Polymer and hybrid thin films from innovative deposition techniques to functional devices

Resume : Undesirable chemical reactions occurring at the electrode-electrolyte interface inside lithium ion batteries (LIBs) create an insulating solid-electrolyte interphase (SEI) layer (~ 1-100 nm thick) on the electrode surface. These reactions reduce the overall energy storage capacity and operational safety of LIBs. This problem is especially severe under high voltage operating conditions, imposing a compromise between energy density and safety of LIBs. Surface modification of LIB electrodes by coating with an artificial SEI (aSEI) layer is widely reported to improve the stability of the electrode, protect against unwanted reactions with the electrolyte, and increase electronic and ionic conductivity of the electrode. However, due to the limitations of existing coating techniques, such as non-uniform film coverage, and poor control over film composition and functionality, the undesirable reactions at the electrode-electrolyte interface were only reduced but not eliminated. Furthermore, the fundamental mechanisms underlying these improvements remain unknown. Designing conformal aSEI layers with uniform thickness and composition is critical to systematically investigate the mechanisms by which such coatings can influence LIB performance and safety. Inspired by the organic-inorganic architecture of naturally occurring SEI layers in LIBs, we demonstrate that by modifying an electrode surface with a hybrid polymeric artificial (aSEI) layer, we can build a physical barrier between electrode and electrolyte; thereby inhibiting undesirable side reactions. We use novel non-line-of-sight deposition processes like chemical vapor deposition (CVD) polymerization to realize such conformal polymeric films with precise thickness and compositional control, which is not possible with existing coating methods like solution processing due to surface tension and dewetting effects.

Resume : A series of high-k, ultrathin copolymer gate dielectrics was synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) via an initiated chemical vapor deposition (iCVD). The highly polar cyanide functional group in the CEA is responsible for the enhanced dielectric constant and the excellent dielectric performance was achieved by incorporating the DEGDVE crosslinker. The chemical composition of the copolymers was systematically optimized by tuning the input flow ratio of each monomers and utilizing the radically non-homopolymerizable property of DEGDVE monomer in order to achieve a high dielectric constant as well as excellent dielectric strength. The copolymer dielectric with the optimized composition showed the dielectric constant greater than 6 and extremely low leakage current densities whose thickness was only 20 nm, which is the outstanding thickness down-scalability of cyanide polymer dielectrics. High-performance organic and oxide TFTs with diverse device configurations were fabricated and the low-voltage (less than 3 V) operations were successfully achieved thanks to the high charge capacitance and excellent dielectric performance of the copolymer dielectric. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics were retained even in 2% of the applied tensile strain, which is one of the most flexible OTFTs reported to date.

Resume : Metal interconnection is a crucial technology for the development of large-scale integrated circuits (ICs). However, conventional via-forming methods for metal interconnection using lithography and etching are not compatible with organic semiconductors due to their susceptibility to high temperature or solvent-based developers. Hence, alternative schemes such as laser drilling or solvent inkjet-printing have been used for implementation of interconnect vias in organic thin-film transistor (OTFT) circuits. They, however, increase the complexity of the manufacturing process. As a result, the process becomes very slow and the cost for process becomes very high. Here we show a novel metal interconnection scheme for facile fabrication of OTFT circuit using an interconnect scheme based on patterned iCVD dielectric polymer. Different from previous approaches which locally remove an insulator to form a via, the proposed scheme selectively adds an insulator to a location where two metals in different layers should not meet each other. We investigate layout design rules for robust circuit layout design and fabricate complementary circuits including inverter, NAND, NOR using the proposed concept, and finally demonstrate exclusive OR circuits based on 3-level metal interconnections and 4 NAND gates to show potential of the proposed scheme as an important component of large-scale integrated circuits.

Resume : The continuing shrinkage in device feature size in integrated circuits demands reliable ultra-low k (ULK) materials to isolate devices and interconnects. Current state of the art ULK is highly porous and therefore faces several reliability issues e.g. mechanical failure. Flexible electronics manufacturing, on the other hand, require mechanically robust ULK materials that are processable at low temperature. Therefore, there is demand for low-temperature curing methods to enhance mechanical and thermal stability without altering the k value. Low-k organosilicate polymers deposited by initiated chemical vapor deposition (iCVD) are promising ULK films due to conformal growth, predictable physical and chemical properties, and near room temperature deposition. In this work, a room temperature UV curing method is used to enhance the thermal and mechanical stability of poly(trivinyltrimethylcyclotrisiloxane) (pV3D3) thin films deposited by iCVD. As-deposited films were systematically treated either thermally or cured with UV light to assess the impact of different curing conditions. A combination of FTIR spectroscopy, optical and thermogravimetric analysis, and mechanical tests were used to characterize the structure of cured films. Annealing in air results in significant film shrinkage (40% at 400°C) which was found to be dominantly due to oxidation. UV cured films at room temperature maintain >90% thickness at 400 °C and render a hybrid organic-inorganic backbone allowing network flexibility and uniform pore size distribution. High temperature annealing, on the other hand, causes various chain length formation, resulting in discontinuity in the film making it vulnerable to fracture and delamination.

Resume : Initiated chemical vapor deposition (iCVD) enables precise control of polymer thin film properties by the deposition parameters. In this sense the method allows, e.g. adjusting of free volume/porosity which governs the dielectric properties of polymer thin films. The solvent-free nature, conformal coverage in mild deposition conditions and accurate thickness control make iCVD a perfect candidate for the deposition of functional dielectrics and its integration to the state-of-the-art microelectronic fabrication processes. In this study we demonstrate the fabrication of low-k dielectric polymer thin films and evaluate their use as electrets for potential applications such as electret microphones. A systematic study was conducted to reveal a correlation between the free-radical polymerization mechanism and dielectric properties.

Resume : Electronic coupling and transfer processes at hybrid interfaces in micro- and nanostructures can be specifically tailored to yield optimized transport and luminescence properties. Semiconductor nanowires represent a particularly interesting platform for the design and fabrication of nanoscale hybrid devices with applications in optoelectronics and sensing because of their large surface-to-volume ratio combined with high crystalline quality and the naturally formed electronic or photonic transport channels. In this talk, we will discuss recent results on the way towards hybrid LEDs composed of inorganic n-conductive ZnO or GaN nanowires and organic p-conductive polymers. Here, oxidative chemical vapor deposition (oCVD) is examined to conformally coat the nanowire cores with thin shells of polypyrrole or poly(3,4-ethylenedioxythiophene). We will discuss the band alignment and formation of electronic defect states at the inorganic-organic interfaces and comment on its implications for the performance of hybrid nanowire LEDs. Finally, the potential of oCVD for the deposition of p-conductive layers in planar and three-dimensional GaN-based LED technology will be discussed.

Resume : Hybrid perovskite based materials, thanks to their attractive optoelectronic properties, have revolutionized the field of photovoltaics, showing high power conversion efficiency competing with silicon and thin film technologies [1]. High reproducibility and stability to moisture over operational time via low-cost fabrication technology, and in particular deposition techniques enabling for large area device fabrication are currently object of study towards photovoltaic market demands [2]. Different approaches have been investigated to control perovskite crystalline structure, morphology and moisture stability such as additive inclusion, thermal annealing, use of different kind and molar ratio of precursors [3]. The most widely used deposition method to obtain a high quality perovskite film requires the dripping of a non-solvent in the last stage of spin-coating, that strongly limits the up-scaling. In our work, we develop a simple one-step deposition method by using a biopolymer as templating additive to control the perovskite film growth. The MAPbI3 precursors solution containing the additive is easily deposited by spin coating and allows for a very thick and smooth film without requiring a dripping solvent. The grain size and the morphology of the film are highly influenced by the precursors and additive concentrations. The performance of the as-made biopolymer-perovskite composite as active layer in a solar cell device was explored in a standard inverted architecture, namely ITO/poly-TpD/MAPbI3-polymer/PCBM/bcp/Al, also compatible with large area processing and potentially flexible devices. The best device showed high PCE up to 17% under standard AM1.5 illumination and very high Voc of 1.07 V, highlighting the potential of this simple approach as general method to allow a control the perovskite film formation in a single step. [1] Correa-Baena, Juan-Pablo, et al. "The rapid evolution of highly efficient perovskite solar cells." Energy & Environmental Science10.3 (2017): 710-727. [2] Zhao, Yicheng, et al. "A polymer scaffold for self-healing perovskite solar cells." Nature communications 7 (2016). [3] Masi, Sofia, et al. "Organic Gelators as Growth Control Agents for Stable and Reproducible Hybrid Perovskite‐Based Solar Cells." Advanced Energy Materials (2017).

Resume : Hybrid structures consisting of both inorganic and organic conductive layers are promising for the development of inexpensive, versatile and tailored electronic and optoelectronic devices such as sensors or light emitting diodes (LEDs). We study the fabrication of planar n-GaN/p-PEDOT (poly-(3,4-ethylenedioxythiophene)) heterostructures. The p-polymer with a film thickness between 100 and 300 nm is grown via oxidative chemical vapor deposition (oCVD). oCVD is a dry deposition approach that allows for controllable polymer deposition out of the gas phase while achieving conformal coverage of the substrate with a thickness control of the deposited polymer layer in the nanometer range. Temperature-dependent current-voltage measurements from room temperature to 150°C were performed on the hybrid GaN/PEDOT-structures. The results show a pronounced diode behavior with rectification ratios up to 10^5 at +/- 2 V. Fitting the I-V-curves of the hybrid interface with diode models strengthens the idea of a predominant thermionic emission and allows to develop a model of the band lineup at the hybrid interface. Furthermore, leakage current densities as low as 100 nA/cm^2 and saturation currents of 0.1 pA could be deduced. A temperature independent activation energy for the electrons to overcome the barrier at the hybrid interface is determined to be 0.3 to 0.35eV. The results provide important information for tailoring the hybrid GaN/PEDOT-interface for applications in LEDs or sensors.

Resume : Perovskite Solar Cells (PSC) have been one of the most promising alternative to Silicon-based photovoltaics in the last 10 years and big efforts have been devoted to the development of new efficient materials and innovative architectures for this class of devices. Their outstanding properties in terms of easy processability, transport and low recombination rate led to very fast development of research activities both on the device implementation and on the characterization sides. This material has recently aroused great interest in the scientific community, as it enabled power-conversion efficiencies of over 20%. Deposition methods and morphological study have also been developed in the common effort of the scientific community to control the crystallization and correlate structure and energy conversion properties in these devices. Here a supramolecular control of the morphology and perovskite crystal growth is presented, aiming at highlighting the profound dependence in the growth mechanisms of these materials if influenced by nucleating agents. A particular attention is devoted to the study of intermolecular interactions occurring in solution deeply modifying the self-assembly process, and their relationship with the properties of the deposited thin film. The function of the additives in PSC is found to be crucial in influencing crystalline order, morphology and photo-physical properties of the final material. Experimental characterization and photovoltaic applications of different perovskite-based nanocomposites perovskite-additives is presented.

Resume : Conductive polymers (CP) combine the electrical properties of semiconductors and metals with the mechanical flexibility and stretch of insulating polymers, and therefore offer a huge potential for light emitting diodes and photovoltaics. During the past two decades, PEDOT:PSS has become one of the most attractive CPs since it can be easily deposited from solution via spin coating. However, deposition on complex 3D-surfaces (nanowires/-trenches, etc.) often results in incomplete and/or inhomogeneous coverage, an issue, that can be overcome by vapor-based deposition technologies. In this work, deposition of PEDOT thin films via solid-state polymerization (SSP), vapor-phase polymerization (VPP) and oxidative chemical vapor deposition (oCVD) will be examined. We are aiming at homogeneous coverage, high optical transparency and electrical conductivity, and report on the role of sample pre- and post-processing strategies, polymerization temperatures and monomer/oxidant properties. Here, advanced opto-electronic properties of PEDOT are intended by applying monomeric, dimeric and trimeric EDOT (3,4-ethylenedioxythiophene) precursors. The oligomeric EDOT structures are synthesized and tested for sublimation while density functional theory (DFT) is utilized to describe their oxidative polymerization and application as potential precursor in VPP and/or oCVD.

