TME.

Authors : Torge Hartig¹, Wiebke Reichstein¹, Margarethe Hauck², Gabriel Chan¹, Mohammadreza Taale³, Christine Arndt³, Florian Rasch², Maximilian Burk¹, Thomas Strunskus¹, Christine Selhuber-Unkel³, Rainer Adelung², Franz Faupel¹, Stefan Schröder¹, Fabian Schütt²
Affiliations : ¹Chair for Multicomponent Materials, Institute of Materials Science, Kiel University, Kiel, Germany ²Functional Nanomaterials Chair, Institute of Materials Science, Kiel University, Kiel, Germany ³Institute for Molecular Systems Engineering, Heidelberg University, Heidelberg, Germany

Resume : Hydrogels are the leading materials for regenerative tissue engineering, e.g. as cell scaffolds, as their physical properties are similar to the properties of native soft tissue. However, for many applications their characteristics need to be tuned in various properties simultaneously to ensure the needed interaction with incorporated cells. In our chosen fabrication technique these properties, like stiffness and mesh size, are not dependent on each other. With respect to this, nano- and micro-engineering of hydrogels has recently shown great potential in order to specifically tailor the properties of hydrogels, e.g. by the incorporation of functional nanoparticles or by micro-structuring. [1] In the here presented study, we demonstrate a new, solvent-free approach to synthesize highly porous functional hydrogels, so-called aero-hydrogels by employing initiated chemical vapor deposition(iCVD) processes. iCVD presents a way to conformally coat different kinds of porous structures with thin layers of polymers. [2,3] A prominent 3D network material mimicking the shape of extracellular matrix is fabricated by utilizing tetrapodal-shaped ZnO microparticles. [4] Hydrogel thin films are deposited via iCVD onto the structure and the T-ZnO network is etched away. A mechanically stable hydrogel network with more than 99% empty space is created. The aero-hydrogel can be used as a cell scaffold where pore size, crosslinking, thickness and stiffness can independently be tuned towards the needs of the respective type of cells. In multilayers electrical conductivity can be incorporated into the aero-hydrogel scaffold facilitating stimulation of cells while the surface properties in the aero material are determined by the hydrogel. References: [1] Arndt, Christine, et al. "Microengineered Hollow Graphene Tube Systems Generate Conductive Hydrogels with Extremely Low Filler Concentration." Nano letters (2021): 3690-3697. [2] Reichstein, Wiebke, et al. "Initiated Chemical Vapor Deposition (iCVD) Functionalized Polylactic Acid–Marine Algae Composite Patch for Bone Tissue Engineering." Polymers (2021): 186. [3] Aktas, Oral Cenk, et al. "Superhydrophobic 3D porous PTFE/TiO2 hybrid structures." Advanced Materials Interfaces (2019): 1801967. [4] Mishra, Yogendra Kumar, and Rainer Adelung. "ZnO tetrapod materials for functional applications." Materials Today (2018): 631-651.

Authors : Eda Güney (1)*, Beril Üstünkaya (1), Bengü Süeda Sengül (1), Ozlem Kutlu (2), Gozde Ozaydin Ince (1,2)
Affiliations : (1) Materials Science and Nanoengineering Department, Faculty of Engineering and Natural Sciences, Sabanci University, 34956, Istanbul, Turkey (2) Sabanci University Nanotechnology Research and Application Center (SUNUM), Sabanci University, 34956, Istanbul, Turkey

Resume : Electrospinning has gained increased attention in tissue engineering and drug delivery applications over the last few decades as the nanofibrous structure of electrospun patches enable site-specific and controlled drug delivery administration. Swelling capacity, biodegradation rate, surface morphology, and cell adhesion capability are important parameters as they highly affect success of patches in the tissue healing process. Therefore, the above-mentioned parameters should be investigated and fine-tuned during the fabrication to enhance the chance of the success of the implanted patches. In this study, the photo-initiated chemical vapor deposition (piCVD) method was used in the coating of thin films onto the biofunctional patches under mild deposition conditions. Photopolymerization was carried out by the short-wavelength emission of UV-light at 254 nm. Firstly, the uncoated and coated nanofiber patches were studied to analyze their degradation and swelling capacity. The nature of the fibers and surface morphology were visualized by monitoring the samples using scanning electron microscopy (SEM). Secondly, the cell adhesion assay was conducted to investigate further the effect of fibers in vitro. The study demonstrated the water absorption and degradation behaviors, and also tissue adhesion capabilities of the patches coated with thin films using the piCVD method along with in vitro experiments. This study will contribute to the ongoing research in the development of patches to be used in tissue engineering and drug delivery applications.

Authors : Sébastien Buchwalder *(1,3), Juan Jose Diaz Leon (2), Antoine Descoeudres (2), Jérôme Steinhauser (3), Aurelio Borzì (4), Antonia Neels (4), Andreas Hogg (3), Jürgen Burger (1)
Affiliations : (1) sitem Center for Translational Medicine and Biomedical Entrepreneurship, University of Bern, Switzerland; (2) CSEM PV-Center, Neuchâtel, Switzerland; (3) Coat-X SA, Switzerland; (4) Empa Center for X-ray Analytics, Swiss Federal Laboratories for Materials Science and Technology, Switzerland; * lead presenter

Resume : Implantable devices require a high degree of biological safety, demanding for efficient protection against body fluids as well as maximal miniaturization. An ultra-tight encapsulation solution which enables safe long-term implantation close to inflammatory tissue and which has a superior temperature stability for multiple sterilization cycles is highly desirable. In this work, it is shown how these needs can be addressed by an innovative thin-film encapsulation technology made of alternating organic and inorganic layers. Parylene, as organic thin film, is a well-established polymer material, exhibiting excellent electrical insulation and dielectric properties, being often the material of choice for biomedical applications. However, parylene barrier properties are not sufficient to ensure a protection for long-term implantation in the human body of several years. The inorganic materials are dense and hence offer extremely good barrier properties, but they are mechanically rigid. Furthermore, inorganics alone suffer from pinhole and micro-crack defects, which induce a poor long-term hermeticity. On the other hand, the combination of parylene with inorganic thin films provides excellent barrier properties and improves the scratch resistance, limiting the water permeation through potential defects. This work investigates the barrier performance of parylene multilayers in combination with inorganic films deposited by low temperature chemical vapor deposition (CVD). Parylene VT-4 thin films, deposited by the standard Gorham process (low pressure CVD), have been used for their excellent thermal stability and their superior performance during deposition to enter into small voids or channels of substrates compared to other parylene materials. Silicon-based layers, deposited by plasma-enhanced CVD (PECVD) have been examined as single layer alone and combined with parylene film as multilayers. For this deposition technique, three precursors and two plasma generation methods (inductively and capacitively coupled plasma) have been tested and evaluated. Similarly, atomic layer deposition (ALD), including thermal and plasma oxidation methods, has been used to compare three metal oxide layers. Water vapor transmission rate (WVTR) measurements have been performed to quantify the thin film barrier performances using an electrolytic detection sensor method. In order to evaluate the thermal stability of the thin film coatings, the WVTR measurements have been carried out on selected layers after applying a heat treatment at 250°C for 5min. The most efficient single layers show a WVTR in the range of 10?3 gm?2d?1, at 38°C and 90% relative humidity conditions. Finally, these single layer WVTR results will be compared with the obtained results of WVTR measurements for parylene-inorganic bilayers combinations.

10:15 Discussion session 1    
10:30 Coffee break    
Biomaterials part II : Meike Koenig
Authors : Matteo Gherardi, Vittorio Colombo, Romolo Laurita, Giulia Laghi
Affiliations : Industrial Engineering Department (DIN) & Industrial Research Centre for Advanced Mechanics and Materials (CIRI-MAM) at Alma Mater Studiorum-Università di Bologna; Industrial Engineering Department (DIN) & Industrial Research Centre for Advanced Mechanics and Materials (CIRI-MAM) at Alma Mater Studiorum-Università di Bologna; Industrial Engineering Department (DIN) & Industrial Research Centre for Health and Technology (CIRI-SDV) at Alma Mater Studiorum-Università di Bologna; Industrial Engineering Department (DIN) at Alma Mater Studiorum-Università di Bologna;

Resume : Organosilicon compounds, such as tetraethyl orthosilicate (TEOS) and hexamethyldisiloxane (HMDSO), are excellent precursors for atmospheric pressure plasma polymerization; the deposited thin films can display a wide range of chemical-physical characteristics, depending on the process parameters, and thus can be tailored with respect to the intended application [1]. Despite the large body of works on the subject available in the scientific literature, there is still a limited understanding of the fundamental mechanisms of atmospheric pressure plasma polymerization of organosilicon precursor. The present work will cover both applicative and fundamental aspects of the deposition process, discussing the following topics: I. Deposition of nanostructured coatings exhibiting antibiofilm and anticlot properties for catheters; II. Production and characterization of surface gradient coatings by single-step deposition of HMDSO [2]; III. Aerosol-plasma polymerization of organosilicon fluorinated precursors for the production of antimicrobial coatings; IV. Analysis of coating characteristics as a function of power to precursor ratio and mechanisms of atmospheric pressure plasma polymerization of organosilicon precursors, investigated through laser induced fluorescence (LIF), two-photon absorption LIF (TA-LIF) and Rayleigh scattering [3,4]. [1] Rino Morent, Nathalie De Geyter, Sandra Van Vlierberghe, Peter Dubruel, Christophe Leys, Etienne Schacht, Surf. Coat. Technol. 1366 203(10-11) 2009 [2] Hediyeh Malekzad, Tommaso Gallingani, Federica Barletta, Matteo Gherardi, Vittorio Colombo, David Duday, Plasma Process Polym. 2000044 18(2) 2021 [3] Federica Barletta, Christophe Leys, Vittorio Colombo, Matteo Gherardi, Nikolay Britun, Rony Snyders, Anton Nikiforov, Plasma Process. Polym. 1900174 17(6) 2020 [4] Federica Barletta, Nikolay Britun, Christophe Leys, Matteo Gherardi, Rony Snyders, Anton Nikiforov, Plasma Process. Polym. 2000149 18(2) 2021

Authors : Lenka Zajíčková, Lucie Blahová, Martina Buchtelová, David Nečas, Jiřina Medalová, Petra Křížková, Anton Manakhov, Anastasiya O. Solovieva, Zdeňka Kolská, Dirk Hegemann
Affiliations : CEITEC Brno University of Technology & Masaryk University, Brno, Czech Republic; CEITEC Brno University of Technology, Czech Republic; CEITEC Brno University of Technology, Czech Republic; CEITEC Brno University of Technology, Czech Republic; Masaryk University, Brno, Czech Republic; Masaryk University, Brno, Czech Republic; Research Institute of Clinical and Experimental Lymphology—Branch of the ICG SB RAS, Novosibirsk, Russia; Research Institute of Clinical and Experimental Lymphology—Branch of the ICG SB RAS, Novosibirsk, Russia; J.E. Purkyně University, Ústí nad Labem, Czech Republic; Empa, St. Gallen, Switzerland

Resume : Synthetic polymers intended for biomedical applications require modification of their intrinsic properties, such as hydrophobicity and bio-inertness, to improve a low acceptance by cell cultures and immobilization of antimicrobial substances. The cell-surface interactions are governed by the physicochemical properties of the surfaces, such as chemical functional groups, surface energy, roughness, and surface charge. We prepared a variety of plasma polymer films either with amine or carboxyl groups using plasma enhanced chemical vapor deposition. The properties of these films can be tuned by variations of the gas feed, power invested in the plasma discharge, and other parameters. Here, I will summarize how these process parameters influence the film properties, including those that are less discussed but turned out to be essential for understanding the behavior of cells adhering to surfaces such as the surface charge or water stability. I will also discuss the extraordinary properties of amine plasma polymers to which non-endothelial cells exhibit very high adhesion. Since plasma polymer surface is an efficient platform for immobilization of biomolecules, I will show the results of the cell proliferation on the surfaces modified by plasma polymers and subsequently soaked into the platelet-rich blood plasma.

