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We have designed, fabricated, calibrated and tested actuators for shear characterization to assess microscale shear properties of soft substrates. Here we demonstrate characterization of dry silicone and hydrated polyethelyne glycol. Microscale tools, including atomic force microscopes and nanoindenters, often have limited functionality in hydrated environments. While electrostatic comb-drive actuators are particularly susceptible to moisture damage, through chemical vapor deposition of hexamethyldisiloxane, we increase the hydrophobicity of our electrostatic devices to a water contact angle 90 ± 3°. With this technique we determine the effective shear stiffness of both dry and hydrated samples for a range of soft substrates. Using computational and analytical models, we compare our empirically determined effective shear stiffness with existing characterization methods, rheology and nanoindentation, for samples with shear moduli ranging from 5-320 kPa. This work introduces a new approach for microscale assessment of synthetic materials that can be used on biological materials for basic and applied biomaterials research.

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Transparent conductive films have become a ubiquitous component of electronic devices ranging from capacitive touch screens in smartphones, tablets, and larger display devices to transparent electrodes in organic light emitting diodes and photovoltaic cells. Indium Tin Oxide (ITO) is the most established transparent conductive film in the market, but has inherent drawbacks because it is a brittle ceramic deposited on plastic. Carestream has developed a silver nanowire transparent conductive film, FLEXX™, that is solution-coated in a continuous roll-to-roll process. For various alternatives to ITO, one of the key potential challenges is in providing sufficient environmental stability needed to ensure a robust product. This paper elucidates the qualification of silver nanowire transparent conductors into touch panel environments that include high temperature, high humidity, exposure to visible and ultraviolet light, thermal cycling, nonoperating thermal shock, and electrolytic electromigration test conditions. For the first time it is shown that silver nanowire transparent conductors can survive all such environments and are suitable for manufacturing scale-up into commercial products.978-1-4799-5622-7/$31.00 ©2014 IEEE