Resume : Miniaturized 3D battery architectures have the potential to meet the power and energy density demands of next generation nano-electronic devices and various sensors. One requirement in the utilization of 3D based electrodes is the incorporation of a pinhole free and conformal solid electrolyte over high aspect ratio structures. Lithium aluminosilicate (LixAlySizO, LASO), a solid oxide Li-ion conductor, synthesized by atomic layer deposition (ALD) is a promising electrolyte material for 3D battery applications due to its adequate ionic conductivity (8.2×10^(-8) S/cm) in thin film applications as well as its ability to improve electrode stability. The self-limiting nature of ALD allows precise thickness and composition control when applied to complex metal oxides. Lithium tert-butoxide (LTB), trimethylaluminum (TMA), and tris(tert-butoxy)silanol (TTBS), were precursors used to synthesize LASO by ALD. In order to further explore potential material properties, ALD deposited LASO was combined with a polymer electrolyte, poly-(tetravinyltetramethylcyclotetrasiloxane) (PV4D4) deposited via initiated chemical vapor deposition (iCVD). The LASO solid electrolyte offers high electrical resistance and chemical stability at the electrochemically active interface, while the pV4D4 solid electrolyte offers improvements in the mechanical integrity of the electrode. A hybrid film consisting of 5 nm LASO and 400 nm PV4D4 demonstrated a room temperature ionic conductivity of 3.4 x 10^(-7) S/cm, showing no significant increase in interfacial resistance. Integration with both 2D and 3D electrodes has shown substantial improvements in cycling and increased Coulombic efficiency. To support the integration of these hybrid electrolytes in microbatteries, the exploration of next generation electrode materials will also be presented. One of the most viable 3D designs is through the use of nanowire electrodes, in which Si and Ge can offer much larger charge capacities than traditional carbon based anode materials, but suffer large volume expansion upon lithiation. Using an in-situ TEM electrochemical characterization technique, dynamic processes and structural changes are able to be observed during the lithiation/delithiation of a SiGe nanobattery in real time. Preliminary results show that ALD LixAlySizO-coated Si0.4Ge0.6 alloy nanowire demonstrates lithiation and delithiation with an intact solid state electrolyte layer with ~39% radial expansion observed upon lithiation.

Resume : In general, oxidative chemical vapor deposition (oCVD) is attractive for conducting polymers, foremost to unite polymerization and doping reactions in order to generate superior electrical properties such as metallic polymers.(1) In addition, oCVD is useful to introduce novel functional backbones to synthesize conductive and functional polymers such as nature-inspired organic backbones.(2) Here we present a facile and oCVD-based route towards conductive-functional biopolymers. We demonstrate a combined polymerization and doping of dopamine and its derivatives. Such conductive polydopamines possess high functional site density paired with an impressive electrical conductivity in the range of 1S/cm. In addition these systems are chemically robust, in particular, against oxidative or reductive degradation. This allows us to apply them for electrocatalytic applications such as the CO2 reduction reaction. We have shown impressive electrocatalysis devoid of metals yielding a CO2-to-formate efficiency of ultimately 80% (overpotential 190mV at 18mA/cm²).(3) Similar performances have been shown only by best-in-class cobalt-based catalysts.(4) These results point at the power of functional and conductive biopolymers as sustainable contenders for electrocatalytic applications. (1) Farka, D.; Coskun, H.; Gasiorowski, J.; Cobet, C.; Hingerl, K.; Uiberlacker, L. M.; Hild, S.; Greunz, T.; Stifter, D.; Sariciftci, N. S.; Menon, R.; Schoefberger, W.; Mardare, C. C.; Hassel, A. W.; Schwarzinger, C.; Scharber, M. C.; Stadler, P. Anderson-Localization and the Mott-Ioffe-Regel Limit in Glassy-Metallic PEDOT. Adv. Electron. Mater. 2017, 1700050 DOI: 10.1002/aelm.201700050. (2) Coskun, H.; Aljabour, A.; Uiberlacker, L.; Strobel, M.; Hild, S.; Cobet, C.; Farka, D.; Stadler, P.; Sariciftci, N. S. Chemical Vapor Deposition - Based Synthesis of Conductive Polydopamine Thin-Films. Thin Solid Films 2018, 645 (August 2017), 320–325 DOI: 10.1016/j.tsf.2017.10.063. (3) Coskun, H.; Aljabour, A.; De Luna, P.; Farka, D.; Greunz, T.; Stifter, D.; Kus, M.; Zheng, X.; Liu, M.; Hassel, A. W.; Schöfberger, W.; Sargent, E. H.; Sariciftci, N. S.; Stadler, P. Biofunctionalized Conductive Polymers Enable Efficient CO 2 Electroreduction. Sci. Adv. 2017, 3 (8), e1700686 DOI: 10.1126/sciadv.1700686. (4) Gao, S.; Lin, Y.; Jiao, X.; Sun, Y.; Luo, Q.; Zhang, W.; Li, D.; Yang, J.; Xie, Y. Partially Oxidized Atomic Cobalt Layers for Carbon Dioxide Electroreduction to Liquid Fuel. Nature 2016, 529 (7584), 68–71 DOI: 10.1038/nature16455.

Resume : Future electronics will be wearable and in close contact to the skin. However, to accommodate deformations such as twisting and elongating, these next-generation electronics need to be stretchable. Stiff materials can be rendered stretchable by structural engineering, e.g., by using meandering structures [1] or buckles [2]. Another viable approach towards stretchable electronics, which is the focus of our work, is the development of intrinsically stretchable electronic materials, devices and circuits. Intrinsically stretchable, conductive films can be formed by adding ionic additives to PEDOT:PSS [3]. In this approach, the ionic additives lead to a charge screening effect [4] and act as dopants and plasticisers. Through these additives, the conductivity and stretchability can be tuned by orders of magnitude. For the realization of stretchable circuits, the patterning of stretchable interconnects that connect the circuit components, such as transistors or capacitors, is very important. Therefore, we developed a process for inkjet printing of intrinsically stretchable PEDOT:PSS-based interconnects and via holes. A customized ink was printed on stretchable polymeric substrates (SEBS, styrene-ethylene-butadiene-styrene) and optimized to achieve a smooth morphology of the printed features by adjusting the surface tension and suppressing the coffee stain effect. The printed interconnects have a conductivity of 700 S/cm, sustain strains above 100% and show good stability in 1000-cycle stretching experiments. Besides the morphology, the electrical properties and the stretchability, we also investigated the bias-stress stability, the long-term stability in ambient air and the cycling stability. The stretchable ink-jet printed conductors can be utilized to build intrinsically stretchable circuits and to interconnect rigid circuit components such as commercial micro LEDs. As a proof of concept, we fabricated a stretchable seven-segment display. [1] Gonzalez et al., Microelectron. Reliab. 48, 825 (2008); Kim et al., Science 333, 838 (2011) [2] Bowden et al., Nature 393, 146 (1998); Kaltenbrunner et al., Nature 499, 458 (2013) [3] Wang et al., Sci. Adv. 3, e1602076 (2017) [4] Ouyang et al., Adv. Funct. Mater. 15, 203 (2005); Döbbelin et al., Chem. Mater. 19, 2147 (2007)

Resume : Poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-co-TrFE)) is recognized as one of the most performing and easy process-able ferroelectric/piezoelectric polymer. Recently interest in P(VDF-co-TrFE) rises again thanks to its application in organic electronic devices such as ferroelectric field effect transistors, non-volatile memories, and piezoelectric nanogenerators. The functionalities of P(VDF-co-TrFE) are dictated by its structure, which, in turns, depends on the processing conditions. Herein we present a study of the relationship that links the structural to the functional properties of ferroelectric P(VDF-co-TrFE) films when they are incorporated in capacitor devices. Different processing protocols were applied aiming to generate films with dramatically different structural characteristics, as verified by DSC and grazing incident wide-angle X-ray scattering (GIWAXS) experiments. The polarization vs electric field hysteresis loops of the resulting devices were recorded and the sensibility of ferroelectric parameters (i.e. remnant polarization, Pr and coercive field, Ec) on the structural characteristics was confirmed. Pr was found to increase linearly with ferroelectric crystallinity, while Ec to decrease. The correlations between the structural characteristics and the ferroelectric properties are discussed, and the impact of ferroelectric crystallinity and crystallite orientation on device performance is highlighted.

Resume : Single crystalline nanowire is considered to be a promising candidate in many nano-electric devices due to its excellent electric properties. Here we report a method to fabricate (Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) nanowires by controlling the hydrothermal synthesis temperature , reactive time and surfactant polyacrylate acid [1-2]. It was confirmed that single crystalline PMN-PT nanowires have been fabricated under optimal synthesis condition by transmission electron microscope and selected area electron diffraction [1]. A device using one nanowire was fabricated to measure the ferroelectric properties of PMN-PT single crystal nanowire. The coercive field, remnant polarization and spontaneous polarization of PMN-PT nanowire are: 2.78 kV/mm, 17.08 μC/cm2 and 31.25μC/cm2, respectively. The piezoelectric coefficient d33 of PMN-PT nanowire was measured by piezoelectric force microscopy (PFM). The d33 value of PMN-PT nanowire was calculated to be 409 pm/V by fitting the PFM results [2]. A piezoelectric nanocomposite based on PMN-PT nanowire were fabricated by dispersing the PMN-PT nanowires into piezoelectric poly(vinylidene fluoride) (PVDF) polymer. The mechanical behaviors of the nanocomposites were investigated. The voltage and current generation of PMN-PT/PVDF nanocomposites were also measured. The results showed that the tensile strength, yield strength, and Young’s modulus of nanocomposites were enhanced as compared to that of the pure PVDF. The largest Young’s modulus of 1.71 GPa was found in the samples with 20 wt % nanowire content. The maximum output voltage of 10.3 V and output current of 46 nA were obtained in the samples with 20 wt % PMN-PT content, which was able to provide a 13-fold larger output voltage and a 4.5-fold larger output current than that of pure PVDF piezoelectric polymer. The current density of PMN-PT/PVDF nanocomposites is 20 nA/cm2 [3]. 81.6 mv output voltage can be generated by 0.1% strain and a linear relationship between output voltage and strain had been also observed in MN-PT/PVDF nanocomposites. The PMN-PT/PVDF nanocomposites exhibited great potential for flexible self-powered sensing applications.

Resume : Polyaniline (PANI) is promising for supercapacitors because of its high electronic conductivity, multiple oxidation states, and high theoretical (pseudo)capacitance. By applying ultrathin, conformal PANI coatings on nanostructured carbon electrodes, energy density can be significantly increased through pseudocapacitance while maintaining high power density with minimal loss of pore access for charge transfer. Here, oxidative chemical vapor deposition (oCVD) is utilized to achieve ultrathin, conformal PANI films around freestanding, binder-free electrospun carbon nanofibers (CNFs) from gas phase aniline monomer and a halide oxidant. Cyclic voltammetry and charge-discharge show enhanced energy and power density compared to bare CNFs. As a result of the ultrathin coating, this electrode material benefits from fast redox reaction kinetics, and very high power density is achieved compared to other PANI-carbon composite electrode materials. In addition, by tuning oCVD conditions, including temperature, pressure and flow rates, PANI chemistry and morphology can be controlled. Enhanced device capacitance is found to be a result of not only the redox activity of PANI but also the rough PANI surface texture that adds electrical double layer capacity. Spectroscopic analyses show that the rough surface is related to oxidant loss during the washing procedure after oCVD PANI deposition.