11:45 Discussion session 2    
Anti-fouling coatings : Rong Yang
Authors : Annalisa Treglia, Fabio Palumbo, Roberto Gristina, Pietro Favia
Affiliations : Annalisa Treglia ; Pietro Favia Department of Chemistry, University of Bari “Aldo Moro”, Bari, Italy Fabio Palumbo; Roberto Gristina Institute of Nanotechnology, National Research Council, Bari , Italy

Resume : Atmospheric pressure plasma allows for the easy modification of materials’ surfaces for a wide range of technological applications. Coupling the aerosol injection of precursors with atmospheric pressure plasma largely extends the versatility of this kind of process; in fact solid and, in general, scarcely volatile precursors can be delivered to the plasma, extending the variety of chemical pathways to surface modification. In this work a novel method has been developed for the deposition of PEG containing coatings with cell repulsive properties. PEG is atomized from a water solution directly in a dielectric barrier discharge where, due to the presence of a film precursor, ethylene, a composite coating is deposited. Morphological characterization evidenced the globular appearance of the coatings due to the presence in the feed of solution droplets. The chemical characterization, and in particular the MALDI-TOF analysis confirmed the presence of PEG-like regions, in an amount decreasing with increasing the ethylene content in the film. Finally, cell adhesion was considerably reduced for the PEG-rich deposited coatings.

Authors : Dirk Hegemann, Qun Ren, Patrick Rupper
Affiliations : Empa, Swiss Federal Laboratories for Materials Science and Technology, St.Gallen, Switzerland

Resume : Many applications would benefit from a rapid-acting antibacterial mechanism without the release of biocidal substances. For instance, metal release can lead to chemical toxicity, short antibacterial durability and antimicrobial resistance. To avoid such effects, photo-generated catalytically active oxygen vacancy sites in TiO2 have been considered as antibacterial surfaces based on the generation of reactive oxygen species (ROS). Stabilized oxygen vacancies in TiOx can be obtained by doping with another metal generating electron-hole pairs with narrow band gaps, thereby promoting the production of highly oxidizing radicals. Here, plasma technology using sputtering from Ti and Ag targets with appropriate deposition conditions is applied to form Ag nanoislets on defective TiOx films [1]. Subsequent plasma post-oxidation stabilized the film and suppressed Ag ion release. Upon storage in the dark over a timescale up to 2 years, ROS generation is maintained, yet with diminishing efficacy – that can, however, be restored by exposure to visible light. The rapid-acting antibacterial properties are found to strongly correlate with ROS generation [2]. In addition, functionalization with hydrophobic plasma polymer films is possible without loss of the antibacterial effect [3]. Such biocompatible coatings offer promising applications for implants and other medical devices. In order to enable insights into the mechanism of the antibacterial activity of AgOx/TiOx catalysts, samples in their native state as well as after storage in water and ambient air were analyzed using a variety of surface characterization and biological methods demonstrating ROS generation as the driving force for rapid antibacterial activity with negligible Ag leaching. Most of all, storage conditions and reactivation relevant for coated products were thoroughly assessed. [1] M. Amberg, P. Rupper, D. Hegemann et al., Nanomed. Nanotechnol. Biol. Med. 11, 845 (2015). [2] F. Pan, F. Zuber, K. Maniura-Weber, Q. Ren et al., Coll. Surf. B: Biointerfaces 206, 111940 (2021). [3] D. Hegemann, P. Rupper, Q. Ren et al., Plasma Process. Polym. 19, e2100246 (2022).

Authors : Laghi G.*(1), Colombo V.(1),(2),(3),(4), Condorelli G.G.(5), Conoci S.(6),(7), Franco D.(6),(7), Gallerani R.(1), Guglielmino S.(6), Laurita R.(1),(2),(8), Morganti D.(7), Traina F.(7),(9) & Gherardi M.(1),(2),(3),(4)
Affiliations : (1) Department of Industrial Engineering, Alma Mater Studiorum-University of Bologna, Bologna, Italy (2) AlmaPlasma s.r.l., Viale G. Fanin 48, 40127 Bologna, Italy (3) Interdepartmental Centre for Industrial Research Advanced Mechanical Engineering Applications and Materials Technology, Alma Mater Studiorum-University of Bologna, Bologna, Italy (4) Interdepartmental Centre for Industrial Research Agrifood, Alma Mater Studiorum-University of Bologna, Bologna, Italy (5) Department of Chemical Science, University of Catania, Catania, Italy (6) Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy (7) IBMTech s.r.l., Via Napoli 116, 95127 Catania, Italy (8) Interdepartmental Centre for Industrial Research Health Sciences and Technologies, Alma Mater Studiorum-University of Bologna, Bologna, Italy (9) Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum-University of Bologna, Bologna, Italy

Resume : Every year millions of people around the world suffering from debilitating bone and joint diseases experience implantation of prosthetic joints [1]. Despite implantation generally improves the patient’s quality of life, at the time of implantation bacteria may adhere to the prosthetic joint surface leading to the onset of the so-called prosthetic joint infections (PJIs) [2]. PJIs typically result in prolonged hospitalization for the patients with huge economic implications for the National Health Services, thus representing a major clinical issue of our times [3]. In the described context, effective strategies to improve the antimicrobial properties of prosthetic joints are highly requested. In this work, a detailed study of a plasma-assisted deposition process aimed to produce functional thin films suitable to avoid bacterial adhesion is presented. Thin films are deposited on flat polyethylene substrates using an atmospheric pressure plasma jet and an aerosolized fluorinated silane precursor. The chemical and physical properties of the deposited films are assessed by Attenuated Total Reflectance – Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Water Contact Angle (WCA) measurements, and Scanning Electron Microscopy (SEM). ATR-FTIR and XPS results show that a tailored fluorine content in the thin films can be obtained by properly setting the ratio between discharge power and flow rate: the lower is the degree of fragmentation of the precursor in the plasma discharge, the higher is the fluorine retention in the deposited films. These findings are further supported by WCA measurements which reveal a higher film hydrophobicity as the precursor fragmentation is reduced. SEM images indicate that the ratio between discharge power and flow rate strongly affects the deposition rate while not inducing substantial differences from a morphological point of view. The antiadhesive properties of the deposited films against Staphylococcus aureus and Pseudomonas aeruginosa are evaluated by means of Live/Dead assay. Biological results demonstrate that the antimicrobial properties of polyethylene substrates can be significatively improved thanks to the presence of the fluorinated silane thin films. This represents a promising outcome for the future applicability of the plasma-assisted deposition process on prosthetic joints. [1] M. Ometti, E. Delmastro, and V. Salini, Musculoskelet. Surg., 1-8 (2022). [2] S. Parsaei, J. Keeney, and J. Marschall, Infectious Diseases, 399-404 (2017). [3] A. Trampuz and W. Zimmerli, Swiss Med. Wkly., 135, 17–18, 243–251 (2005).

Authors : Trisha L. Andrew, Ruolan Fan, Kwang-Won Park, Peiyao Zhao
Affiliations : University of Massachusetts Amherst

Resume : Wearable sensors, particularly wearable electrochemical sensors, whose potential to monitor and respond to the wearer’s detailed health signals in real time, are regarded as attractive alternatives to traditional bulky analytical instruments. However, unlike the well-controlled laboratory-based sensors whose analytical performance is largely determined by the active electrode materials, on-body monitoring also requires the sensing system itself to be encapsulated to prevent fouling and retain function under changing microenvironments. In particular, signals from enzyme-based sensors suffer from degradation due to fouling and storage under suboptimal conditions, which creates false positives and false negatives. Therefore, a protective layer that preserves the shelf stability and longitudinal function of biosensors is necessary, which can also be easily applied over the many flexible and textures substrates where nascent sensors have been fabricated. Photoinitiated chemical vapor deposition (piCVD) creates thin and porous polymer films directly on the surface of many biosensors without harming the biorecognition element or interfering with the sensor structure. This surface-restricted chain growth process affords uniform coverage and strong interfacial adhesion of the resulting polymer encapsulation layers, which enable the whole sensing area to be fully covered. The amorphous polymer films formed via piCVD also allow rapid ion and analyte diffusion to underlying sensor elements and, therefore, facilitate quick sensing responses. Furthermore, piCVD films maintain their morphology after being dehydrated and rehydrated over multiple days demonstrating their excellent stability as surface protective layers. The promising features of thin polymer films created via piCVD may serve as a new encapsulating idea to be applied to various wearable sensors with different substrates and serve as a new strategy to extend the shelf life and functionality of biosensors.

Authors : Amelia Whiteley, Guillaume Nonglaton, Vincent Jousseaume
Affiliations : Univ. Grenoble Alpes, CEA, LETI, F-38000 Grenoble;Univ. Grenoble Alpes, CEA, LETI, F-38000 Grenoble;Univ. Grenoble Alpes, CEA, LETI, F-38000 Grenoble

Resume : Biofouling is a phenomenon that can have an impact in so many different fields ranging from the marine industry to biomedical implants. This makes biofilms a global threat that needs to be addressed rapidly. More specifically, medical implants are prone to causing nosocomial infections: this is the case of 5 to 10 % of dental implants, and 1 to 2 % of artificial joints. Antibiotics and nanoparticles are classic answers; however, more and more concern over antibioresistance and possible toxicity are leading to many efforts in finding other solutions. Biomimicking is one of them, as many species are capable of repelling parasites in their natural environment. For example, the nanostructure of the lotus leaf, created by wax crystals, leads to a hydrophobic surface capable of self-cleaning as water droplets simply roll off, taking any particles with them. The combination of chemistry and topography as found on the lotus leaf and many other organisms is what we will try to achieve in this work. The idea is therefore to combine nano and microstructures with a polymeric thin film to obtain complex surfaces with antibiofouling and bactericidal properties. To do so, initiated Chemical Vapor Deposition (iCVD) was the chosen technique, due to some of its major advantages. Indeed, it allows the formation of conformal polymer thin films on 3D structures, thus conserving both the chemical functions and the topography of interest. This method is advantageous for the absence of solvents, often prohibited in medical devices. Microstructures with micrometric pillars or trenches were created by nanoimprint lithography of an organosilicate resin. Additional plasma treatments were performed on some samples in order to induce an additional roughness at the nanometric scale. The samples were incubated with E. coli and fluorescent microscopy experiments were carried out using LIVE/DEAD viability staining. It was shown that bacteria behave differently on flat and structured surfaces. Indeed, it seems the structured samples have a bactericidal effect. However, they also seem to enhance bacterial adhesion which needs to be avoided to inhibit biofilm formation. To do so, using hydrophobic and hydrophilic polymers could be a solution. Poly(V3D3) and Poly(VP) respectively show these properties, and have both been successively deposited by iCVD. Using physico-chemical characterizations and microbiology experiments, this study enables to evaluate the potential of bioinspired surfaces combining these polymers of interest with structured surfaces in order to reduce biofilm formation.

Authors : Joerg Lahann
Affiliations : Biointerfaces Institute, University of Michigan, Ann Arbor, MI 48109, USA

Resume : Our improved understanding of molecular biology, microfabrication, and materials chemistry has stimulated cross-fertilization of two fields that have witnessed increasing overlap in the last few decades: biology and nanofabrication technologies. In my presentation, I will discuss current advances in the design of multifunctional biointerfaces using chemical vapor deposition (CVD) polymerization. Using CVD, a chemically diverse group of reactive coatings with one or multiple advanced functions has been synthesized. Beyond chemical and biological modifications, we have discovered that chemical vapor deposition can be performed on surfaces coated with thin films of liquid crystals (LCs) to synthesize organized assemblies of polymeric nanofibers with precisely controlled diameters, lengths, and interfacial chemistry. CVD polymerization of chiral precursors has resulted in Enantiomorphically pure polymer nanohelices. These methodologies are likely to find broad application in contexts such as energy harvesting, wetting, biological assays, or design of stimuli-responsive optical films.

