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

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.

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

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.

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 et.al, Langmuir (2019),35 (30), 9677-9683 (2) A. Demaude et al. Submitted.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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).

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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; https://www.nccn.org/professionals/physician_gls/pdf/head-and-neck.pdf

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.

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.