Resume : Current information processors are predominantly based on complementary metal-oxide-semiconductor (CMOS) transistors. However, CMOS scaling have started to face significant challenges and besides the physical limits, the conventional computing paradigm based on binary logic and Von Neumann architecture is becoming inefficient with onset of big data revolution and growing complexity of computation. Neuromorphic computing is the state-of-the-art research trend in the field of memory and logic devices where the goal is to build a versatile computer that is efficient in terms of energy and space, homogeneously scalable to large networks of neurons and synapses, and flexible enough to run complex behavioral models of the neocortex as well as networks inspired by neural architectures. Memristors, with their gradually changing conductivity can mimic the biological synapses. Low energy consumption, ultrafast operation and small dimensions are the most essential requirements for a memristor to perform tasks like a synapse. A ferroelectric tunnel junction (FTJ), where gradual modulation of conductance can be achieved by controlled rotation of ferroelectric domains, can act efficiently as a synapse. Here, we report FTJs with a spin-coated organic ferroelectric P(VDF-TrFE) tunnel barrier. We have measured 10^7% tunneling electroresistance at room temperature [1] together with reproducible memristive behavior based on variable amplitude and duration of the applied voltage pulses. Fast switching, long data retention of intermediate conductive states and spike-time-dependent plasticity make them extremely promising for neuromorphic applications. [1] S. Majumdar et al., Adv. Func. Mater. (2017) DOI: 10.1002/adfm.201703273

Resume : As we move to a cleaner energy economy to mitigate fossil fuel depletion and pollution, new technologies are pursued to harvest and store energy from more sustainable, albeit intermittent, resources like the sun, wind, and water. Many of these technologies rely on electrochemical devices with high surface area electrodes to enhance conversion efficiency and energy density. To further push the boundaries on systems performance, new materials and architectures are sought after. Among them, polymers are attractive given their vast chemical and physical tunability to deliver more enhanced properties at lower cost, less stringent requirements, lighter weight, and with more sustainable sourcing. Here, this talk will discuss our efforts in applying initiated and oxidative chemical vapor deposition (iCVD, oCVD) strategies to engineer polymer electronic materials for energy capture and storage. Specifically, examples will highlight the use of iCVD to enable polymer electrolyte dye sensitized solar cells and electroactive polymer supercapacitors. Central to these efforts is our fundamental understanding of mass transport and reaction kinetics to promote uniform growth and conformal coating of highly porous nanostructured electrodes. This enables strong interfacial integration and connection of the polymers within the device architectures for enhancing performance. Overall, this talk aims to demonstrate the strengths of iCVD and oCVD in realizing more sustainable energy alternatives.

Resume : Future applications, such as wearable electronics, flexible/transparent displays, or solar energy conversion/storage devices, require materials with more versatility, integrated functions, and environmentally-responsible processing. Organic semiconductors are well-suited to these requirements; however, their electrical properties and environmental stability are worse. Hybrid materials could mitigate these trade-offs. This work describes organic and hybrid thin film deposition using matrix-assisted pulsed laser evaporation to control structure and properties and to improve the performance of optoelectronic and energy-related devices. Specifically, one variation of the technique is presented: resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE), which uses a low-energy IR laser to minimize degradation of organic components. In addition, the frequency of the IR laser energy is resonant with hydroxyl bond vibrational modes such that a frozen emulsion (guest material dissolved in an organic solvent and water) can be used as the target. The unique advantage of this emulsion-based RIR-MAPLE is that energy from the IR laser is absorbed by water in the frozen emulsion, which evaporates and gently transfers the guest material to the substrate with minimal solvent exposure and degradation. The development of emulsion-based RIR-MAPLE for polymer and hybrid nanocomposite films will be described, as well as recent results related to hybrid perovskites.

Resume : Wearable electronics is emerging as a new and promising field that may revolutionize our life in the near future, and it is currently limited by finding matching power systems with high energy density, good flexibility and high stretchability.[1-4] Among them, stretchable fiber-shaped supercapacitors (SFSSs) are considered as one of the most promising candidates as they can be easily realized by winding fiber electrode on elastomeric substrate or assembling fiber electrodes into a helical structure.[5, 6] However, on one hand, it remains challenging to achieve both high energy density and high stretchabilities based on the available technologies. Herein, an all-in-one fiber electrode combining the function of traditional metal wire and energy storage has been designed and synthesized to solve the above problem. A crystalline conductive polymer (CP) fiber that displayed combined high conductivity, flexibility, specific capacitance and wide electrochemical window was discovered to simultaneously realize high energy storage and serve as conducting wire. The designed fiber material from poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrene sulfonate) (PSS) after treatment by sulfuric acid (denoted as PEDOT-S:PSS) showed high tensile strength of 112 MPa and high electrical conductivity of 1731 S cm-1 due to the structure rearrangement and ordered crystallized structure. The resulting symmetric SFSSs achieved a wide potential window of 1.6 V, specific capacitance of 93.1 mF cm-2 (or 74.5 F cm-3) at 50 µA cm-2 and high energy density of up to 33.2 µW h cm-2 (26.4 mW h cm-3) based on single fiber electrode. To the best of our knowledge, it represents the highest energy density in the available FSSs. They can be repeatedly stretched by 800%, and the specific capacitance can be well maintained after stretching for 200 cycles and bending for 2000 cycles. [1] J. Bae, M. K. Song, Y. J. Park, J. M. Kim, M. Liu, Z. L. Wang, Angew. Chem. Int. Ed. 2011, 50, 1683. [2] X. Wang, K. Jiang, G. Shen, Mater. Today 2015, 18, 265. [3] W. Weng, S. He, X. Sun, H. Peng, Angew. Chem. Int. Ed. 2016, 55, 6140. [4] W. Zeng, L. Shu, Q. Li, S. Chen, F. Wang, X. M. Tao, Adv. Mater. 2014, 26, 5310. [5] Z. Yang, J. Deng, X. Chen, J. Ren, H. Peng, Angew. Chem. Int. Ed. 2013, 52, 13453. [6] Y. Shang, C. Wang, X. He, J. Li, Q. Peng, E. Shi, R. Wang, S. Du, A. Cao, Y. Li, Nano Energy 2015, 12, 401.

Resume : Fluorinated polymers such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) derivatives have been widely used to generate negative triboelectric charges when they are in contact with other positive triboelectric materials, but the relationship between their molecular structures and the triboelectric properties is still unknown. Herein, we find that the number of fluorine units and molecular weight of fluorinated polymers directly affect the dielectric constants of dielectric layers, which are closely related with the triboelectric output performances. Among different fluorinated polymers, poly (2,2,2-trifluoroethyl methacrylate) (PTF) polymers with three fluorine units and Mw of ~20 kg/mol show the best triboelectric output performances than other polymers. Furthermore, we demonstrate that the elastic modulus and thickness of dielectric layers significantly affect the triboelectric performances. In particular, PTF polymers on polydimethylsiloxane (PDMS) dielectric layers exhibit 3 times higher dielectric constant and 40 times higher triboelectric performances than those of PTF on polyethylene terephthalate (PET) layers, which can be attributed to the conformal contact by the elastic PDMS layers. Our molecular engineering strategy to control the dielectric constants of fluorinated polymers can be a robust platform for the fundamental studies and high performance triboelectric device applications.

Resume : Stimuli-responsive hydrogels (SRH) represent a class of materials capable of reversibly switching their morphological and physicochemical characteristics. In this communication, we present an example of SRH, namely an ultrathin poly(acrylic acid) film (ca. 6 nm) obtained by Surface-Initiated Atom transfer Radical Polymerization, grafted onto the gate electrode of a p-type Electrolyte-Gated FET (EGOFET). The resulting modified EGOFET was studied showing that it is possible to correlate the hydrogel swelling state to the transistor output characteristics. In particular, increase of pH leads to a decrease of drain current. We hypothesize that the hydrogel swelling process occurring in basic medium causes an increase of the threshold voltage absolute value due to the abrupt and intense increment of the negative charge density on the gate electrode/electrolyte interface. The drain current variation during the modification of the electrolyte pH allows a quantitative analysis of the hydrogel switching kinetics. This work shows the relevance of the EGOFET as an analytical tool in the broad sense, i.e. able to follow in real-time phase transition processes of stimuli-responsive materials, but also the relevance of using a hydrogel for field-effect based (bio)detection according to the ability of such material to overcome the Debye length problematics.

Resume : Oxide semiconductors have been researched for the realization of flexible and transparent electronics and tuning work function of contact material is crucial for devices to achieve high performance. One of the strong candidates for flexible transparent electrodes is carbon based materials and controlling work function through doping hetero atom such as nitrogen has been researched. Among many method to obtain nitrogen-doped carbon, pyrolysis of biomolecules has been highlighted due to simple and inexpensive process that gives rise to obtaining high atomic percent of nitrogen. Polydopamine, which is inspired by adhesive proteins in mussel, is considered as the precursor of pyrolysis and metal chelation before pyrolysis is utilized for reducing resistivity. As a result, pyrolyzed polydopamine-Cu hybrid film shows the lowest resistivity (1.4 *10-4 ohm cm) in pyrolyzed carbon so far. The pyrolyzed film also shows high transparency(~85%) and stability under bending test up to more than 106 cycles. The pyrolyzed films are further adopted as the source and drain of oxide semiconductor field effect transistor, and the device performance is comparable to that calculated from the device using molybdenum as source and drain, which is explained by work function of pyrolyzed hybrid films.

Resume : All polymers are subject to stressors that result in material aging and, in severe cases, material failure. Aging is particularly important for polymer coatings, which may have mechanical deposition stress and are in direct contact with environmental stressors such as heat and light. We demonstrate that plasma polymers have a strong and fast oxidative response when photochemically aged. This aging pathway is directly tied to plasma-based decomposition processes that occur during deposition. We utilize plasma-free initiated chemical vapor deposition (iCVD) to develop polymer films with very low intrinsic stress (0-20 MPa) and high thermal and photochemical stability. Low intrinsic stress allows films to be grown arbitrarily thick on fragile substrates. Chemical stability is demonstrated by characterizing material changes to long-term exposure (>1 year) of environmental stressors. A unique diagnostic shows that iCVD poly(divinylbenzene), relative to a plasma polymer, has a 1000-fold decrease in a photoluminescence process tied to the density of photoactive defects. Avoiding monomer fragmentation during deposition is critical in the design and vapor deposition of robust polymer coatings. Enabled by these results, we will also discuss recent efforts to integrate iCVD materials into small-scale device manufacturing processes. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-744040

Resume : The phenomena, dewetting of a film occurs when an ultra-thin film ruptures and forms isolated random droplets on smooth defect free substrates due to destabilizing Van der Waals interaction between surface and interface [1]. It can be used as an effective tool for fabrication of nano and meso structures of polymers and functional materials. Here, we have reported a very unique and rapid dewetting process of 5CB liquid crystal (LC) in a single spin coating process. Spin coating with very dilute solution of casting materials fails to form a continuous film but ruptures the solution layer during the spin coating process and results in isolated, periodic, regular size droplets. This phenomena is termed as spin dewetting [2]. Here, we have reported the morphological evaluation of 5CB liquid crystal from spin dewetted droplets to continuous films with increasing solution concentration (Cn) on flat and topographically patterned Poly (methylmethacrylate)(PMMA) substrates. We observed, periodicity (λD) and diameter (dD) of spin dewetted droplets reduce with increasing Cn in the spin dewetting regime. Interesting this trend of reducing λD with Cn is opposite than the observation of thermal or solvent vapor induce dewetting of thin films. Radial texture is observed for hemispherical spin dewetted 5CB droplets under cross polarized microscope due to opposite anchoring at LC-PMMA interface (planar anchoring) and LC-air interface (homeotropic anchoring). The Schlieren texture is observed for continuous 5CB film. Finally, we show alignment and formation of array of LC droplets by guiding the spin dewetting process on topographically patterned substrates. Significant miniaturization for 5CB droplets is obtained on patterned substrates. The brushes of the schlieren texture of the continuous films over the patterned substrates are also aligned along the direction of the patterns. References: 1. Reiter, G. Dewetting of thin polymer films. Phys. Rev. Lett. 1992, 68, 75-78. 2. Bhandaru, N.; Das, A.; Salunke, N.; Mukherjee, R. Ordered alternating binary polymer nanodroplet array by sequential spin dewetting. Nano Lett. 2014, 14, 7009−7016