15:30 Discussion session 3    
15:45 Coffee break    
Thin films for energy : Nicolas Boscher
Authors : Afshin Dianatdar, Adrivit Mukherjee, Giovanni Fortunato, Ranjita K. Bose
Affiliations : University of Groningen

Resume : Chemical vapor deposition (CVD) is a well-known technique for the synthesis of inorganic coatings and thin films. In milder variants of CVD, known as initiated CVD and oxidative CVD, organic polymers can be synthesized. The monomer in addition to an initiator or oxidant are introduced into a vacuum reactor in the vapor phase, after which they undergo a one-step surface polymerization to yield solid thin films or coatings. The advantages of these techniques are the ability to produce multilayered films and devices on a variety of delicate or porous substrates resulting in a high degree of coating conformality. We have used initiated chemical vapor deposition (iCVD) to develop materials with tunable and gradient mechanical stiffness. We use bifunctional monomers such as allyl methacrylate to achieve thermal radical initiation in the iCVD process, leaving one functionality intact for further crosslinking via ultraviolet (UV) radiation. The UV crosslinking enables us to achieve a gradient in crosslinking and stiffness thus making these materials attractive as implantable scaffolds where tunable mechanical properties are desired. In this work we will also present recent work on synthesis of polypyrrole using oxidative chemical vapor deposition (oCVD) where polymer synthesis, doping, and film formation were combined in a single processing step. By carefully tuning the reaction parameters of deposition temperature, reactor pressure and oxidant to monomer flow rate ratio, homogeneous polypyrrole films with a record conductivity of 180 S cm−1 for a solvent-free method were produced. These polymers were used further for two applications: sensors and energy storage. For the piezoresistive strain sensors, polypyrrole was coated onto flexible substrates with porosities on different scales such as electrospun fiber-mats, phase-separated hydrogel membranes as well as 3D printed lattices. These substrates allowed us to obtain sensors with tunable mechanical and electrical properties. The results of the piezoresistive strain sensing behavior, gauge factors and cyclic stability will be shown. For the electrochemical energy storage electrode, polypyrrole was coated on a commercially available carbon fiber mat. The electrodes were characterized via cyclic voltammetry, galvanostatic charge-discharge measurements, and cyclic thermal stability tests. In summary, this presentation will highlight recent advances of iCVD and oCVD for biomedical and energy applications.

Authors : Deepak Bansal
Affiliations : Luxembourg Institute of Science and Technology

Resume : Porphyrins belong to a widespread class of compounds playing a key role in natural catalytic phenomena such as photosynthesis and respiration. Their properties can be easily tuned from the attachment of substituents to one or several of the eight β- and four meso- positions of the porphin ring and/or from the introduction of a cation inside the porphyrin core. In recent times, the cooperative effect promoted by conjugated covalent links between porphyrins was demonstrated for catalytic applications. Particularly, directly fused metalloporphyrin conjugated polymers display interesting opto-electronic and electrocatalytic properties. In general, despite of their attractive electronic, electrochemical, and optical properties, including an extremely red-shifted absorption up to the infrared, directly fused porphyrin conjugated polymers struggle to meet the requirements of practical applications due to their very weak solubility and non-meltability. In this context, Oxidative Chemical Vapor Deposition (oCVD) has afforded a promising solution to prepare and engineer multiply fused porphyrin conjugated polymers directly on the desired surface, overcoming the limitation related to solution-based approaches. Herein, we show the oCVD technique to prepare different di-meso-substituted Ni(II) porphyrin conjugated polymers containing phenyl groups with variety of substituents. The substituted groups on phenyl rings are shortlisted based on their electron donating, withdrawing and steric properties. High resolution mass spectroscopy displays the formation of doubly and triply fused porphyrin oligomers. Direct linkage between metalloporphyrins results in the increased conjugation between metalloporphyrin’s leading to the absorption in NIR region. All the polymerized material exhibits improved conductivity and electrocatalytic properties in comparison to monomers. Computational calculations also display interesting delocalization of frontier molecular orbitals on the polymerized metalloporphyrinoids. This study paves the way toward the engineering and future implementation of porphyrin-based systems comprising of donor-acceptor properties for clean and efficient solar fuel production.

Authors : Siamak Nejati Syed Ibrahim Gnani Peer Mohammad
Affiliations : University of Nebraska

Resume : Porphyrins and metalloporphyrins are known precursors to synthesize organic frameworks. It has been shown that porphyrins and metal-porphyrins can be employed as electrocatalysts for oxygen reduction reaction (ORR) and carbon dioxide reduction reactions. These reactions are essential to many schemes and processes and are interdisciplinary topics. There are so many other applications for these materials such as an active component in optical switches, photocatalysts, separation materials, etc. Here, the focus is given to the unique feature of tetrakis(4-aminophenyl)porphyrin (TAPP) that can go through polymerization and create phenazine linkage, forming porous conjugated frameworks that further assemble in 3D and construct covalent organic frameworks (COFs). Here, we report on the bottom-up and dry assembly of pTAPP and their derivatives to create active materials. We report on the control we achieved on the reaction selectivity and separation performance of the thin films deposited through the oxidative vapor phase polymerization pathway and explore various strategies to control the film structure and properties. The appearance of crystalline domains and heterostructure of pTAPP with a sub-micron length scale and the p-p stabilized superstructure will be discussed. This is the first report on a solvent-free synthetic pathway to form nanoscale crystallites of COFs.

Authors : B. Reeja-Jayan
Affiliations : Department of Mechanical Engineering, Carnegie Mellon University

Resume : We describe our efforts in applying electromagnetic fields to engineer a novel platform that can precisely engineer a broad palette of materials and architectures blending together highly thermally stable ceramics with heat sensitive polymers. Such low temperature processing can realize novel polymer-ceramic and metal-ceramic/polymer composites. These efforts are supported by Chemical Vapor Deposition (CVD) polymerization, which can grow over 70 polymer chemistries ranging from dielectric to highly conducting. Additionally, these low temperature methods allow for direct processing of such hybrid, multifunctional material assemblies on flexible, light-weight substrates for technologies related to energy storage and sensing. We further deploy both in-situ and operando x-ray synchrotron tools to formulate a fundamental understanding of dynamic structural changes at hetero-interfaces within such devices, which is key for improving operational efficiency and stability.

17:45 Discusson session 4    
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Biomaterials part III : Meike Koenig
Authors : Hsien-Yeh Chen
Affiliations : Department of Chemical Engineering, National Taiwan University

Resume : Functionalized poly(p-xylylenes) can be deposited via chemical vapor deposition (CVD) polymerization to generate polymer materials. For instance, such a CVD process can prepare the polymer as a thin polymer coating that can be generically applied to a wide variety of substrates and establish a reactive interface that allows for further modification; related applications have been shown to provide engineered interface properties to resist bacteria/biofilm formation, to prevent non-specific adsorption of proteins and cells (antifouling), and to manipulate cellular activities including proliferation, differentiation, and spheroids formation for a range of cells and stem cells. Furthermore, the coating technology has used for the encapsulation of liquids and to result in a revolutionary production of a intraocular lens (IOL), and the new IOL ehxibited: (i) enhanced compatibility and stability to avoid leaching of potential harmful substances to the surrounding biological environment and (ii) customizable optical and biological properties for diverse patient needs. Finally, instead of forming conventional thin films, the vapor deposition of the poly-para-xylylene polymers on a dynamic substrate, i.e., sublimating ice, was found to produce three dimensional bulk materials and composites with controllable porosity and size.

Authors : Gargi Ghosh, Nae-Eung Lee
Affiliations : Gargi Ghosh, Nae-Eung Lee School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Republic of Korea; Nae-Eung Lee SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Republic of Korea; Research Centre for Advanced Materials Technology, Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Republic of Korea; Samsung Advanced Institute for Health Sciences & Technology (SAIHST), Sungkyunkwan University, Suwon, Gyeonggi-do 16419, Republic of Korea; Institute of Quantum Biophysics (IQB), Sungkyunkwan University Suwon, Gyeonggi-do 16419, Republic of Korea; Biomedical Institute for Convergence at SKKU (BICS), Sungkyunkwan University Suwon, Gyeonggi-do 16419, Republic of Korea.

Resume : Wearable bio-electronics require materials with a variety of properties, including stretchability, toughness, optical transparency, biocompatibility, processability, and recyclability. However, creation of such materials, however, has been hampered due to the challenges of balancing these properties. Many soft materials are either mechanically durable but thermally unstable. Or they are thermally and chemically stable but non-deformable. Therefore, there is a requirement for the compromise among various physical and chemical properties for certain applications. For example, stiff materials like thermoset polyimides have very high thermal and chemical stability but poor formability and mechanical stretchability. And, a frequently used elastomer in soft electronics, PDMS, has high stretchability and moderate thermal stability but it lacks formability (such as moldability) and mechanical toughness. Also, PDMS has other limitations like undesired non-specific absorption of small hydrophobic molecules, high gas permeability, leaching, impedance to flow of polar liquids in the microchannels and swelling in the presence of hydrocarbon solvents. Other thermoplastic copolymers like PU, SBS and SEBS have certain benefits like tunable mechanical properties, good formability but again it lacks the thermal and chemical stability. Herein, we report intrinsically stretchable thermoplastic copolymers with a random sequence of hard and soft domains in the polyimide backbone in which their superior traits are harnessed to enable the properties of the copolymer tunable and balanced. The significance of this work is the synthesis of new copolymer with balanced properties of high mechanical toughness and modulus similar to human skin (forehead and arm), good thermal stability, high chemical resistance, optical transparency, biocompatibility, low water vapor transmission rate, good formability, and recyclability. In addition, the polymer is easily processable, allowing for the fabrication of fibers, thin films, and molded parts for soft electronics. Furthermore, the utility of the copolymer was successfully demonstrated for a wearable temperature sensor on the stretchable copolymer and a copolymer-based fully stretchable sweat collection patch, suggesting that they have great potential in soft electronics. Keywords: copolymer, thermoplastic, stretchable, tough, recyclable, high stability, processability, soft bio-electronics

Authors : Dong Hee Kang, Hyun Wook Kang
Affiliations : Advanced Fluidics & Nano Technology Lab, Department of Mechanical Engineering, Chonnam National University, Gwangju, Korea, Republic of

Resume : Depending on the electrical and geometrical characteristics of nanofiber (NF) membrane, filtration efficiency is influenced by the size of airborne pollutants. The pollutants in the air are classified into various types such as a mixture of solid particles (dust, combustion products, soot, smog, etc., diameter 0.1~100 μm), biomolecules as bacteria (0.5~10 μm) and viruses (1~10 nm), and liquid droplets. Electrospun (ES) NF membrane-based filtration is a simple technique to improve mechanical and electrical particulate matter (PM) filtration performance. PM filtration efficiency improves as the fiber diameter decreases to tens of nanometers in a constant thickness NF membrane. However, the pressure drop increases exponentially which shows an existing trade-off relationship with PM filtration efficiency. Electrical charges from an external source are supplied to reduce the pressure drop of the filter with high filtration efficiency without geometrical variation. In this research, a triboelectric hybrid membrane filter is developed with superior fine PM filtration and filter regeneration characteristics. A hybrid membrane is vertically stacked with stacking layers (the ES PVDF NF layer on the Nylon mesh layer) for the generation of the triboelectric charges inside the filter via the bending-release cycle. As the number of the NF-mesh layers increases, electrostatic charges remain in the multilayer filter for a long time. Electrostatic charges with a high-density effect to improve filtration efficiency as the PM size is smaller. The super-hydrophobic PVDF NF layer has low surface energy to be easily removed for charged impurities adhering to NF by vanishing the electrostatic interaction through immersion with a polar liquid as ethanol. After the ethanol dipping and drying process of the hybrid membrane, the NF layer is maintained without damage. And NF layer restores the electrostatic charges via the re-charging process without degradation to filtration performance. As well as the simple stacking process, Fabrication of the ES NF layer based on a mesh layer has an advantage in continuous mass production of the hybrid filter membrane. The Nylon mesh layer prevents physical deformation and damage to the PVDF NF layer in the hybrid membrane. As a result, the washable PM filter can be enhancing the filtration efficiency for fine particles (<2.5 μm) by recovering surface charges from the triboelectric characteristics of the vertically stacked PVDF NF-Nylon mesh layers. With the increased effective contact area of triboelectric layers, they contribute to maintaining a high density of electrostatic charges inside the PVDF NF layer. Also, increasing the total thickness of the membrane through the addition of a Nylon layer improves the volumetric capacitance to capture particles, enhancing the membrane life and delaying reaching the limiting pressure drop.

