Cell migrations on substrates are important in diverse processes such as wound healing, embryogenesis, and pathologies like cancer metastasis. An understanding of the cellular mechanobiology during migration requires development of suitable engineering platforms to better represent the anisotropic in vivo cellular environment and measure traction forces due to cell adhesion. We fabricated a custom elastomeric micropillar array detector (mPAD), comprised of alternate ridge and pillar topographical features, using a lithographic fabrication method that creates an anisotropic microenvironment and also permits the measurement of traction forces. We used the finite element method to compare predictions of calculated tractions for pillar geometries with different aspect ratios using linear and nonlinear constitutive models. These simulations showed the importance of pillar aspect ratios and constitutive models in computing resulting tractions. We cultured 3T3 fibroblasts on the engineered mPAD and characterized cellular migrations over a three hour period. Our results show highly elongated cellular and nuclear morphologies on the mPAD substrates as compared to cells cultured on control elastomeric substrates. Cells on mPADs demonstrated persistent directional motion along ridges as compared to random movements on control substrates. These results showed the importance of substrate anisotropy in the alignment of fibroblasts on mPAD. We also measured differences in the cellular tractions along the length of the cell on mPAD substrates. Engineered mPADs are hence useful in directing cellular motions and in delineating mechanobiological processes during adhesion and migration.

5Conducting polymers combine the advantages of metal conductivity with ease in processing and biocompatibility; making them extremely versatile for biosensor and tissue engineering applications. However, the inherent brittle property of conducting polymers limits their direct use in such applications which generally warrant soft and flexible material responses. Addition of fillers increases the material compliance, but is achieved at the cost of reduced electrical conductivity. To retain suitable conductivity 10 without compromising the mechanical properties, we fabricate an electroactive blend (dPEDOT) using low grade PEDOT:PSS as the base conducting polymer with polyvinyl alcohol and glycerol as dopants. Bulk dPEDOT films show a thermally stable response till 110 ºC with over seven fold increase in room temperature conductivity as compared to 0.002 Scm -1 for pristine PEDOT:PSS. We characterized the nonlinear stress-strain response of dPEDOT, well described using a Mooney-Rivlin hyperelastic model, 15 with ductility of ~five times its original length and report elastomer-like moduli. Dynamic mechanical analysis shows constant storage moduli over a large range of frequencies with corresponding linear increase in tan (δ) values. We relate the enhanced performance of dPEDOT with the underlying structural constituents using FTIR and AFM microscopy. These data demonstrate specific interactions between individual components of dPEDOT, their effect on surface topography and material properties. Finally, 20 we show biocompatibility of dPEDOT using fibroblasts that have comparable cell morphologies and viability as control; making it attractive as a biomaterial. 65 Hookean (NH) form of hyperelastic constitutive model, given by = ( 1 2 + 2 2 + 3 2 − 3) where ; = 1: 3 are stretches in the principal directions respectively. These experimental data