Resume : Solution-processed organic field-effect transistors (OFETs) are a reliable platform for ubiquitous sensing applications in environment monitoring, food waste management and digital health due to their excellent mechanical flexibility, low-cost fabrication and ease of large-scale manufacturing. In comparison to chemiresistors, OFET based sensors benefit from multiparametric outputs and offer better sensitivity through the amplification of the transistors and fast response/recovery times. To meet the portability and wearability requirement of the targeted sensor applications, low-voltage OFETs with good long-term environmental and operational stability is essential. Here, we report unencapsulated, air-stable OFETs for use in sensor arrays. To achieve low voltage operation (< -3V) and stable device performance, a solution-processed high-k/low-k polymer dielectric stack is used. The less polar low-k polymer effectively suppresses water adsorption and improves device stability. Different UV-crosslinked low-k polymers are tested and device stability is evaluated for several weeks of operation. To provide differentiation in response to various analytes (e.g. alcohols and esters), pristine and blends of poly(3,6-di(2-thien-5-yl)-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione)thieno[3,2‐b]thiophene) (DPPTTT) is used as the active layer. The OFETs exhibit field-effect mobility in excess of 1 cm2V-1s-1, ON current of ~ 1μA, improved environmental stability in ambient air and fast sensor response/recovery. The high yield and reproducibility of these OFETs enables large-area production of sensor arrays with high sensitivity and selectivity suitable for use in environmental monitoring devices.

Resume : Molecular layer deposition (MLD) has received increased interest in recent years for the deposition of organic thin films. This vapor-phase, layer-by-layer technique, which relies on the same self-limiting precursor saturation as atomic layer deposition (ALD), has shown promise for the development of applications that require conformal, organic-containing coatings, such as photoresists, batteries, and catalysts. However, despite recent developments in MLD, several fundamental questions remain about the MLD growth mechanism as well as the molecular-level structure of the resulting films. Results will be presented of our recent studies to understand MLD mechanisms and bonding. By examining trends in film properties across a series of organic MLD precursors that form polyurea films, we show that changes in growth rate between different precursors are not caused by differences in length of molecular precursors, chain orientation, or film density, but rather are caused by differences in the frequency of chain terminations. Studies in which the polymer chains are intentionally terminated provide evidence that precursors can be absorbed into the MLD film and reintroduce reactive sites that lead to continuation of film growth. Studies of the structure of the polyurea MLD films suggest that films consist of a mixture of horizontally aligned layers of paracrystalline polymer segments with upward growing chains. We will also describe new MLD chemistries, including photo-initiated MLD (pMLD) and hybrid organic/inorganic MLD. pMLD provides the possibility to create apolar linkages in the formation of nanoscale organic films. Furthermore, 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. This hybrid 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 : The combined ALD/MLD (Atomic/Molecular Layer Deposition) technique for the deposition of hybrid inorganic-organic materials is strongly emerging as a highly viable technology for the fabrication of fundamentally new types of layer-engineered hybrid thin films, superlattices and nanolaminates. The technique has already been extended to cover a wide multitude of metal and organic components combined into both amorphous and crystalline thin films to provide us with an exciting property palette. In this lecture I will discuss the basics of the ALD/MLD technique, design of new deposition processes, properties of the thus deposited thin films and their possible future applications. Examples of the applications considered include the use of these materials in flexible barrier coatings, thermoelectrics, optoelectronics and Li-ion microbattery.

Resume : The organic-inorganic hybrid systems have attracted great attention because of their potential applications in several fields of material science such as sensors, dye sensitized solar cells,optoelectronics and heterogeneous catalysis. In these systems, transition metal oxides thin films,such as NiO,are the most promising inorganic materials, due to their wide spectrum of magnetic,electrical, and optical properties. As a metalorganic component, the Eu(III)complexes have attracted growing interest as efficient downshifter and as a probe to sense the chemical environment.For a variety of applications,the possibility of fast,high efficiency and reproducible assembly method of molecules into nanostructured solid substrates is of a great importance. In the present work,we applied for the first time a full vapor phase approach based on the sequential steps of (i)Metal-Organic Chemical Vapor Deposition(MOCVD) of the inorganic NiO thin films,and (ii)the molecular layer deposition(MLD) to link on the activated surface in a covalent way an Eu(β-diket)3L complex,where β-diket is a β-diketone and L is a Lewis base.An accurate X-ray photoelectron characterization confirmed the optimal parameter condition of the activation step and of the covalent anchoring of the luminescent Eu(III) adduct on the NiO films.Emission spectroscopy in the visible range for the hybrid NiO/Eu(III) system shows that an accurate control of the Eu(III)coordination sphere may tune the luminescence of the monolayers.

Resume : Organic molecular semiconductors have become very promising candidates for transistors, resistors and photoswitches because of their flexibility, tunable characteristics and ease of manipulation. However, the low magnetic transition temperature makes the operation at room temperature difficult to achieve. Metal-Phthalocyanine (MPc) which possesses a spin-bearing transition metal ion accommodated in the centre of the conjugated ring has been studied extensively due to its combination of semiconducting and magnetic properties. By increasing the strength of magnetic coupling and exchange interaction as well as choosing a suitable central metal, the magnetic transition temperature has the potential to reach room temperature. This research aims to obtain high-temperature MPc-based magnetic semiconductors with novel strategies manipulating the thin film structure. The ideal ferromagnetic system should possess facially stacking structures, strong magnetic couplings, high exchange interactions and magnetic ordering temperatures above the boiling point of liquid nitrogen. Computational simulations by density functional theory combined with D3 dispersion correction and experimental characterizations will be compared. The success of this research will provide a solid foundation for future strategies in obtaining room temperature magnetic molecular semiconductors which could have unprecedented applications in spintronics.

Resume : Atomic/molecular layer deposited (ALD/MLD) inorganic-organic thin films form a novel class of hybrid materials whose composition and functional properties can be precisely tuned by controlling the relative number of ALD and MLD deposition cycles, a/b[1]. One class of these materials are the so-called zincones that can be deposited for example from diethyl zinc (ZnEt2) and hydroquinone (HQ) precursors resulting in (Zn-O-C6H6-O)b structured hybrid films[2]. When this deposition route is coupled with an ALD process for ZnO using ZnEt2 and H2O precursors, ((ZnO)a(Zn-O-C6H4-O)b)c multilayer thin films can be fabricated. Provided the π electrons from the aromatic HQ molecules, these type of Zn-based inorganic-organic hybrid thin film have arisen interest for their electronic properties, particularly for their transparent conducting[2] and thermoelectric properties[3]. However, the drawback with some of these hybrids is that they may show instability towards moisture in ambient conditions, namely change in thickness, refractive index and chemical composition[4]. Here in this study, we show through ellipsometric porosimetry[5] that the instability observed in the hybrid zincone (Zn-O-C6H6-O)b films is intimately related to their initial open microporosity (1.21 vol.%, 0.42 < d < 2 nm; d = pore diameter). The open pores provide permeation paths for moisture, which enables reactions of moisture with the weak Zn-O bonds. This results in dissociation of Zn-O-HQ structure and conversion of the zincone films to a micro/mesoporous film with 39.3 % open porosity after 24 hours of exposure to ambient air (22 ˚C, 58 % RH). By increasing the number of ZnO ALD cycles in between the Zn-O-C6H6-O MLD units in ALD/MLD multilayer films, the initial open microporosity content of the films gradually decreased to less than 0.05%. For such compositions, the films showed no change in their physical and chemical properties after exposure to the ambient air for 24 hours. Thus, control over micro-porosity is found as one of the keys for controlling the stability of the ALD/MLD hybrid thin films. Furthermore, it was found out via in-situ SE measurements that the nucleation for the ALD growth of the ZnO layers during the growth of the ((ZnO)a(Zn-O-C6H4-O)b=1)c films is delayed. The ZnO growth recovers its steady state after around 5 ALD cycles. Due to this nucleation delay of ZnO on the Zn-O-C6H4-OH terminating surface, the lateral connectivity of the ZnO layers in the ((ZnO)a(Zn-O-C6H4-O)b=1)c multilayers takes place for compositions which ZnO recovers its steady-state growth rate. Then bulk-like crystalline wurtzite ZnO is seen to form via Fourier-transform infrared and X-ray diffraction experiments. Moreover, it is shown that the lateral closure of the ZnO layers triggers electrical conductivity in the films, vital for their potential application in e.g. flexible transparent electronics. [1] Dameron, A.A., Seghete, D., Burton, B.B., Davidson, S.D., Cavanagh, A.S., Bertrand, J.A., and George, S.M. (2008) Molecular Layer Deposition of Alucone Polymer Films Using Trimethylaluminum and Ethylene Glycol. Chem. Mater., 20, 3315–3326. [2] Yoon, B., Lee, B.H., and George, S.M. (2012) Highly Conductive and Transparent Hybrid Organic − Inorganic Zincone Thin Films Using Atomic and Molecular Layer Deposition. J. Phys. Chem. C, 116, 24784−24791. [3] Niemelä, J.-P., Karttunen, A.J., and Karppinen, M. (2015) Inorganic–organic superlattice thin films for thermoelectrics. J. Mater. Chem. C, 3 (40), 10349–10361. [4] Choudhury, D., Rajaraman, G., and Sarkar, S.K. (2015) Stability of molecular layer deposited zincone films: experimental and theoretical exploration. RSC Adv., 5, 29947–29952. [5] Aghaee, M., Perrotta, A., Starostin, S.A., de Vries, H.W., van de Sanden, M.C.M.R., Kessels, W.M.M.E., and Creatore, M. (2017) On the synergistic effect of inorganic/inorganic barrier layers: An ellipsometric porosimetry investigation. Plasma Process. Polym., 14 (10) DOI: 10.1002/ppap.201700012

Resume : Direct chemical coupling of organic polymers with active inorganic materials offers many opportunities, but new techniques are needed to interconnect materials while maintaining favorable functionality of the individual organic and inorganic components. Moreover, approaches for materials coupling that can maintain or improve overall process flexibility are particularly valuable. Metal-organic frameworks (MOFs) are crystalline solids comprised of reactive metal clusters connected via organic ligands, producing large porosity and high surface area. A wide variety of MOFs have proven effective in gas adsorption, separations, and catalysis. MOFs are most commonly synthesized as bulk powder, and processes to adhere them to functional devices, such as polymer fabrics, typically decrease the porosity and adsorption capacity. MOF thin films on flexible fibrous substrates are good candidates for gas filtration, membrane separation, catalysis and biomedical applications. Our group has developed a platform technology that addresses the critical challenges for MOF integration on fibers. Inspired by the favorable growth of MOF thin films on ceramic substrates like alumina, we deposited metal oxide coatings onto fiber substrates using atomic layer deposition (ALD) to form an inorganic surface on polymers for heterogeneous MOF nucleation and growth. We found that ALD Al2O3 enables the formation of highly conformal Cu-BTC thin films on polypropylene fibers in both solvothermal and layer-by-layer growth. Growth uniformity, MOF mass loading and overall BET surface were all significantly enhanced with ALD nucleation layers. Similar synthetic strategy was also applied to Zr-based UiO MOFs using ALD TiO2 layers. Conformal UiO MOF thin films including UiO-66, UiO-66-NH2 and UiO-67 were obtained on ALD-coated nylon-6 nanofibers. Cu-BTC functionalized polypropylene nonwoven fabrics exhibit large adsorption capacity for toxic industrial chemicals such as NH3 and H2S. Micro-breakthrough tests show that the dynamic loadings of ammonia for solvothermally-grown CuBTC coatings on polypropylene fibers are up to 5.68 mol/kg(MOF+fiber). Zr-based UiO MOF thin films on ALD-coated nylon-6 nanofibers were applied for catalytic degradation of chemical warfare agents. Half-lives of CWA simulant DMNP are less than 8 min with UiO-66-NH2 and UiO-67 thin films on nylon-6@TiO2 nanofibers, while half-lives of GD are all less than 4 min with our MOF-nanofiber catalysts. These results all demonstrate the excellent adsorption and catalytic performance of our MOF-functionalized fibers. These MOF-fiber composites are also very promising for the development of gas filters, protective suits, and potentially smart textile materials.