10:00 Discusson session 5    
10:15 Coffee break    
Mechanism of deposition/Deposition on patterns : Dirk Hegemann
Authors : Annaëlle Demaude*, Juliette Zveny*, Michael Gordon°, François Reniers*
Affiliations : * Chemistry of Surfaces, Interfaces and Nanomaterials, Université libre de Bruxelles, Brussels, Belgium ° Chemical Engineering Dept. University of California, Santa Barbara, USA

Resume : Dielectric barrier discharges (DBDs) are cold plasma, usually operating at atmospheric pressure, are widely used for gas conversion (ozone synthesis, CO2 conversion, nitrogen fixation,…), for surface functionalization and surface cleaning. Due to their intrinsic advantages over other approaches (no use of solvents like in conventional chemistry, no need of vacuum technologies and chambers like in PVD and PECVD, ability to work in air, at room temperature), they are also used for thin film deposition. Inorganic, organic, or mixed coatings can be successfully deposited. However, due to the small mean free path at atmospheric pressure and the low energy available in cold atmospheric plasma, combined with the inhomogeneous character of many DBDs, good control of the crystallinity (for inorganic coatings), degree of cross-linking (polymers) and more generally of the chemistry of deposited coating is sometimes difficult to achieve. Therefore, realizing patterned coatings using a DBD is even more challenging. The talk will present different approaches to easily obtain patterned coatings using a DBD. Hybrid hydrophilic/hydrophobic patterns will be chosen as a case study. The synthesized samples are characterized using WCA, µ-IR spectrometry, µ-XPS, and profilometry. In a first approach (1), conventional masks will be used, together with a combination of two precursors. The effect of a post-treatment to make the surface locally hydrophilic is discussed. In a second approach (2), advantage will be taken from the non-homogeneous behavior of the discharge by exploiting the differences in electron density, reactive species density and energy density existing between the filaments and the inter-filament spacing in a filamentary discharge. A special reactor allowing to immobilize the filaments and to study them using a high speed camera was designed. It is shown that the coating deposited is characterized by a pattern consisting in spots of sub-millimeter size located under the filaments, surrounded by flat areas, both exhibiting different hydrophilicity, roughness, thickness and chemistry. The effect of the different approaches (masks – immobilized filaments), and of the process parameters (precursor chemistry and concentration, plasma power, burst or continuous mode, substrate nature,..) on the coatings is discussed as well as the possibilities and limits of both approaches. References : (1) A. Demaude, Langmuir (2019),35 (30), 9677-9683 (2) A. Demaude et al. Submitted.

Authors : Chara Zavvou, Chloé Guérin, Aude Lefevre, Vincent Jousseaume
Affiliations : Univ. Grenoble Alpes, CEA, Leti, F-38000 Grenoble

Resume : Initiated Chemical Vapor Deposition (iCVD) relies on a radical polymerization on a surface from a vapor phase. Among its numerous advantages, it offers a large library of monomers available, including organosilicates, and the possibility to fabricate homogenous polymeric thin films. iCVD is generally presented as a technique that allows highly conformal polymer deposition on nanoscale structures (porous structures, nano-objects, trenches, …). However, there are only few works studying in detail the impact of the aspect ratio (AR) on the conformality and none on organosilicate polymers. Though, this is very important especially in micro-nanotechnologies where the need to cover 3D structures is a major challenge (for instance dielectrics for 3D capacitors, insulators for Trough-Silicon Via, sensitive layers for Nano-Electro-Mechanical Systems, ...). In this work, the conformality of poly(V3D3), an organosilicate polymer, is studied. For this purpose, P(V3D3) thin films were deposited in different deposition conditions, especially at different substrate temperatures, this parameter critically influencing the polymerization process and the deposition rate. The depositions were performed on different structures etched in silicon and having different aspect ratio features (trenches, holes, with aspect ratio (AR) between 1 and 20) which were characterized by SEM cross section observations. Thus, an optimization of process parameters could be defined to achieve a 100% step coverage for AR<20 structures. At the same time, we demonstrate that the step coverage degrades as the deposition rate increases. It is also highly dependent on the aspect ratio and can fall down to values below 50% for AR>20. From this study, we propose a phenomenological model where the covering is not limited by the diffusion rate or the sticking probability but by the recombination loss during collisions of the radicals with the side-walls of the feature (recombination limited growth model). Finally, the impact of annealing on these 3D-optimized depositions is also evaluated. Indeed, the materials integrated in microelectronic devices must be able to withstand the thermal budgets of the processes used for the integration of the components. Thus, the impact of annealing under N2 between 100 and 400°C on the physico-chemical properties (using ellipsometry, FTIR, TGA and DSC measurements) and on the conformality is discussed.

Authors : Prof. Claus-Peter Klages, Lars Bröcker
Affiliations : TU Braunschweig, Institute for Surface Technology

Resume : Deposition mechanisms of plasma-enhanced chemical vapor deposition (PECVD) processes activated by dielectric barrier discharges (DBDs) at ambient pressure are to this date not fully understood. It is generally not clear, for example, to what degree radicals on the one hand and ions on the other take part in formation of plasma polymers: Radicals are often assumed to be the only film-forming species whereas the production of precursor ions via direct electron ionization and, in mixtures with suitable carrier gases, via Penning ionization is possible. Using single-filament DBDs (SF-DBDs) with short gas residence times in mixtures of hexamethyldisiloxane (HMDSO) and argon we have shown that cations produced from the monomer are main contributors to film formation if precursor fractions do not exceed a few 100 ppm. For larger precursor concentrations ionic oligomerization increasingly contributes to the deposition process. Studies of thin film formation under conditions of dominating ionic deposition can lead to a better understanding of the underlying mechanisms and possibly to new processes and applications. In the present contribution, we report results of SF-DBD investigations extended to several oxygen-free organosilanes containing the trimethylsilyl group: tetramethylsilane (TMS), hexamethyldisilane (HMDS), allyltrimethylsilane (ATMS) and vinyltrimethylsilane (VTMS). A generally diffuse plasma appearance as well as strong decline of ignition voltage and dissipated energy for monomer fractions growing up to a few 100 ppm indicate the dominance of a Penning mechanism. The identity of film-forming ions produced via Penning ionization of the monomer by excited argon species is mostly unknown so far. A comparison of deposited film volumes obtained directly from profilometric measurements with volumes calculated from the transferred charge and the mass of potential fragment ions can give a useful indication. In the case of HMDS, for example, this comparison makes a deposition of the pentamethyldisilyl cation likely, whereas the trimethylsilyl cation was the main fragment ion in mass-spectrometric investigations with electron-collision ionization. For elemental and structural analysis of the plasma polymers FTIR-ATR, Raman and WDXS measurements were used. Interestingly, spectra of deposits obtained by single-filament DBDs often resemble spectra reported for films obtained by low-pressure plasma processes. To analyze the amount of characteristic moieties in the plasma polymer such as -CH3, -CH2-, Si-H, and Si-O-Si, transmission FTIR spectra of model substances were used to derive the integrated intensities of the corresponding vibrational bands. Oxygen-to-carbon ratios determined from this analysis are in good agreement to the WDXS data.

Authors : Rony Snyders, Nathan Vinx, Pascal Damman, Philipe Leclère, Damien Cossement, Damien Thiry
Affiliations : Chimie des Interactions Plasma-Surface (ChIPS), University of Mons and Materia Nova Research Center, Parc Initialis, Mons Chimie des Interactions Plasma-Surface (ChIPS), University of Mons Interface et Fluides Complexes (Influx), University of Mons Laboratory for Chemistry of Novel Materials (CMN) Materia Nova Research Center, Parc Initialis, Mons Chimie des Interactions Plasma-Surface (ChIPS), University of Mons

Resume : Plasma polymerization has become a well-established technique for the synthesis of organic thin films referred as plasma polymer films (PPF). Thanks to important research efforts, it is today possible to decently control the chemical composition of the PPF, even if the synthesis mechanism are considered as complex. In order to address new applications for this class of material, it appears that an additional control of the mechanical properties of the PPF becomes more and more a key requirement as well. In this context, our group has contribute through collaborative works to the development of an innovative approach allowing for tunning the mechanical properties of PPF. This approach is based on the fine control of the growth temperature of the PPF films (Ts). In the present work, the synthesis of propanethiol PPF is considered as a case study. By means of state-of-the-art AFM characterization-based techniques including Peak Force Quantitative Nanomechanical Mapping (PFQNM), nano Dynamic Mechanical Analysis (nDMA) and “scratch” experiments, we demonstrate that the mechanical behaviour of the PPF evolves from a high viscous liquid (i.e. viscosity ~ 106 Pa.s), to a viscoelastic solid (loss modulus ~ 1.17 GPa, storage modulus ~ 1.61 GPa) and finally to an elastic solid (loss modulus ~ 1.95 GPa, storage modulus ~ 8.51 GPa) as a function of Ts. This behaviour is attributed to strong modifications of the surface glass transition temperature of the polymer-plasma network evaluated by a Tof-SIMS-based methodology. The evolution of the glass transition temperature is further understood by establishing a correlation with the chemical composition of the PPF and, especially, by considering the crosslinking density of the PPF network and the presence of unbounded molecules acting as plasticizers. In the context of this work, this understanding is exploited for the fabrication of nanopatterns that could be utilized in many application fields including for the development of biological platforms.

12:15 Discusson session 6    
Hybrid thin films : Rong Yang
Authors : Fiorenza Fanelli, Antonella Uricchio, Teresa Lasalandra, Gael Plantard, Francoise Massines
Affiliations : National Research Council (CNR), Institute of Nanotechnology (NANOTEC), Bari, Italy; Department of Chemistry, University of Bari “Aldo Moro”, Bari, Italy; University of Perpignan Via Domitia, Perpignan, France; Laboratoire Procédés Matériaux et Energie Solaire, PROMES-CNRS, UPR 8521, Perpignan, France

Resume : Low-temperature atmospheric pressure plasmas (APPs) have received enormous attention in surface engineering over the last two decades. They have opened unprecedented opportunities to tailor the surface properties of materials as well as to prepare a variety of thin films with different chemical compositions, structures, and morphologies. In this context, the aerosol-assisted APP deposition has recently emerged as a very promising and versatile technique to prepare nanocomposite (NC) films [1,2]. It has been shown that the possibility of combining the aerosol of either nanoparticle dispersions or precursor solutions with a low-temperature APP allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. In this contribution, we will present our recent advances in the development of aerosol-assisted APP deposition processes for the preparation of organic-inorganic NC coatings. Particular attention will be given to process optimization and to the composition, structure and functional properties of the deposited coatings [3-5]. We will finally discuss the potential of the deposition technique for the preparation of superhydrophobic surfaces, of filtration and absorbent materials for oil-water separation, as well as of macroporous photocatalytic materials for the degradation of organic pollutants in water [3,6]. [1] F. Fanelli, F. Fracassi, Plasma Chem. Plasma Process., 2014, 34, 473–487. [2] A. Uricchio, F. Fanelli, Processes, 2021, 9, 2069. [3] F. Fanelli, A.M. Mastrangelo, F. Fracassi, Langmuir, 2014, 30, 857−865. [4] P. Brunet, R. Rincón, J.-M. Martinez, Z. Matouk, F. Fanelli, M. Chacker, F. Massines, Plasma Process. Polym. 2017, 14, e1700049. [5] F. Fanelli, A.M. Mastrangelo, G. Caputo, F. Fracassi, Surf. Coat. Technol., 2019, 358, 67–75. [6] A. Uricchio, E. Nadal, B. Plujat, F. Massines, G. Plantard, F. Fanelli, Appl. Surf. Sci., 2021, 561, 150014.

