Strain sensors with different architectures, such as single sensors, sensor arrays and a sensor matrix have been developed by inkjet printing technology. Sensors with gauge factors up to 2.48, dimensions of 1.5 mm × 1.8 mm and interdigitated structures with a distance of 30 μm between the finger lines have been achieved based on PeDOT (poly(3,4-ethylenedioxythiophene) and conductive ink. Strain gauges based on silver ink have also been achieved with a gauge factor of 0.35. Performance tests including 1000 mechanical cycles have been successfully carried out for the development of smart prosthesis applications.
Pulsed-plasma polymerization has been used to deposit ultrathin layers of pentafluorophenyl methacrylate by using low duty cycles and low power input. The monomer structure can be retained such that the chemical reactivity of the active ester group could be studied using the reaction with a simple amine. The film properties in aqueous phosphate buffer have been investigated using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and real time surface plasmon resonance spectroscopy. The films react readily with diaminohexane and immunoglobulin (IgG), yet the reactivity shows a dependence on the extent of hydrolysis of the ester group.
Summary: Material coating of surfaces can enhance receptivity for cells and biological compounds. Existing plasma coating technologies and possible materials are limited. A new polymer from pentafluorophenyl methacrylate (PFM) monomer was synthesized, and was plasma enhanced chemical vapor deposited on silicon wafers. The optimal plasma polymerization parameters for the PFM monomer and its copolymerization with the cross‐linking agents 1,7‐octadiene and 1,4‐butanediol divinyl ether co‐monomers were established. All the resulting polymer coatings leave the labile pentafluorophenyl group on the surface, enabling a rapid reaction with an amino‐terminated biotin ligand and allowing layer‐by‐layer self‐assembly of biotin‐streptavidin. In addition, the deposited polymer layers showed an extremely flat morphology with a nanoscale average roughness. This approach provides an easy means of obtaining functionalized surfaces which can enhance and control the biocompatibility of bulk materials. Merging the versatility of plasma polymerization processes, via simple monomers and reaction conditions, with biological platforms that enable target of cell adhesion brings us closer to the ultimate goal of controlling cell function through structured surfaces for their application in tissue engineering.
Perfluorophenyl methacrylate (pp‐PFM) was plasma‐polymerized using low duty cycle conditions to yield a surface rich in active ester groups. The reactivity of this surface towards different primary amines was investigated using infrared reflection absorption spectroscopy (IRRAS) and micromechanical cantilever (MC) sensors. While IRRAS provided information on the chemistry, the MC sensors technique gave insights into volume changes induced by the reactions of the polymer film. We found that the volume change upon reaction was different for each of the amines studied and correlated this to the ability of the amines to diffuse into the polymer matrix. The changes observed can be related to reactions occurring either at the liquid–solid interface or to reactions occurring within the matrix of the polymer and appear to be related to the chemical structure of the amines.
Flexible thin film solar cells are an alternative to both utility-scale and building integrated photovoltaic installations. The fabrication of these devices over electrically conducting low-cost foils requires the deposition of dielectric barrier layers to flatten the substrate surface, provide electrical isolation between the substrate and the device, and avoid the diffusion of metal impurities during the relatively high temperatures required to deposit the rest of the solar cell device layers. The typical roughness of low-cost stainless-steel foils is in the hundred-nanometer range, which is comparable or larger than the thin film layers comprising the device and this may result in electrical shunts that decrease solar cell performance. This manuscript assesses the properties of different single-layer and bilayer structures containing ceramics inks formulations based on Al2O3, AlN, or Si3N4 nanoparticles and deposited over stainless-steel foils using a rotogravure printing process. The best control of the substrate roughness was achieved for bilayers of Al2O3 or AlN with mixed particle size, which reduced the roughness and prevented the diffusion of metals impurities but AlN bilayers exhibited as well the best electrical insulation properties.
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