Resume : Vapor phase infiltration (VPI) is an emerging processing technology for infusing polymers with inorganic constituents to create new organic-inorganic hybrid materials with novel electrical, chemical, and/or physical properties. These new materials can have applications as chemical barriers, filtration media, or photolithographic hard masks. This talk will focus on our development of a fundamental VPI processing kinetics phenomenology to create a pathway for rational design of material composition and structure. By measuring VPI compositional profiles as a function of space or time and temperature, we can extract fundamental energy barriers for the sorption, diffusion, and reaction processes and delineate amongst different rate limiting steps. In our materials development, we often find that partial infiltration of a polymer film, fiber, or foam is sufficient to impart desired properties; so rational design of the infiltration kinetics can enable desired performance without waste in processing time or materials. Here, we will demonstrate several examples including our work to create chemically insoluble polymers and membranes. We find, for example, that infiltration depths of about 0.75 microns are sufficient to yield PMMA chemically insoluble in organic solvents regardless of whether it is in a thin film geometry or a macroscopic plexiglass object of centimeters in dimension. By using our processing kinetics model we can reproducibly protect arbitrary plastic components using this VPI method.

Resume : Piezoresistive (PR) polymer based composites with carbon nanostructures are increasingly being developed for a wide variety of sensing applications. The most studied carbon nanostructures have been carbon nanofibers and nanotubes and, recently, graphene and their intrinsic properties and aspect ratio strongly influence the percolation threshold and the PR response of the corresponding composites. To produce transparent, flexible or highly stretchable PR sensors, thermoplastic and elastomer polymers can be used as matrices. Triblock copolymer styrene/ethylene-butylene/styrene (SEBS) combines the mechanical properties of the rubbers without vulcanization. Within the thermoplastics, semicrystalline poly(vinylidene fluoride) (PVDF) show excellent electroactive properties to produce sensors or actuators. Conductive nanocarbonaceous/polymer composites have been prepared by solvent casting based on SEBS and PVDF and conductive fillers (nanotubes and graphene). The influence of polymer and filler type and content will be presented and discussed as well as the functional PR response that can reach gage factors up to 100 and maximum functional deformations above 20%, being therefore suitable for the desired applications. Work supported by the Portuguese Foundation for Science and Technology (FCT) -UID/FIS/04650/2013, PTDC/EEISII/5582/2014 and SFRH/BPD/110914/2015 (PC) - and from the Basque Government Industry Department under the ELKARTEK program.

Resume : Despite the astonishing progresses reached in the last five years, perovskite films still lack some stability. It is well known that UV light and humidity affect strongly perovskite-based solar cell performances. We herein investigate the degradation process of perovskite-based CH3NH3PbI3 thin films without encapsulation in presence of direct UV light. In particular, we are interested in the UV irradiation effect on structural, morphological and optical properties of the perovskite thin film. Experimental results show a serious degradation of the perovskite proprieties after 12 hours exposure to UV light. The main objective of this work is to show that it is possible to improve the MAPbI3 stability upon UV by the adequate incorporation of the bromide atoms in the perovskite matrix. In fact, it has been found that the CH3NH3Pb(I1-xBrx)3 perovskite exhibits a better stability, distinctly when the bromide fraction is above 20%. We think that the observed improvement is linked to the structural transition from the tetragonal phase to the more stable cubic structure as shown by the XRD results.

Resume : BaSnO3, SrTiO3 and other inorganic perovskite materials have been gradually studied as the electron transport layer or mesoporous structure of perovskite solar cell devices, and the device has been achieved more than 20% efficiency with La-BaSnO3 as transport layer. The emphasis is on improving the stability of devices. Because of the sudden termination of the lattice at the surface of the crystal, an unsaturated suspension bond is often found at the surface and forms a surface state. In actual devices, the unstable chemical bonds formed by dangling bonds of perovskite will cause the impurities or defects, and distort the surface structure of the crystal. On the other hand, the contact of similar materials will induce nucleation. If a material with definite shape is used as the core, the perovskite precursor solution can be introduced into the form of "template", which will affect the grain morphology of perovskite thin films. And the inorganic perovskite material will enhance the stability of the device. We synthesized the BiFeO3 particles with specific morphology by hydrothermal method. We tried to supersaturate them in the anti-solvent, and prepared perovskite films by one-step method, so that BFO could induce MAPbI3 heterogenous nucleation and exist independently in the films as a “seed”. Many materials as additives which combine with precursor to form mesophase complexing state and do not remain in functional layer after thermal annealing have been widely concerned. It is reported that the MAAc and Lewis base thiosamide thio-semicarbazide (TSC) have been introduced into perovskite precursors, and the large size perovskite thin films without anti solvent treatment have been prepared by one-step spin coating. And ideal perovskite film with the device conversion efficiency of 18.76% were obtained by using MASCN as an additive. According to the above research, we tried to use Pb(Ac)2 lead acetate as lead source, polyethylene glycol (PEG) as additive, the perovskite thin film crystallinity has increased by ten times, and the corresponding PCE of devices has been increased by nearly ten percent.

Resume : The fluoride polymers like P(VDF-TrFE-CTFE) with high piezoelectricity and ferroelectricity are attractive due to their potential applications for electromechanical devices including sensors, actuators, transducers and artificial muscles. However, although the strain response in electrostrictive terpolymer is very high, a relatively high driving electric field (>70 Vμm-1) should be applied in order to yield the applicable mechanical output. Therefore, to achieve a large electromechanical strain and a high strain energy density at a relatively low external electric field, a high dielectric constant is required. Herein, we modified the P(VDF-TrFE-CTFE) with oxidized carbon blacks (OCB) to improve the dielectric constant. The unimorph P(VDF-TrFE-CTFE)/2.75%OCB cantilever with the thickness of 8 μm produced the deflection of about 248.1 μm which is twice than that of pure terpolymer, when applied to 90 V (11.2 V/ μm). The enhanced electromechanical performance shows a potential of P(VDF-TrFE-CTFE)/OCB nanocomposites in a real application.

Resume : Conductive nanofibers are highly attractive for application in biosensor and biomedical fields owning to high surface-area-to-volume ratio, interesting doping/de-doping chemistry, ease of modification, biocompatibility, and integration capability in miniaturized systems. We propose a novel and robust method of preparing conductive nanofibers via electrospinning and post-acid doping process that enables versatile functionalities of nanofibers. Non-conductive emeraldine base polyaniline was mixed with a supporting polymer and spun onto ITO electrodes for ensuing electrochemical characterization. The nanofibers were then converted into conductive form by soaking into acid solution, termed ‘post-spinning doping process’. Critical parameters including doping success, e.g. choice of acid, solvent, and incubation time, were investigated. Furthermore, thermal treatment of the nanofibers improved the current response in terms of sensitivity and stability. The as-prepared nanofibers/ITO exhibited 5-fold higher signal than that of bare ITO for ferri/ferro cyanide. Bioanalytically, the modified electrode demonstrated interesting characteristics as the nanofiber coating lead to a suppression of interferences of ascorbic acid in electrochemical detection of dopamine. Also, the post-doped nanofibers served as a greater support than bare ITO for polydopamine formation which is highly useful for diverse applications including in energy, sensing, and biological and biomedical fields.

Resume : Transparent heat mirrors (THMs) are used to reduce energy because they block external IR rays in hot climates and preserves internal heat in cold climates used in energy-efficient buildings, cars, and greenhouses. In this study, we proposes a novel self-cleaning transparent heat mirror (SC-THM) produced by continuous roll-to-roll sputtering. Silver/silicon nitride multilayer was deposited on transparent polyethylene terephthalate films. A Plasma polymer fluorocarbon (PPFC) thin was deposited on a silver/silicon nitride multilayer structure using carbon nanotube/polytetrafluoroethylene composite target. The optimized thicknesses of each layers of SC-THM were derived from optical simulation. The optimized SC-THM the visible light transmittance was 60.67 % at a wavelength of 406 nm and the infrared transmittance was 6.86% at a 1,000 nm wavelength. We calculated performance parameter using air mass 1.5 solar spectral irradiance spectrums. At optimized SC-THM structure, the value of the performance parameter Tvis/Tsol was 1.70. The SC-THM exhibited good water repellency of more than 111o achieved by applying a low surface energy PPFC top layer.

Resume : Stretchable electronics such as stretchable displays, transistors, sensors, human-health monitoring devices have attracted great interest. To substitute ITO electrode, the advance of stretchable electrodes prepared by simple process is important for stretchable electronics. We fabricated highly transparent and stretchable Ag nanowire (NW)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hybrid electrodes by using brush-painting on stretchable polyurethane(PU) substrate for stretchable electronic devices. We obtain writable and paintable electrodes with a low sheet resistance of 19.7 Ohm/square, high optical transmittance of 88.64% and outstanding stretchability by a brush painting of Ag NW and PEDOT:PSS mixed ink comparable to conventional ITO electrode. Effective embedment of the Ag NW into the conductive PEDOT:PSS layer led to metallic conductivity as well as good stretchability. The brush painted Ag NW/PEDOT:PSS hybrid electrode showed a higher strain 30% from its original length without a critical resistance change than Ag NW or sputtered ITO electrode. In addition, we investigated mechanical properties of the hybrid electrode using specially designed bending test, rolling test, and twisting test for 10,000 cycles. Cross-sectional TEM images showed that the electrodes were laterally aligned to the PU substrate due to shear stress of the brush. Also, we demonstrated applications using the Ag NW/PEDOT:PSS electrodes that are stretchable interconnectors for stretchable and wearable thin film heaters. These results provide clear potential for widespread application in next-generation, stretchable electronics.

Resume : Sodium ion supercapacitors are being considered as an alternative to lithium based systems because of their large natural abundance, cost effectiveness and low environmental impact. Amongst the various sodium based electrode materials, NaMnPO4 is showing tremendous promise for large scale application. Similar to what LiFePO4 did for the Li-ion storage devices, NaMnPO4 and its derivative can have comparable impact on Na-ion based technologies. We will present a simple, fast and cost-effective synthesis protocol for achieving NaMnPO4 with tunable morphologies. The material shows reasonably high electrochemical response, which makes it useful for Na-ion supercapacitors and batteries. An evident limitation of this material is its low cycling stability, which can lead to performance loss. Therefore, we have proposed the strategy of coating NaMnPO4 particles using suitable conducting shell, which can stimulate conductive contact between the electrolyte and active electrode materials. Such coated material can then be used to form efficient cathodes. The electrochemical behaviour of bare and coated NaMnPO4 was investigated in various electrolytes (NaOH, Na2SO4, NaNO3) using three electrode configuration. Specific capacitance values for bare and polyaniline coated NaMnPO4 were ̴ 83 F/g and ̴ 191 F/g, respectively @1A/g current density in 2M NaOH. The use of these materials in actual devices will also be presented in the paper.