Authors : Mark D. Losego
Affiliations : Georgia Institute of Technology

Resume : Vapor phase infiltration (VPI) is a new processing technology for infusing polymers with inorganic constituents to create unique organic-inorganic hybrid materials with novel chemical, electrical, optical, and mechanical properties. These new materials have been used in applications ranging from energy harvesting to filtration media to photolithographic hard masks. This talk will explore our current understanding of the final hybrid structure and our use of electron microscopy, spectroscopy, and density functional theory (DFT) to understand the inorganic’s chemical state and its bonding structure to the polymer. Several example applications will be discussed and it will be shown how an understanding of the processing kinetics and chemical structure can be used to scale the VPI process to treat macroscale objects – including plastic components and textiles – as well as the additional complications and/or opportunities that avail themselves from process scale-up.

Authors : Lisanne Demelius, Katrin Unger, Anna Maria Coclite
Affiliations : Institute of Solid State Physics - Graz University of Technology

Resume : The trend towards ever smaller feature sizes in microelectronic device architectures fuels the interest in vapor-based deposition techniques that allow for the fabrication of highly uniform and conformal thin films. Initiated chemical vapor deposition (iCVD) and plasma-enhanced atomic layer deposition (PE-ALD) are two important candidates able to meet these requirements. While PE-ALD is a powerful tool to deposit thin films of various inorganic compounds with precise control of film thickness at low temperatures, iCVD allows for the thin film deposition of a wide range of (functional) polymers while fully retaining their rich chemistry. By combining iCVD with PE-ALD, highly conformal and smooth organic-inorganic multilayers can be obtained that represent the basic building block of a whole range of applications from thin film encapsulations to (bio-)sensors and other functional devices. A prerequisite for the successful integration of these techniques into novel device architectures is a thorough understanding of the growth processes and interface formation. While the mechanisms determining growth during thermal ALD on polymers are quite well-understood, little is known on PE-ALD growth on organic substrates. Our work aims to fill this gap by providing fundamental insights into the growth process and interface formation during PE-ALD of ZnO on selected iCVD polymer thin films. Initial growth of ZnO on the iCVD polymers was monitored via in-situ spectroscopic ellipsometry and the resulting thin films were further characterized in terms of crystallinity, interface and surface morphology and elemental composition. To gain a better understanding of how the chemical structure of the polymer influences precursor-substrate and plasma-substrate interactions, three polymers with varying reactivity with the ALD precursor were studied: hydroxyl-rich poly hydroxyethylmethacrylate (pHEMA), carbonyl-rich poly ethylene glycol dimethylacrylate (pEGDMA), and the weakly reactive poly(2,4,6,8-tetravinyl-2,4,6,8-tetramethyl cyclotetrasiloxane) (pV4D4). Our results show that film formation on the iCVD polymers is a consequence of two competing processes: ZnO PE-ALD growth and plasma etching of the polymer substrate. During the initial ALD cycles, polymer etching dominates, resulting in an overall decrease in thickness. At a certain point, ZnO growth takes over and the regime of normal ALD growth behaviour is entered. The strength of etching is proportional to the applied plasma power and depends strongly on the type of polymer with almost negligible thickness losses for pV4D4 and strongest etching for pHEMA. Despite the initial etching, the resulting thin films exhibit sharp interfaces and a quality, in terms of surface roughness, crystallinity and ZnO density, comparable to those of ZnO deposited on silicon.

Authors : Stacey F. Bent
Affiliations : Department of Chemical Engineering, Stanford University

Resume : Organic functional layers can be used to tune electronic, chemical and mechanical properties of a substrate and to add active functionality. In recent years, molecular layer deposition (MLD) has received increased interest for the deposition of surface-bound oligomeric and polymeric thin films. An advantage of MLD over other organic deposition techniques is that it relies on the same principle of self-limiting surface reactions as atomic layer deposition (ALD), allowing it to conformally deposit films with atomic-level thickness and compositional control. Moreover, the functionality of the MLD assembly can be finely tuned by changing the nature of the organic moieties within the film. In this talk, we will present results on MLD of pure organic nanoscale films as well as hybrid organic-inorganic assemblies. Both thermal polymerization MLD reactions and photo-initiated MLD, which provides for direct carbon-carbon bond formation of covalently-bound organic multilayers, will be described. We also introduce the technique of ionic liquid assisted MLD, which allows access to a solvent-like environment in the vacuum deposition process. Further, by combining a metal precursor typically associated with ALD and an organic counter reactant monomer associated with MLD, films of hybrid materials can be grown. A combination of microscopy, spectroscopy, and x-ray scattering studies provides insight into both the growth mechanisms and the structure of the resulting organic and hybrid films. The MLD process provides the opportunity to create new material architectures, combining the characteristics and benefits of the parent materials in a way that may lead to novel electrical, magnetic, and catalytic properties.

16:45 Discusson session 7    
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Porous thin films and multilayers : Yumin Ye
Authors : Alberto Perrotta
Affiliations : National Research Council (CNR) - Institute of Nanotechnology (NANOTEC)

Resume : Functional organic and inorganic thin films offer innovative solutions for a plethora of technological applications: organic electronics, smart (bio) devices, membrane technology, photocatalysis, sensors and drug delivery systems. The applicability of such thin films strongly depends on the versatility of the synthetic method in tailoring the chemical-physical properties of the materials. In this perspective, porosity is one of the most (un)wanted properties in thin films fabrication. When the thin films are adopted as barriers, (nano)pores could be detrimental in blocking the targeted species and the fabrication methodologies aim at producing pore-free thin films or being able to “heal” the layer barrier properties. On the contrary, functional porous materials are gaining a fundamental role in nano-technology in a broad variety of fields, from catalysis to permeation membranes, from (bio)sensors to batteries. (Nano)pores’ fabrication methods are intensively investigated when properties such as surface area or size-dependent selectivity are sought. The implementation of simple methodologies for the engineering of controlled porosity and its characterization in thin films is not trivial, due to the intrinsic lack of control in pore content for the classical thin film fabrication methods. The research on the porosity and its impact will be presented for thin polymeric films obtained via (plasma-based) dry deposition methods such as plasma enhanced-chemical vapor deposition (PE-CVD), initiated CVD (iCVD) and molecular layer deposition (MLD). Three main case studies will be shown, touching upon the fundamental aspects of porosity. i) The undesired porosity will be investigated specifically in the field of protective coatings applied to organic electronics. Optical and analytical methods for the characterization of such (intrinsic) porosity will be presented, with an overview on the processing aspects leading to its formation and curing. ii) The functional porosity of polymeric thin films will be presented as second case when applied to sensing technologies. Stimuli-responsive polymers will be investigated in terms of their accessible porosity and its evolution as a function of the processing conditions. iii) Finally, the possibility of a “latent” porosity in hybrid polymeric thin films will be presented. The exploitation of chemically selective weakness will be shown as a path to derived nanoporous materials. The road to the so-called polymer-derived ceramics starts from the pristine chemical functionalities and their processing, and vapor phase methods will show once more their versatility in the material engineering.

Authors : Stefan Schröder
Affiliations : Institute for Materials Science, Kiel University, Kiel, Germany

Resume : The ongoing trend of device miniaturization and consequent need for new thin film materials on the nanoscale is noticeable in many application fields including dielectric and electronic applications of polymers. Initiated chemical vapor deposition (iCVD) accomplishes these new tasks and allows to fabricate new tailored polymer thin films. The process enables solvent-free deposition of high-quality coatings from the vapor phase on large-area substrates, complex geometries as well as temperature-sensitive samples. This talk shows how the advantages of the iCVD process can be applied in order to develop new materials or to improve existing electronic applications. This involves the use of homopolymers as well as tailor-made copolymers such as gradient copolymers [1]. Experimental and theoretical investigations on charge storage in thin film electrets will be presented [2] together with new results on charged iCVD layers. These iCVD coatings are used in various applications such as magnetic field sensors or energy generators [3]. Furthermore, it will be demonstrated how the performance of existing sensor devices such as gas sensors can be improved by special iCVD coatings [4]. In addition, the functionalization of new organic electronic materials is shown. To obtain better control of the film growth on the lower nanoscale, and to better understand the underlying reaction mechanisms, new approaches using in-situ quadrupole mass spectrometry as well as theoretical calculations are presented [5]. 1. S. Schröder et al., Mater. Today 37 (2020). 2. S. Schröder et al., Sci. Rep. 9 (2019). 3. M. Mintken et al., Nano Energy 56 (2019). 4. S. Schröder et al., Mater. Today Chem. 23 (2022). 5. S. Schröder et al., J. Phys. Chem. A 125 (2021).

Authors : Hernandez Rodriguez, G., Coclite, A.M.,
Affiliations : Institute of Solid State Physics, Graz University of Technology, Graz, Austria

Resume : The aim of this study is to develop a novel approach for anti-icing systems through the design of gradient polymer thin films via initiated chemical vapor deposition (iCVD). The proposed design contemplates monomers of different nature and properties, an acrylate with high fluoro-content and an organosilicon, namely, perfluorodecyl acrylate (PFDA) and tetravinyl tetramethyl cyclotetrasiloxane (V4D4), respectively. A gradient polymer can be described as a continuous structure that exhibits a progressive conversion from species A to species B, hence, a structure consisting of two homopolymers on each end and a copolymer in-between is obtained. In this case, a vertical structure is constructed where V4D4 lies on the bottom in contact with the substrate and PFDA on the top. The multiple vinyl groups of V4D4 allow the formation of a highly cross-linked network that provides good adhesion properties, contrary to PFDA whose high content of fluorinated groups prevent, however, these groups grant high hydrophobic properties which are potentially suitable for anti-icing systems. Furthermore, by employing the proper deposition parameters, it is possible to induce a degree of crystallization over the fluorinated groups of PFDA, and through crystallization, the hydrophobic properties can be enhanced. By making a gradient polymer it is possible to fully retain the properties of both monomers, this approach is advantageous over simply random copolymerization or stacked layers in terms of adhesion, mechanical properties, and processing. Using iCVD, the creation of these sophisticated structures is possible in one step, in a solvent-free environment, over substrates of different nature, and with high precision over the thicknesses of each component. The gradient polymers were characterized by IF spectroscopy, atomic force microscopy, and x-ray diffraction. To assess the design of the gradient polymers, it is required to characterize the surface properties of the thin films and analyze their behavior under icing events. Therefore, we performed observations on the nucleation and propagation of ice over the films. It is through the understanding of the physical properties and the nature of icing events that it is possible to improve the icephobic performance of the gradient polymers.

10:15 Discusson session 8    
10:30 coffee break    
Sensors based on thin films : Junjie Zhao
Authors : Maximilian H. Burk (1), Stefan Schröder (1), Stefan Rehders (1), Thomas Strunskus (1), Rainer Herges (2) and Franz Faupel (1)
Affiliations : (1) Faculty of Engineering, Kiel University, Kaiserstr. 2, 24143 Kiel, Germany. (2) Otto-Diels-Institute for Organic Chemistry, Kiel University, 24118 Kiel, Germany.

Resume : Initiated chemical vapor deposition (iCVD) is a solvent-free, cost efficient technology for the synthesis of highly conformal organic thin films directly from the vapor phase. Due to generally mild reaction conditions the individual functionalities of the used monomers are preserved, enabling the homogeneous coating of almost every kind of substrate without the risk of solvent interference or pore clogging. This allows for example the tailored synthesis of super hydrophobic fluoropolymers with application as electret layers as well as the highly innovative deposition of gradient layers with superb adhesion properties. Moreover, iCVD is highly interesting in the field of biocompatible coatings and controlled drug release [1,2] When it comes to the design of novel functional coatings, smart surfaces must be based on the ability to perform controlled, reversible transitions upon application of an external stimulus. Recently we were first to demonstrate the utilization of a solid chromophoric compound within the iCVD process which lead to the synthesis of photoswitchable co-polymer thin films, using a functional diazocine (a bridged azobenzene) as switchable unit. [3] Photoswitchable molecules are able to undergo a reversible transition upon illumination with monochromatic light which can lead to a change in absorption, dipole moment or geometry. Due to the underlying nature of iCVD it was possible to combine a highly hydrophilic monomer with a rather hydrophobic chromophore, without the risk of phase separation or unwanted side reactions. Upon illumination with blue light it was possible to induce photoisomerization of the incorporated photoswitch, leading to a reversible change in color as well as expansion/contraction of the thin film. Using iCVD we showed the deposition of photoswitchable patterned coatings on glass, the deposition on flexible substrates and the creation of functional surfaces that can be written on with a conventional blue laser pointer. [4] In our current research we focus on the fabrication of freestanding polymer structures with incorporated photoswitchability to efficiently translate photoisomerization on the microscopic- to movement on the macroscopic scale with the intention of creating photomechanical cell scaffolds. References: 1. S. Schröder et al., Sci. Rep. 9 (2019). 2. S. Schröder et al., Mater. Today 37 (2020). 3. M. H. Burk et al., Macromolecules 53 (2020). 4. M. H. Burk et al., ACS Appl. Polym. Mater. 3 (2021).

Authors : Alexander Dallinger, Paul Kindlhofer, Francesco Greco, Anna Maria Coclite
Affiliations : Alexander Dallinger: Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, Graz (Austria); Paul Kindlhofer: Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, Graz (Austria); Francesco Greco: Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, Graz (Austria), The Biorobotics Institute, Scuola Superiore Sant’Anna, Viale R. Piaggio 34, 56025 Pontedera (Italy); Anna Maria Coclite: Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, Graz (Austria);

Resume : By laser scribing with a CO2 laser onto a polymer precursor like polyimide, it is possible to create conductive tracks by laser-induced pyrolysis. So-called laser-induced graphene (LIG) is obtained in this process, which consists of a porous 3D structure with a high surface area and good conductivity. By embedding the LIG into a stretchable and soft polydimethylsiloxane matrix, a conductive and stretchable composite was created. The electro-mechanical properties of this LIG composite were investigated. We realized various kinds of soft actuators based on LIG composites. The embedded LIG is used as a joule heating element to trigger a thermoresponsive actuation in the composite. By coupling the LIG/PDMS composite with a thin film of a smart humidity-responsive hydrogel (poly-(N-vinycaprolactam), pNVCL) by means of initiated chemical vapor deposition (iCVD), we realized a multi-responsive soft actuator. The actuator performance was characterized and a demonstrator was fabricated. Thanks to the piezoresistive behaviour of the embedded LIG the bending angle of the soft actuating structures could be measured.

Authors : Taher Abu Ali, Dr. Barbara Stadlober, Prof. Anna Maria Coclite
Affiliations : 1. Graz University of Technology, Institute of Solid State Physics 2. Joanneum Research, Institute for Surface Technologies and Photonics

Resume : This work presents a multi-stimuli responsive sensor for artificial skin applications. The sensor is responsive to surrounding changes in force, humidity and temperature. The developed design consists of a hydrogel core, responsive to temperature and humidity changes; and a piezoelectric shell for force detection. Swelling of the hydrogel core, in response to humidity and temperature, mechanically strains the piezoelectric shell and generates detectable electric charge. The two materials are combined into core-shell nanorod structures, using state-of-the-art vapor-based deposition techniques. These deposition techniques provide control over material’s mechanical, optical and electrical properties in addition to film’s conformity and uniformity. Moreover, the core-shell nanorods are deposited into a nanostructured UV-curable resin, which allows the fabrication of the embedded core-shell nanorods. 1. Piezoelectric zinc oxide is synthesized using plasma-enhanced atomic layer deposition (PE-ALD).In PE-ALD, substrate temperature defines the deposited film’s crystalline properties. A combination between (100) and (002) crystallographic orientations gives control over zinc oxide’s piezoelectric properties. In this work, piezoelectric zinc oxide layer with combined (100) and (002) preferential orientation is deposited at low temperatures, which is advantageous for when flexible substrates. 2. humidity and temperature responsive hydrogel, Poly-N-vinylcaprolactam (pNVCL), is synthesized using initiated chemical vapor deposition (iCVD). The dry vapor-phase technique gives control over the lower critical solution temperature (LCST), amongst other material properties. 3. The multi-stimuli responsive core-shell nanorods are deposited into nanostructured UV-curable polyurethane acrylate (PUA) resin, with nanoholes having a diameter d = 500 nm, height L = 500 nm and pitch = 1000 nm, achieved using UV nanoimprint lithography (UV-NIL).

Authors : Adrivit Mukherjee, Sara Selenica, Dr. Ajay G. P. Kottapalli, Prof. Marleen Kamperman, Dr. Ranjita K. Bose
Affiliations : Product Technology, Department of Chemical Engineering, Engineering and Technology Institute (ENTEG), University of Groningen, The Netherlands; Product Technology, Department of Chemical Engineering, Engineering and Technology Institute (ENTEG), University of Groningen, The Netherlands; Advanced Production Engineering (APE), Engineering and Technology Institute Groningen (ENTEG), University of Groningen, The Netherlands; Polymer Science, Zernike Institute for Advanced Materials (ZIAM), University of Groningen, The Netherlands; Product Technology, Department of Chemical Engineering, Engineering and Technology Institute (ENTEG), University of Groningen, The Netherlands

Resume : Oxidative Chemical Vapor Deposition (oCVD) is an all-dry technique, which enables the growth of high-quality conjugated polymers (CPs). oCVD accomplishes polymerization of a conductive network, conducts doping, and deposits coatings of uniform thickness in a single processing step at near room temperatures. Deposition via vapor phase during oCVD eliminates the challenges of insufficient monomer solubility of CPs and other solvent related difficulties such as dewetting, solvent damage etc. faced by traditional methods. Further, unlike conventional techniques, oCVD operated at mild conditions, provides additional advantages, such as the ability to conformally coat delicate substrates or three-dimensional porous microstructures. In our work, we use oCVD to engineer conductive polymer composites (CPCs). CPCs are prominent candidates for a broad range of biomedical applications that rely on electrical conductivity, such as flexible and wearable piezoresistive strain sensors. We have developed hybrid CPCs with tunable mechanical and electrical properties. Ultra-thin conductive coatings of intrinsically conductive polypyrrole (PPy) have been realized on different flexible substrates with variable porosities such as electrospun fiber-mats, polyelectrolyte membranes prepared via aqueous phase-separation with gradient microstructures as well as 3D printed lattices. The porous interconnected microstructures serving as a template, guides the in-situ vapor phase polymerization of a CP backbone into the matrix by oCVD. The relatively thin oCVD PPy coatings render the substrates electrically conductive (measured conductivity ≈ 102 S/m) while preserving the stretchability of the underlying substrates which record fracture strain more than 400%. FTIR spectroscopy confirms the successful deposition of doped PPy, and SEM imaging shows conformal coating of oCVD PPy within the microstructure. The thermal stability of the oCVD PPy coatings have been investigated using TGA and programmed temperature pyrolysis. Synergistic interpenetrating CP chains throughout the matrix can be used to reversibly tune mechanical and electrical properties of the designed CPC. The impact of oCVD PPy coating thickness and conductivity on the mechanoelectrical properties of the CPCs will be presented. The results show that the fabricated CPCs are piezoresistive, demonstrate gauge factors as high as 100 with good cyclic stability.

Authors : Iulia ANTOHE1*, Andrei Stochioiu1, Luiza-Izabela JINGA1, Andreea MIHĂILESCU1, Gianina POPESCU-PELIN1, Vlad-Andrei ANTOHE2,3 and Gabriel SOCOL1*
Affiliations : 1 National Institute for Lasers, Plasma and Radiation Physics, Atomistilor 409, 077125 Magurele, Romania 2 Institute of Condensed Matter and Nanosciences (IMCN), Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium. 3 Research and Development Center for Materials and Electronic & Optoelectronic Devices, Faculty of Physics, University of Bucharest, 077125 Măgurele, Romania * Corresponding authors:;

Resume : Hydrogen measurement is crucial in emerging industries that employ liquid H2 as an energy source. Hydrogen gas leak detectors, such as the one described in the present work, are used to prevent any accident because of the high explosion risks it has in the presence of air, as these can lead to serious injuries and damage. Polyaniline (PANi) has been proven to be an advantageous material for producing gas sensing devices, having very good sensitivity and short response times [1]. Moreover, the addition on top of the sensor of a very thin film of poly(methyl methacrylate) (PMMA) acted as a selective filtration layer, allowing only H2 to penetrate for measurement [2]. In this work thus, conductive PANi thin films were obtained via chemical polymerization of aniline directly on interdigited gold substrate and have been characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and then electrically characterized in a gas chamber. Aniline was polymerized on the substrate in an acidic solution bath with ammonium persulfate and hydrochloric acid according to a method described in the literature [3,4]. PMMA solution was deposited by spin coating. The electrical properties of the sensor inside the gas chamber have been investigated using a source-meter while under direct expose to hydrogen gas at varying concentrations. The developed PANi based sensor proved to be a very good hydrogen gas detector with reasonable sensitivity at very low concentrations of just 1 ppm H2. References: 1. H. Bai, G. Shi. Materials Science and Engineering: Concepts, Methodologies, Tools, and Applications 7 (2007) 267–307. 2. J. Hong, S. Lee, J. Seo, S. Pyo, J. Kim and T. Lee. ACS Appl. Mater. Interfaces 7 (2015), 3554−3561. 3. A. Attout, S. Yunus, P. Bertrand. Surface and Interface Analysis 40 (2008) 657–660. 4. A.B. Nagare et al. Journal of Materials Science: Materials in Electronics 30 (2019) 11878–11887. Acknowledgements: This work was financially supported by the National Authority for Research and Innovation in the frame of Nucleus Programme - LAPLAS VI (contract 16N/08.02.2019) and by the Executive Agency for Higher Education, Research, Development and Innovation (UEFISCDI) funding, Project PD 195/2020 (PN-III-P1-1.1-PD-2019-0466) and Project TE 115/2020 (PN-III-P1-1.1-TE-2019-0868). We also acknowledge the doctoral scholarship from University of Bucharest, Faculty of Physics.