Resume : Due to their superior properties, graphene nanoplatelets (GNP) have gained great interest in recent years to be used as highly efficient fillers for the production of polymer composites. In the preparation of such composites, the uniform dispersion of the nanoplatelets in the matrix is very important to improve the properties of the final composite since pristine GNPs tent to aggregate during the mixing process. To ensure the better dispersion and compatibility between filler and matrix, surface modification of GNPs is a preferable way. In this study, it is aimed to functionalize the surfaces of GNPs by using rotating-bed plasma enhanced chemical vapor deposition (PEVCD) method. A thin layer of poly(glycidyl methacrylate) (PGMA) was coated on the surfaces of GNPs to ensure complete wetting and uniform dispersion in the epoxy matrix. With the continuous agitation of the particles during PECVD, the GNP surfaces are exposed uniformly to the plasma, which is very limited when the particle bed is stationary. Epoxy composites filled with pristine and plasma-modified GNPs were prepared at different loading levels. The effect of plasma modification of GNPs on the structure and morphology of epoxy composites was evaluated using XRD and SEM techniques. The role of PECVD modification of GNPs on the mechanical properties of epoxy composites was investigated in detail. It was observed that PECVD modification of GNPs with PGMA improved the mechanical properties of final composites.

Resume : For laboratories with little vacuum experience and without easy access to machine shop facilities we have developed an iCVD system assembled from commercially available vacuum components. The vacuum chamber is a novel design available from Ideal Vacuum LLC. The chamber is a 6 inch cube consisting of an open frame with plates which are bolted to the frame to form the chamber walls. Plates with various options (KF vacuum connection, heated or cooled stages etc.) are available and can be bolted to any face of the cube frame allowing for extreme flexibility in configuring the system. Pumping, valves, monomer and initiator supply is accomplished using standard KF and VCR vacuum components. We will show detailed photographs of the system along with a parts list. The only custom machining needed is for the filament array which can easily be constructed by any university or online machine shop.

Resume : We have investigated effect of in-situ plasma treatment on water-vapor permeation barrier properties of Al2O3 layer for application to encapsulation layer in organic electronic devices. A 150-nm-thick Al2O3 barrier layer was prepared by plasma enhanced digital chemical vapor deposition (D-CVD) system on flexible substrate. Self-limited behavior was observed which enables to precise control of thickness as in the case of atomic layer deposition (ALD). Before taking out barrier coated substrate from D-CVD system, in-situ oxygen (O2) plasma treatment was carried out for 30 s at the plasma power of 300 W. Surface roughness measured in peak-to valley value was improved from 3.167 to 1.692 nm after O2 plasma treatment that confirms very smooth film was prepared. Pores and defects were sealed by plasma treatment and no defects and pin-holes were observed by high resolution transmission electron microscope from the barrier layer which is suitable for water-vapor permeation barrier. The density of prepared Al2O3 layer was improved by in-situ O2 plasma treatment from 2.83 to 3.03 g/cm3 although deposition rate was further increased compared to ALD. The ratio of Al:O was measured to be 1:1.49 whereas that without plasma treatment was 1:1.35. Water-vapor transmission rate of in-situ O2 plasma treated 150-nm-thick Al2O3 layer was measured to be 4.12×10-5 g/m2/day which was maintained to 2500 hours of exposure time whereas that obtained from non-O2 plasma treated one was drastically increased after 100 hours of exposure time.

Resume : With increasing interest in textile-based wearable electronic devices, there is a considerable need to develop stretchable and elastic conductors that can be directly patterned on a fabric. Here, we demonstrate a directly patternable, stretchable, and wash-resistant PEDOT:PSS composite ink. Water-based PEDOT:PSS composite ink is not absorbed when dropped on a highly hygroscopic fabric, which enables direct patterning of the PEDOT:PSS electrode on the fabric without pretreatment. The PEDOT composite incorporates the PEDOT network structure in the elastomer matrix, ultimately exhibiting high stretchability of over 300%, and excellent durability for mechanical bending. Even after repeated washing with strong oxygen bleaching agent, conductivity of the composite was maintained. To highlight the potential application of this composite for e-textiles, we demonstrate printing of a stretchable and mechanical durable LED interconnect on the fabric.

Resume : Fibre-based electronics, including fibre-based electrode, light emitting fibre, energy generating and storage fibres and fibre-based sensors, refer to a new generation of electronics. With integrating electronic functional materials into micro to nano fibres, fibre-based electronics possess unique properties, which are unachievable from traditional planer and rigid electronics, such as flexibility, transparency, breathability and deformability. Fibre-based electronics can be assembled into electronic textiles and wearable device, changing the way people interact with electronic device currently. This project presents an efficient one-step deposition process to produce micro/nano conductive silver fibres. A self-developed Core-Shell Low-Voltage Electrospinning [1] (Co-LEP) is set up to fabricate silver fibre based on a reactive silver ink [2], and this is a one-step process under mild temperature (<90℃), without needing any post processing like annealing. Characterization shows the silver fibre has a core-shell structure with continuous silver phase being wrapped by a polymer shell, as shown in Figure 1b. The continuous silver core provides the fibre with a higher conductivity than fibres with dispersed metallic particles inside. Mechanical testing shows that the fibre’s Young’s Modular and ultimate strength are similar with human skin, which makes it perfect for wearable electronics. Besides, the fibre acquired in this project has a desirable bending stability, and experiments show repeated bending does not compromise conductivity, which is another essential feature for making electronic textile.

Resume : CsPbX3 (X = Cl, Br, I) inorganic perovskite quantum dots (QDs) are potential materials for illumination and display applications because of their excellent photophysical properties. However, they have low chemical yield, and are structurally unstable and moisture sensitive under ambient conditions. Here, we show that microwave-assisted strategy for the synthesis of CsPbX3 QDs provides an approach to increase the yield. The as-prepared CsPbX3 QDs show high photoluminescence quantum yield, optically tunable wavelength and narrow full width at half maxima emission line (varying from 12 to 36 nm) covering the entire spectrum of the visible range. In order to overcome the poor stability, we have developed a silica encapsulation method to form QD@SiO2 that enhances their thermal stability and photochemical stability. White light-emitting diode (WLED) is further fabricated by using the as-prepared green-emitting and red-emitting silica-coated CsPbX3 QDs as color conversion materials on 365 nm GaN LED chip

Resume : The Remote Plasma Assisted Vacuum Deposition (RPAVD) process is a versatile methodology for the fabrication of functional nanocomposites from non-chemically polymerizable organic or organometallic functional molecules (1). This approach combines the physicochemical reactions involved in plasma polymerization processes with the vapor deposition of functional molecules of interest for the target application requirements. The obtained cross-linked polymer films are insoluble and thermally stable. These films can incorporate a controllable concentration of virtually any kind of thermally stable photo-functional molecule. The method is scalable at wafer level and fully compatible with the use of solvent-sensitive and delicate substrates. The process has been initially applied for the development of optical thin films and photonic devices including optical filters, photonic sensing chips and lasing media (2). However, the properties of the films can be tailored to other functional applications like the development of controlled wetting and ice retarding surfaces, antimicrobial surfaces and high-performance dielectric ultrathin films. In addition, we will show some results about how the synthetic approach can be adapted for the synthesis of supported nanostructures with custom-made geometries. (1) Langmuir, 2006, 6719, J. Mater. Chem. C, 2014, 2, 6561, J. Phys. Chem. C, 2012, 8731 (2) Adv. Mater. 2011, 761, Sensor Act. B, 2016, 649, ACS Appl. Mater. Interfaces 2017, 9, 8948.

Resume : Al/PTFE multilayer films with different structures were deposited by magnetron sputtering and response behaviors of the specimens under single pulsed laser loading were studied by analyzing the after loading specimens, test results showed that the multilayered structure, including the modulation ratio, the thickness of each layer, influences the reaction. Finer structured films went under more fierce reaction than course structured ones when loaded by laser pulse of identical parameters, the more Al/F atomic ratio deviate from balance, the less strong reaction were observed. No specimens developed continuous reaction, though it is clear that pulsed width have a dominate influence on the effects compared to laser power.

Resume : Plasma enhanced chemical vapor deposition (PECVD) method offers advantageous properties over traditional wet coating techniques. For instance, solvent-free PECVD prevents agglomeration and sticking between particles, which is very important especially for nanoscale particles. The aim of this study is to improve the polymer thin film coating uniformity on nano and micro size particles (CNT, expanded perlite) using rotating bed. The basic reason behind the use of rotating bed in PECVD process is to ensure the continuous agitation and mixing of the particles during the deposition. In this way, the particle surfaces can be exposed uniformly to the plasma discharge. In order to evaluate the influence of rotating bed on the coating uniformity; the same amounts of particles were coated under the same conditions by using rotating and stationary bed separately. Then, chemical and morphological properties of particles were determined by FTIR, XPS, SEM, TEM and contact angle measurements. According to the results, it was observed that the coating uniformity of both the individual particle and through the particle bed were improved using rotating bed as compared to the deposition was conducted under stationary bed conditions.

Resume : The development of new fabrication methods for the nanostructural control is crucial to synthesize rationally designed materials with enhanced properties.[1,2] Plasma activated methods have recently evolved towards the controlled deposition of nanoscale materials.[3–4] Advantages of these methods relay in their straightforward scalability, low temperatures and high accuracy in the composition as well as on the morphological control as microstructure, texture or alignment.[3–4] However, a critical bottleneck for the application of procedures for the deposition of nanoscale materials is the limited availability of volatile metalorganic and metal halide precursors. The present work stablishes the bases for a vacuum and plasma supported methodology for the fabrication of metal or metal-oxide nanostructured layers with controlled microstructure by using metal-porphyrins and phthalocyanines as precursors.[5-7] The layers synthesized range from compact to porous films as well as low dimensional nanostructures such as 2D networks, nanowires or nanocolumns, with a wide range of applications such as optic, optoelectronic, catalysis or solar cells, among others. 1 W. Xiong et al. Front. Optoelectron. 8(2015)351 2 C. Cheng et al. Nano Today 7(2012)327 3 K. Ostrikov et al. Adv. Phys. 62(2013)113 4 A. Barranco et al. Prog. Mater. Sci. 76(2016)59 5 A.N. Filippin et al. Adv. Mat. Int. 4(2017)1601233 6 M. Alcaire et al. Plasma Process. Polym. 3(2016)287 7 M. Alcaire. et al. Nanoscale 3(2011)4554

Resume : Poly(vinylidene fluoride) (PVDF) and its copolymers are the polymers with the highest electroactive properties, being the β phase the main responsible for its piezoelectricity. The incorporation of ionic liquids (ILs) into the PVDF matrix allow to tailor the physico-chemical properties, improve the electroactive response and/or to add new functionalities. In the present work, IL/PVDF and IL/PVDF co-polymers, were evaluated for the development of IL/polymer composite bending actuators. The selected IL [C2mim][NTf2] was introduced within different polymer matrices in concentrations of 10, 25 and 40 wt%. The thermal, mechanical and electrical properties of the polymer/IL composites are strongly dependent on the IL content. The frequency and voltage dependent bending response is the largest for the IL/PVDF-TrFE composites with values up to ~3.5 mm using a frequency of 100 mHz and an applied voltage of 5V, respectively. The bending mechanism will be discussed as well as how to optimize it based on the proper selection of IL anion and cation. Acknowledgements This work was supported by: Portuguese Foundation for Science and Technology (FCT) (UID/FIS/04650/2013, PTDC/CTM-ENE/5387/2014 and grants SFRH/BD/90215/2012 (J.C.D.), SFRH/BPD/121526/2016 (D.M.C) and SFRH/BPD/112547/2015 (C.M.C.); Spanish Ministry of Economy and Competitiveness (MINECO) - MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK Program.

Resume : We report the fabrication of novel synthetic polymer coatings using poly[(2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide] (PMEDSAH) and the mechanism of ‘grafting-to’ polymerization. We introduce a two-step technique involving the chemical vapor deposition (CVD) polymerization of an aldehyde group-functionalized [2.2]paracyclophane as the first step and the immobilization of PMEDSAH on the reactive polymer coating as the second step. CVD polymerization of [2.2]paracyclophanes with an aldehyde functional group results in poly(4-formyl-p-xylylene-co-p-xylylene) polymeric thin films directly on the surface of a substrate. CVD polymers can be used as conformal surface modification layers for a range of different substrates (polystyrene, Teflon, stainless steel, glass, silicon, rubber, etc.). 2-(methacryloyloxy)ethyl dimethyl-(3-sulfopropyl)ammonium hydroxide (MEDSAH) was polymerized in solution using atom transfer radical polymerization (ATRP) and a functional ATRP initiator. The resulting functional polymers were immobilized on the aldehyde-functionalized reactive coatings with a dihydrazide spacer. The polymer thin films were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). The thickness of the grafted PMEDSAH films were measured by ellipsometry. The physicochemical characteristics of these surfaces influence the growth of human embryonic stem (hES) cells in vitro. hES cells have been defined as self-renewing cells that can give rise to many types of cells of the body. The development of a standardized and defined environment for the culture of hES cells is an essential step for their use in therapeutic purposes. These surfaces also hamper the non-specific adsorption of proteins. Our results demonstrate that H9 hES cells attached efficiently to these PMEDSAH coated surfaces. Serial passaging of H9 cell line in the PMEDSAH coatings preserved their normal karyotype and expressed characteristic hES cell markers. Altogether, these results demonstrate the ability of PMEDSAH coatings as potential biointerfaces for the design of cell culture substrates and other devices of medical interest.

Resume : The wide range of available chemistries and the ability to tailor bulk and surface properties independent of one another make iCVD polymer coatings a tool applicable to a significant number of commercially attractive applications. iCVD polymer deposition presents a range of attractive benefits for commercial coating processes including: high polymer chemical specificity, conformal coating of micro- to nano-scale substrate features, the ability to produce coatings with material properties impossible to form by wet processes due to the insolubility or morphology of the coating, and low thickness polymer coatings which could not be applied from solution. GVD has found commercial success with iCVD polymer coating by targeting technical problems associated with the most advanced product designs within a given market space. As our leading-edge customers? approach then expands throughout the market, the need for our coating solution expands as well. Despite the many attractive features of iCVD polymers, the commercial application of vacuum based processing also presents challenges of cost and throughput which require individual applications to be carefully vetted for their suitability. There are many market, safety, and process variables to consider. What efficiency will be required of the industrialized process to meet coating cost targets? How will effluent from the vacuum process be handled safely and what volume of waste will be generated? What chamber design is required to satisfy production volume and handling needs? Will coating be handled by the producer of the substrate parts or will an outside coating provider be necessary? And, most importantly, what technical solutions currently exist to solve the targeted problem? These challenges will be detailed in this talk through a case study of GVD?s newest iCVD product, SignalSeal, and its commercial application within the RF electronics space.

Resume : The role of vapor-phase Parylenes in bringing life-enhancing technologies to the market continues to grow rapidly due to increasing demand for products that are more reliable and advances in other technical fields. During the past five decades, several major breakthroughs in Parylene technology led to the successful development of many commercial products that play significant roles in our life. In addition, recent Parylene advancements have created opportunities to enable future technologies. This presentation will provide an overview of fifty years of advances in Parylene technologies, including microRESIST® Antimicrobial Parylene Technology, and will discuss how currently available Parylenes differentiate themselves from other available polymeric materials for the technologies of the future, particularly for medical and electronics fields. Additionally, this paper describes the methods to obtain Parylene hollow nanospheres and nanotubes and their potential applications. Various types of spheres and particles with different functionality are also explored. Examples of current and future applications include circuit card assemblies, MEMS, LEDs, sensors, lab-on-a-chip devices, pacemakers, stents, electrosurgical tools, cochlear implants, neurostimulation devices, elastomers and flexible electronics, to name on a few. Due to these advances, several new commercial applications that will have significant impact in medical electronics and other areas can now be developed.

Resume : The unique chemical vapor deposition coating of thin poly(p-xylylenes) enables the preparation of novel materials with complex morphology. We have investigated PPX coatings for the functionalization and stabilization of two-dimensional electrospun nonwovens and ultralight three-dimensional fibrous sponges. The PPX coating of catalyst loaded electrospun nonwovens and sponges allowed the multiple use of catalysts [1,2] and increased the reactivity considerably in sponges [2]. Moreover the PPX coating of sponges increased their morphological stability and resulted in superhydrophobicity as well as excellent heat insulation of the sponges [3,4]. The PPX coating of sponges also enabled high loading of the antimalarial drug Artemisone and its tailored release from sponges [5]. The performance of all these films depends significantly on the nature [6], porosity [7], and the permeability [8] of the PPX films. [1] F. Mitschang, H. Schmalz, S. Agarwal, A. Greiner, Tea-Bag-Like Polymer Nanoreactors Filled with Gold Nanoparticles, Angew. Chem. Int. Ed. 2014, 53, 4972-4975. [2] G. Duan, M. Koehn-Serrano, A. Greiner, Highly Efficient Reusable Sponge-Type Catalyst Carriers Based on Short Electrospun Fibers, Macromol. Rapid Commun. 2016, DOI: 10.1002/marc.201600511. [3] G. Duan, S. Jiang, T. Moss, S. Agarwal, A. Greiner, Ultralight open cell polymer sponges with advanced properties by PPX CVD coating, Polym. Chem. 2016, 7, 2759–2764. [4] S. Jiang, G. Duan, U. Kuhn, M. Mörl, V. Altstädt, A. L. Yarin, A. Greiner, Spongy Gels by a Top-Down Approach from Polymer Fibrous Sponges, Angew. Chem. Int. Ed. 2017, 56, 3285-3288. DOI:10.1002/anie.201611787 [5] G. Duan, A. R. Bagheri, S. Jiang, J. Golenser, S. Agarwal, A. Greiner, Exploration of macroporous polymeric sponges as drug carriers, Biomacromolecules 2017 DOI: 10.1021/acs.biomac.7b00852. [6] A. K. Bier, M. Bognitzki, J. Mogk, A. Greiner, Synthesis, Structure, and Properties of Alkyl Substituted PPXs by Chemical Vapor Deposition for Stent Coatings, Macromolecules 2012, 45, 1151-1157. [7] P. Hanefeld, F. Sittner, W. Ensinger, A. Greiner, Investigation of the ion permeability of poly(p-xylylene) films, e-Polymers 2006, No. 26. [8] V. Wesp, J. Zakel, M. Schaefer, I. Paulus, A. Greiner, K. M. Weitzel, Highways for ions in polymers-3D-imaging of electrochemical interphase formation Electrochimica Acta 2015, 170, 122-130. DOI: 10.1016/j.electacta.2015.04.117

Resume : An advanced material interface is modified by using a substrate-independent coating of switchable poly-para-xylylene. This advanced version of poly-para-xylylene comprises an integrated disulfide moiety within the functional side group, and the switching phenomenon between the immobilized functional molecules is triggered by the redox thiol−disulfide interchange reaction. These dynamically well-defined molecules on the surfaces respond simultaneously to altered biological properties and controlled biointerfacial functions. Three examples, switching wettability, reversibly altered cell adhesion activity and programmed manipulation over cell differentiation pathways, are demonstrated. Switching of the surface wettability was achieved through the interchange of a hydrophobic perfluorodecanethiol and a hydrophilic peptide, Cys-Lys-Asp-Lys-Asp-Asp (CKDKDD). The reversibly altered cell adhesion activity was carried out between a cell-repellent state and a cell-adherent state via the immobilization and interchange of two selected biomolecules: a thiol-terminated PEG and a RGDYCC peptide. The controlled immobilization and displacement of the fibroblast growth factor (FGF-2) and bone morphogenetic protein (BMP-2) were demonstrated on cell culture substrates, and the resulting surfaces provided a programmable induction of cellular responses in proliferation and osteogenesis toward the cultured bone marrow mesenchymal stem cells (BMMSCs) and murine preosteoblasts (MC3T3-E1).

Resume : For many years, coatings from unsubstituted, as well as mono and dichlorated poly(p-xylylene) fabricated via Chemical Vapor Deposition (CVD) polymerization have already been widely applied, for instance in the semiconductor industry and in biomedical areas. By using a great variety of otherwise functionalized [2.2] paracyclophane-derivatives as a starting material, we are able to produce diverse homopolymer, copolymer or copolymer gradient coatings for the subsequent immobilization of active moieties, such as proteins or signal molecules.[1] Patterning techniques, for instance microcontact-printing or nanolithography, allow spatial control of the distribution of immobilized molecules on the surface.[2] Additionally, coatings with patterned functionality can be fabricated applying the VAMPIR-process (vapor-assisted micropatterning in replica structures) or exploiting selective deposition on pre-patterned substrates.[3] Current research focuses on the usage of these coatings for various applications, such as sensor systems, membrane functionalization or cell culturing.[4] [1] J. Lahann, Polymer International 2006, 55, 1361. [2] H.-Y. Chen, et al., Journal of the American Chemical Society 2010, 132, 18023. [3] M. Koenig, J. Lahann, Beilstein Journal of Nanotechnology 2017, 8, 1250. [4] A.-L. Winkler, M.Koenig et al., Biomacromolecules 2017, 18 (10), 3089.

Resume : Recent interest in the production of functional nanomaterials with well-defined optical, electrical and bio-adhesive/bio-repulsive properties triggered off the development of novel plasma-based approaches for synthesis of such materials. Among them, deposition techniques based on gas aggregation sources of nanoparticles receive increasing attention. Gas aggregation sources are versatile in terms of materials to be processed (metals, metal oxides, plasma polymers). They can be also implemented in line with other plasma-based techniques such as plasma enhanced chemical vapor deposition or magnetron sputtering. As it will be shown such combination may enable the fabrication of nanomaterials with various forms and architectures that range from heterogeneous metal/plasma polymer nanoparticles, coatings with gradient surface properties, nanocomposite materials with metallic inclusion embedded in plasma polymer matrix, sandwiched multi-layer structures, porous nanocolumnar films of plasma polymers or surfaces with hierarchical surface roughness. The application potential of such materials will be demonstrated on examples of coatings with tailor-made antibacterial efficiency, materials with tunable optical properties needed for ultrasensitive biodetection or coatings with extremely low wettability and its enhanced temporal stability. This work was supported by grant GACR 16-14024S from the Grant Agency of the Czech Republic.

Resume : Surface modification plasma processes are generally optimized on flat, generally smooth substrates, with processes run at low or at atmospheric pressure. This is still the early stage of optimization of plasma processes, for biomedical as well as for other applications. The diffusion of plasma processes in many different fields today, indeed has multiplied the kind of possible substrates in term of size, form, material and topography, and this is true also for applications in biomedical materials. Flat substrates now are probably an exception rather that the routine. For example, plasma processing of micro/nanometric particles or of porous materials (e.g., scaffolds for Tissue Engineering) are often necessary. In certain cases the substrate is not even used, and free standing coatings (NanoFilms, NFs) can be produced by PE-CVD processes. Deposition processes were usually performed with gas and/or vapor mixtures feeds; nowadays also aerosols of solutions or of suspensions of nanoparticles are being more and more utilized as feeds in PE-CVD. In this talk recently developed “exotic” PE-CVD processes developed at the lab of the author will be described, of potential use in biomedical applications, namely: the functionalization of scaffolds for Tissue Engineering, the deposition of free-standing NanoFilms, and the deposition of bio/nano composite coatings from aerosol-assisted Atmospheric Pressure discharges.