Authors : Francesco Decataldo, Laura Grumiro, Maria Michela Marino, Francesca Faccin, Catia Giovannini, Martina Brandolini, Giorgio Dirani, Francesca Taddei, Davide Lelli, Marta Tessarolo, Maria Calienni, Carla Cacciotto, Antonio Lavazza, Vittoria Cattani, Beatrice Fraboni, Alessandra Scagliarini and Vittorio Sambri
Affiliations : Department of Physics and Astronomy, Alma Mater Studiorum - University of Bologna Francesco Decataldo, Marta Tessarolo, Maria Calienni, Beatrice Fraboni; Unit of Microbiology, The Great Romagna Hub Laboratory, Pievesestina (Cesena) Laura Grumiro, Maria Michela Marino, Martina Brandolini, Giorgio Dirani, Francesca Taddei, Vittorio Sambri; Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna “Bruno Ubertini” (IZSLER), 25124 Brescia, Italy Francesca Faccin, Davide Lelli, Antonio Lavazza Department of Experimental, Diagnostic and Specialty Medicine- DIMES, University of Bologna Catia Giovannini, Carla Cacciotto, Alessandra Scagliarini, Vittorio Sambri Center for Applied Biomedical Research (CRBA), S.Orsola-Malpighi University Hospital, 40138 Bologna, Italy Catia Giovannini DVM, Department of Veterinary Medical Sciences, University of Bologna Vittoria Cattani

Resume : Since the outbreak of the Covid-19 pandemic, researchers have refocused their efforts on viral neutralization assays and neutralizing antibody quantifications for vaccination pre-clinical studies and long-term efficacy. Nowadays, the gold standard to assess antibody titer is the plaque reduction neutralization test (PRNT), an end-point assay which evaluates the highest serum antibody dilution that neutralizes viral replication, by inspecting the cytopathic effect (CPE) induced on cell cultures.[1] Here, we have designed and implemented an accurate real-time technique for quantitative serum neutralization assay, employing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (Pedot:Pss)-based Organic Electrochemical Transistors (OECT) for the automated evaluation of the CPE induced by Sars-Cov-2 on Vero E6 cells, using a customized prototype for in-vitro measurements inside the incubator.[2,3] Transistors seeded with viral proliferating cell cultures reported faster time responses during the experiment, caused by the disruption of the cell layer grown onto the active area of our devices. On the contrary, when neutralizing antibodies stopped the viral infection, OECT data superimposed with standard control growth. The device reliability was proved using optical imaging (cell layer evaluation), Quantitative Reverse Transcription Polymerase Chain Reaction (investigating viral proliferation) and standard PRNT assays, obtaining robust matching. We noted that OECTs allowed to extract the neutralizing test outcome in less than 48h, earlier than the usual 72-hour required for PRNT screening, without the need of cell staining or fixing at the end of the experiment. Furthermore, the devices can be revitalized and re-used for up to three consecutive experiments, reducing plastic waste and their effective cost/experiment Our low-cost and scalable devices have the potential to speed-up large-scale viral neutralization screening without the need for cancerous staining or highly specialized operators. Finally, owing to the versatile nature of the proposed assay and the possibility to optimize the device geometry/dimensions to match the cell lines under test, the technology could be easily transferred to assess neutralizing antibody response towards different viruses in their permissive cell substrates.

12:15 Discussion session 9    
Thin films for (opto)electronics : Shannan O'Shaughnessy
Authors : Stiff-Roberts, A.D.*(1)(2) and Zhang, B.(1).
Affiliations : (1)Department of Electrical & Computer Engineering, Duke University, Durham, NC USA (2)University Program in Materials Science & Engineering, Duke University, Durham, NC USA * lead presenter

Resume : This work investigates the synthesis of polymer thin films for optoelectronics via emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE). Emulsion-based RIR-MAPLE is unique compared to other deposition techniques because thin films are formed by the direct transfer of intact, emulsified polymer particles from the target to the substrate. The chemistry, composition, and morphology of the emulsion in the deposition target has a direct influence on the morphology of thin-films and the resultant optoelectronic properties. Specifically, RIR-MAPLE uses a low-energy infrared laser with a peak wavelength of 2.94 microns to irradiate a polymer emulsion target for deposition. The laser energy is resonant with the vibrational mode of hydroxyl bonds but is not absorbed by the target polymer to be deposited, thereby enabling a gentle deposition approach. Because the solvents appropriate for most conducting polymers do not contain hydroxyl bonds, frozen emulsion targets comprise a polymer/primary solvent ‘oil’ phase within a continuous water-ice phase. In this way, the hydroxyl bonds in the water-ice matrix resonantly absorb the incident laser energy such that the water-ice matrix sublimates. Importantly, the laser energy is not thermally confined, thus the target area irradiated by the laser melts to some degree, and kinetic energy from the water-ice matrix sublimation ejects emulsified polymer particles in droplets with primary solvent towards the substrate. It is important to note that emulsion-based RIR-MAPLE relies on a surfactant to blend the non-polar (polymer and primary solvent) and polar (water) components of the target into a metastable mixture. The conjugated polymer polyfluorene (PFO) has been used as a model system to explore the correlation between emulsion chemistry and film morphology. Considered a promising material for blue light emitting diodes (LEDs), PFO is an interesting polymer for investigation because small concentrations of its crystalline phase, β-PFO, lead to significant changes in the optoelectronic properties of films and devices. In this work, the primary solvent choice, surfactant choice, and other emulsion properties are correlated to β-PFO concentration, film morphology, and LED device performance from the resulting films. This careful study of the effect of emulsion properties on film morphology and device performance provides insight to process-morphology-performance relationships for RIR-MAPLE-deposited polymer films.

Authors : Yineng Zhao, Wyatt Tenhaeff
Affiliations : Materials Science Program, University of Rochester; Department of Chemical Engineering, University of Rochester

Resume : In this work, a flexible and transparent polymer film was in situ synthesized by initiated chemical vapor deposition (iCVD) on a flexible and soft polymer substrate. The polymer film was a highly crosslinked and fluorinated diacrylate–poly(1H,1H,6H,6H-perfluorohexyl diacrylate) (pPFHDA). The deposition was realized by an iCVD with forced vapor transport, which enabled vapor delivery of a nonvolatile monomer such as PFHDA. During the deposition, the monomer and the substrate were kept at around room temperature, and the deposited coating showed high uniformity and conformality. This was believed to be the first report of vapor deposition of pPFHDA. The film exhibited excellent barrier performance against liquid and was also completely transparent to light from 300 nm to 1690 nm wavelength. pPFHDA coatings with thicknesses in hundreds of nanometers were found to be impermeable to high-index optical fluid for more than two months at 70°C, which was equivalent to a four-year lifetime at room temperature. The barrier performance was achieved even after the layer was subject to equibiaxial strain which demonstrated that the pPFHDA layer can accommodate mechanical deformation, making it a compelling solution as an optical-grade barrier layer for flexible optics/optoelectronics. Such excellent barrier performance was attributed to the highly crosslinked structure which greatly reduced the free volume in the polymer accessible to permeant molecules to diffuse through. On the other hand, the highly crosslinked structure also guaranteed an amorphous morphology in that potential crystallization was prohibited; hence, the fluoropolymer would not become ‘white and translucent due to light scattering by crystallites. The pPFHDA film was thermally stable to 300°C for at least 10 hours and no phase/glass transition of any sort at least in a 180°C-temperature window. Such properties of a polymer barrier layer make it a compelling alternative to inorganic coatings for optics. Despite high transparency and excellent barrier performance, inorganics are intrinsically brittle, and they crack even slightly strained. For this reason, inorganics cannot make barrier layers for flexible optics, such as varifocal liquid lenses. Such lenses mimic the mechanism of a human eye where transparent optical fluid is encapsulated between two flexible membranes. They are particularly useful in volume-limited applications, such as miniature medical devices and wearable augmented reality (AR) equipment. However, it requires that no optical fluid can permeate into the elastomeric membranes; otherwise, the lens would be damaged. Therefore, a barrier layer that does not crack under deformation, such as the pPFHDA barrier layer, is in demand on the elastomeric membranes in contact with the optical fluid.

Authors : Wyatt E. Tenhaeff
Affiliations : Department of Chemical Engineering, University of Rochester

Resume : Enormous opportunities exist for flexible optical, electrical, and optoelectronic devices. Their flexibility and deformability allow them to be shaped into complex form factors for integration into consumer products, wearable systems, textiles, or even human tissue. They can also be fabricated on low cost thermoplastic substrates for low cost roll-to-roll processing. While extensive research has been dedicated to developing new materials and device designs, the thin film coatings are equally important components that must be engineered to accommodate this flexibility. Thin films are frequently used for surface energy modification, barrier coatings (for both gases and liquids), waveguides, and optical interference coatings, for example. In this talk, the development polymer thin film technologies for two distinct flexible applications will be discussed. Both applications utilize initiated chemical vapor deposition (iCVD) for its exceptional control over the deposited polymer film’s composition and thickness. The ability to deposit crosslinked, insoluble films at low temperature on thermally sensitive substrates is also an enabling property. The first application is the development of polymer thin film barrier layers for varifocal lenses. These barrier layers must prevent permeation of the oil-based optical fluid into soft polymeric lens, while remaining transparent throughout the visible spectrum. A fluorinated diacrylate monomer was deposited to prepare crosslinked films of poly(1H,1H,6H,6H-perfluorohexyl diacrylate) (pPFHDA) with thicknesses of several hundred nanometers. The pPFHDA coating is transparent over the 300 - 1690 nm wavelength range and thermally stable to 300°C. The coatings, irrespective of thickness, were found to be impermeable to high-index optical fluid for more than two months at 70°C, which is equivalent to a four-year lifetime at room temperature. The mechanical compliance of these films was compared to typical optical layer materials by studying mechanical fracture behavior as a function of strain with optical profilometry. For the second application, a series of high refractive index polymer films were developed with refractive indexes ranging from 1.7 – 2.0 and good transparency throughout the visible spectrum. The polymer film chemistry is based on poly(4-vinyl pyridine) (P4VP). Charge-transfer complexes (CTCs) were formed between P4VP and halogen compounds (chlorine to iodine), prepared by a simple vapor phase infiltration of halogen compounds, increasing the RI of the P4VP thin film from 1.58 to 2.0 or higher, while maintaining the conformal and smooth nature of as-deposited thin films. The refractive index is readily tune through copolymerization with comonomers that are chemically inert to halogens. Detailed optical characterization of these film formulations will be presented, along with approaches to further enhance the physical and thermal stability of the coatings.

Authors : Kenneth K. S. Lau
Affiliations : Department of Chemical and Biological Engineering, Drexel University

Resume : Initiated and oxidative chemical vapor deposition (iCVD, oCVD) are two thin film deposition techniques for making a broad range of polymers, including addition polymers like acrylates, vinyls and ethers, and conducting polymers like thiophenes, pyrroles and anilines. To form these polymers, monomer reactants, which are typically liquids or solids, must be vaporized for delivery into the reaction chamber. To avoid precursor condensation, monomer vapors need to be below their respective saturation point at the substrate surface, i.e., under sub-saturated monomer conditions. This typically leads to deposition behavior that is adsorption-limited, i.e., the amount of adsorbed monomer controls the polymer growth rate and deposition kinetics. As such, a colder substrate promotes monomer adsorption that in turn allows for faster deposition. In addition, polymers are typically grown without any linking chemistries with the underlying substrate surface. This has enabled a wide range of substrates to be coated, including silicon wafers, glass, membranes, fabrics, paper, and micro/nano fibers, tubes and particles. As such, these deposition methods are typically considered to be substrate-neutral, i.e., the substrate has no significant influence on deposition behavior. In this talk, we will highlight our efforts in probing outside these typical processing conditions and deposition behavior. Specifically, we will show reaction-limited deposition behavior, where a hotter substrate enables faster deposition, can be achieved. We will also show that the substrate chemistry can have a significant impact on deposition behavior, leading to inhomogeneous or selective nucleation and growth. We will discuss these atypical deposition behaviors in the context of enabling various applications, including surface engineering, area-selective deposition, and energy.

16:45 Discussion session 10    
17:00 coffee break    
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Functional thin films : Anna Maria Coclite
Authors : Ditte, K.(1,2), Nguyen Le, T. A.(3,4), Ditzer, O.(1,2), Sandoval Bojorquez, D. I.(3), Chae, S.(1), Bachmann M.(3,4), Baraban, L.(3), Lissel, F.(1,2)
Affiliations : (1)Leibnitz Institute of Polymer Research Dresden e.V., Germany (2)Faculty of Chemistry and Food Chemistry, Dresden Technical University, Germany (3)Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Germany (4)Faculty of Medicine Carl Gustav Carus, Dresden Technical University, Germany

Resume : In the midst of the COVID-19 pandemic, adaptive solutions are needed to allow us to make fast decisions and take effective sanitation measures, e.g., the fast screening of large groups (employees, passengers, pupils, etc.). Although being reliable, most of the existing SARS-CoV-2 detection methods, like polymerase chain reaction (PCR) or lateral flow immunosensors (conventional antigen test), lack the ability integrated into garments to be used on-demand. Here, we report – at the proof-of-concept level – an organic field-effect transistor (OFET)-based biosensing device detecting of both SARS-CoV-2 antigens and anti-SARS-CoV-2 antibodies in less than 20 min. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting triblock copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti-S1 Abs, respectively. The obtained sensing platform is easy to realize due to the straightforward solution-based fabrication of the TBC film and the utilization of the reliable physical adsorption technique for molecular immobilization. The device demonstrates high sensitivity of about 19%/dec and a limit of detection (LOD) of 0.36 fg/mL for anti-SARS-Cov-2 antibodies and, at the same time, a sensitivity of 32%/dec and a LOD of 76.61 pg/mL for the virus antigen detection. The TBC was used as an active layer is soft, has a low modulus of 24 MPa, and can be stretched up to 90% with no crack formation of the film. With proper transfer to a stretchable-flexible substrate, the presented concept offers the possibility to realize stretchable biosensors, which might allow the fabrication of wearable platforms for on-the-fly detections of biomolecules to aid reducing – and eventually stop – the spread of COVID-19 and future pandemics.

Authors : Rasha Algerhami, Nigel Clarke
Affiliations : Physics and astronomy department University of Sheffield United Kingdom

Resume : We consider a numerical model to describe the phase transition from liquid to solid phases that leads to the emergence and growth of a single crystal from a simple melt system. The model is based on a nonconserved phase-field model by discretising space and time according to the finite difference method. A local free energy density was used to account for the meta-stable states in crystallisation. Numerical calculations were performed to explore the impact of constant and non-constant mobility on the growth process with different values of interfacial energy for y-direction (k_y). The results showed significant effects of 〖 k〗_y on the shape and growth rate of crystals, while the effect of non-constant mobility is less. In addition, another numerical model was implemented to investigate the effects of confinement on the rotation behaviour of single crystal with different shapes, such as ellipse, rectangle and rhombus, undergoing simple shear flow. Several simulations were performed using ratios (R) between the crystal's longest and shortest principal axes and ratios (S) between shear zone width and crystal’s shortest principal axis. The results obtained revealed that the crystal rotation is strongly affected by relative confinement.

Authors : Gargi Ghosh, Nae-Eung Lee
Affiliations : School of Advanced Materials Science and Engineering, Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do 16419, Republic of Korea

Resume : Biodegradable and biocompatible materials are one of the ideal platforms for on-skin and implantable electronic devices. Biodegradable stretchable electronics are promising for future stretchable electronics because of their ability to physically disappear from the environment thus rendering them environmentally and human-friendly. But to wear them comfortably, the materials composing them must possess multiple properties such as compliance, toughness, elasticity apart from biocompatibility and biodegradability. Currently, materials utilized for most biodegradable electronic devices are rarely stretchable and hence have limited conformality in wearable and implantable devices. Here we report a biodegradable, biocompatible, conductive, and stretchable composite microfiber of poly (glycerol sebacate) (PGS) and polyvinyl alcohol (PVA) for transient stretchable device applications. Compositing high-strength PVA with stretchable and biodegradable PGS, a stretchable and tough microfiber with tunable properties was obtained. This microfiber demonstrates high toughness and good extensibility. Furthermore, the stretchable microfiber was incorporated with gold nanoparticles (Au-NPs) to be applied as a stretchable strain sensor which showed stable current response under cyclic and dynamic stretching at 30% strain and even showed the capability of monitoring the strain produced by tapping, bending, and stretching of the finger, knee, and esophagus. Besides, this sensor is non-toxic and irritation-free to human skin, so that it can be worn comfortably onto human skins for long-term health monitoring. Considering the biodegradable, stretchable, and skin-comfortable features of composite materials of PGS/PVA, this sensor can provide great potential for transient and environment-friendly stretchable electronics for applications in on-skin or implantable health-monitoring devices with reduced environmental footprint. Keywords: Transient electronics, Stretchable electronics, Microfiber, Poly(glycerol sebacate) Poly(vinyl alcohol), Biodegradable

Authors : A.Groza1, B.Bita1, E.Stancu1, C.Staicu1, O.Pompilian1, C.Ciobanu2, S.Iconaru2, D.Predoi2
Affiliations : 1National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, P.O. Box MG 36, Magurele, 077125 Bucharest, Romania 2National Institute of Materials Physics, Atomistilor Street, No. 405A, P.O. Box MG 07, 077125 Magurele

Resume : The deposition of hydroxyapatite or calcium phosphate-based compounds as coatings on metallic or polymeric substrates is of interest for biomedical applications such as bone substitution or bone regeneration [1]. Nowadays, implants and prostheses are covered with hydroxyapatite layers for stimulating their integration into the human body. Moreover, these layers are bioactive and can promote interfacial bonds with the soft tissue. By doping the hydroxyapatite structure with different ions such as Mg2+, Ag+, Ce3+, Eu3+, Sm3+, the chemical and biological activity of the synthesized compound can be improved [1]. Mg represents the most important chemical element, which can substitute with calcium in the apatite structure and is naturally present in the human bones and teeth. The incorporation of Mg2+ ions into the hydroxyapatite structure and the formation of Mg3(PO4)2 bonds is very helpful for bone mineralization and calcification process, by diminishing the bone fragility [1]. The magnetron sputtering discharges represent a powerful technique for the generation of hydroxyapatite-based composite layers with optimal physicochemical properties. In our previous works [2] we showed that the plasma parameters have also a substantial influence on the morphology of the layers. The results presented in this paper envisaged the study of the mechanical properties of magnesium doped hydroxyapatite/chitosan layers generated by magnetron sputtering technique before and after their exposure to electron beams of 5 MeV energies. The exposure to ionizing radiation in a linear accelerator dedicated to medical use was performed by delivering up to 50 Gy radiation doses in fractions of 2 Gy radiation doses per 40 seconds. These dosages correspond to radiotherapy treatments protocols for bone cancers [3]. The measurements of the following parameters such as global hardness, friction coefficients, or Young module of the magnesium doped hydroxyapatite/chitosan composite layers irradiated with electron beams are essential in the evaluation process of the magnesium doped hydroxyapatite/chitosan layers as possible candidates for coating orthopedic implants and prosthesis. References 1. Predoi D., Iconaru S. L., Predoi M. V., Stan G. E., Buton N., Synthesis, Characterization, and Antimicrobial Activity of Magnesium-Doped Hydroxyapatite Suspensions, Nanomaterials, 2019, 9, 1295; doi:10.3390/nano9091295 2. Dreghici, D.B.; Butoi, B.; Predoi, D.; Iconaru, S.L.; Stoican, O.; Groza, A., Chitosan– hydroxyapatite Composite Layers Generated in Radio Frequency Magnetron Sputtering Discharge: From Plasma to Structural and Morphological Analysis of Layers. Polymers 2020, 12, 3065. 3. NCCN Guidelines Version 2.2020;

Authors : Alina Vladescu1, Anca C. Parau1, Diana M. Vranceanu2, Iulian Pana1, Gabriela A. Juravlea1, Gianfranco Palumbo3, Giuseppina Ambrgio4, Cosmin M. Cotrut2
Affiliations : 1National Institute of Research and Development for Optoelectronics - INOE 2000, 409 Atomistilor St., R077125, Magurele, Romania 2University Politehnica of Bucharest, Faculty of Materials Science and Engineering, 313 Spl. Independentei, Bucharest, RO60042, Romania 3Department of Mechanics, Mathematics and Management, Politecnico di Bari, Via Orabona4, 70126, Bari, Italy 4Department of Mechanical, Energy and Management Engineering - University of Calabria, P. Bucci, 87036 Rende (CS), Italy

Resume : In the last years, the most challenging topic is to obtain resorbable biomaterials proper for resorbable implants which should have a controlled release behavior along with good biocompatibility, anti-inflammatory, antimicrobial activity, and nontoxicity. The aim of the current presentation is to give a solution for decreasing the dissolution rate of AZ31B alloy by coating with hydroxyapatite (HAp) as possible resorbable material used for biomedical applications. Moreover, to diminish HAp dissolution rate the Mg and Si elements were used as dopants. The coatings were obtained by RF magnetron sputtering technique and three different cathodes made from HAp, MgO and SiO were used. Comparatively research was performed in terms of their elemental and phase composition, mechanical characteristics (roughness, hardness, adhesion, elastic modulus), and degradation rate in SBF and DMEM at 37°C. HAp coating without Mg and Si addition was used as reference coating and AZ31B uncoated alloy as well. We acknowledge the support of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, projects ERANET-M-ISIDE-1, no. 171/2020 (INOE2000 partner) and ERANET-M-ISIDE-2, no. 172/2020 (UPB partner), within PNCDI III, POR Calabria 2014-2020 (Consorzio M-ERA.NET 2, Call 2019), CUP J28I17000120005 and Romanian National Core Program no.PN18N-01-02/2019.

Authors : M. Socol1, N. Preda1, C. Breazu1, A. Costas1, G. Petre1, A. Stanculescu1, I. Stavarache1, A. Stochioiu2, G. Socol2, M. Girtan3
Affiliations : 1National Institute of Material Physics, 405A Atomistilor Street, 077125, Magurele, Romania 2National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Street, 077125, Magurele, Romania 3Photonics Laboratory, (LPhiA) E.A. 4464, SFR Matrix, Université d’Angers, Faculté des Sciences, 2 Bd Lavoisier, 49045 Angers, France

Resume : Nowadays, due to the indium depletion and its increased price, there is a large concern regarding the replacement of indium tin oxide (ITO) in the electronic devices, especially in the organic photovoltaic cells and organic light emitting devices. However, it is difficult to replace this transparent conductive electrode (TCE) considering that ITO is featured by high transmittance, low electrical resistivity and reduced roughness. Recently, the multilayer transparent conductive electrodes (MTCE) based on dielectric/metal/dielectric (DMD) materials have attracted the attention of the researchers taking into account that small amounts of materials are required to develop electrodes with specific and suitable characteristics. The most investigated MTCE are based on zinc oxide (ZnO) and gold (Au) or silver (Ag) in the following DMD layer configuration: ZnO/Au(Ag)/ZnO. In comparison with ITO, DMD structures are characterized by high mechanical flexibility and compatibility with the flexible substrates, properties that recommend them in the development of the organic solar cells. In this study, we report the fabrication of a DMD structure based on guanine/Ag/guanine on various rigid and flexible substrates (glass, polyethylene terephthalate, flexible glass) by thermal vacuum evaporation. The properties of the DMD electrodes were investigated from structural, morphological, optical and electrical point of view. The morphological investigations evidence that regardless the substrate type, the obtained DMD are featured by a lower roughness. The optical and electrical investigations showed that the fabricated DMD structures can be applied in the field of flexible transparent electrodes being characterised by adequate transparency and sheet resistance.

10:20 Discussion session 11 and Closing remarks    

No abstract for this day

Symposium organizers
Anna Maria COCLITEGraz University of Technology

Petersgasse 16 - 8010 Graz, Austria

+43 3168738970
Meike KOENIGKarlsruhe Institute of Technology

Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

+49 721 60822108
Nicolas BOSCHERLuxembourg Institute of Science and Technology (LIST)

41, rue du Brill, L-4422 Belvaux, Luxembourg

+352 275 888 578
Rong YANGCornell University, USA