Resume : Stimuli-responsive materials have properties that depend on the environment in which they are used. In most cases, the material itself is formulated to react to the corresponding stimulus. However, many phenomena occur at the surface of the material. In this context, our group works on stimuli-responsive surfaces based on plasma polymer thin films whose properties vary according to their environment. More precisely, the aim of this study is the investigation of the reactivity in a thermoreversible reaction of functional coatings fabricated by pulsed plasma polymerization and their subsequent use for innovative applications. A thermodynamics study has been carried out to characterize Diels-Alder reversible reaction on coatings with various physico-chemical properties. For this purpose, the reaction progress of cycloaddition was monitored by several surface characterization techniques (PM-IRRAS, XPS, contact angle measurements). It can be noticed that coatings with different crosslinking rates strongly differ in entropy and enthalpy contributions of Gibbs energy. The thermodynamics methodology developed here leads to a better understanding of interfacial reactivity via Diels-Alder reaction on such plasma polymer thin films. These stable, functional polymer coatings with thermoreversible properties constitute, among others, an outstanding platform for controlled immobilization and release of biomolecules onto/from a multitude of substrate materials.

Resume : Noble metal nanoparticles made of silver and gold have been extensively used in various fields including biotechnology, catalysis and optics. Many studies aim at designing well-defined particle size and shape in order to control the properties of the colloidal solution of nanoparticles. However, fewer studies report on metallic nanoparticles embedded in polymer thin films and the subsequent use of such nanocomposite thin films. Our group work on the design of smart (nanocomposite) coatings assisted by pulsed plasma polymerisation, which can be fabricated on many types of materials. In this study, we investigate more precisely the influence of the nature of the chemical groups present within the plasma polymer, the operating conditions of pulsed plasma polymerization as well as the synthesis protocol of silver nanoparticles on the size, shape and distribution of these nanoparticles within the nanocomposite coating. XPS, TEM and AFM characterizations have enabled to understand and control the fabrication process and the morphology of metal nanoparticles into the functional plasma polymer. These results are a promising milestone for the design of original smart nanocomposite thin films whose properties vary with respect to the size and shape of the embedded nanoparticles. Anti-bacterial and optical properties of these coatings are currently under investigation.

Resume : The common definition of “surface” includes surface atoms and molecules, practically extending at the most three layers – typically up to one nanometer. This definition is justified by the fact that many surface properties such as chemistry, wettability or charge density are determined by the top most surface layer. Far less explored are effects due to interactions with deeper subsurface layers, i.e. the region extending over several nanometers underneath the “surface”. This subsurface region, however, might significantly contribute to molecular adsorption at the surface via long-range (i.e. >10 nm) interaction forces. To make use of such subsurface effects, plasma polymer films (PPFs) with defined architecture in the nanoscale were deposited comprising a hydrophobic-to-hydrophilic vertical chemical gradient structure. The organic/inorganic hybrid thin films were generated by depositing 1-15 nm-thick layers of plasma-polymerized HMDSO on a hydrophilic, nanoporous base layer of SiOx (with O2/HMDSO in the plasma). Diffusion of water through the hydrophobic terminal layer is still enabled despite the hydrophobic surface properties yielding hydration of the hydrophobic/hydrophilic gradient structure as demonstrated by neutron reflectometry measurements. The hydrated films were found to strongly affect protein adsorption at the surface thanks to long-range interaction forces exerted by oriented water molecules. Thereby, additional control over adsorption processes and modulation of protein adsorption is enabled which is relevant, e.g., for tissue engineering, wound dressing etc. Adjusting the thin film architecture of plasma polymer films thus provides an additional parameter to modulate surface properties of materials.

Resume : Smart polymers which alter its chemical and/or physical properties with respect to a stimulus such as temperature, pH, electric /magnetic fields are used in various areas including drug delivery, tissue engineering, bio separation and textile. Poly (diethyl amino ethyl methacrylate) (PDEAEMA) is an important pH responsive polymer, which has potential applications particularly in bio medical sector. There are several reports on polymerization of PDEAEMA by atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) and emulsion polymerization. Thin polymeric films of PDEAEMA can also be formed on the different surfaces using vapor based techniques i.e. chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD). PECVD offers the advantages of being solventless, low-cost, reliable and environmentally friendly process. In addition, PECVD is time efficient process and it can be applicable for fragile and geometrically complex substrates as well. In this study, PDEAEMA polymeric thin films were deposited using a planar inductively coupled plasma system in continuous and pulsed modes. FTIR and XPS results showed that polymers synthesized under pulsed plasma conditions have closer resemblance with monomer structure. The effect of substrate temperature and duty cycle on polymer structure were investigated. It was also shown that there is a correlation between deposition rate and duty cycle.

Resume : Materials exhibiting simultaneously high strength, elastic modulus and toughness are desirable for many applications. Unfortunately, for non-metallic materials these properties are often mutually exclusive. Nacre, bone and wood are examples how nature has solved this problem by combining hard and soft building blocks via molecular assembly. The exceptional mechanical properties of such natural hybrid materials have prompted the fabrication of bio-inspired composites. Among all methods available for the preparation of multifunctional nanostructured composite materials, the Layer-by-Layer technique is currently one of the most widely used due to its simplicity and versatility in combining a plethora of available nano-objects and macromolecules into finely tuned multifunctional architectures with nanometer scale control. The talk will illustrate some of our recent results on “elasto-rigid” hybrid materials prepared by combining hard nano-reinforcing elements like clays and microfibrillated cellulose, providing the strength and the stiffness to the composites, with soft polymer building blocks, allowing for stress and strain redistribution among the hard elements via interlayer shearing. Formation and growth of isotropic and anisotropic multilayer films will be presented and their optical and mechanical properties will be discussed as a function of structure, composition and preparation conditions.

Resume : Initiated plasma enhanced chemical vapor deposition (i-PECVD) is a novel technique that can produce well defined defect free polymeric films on many different substrates with low energy inputs. Fast deposition rates, high degree of functional group retention and conformal deposition are desired for most of the applications. In iPECVD, the chemical species called the initiator can easily be dissociated into reactive chemical species at low plasma powers due to their weak bonds. The basic reason behind the use of initiator in PECVD is to keep the plasma power low enough just to break the weak initiator bonds, so that the undesired monomer fragmentation ad chemical functionality lost would be avoided. In this study, thin films of acrylic polymers were deposited on different surfaces using i-PECVD method. The plasma (RF: 13.56 Mhz) was inductively coupled into a vacuum reactor by an outer planar-coil antenna through a quartz window. The use of tert butyl peroxide (TBPO) as an initiator allowed some coatings at very low (less than 1 Watt) plasma powers. The effects of plasma power, substrate temperature and reactant flow rates on the deposition rates, chemical and morphological properties of deposited films were investigated. FTIR and XPS analyses of the deposits indicated very high retention of functional groups at low plasma powers. Being a dry, low-cost, reliable and environmentally friendly process, the i-PECVD technique developed in this study can be used to deposit similar acrylic thin films on many industrially important surfaces.

Resume : In many synthesis reactions, plasma provides a convenient alternative to thermal heating or chemical reactants. Notably, plasma-enhanced chemical vapour deposition (PECVD) processes have already led to the simultaneous synthesis and deposition of a wide variety of functional materials. Nevertheless, due to the intrinsic nature of plasmas, composed of many reactive species over a wide energy range, a non-negligible number of side reactions occurs. The non-specificity of the plasma-induced reactions imply that the chemical structure of monomers is only partially retained in PECVD and the resulting thin films, called “plasma-polymers”, strongly differ from conventional polymers. Tremendous efforts have been made to mitigate the negative impact of plasma and promote conventional polymerization pathways. In this presentation, we report the latest advances in the PECVD of polymer thin films with a particular emphasis on (i) the initiated PECVD (iPECVD), which involves a polymerization initiator that allows to keep the plasma power low enough to reduce any undesired monomer fragmentation while producing well-defined polymerisation-initiating radicals and (ii) the plasma-initiated CVD (PiCVD), relying on the low frequency repetition of nanosecond pulsed discharges that allows to temporally isolate plasma and yield to an unprecedented degree of polymerization for both plasma and atmospheric CVD processes. Applications of functional polymer layers by iPECVD and PiCVD will also be presented.

Resume : Polymers provide extraordinary opportunities for functionalizing surfaces integrated into flexible devices contributing to a significant advancement in thin-film technologies.[1] Among polymers with heterocyclic structures, Poly(3,4-ethylenedioxythiophene) is one of the most promising owing to its exceptional stability, transparency, and electrical conductivity. Nevertheless, it is difficult to process PEDOT into thin-films by traditional solution-based methods. Plasma Radicals Assisted Polymerization via Chemical Vapor Deposition (PRAP-CVD) is a novel technique able to overcome the challenges caused by the conventional techniques. [2] This process is based on the concomitant but physically separated injection of low-energy oxidative radical initiators and vaporized monomer species into a reactor where the temperature and pressure are finely controlled. Reagents are uniformly introduced through the showerhead surface over the entire area of deposition. PRAP-CVD is a completely dry process which includes the possibility of processing solvent-sensitive substrates such as textile and paper. All effects coming from rinsing procedure are fully overcome. Therefore it is possible to modify only the surface of substrate without interfering with its bulk properties, guarantying an extreme conformity film/surface. The deposited films are stable in air both in terms of chemical composition and conductivity over one year. [1] B.R. Pistillo et al in Recent Research in Polymerization Ed. Nevin Cankaya, Turkey 2018 ISBN 978-953-51-5630-7 [2] B. R. Pistillo et al. Royal of Society Chemistry Advances 2017, 7, 19117

Resume : Atmospheric pressure plasma-initiated chemical vapor deposition (AP PiCVD) process has recently been demonstrated to form conventional homo polymers using temporally isolated dielectric barrier discharges, i.e. nanosecond plasma pulses at duty cycles in the range of several tens of ppm. The simultaneous synthesis and growth of polymer layers yielded films with unprecedented weight-average molar mass (ca. 94,000 g/mol), an excellent retention of the chemical functionalities as well as ultra-low roughness and perfect conformality. In this work, thanks to a comprehensive high-resolution mass spectrometry study, we demonstrate how the association of plasma mechanisms and conventional free-radical mechanisms ensure the atmospheric polymerization of vinylene monomers in AP-PiCVD. Ultra-short discharges (i.e. tens of nanoseconds) generate monomer-based adducts, arising from a statistical breakdown of the molecule, which are able to initiate/terminate the polymer chains. The long off time (i.e. several to tens of milliseconds) strongly favoring conventional free-radical polymerization mechanisms as long as radical species remain active. The relationships between the thin film’s properties and their respective monomers are discussed and guidelines are made to select appropriate AP-PiCVD monomers.

Resume : The insulating properties of organosilicon materials make them attractive candidates for several applications such as passivation layers and inter layer dielectric (ILD) in microelectronics. Inclusion of nanoporosity is a pathway to obtain ultralow-k films which can be generated by growing polymer layers from cyclic monomers. However, the plasma deposition of constitutive porous insulating layers is difficult, due to the dissociation of the ring. The present work investigates for the first time the one-step, solvent and chemical initiator-free atmospheric-pressure plasma-initiated chemical vapor deposition (AP-PiCVD) of cyclic organosiloxane and organosilazane monomers for the preparation of ultra-thin dielectric polymer layers. Using an ultra-short square wave pulse generator to ensure the polymerization initiation and avoid the ring fragmentation, AP-PiCVD allowed the fast synthesis of conventional and highly conformal insulating polymer layers. Absorption of water would lead to an increase of the resulting k value, therefore, it is noteworthy to mention that FTIR of the as-deposited layers did not show –OH incorporation. In addition, SEM and AFM investigations showed that all the organosilicon films are nearly atomically smooth and pinhole-free, retaining a perfectly planar morphology even after 24 hours of immersion in various solvent. The as-deposited organosiloxane layers have shown a low k value (2.5 ≤ k ≤3) contrary to the organosilazane films which have shown a dielectric constant in the order of magnitude of silicon dioxide (~4.2). Low leakage current densities, below ~10-8 A/cm2 at 1 MV/cm are measured, even for thicknesses as thin as 12 nm confirming the down scalability of the insulating properties.