Flexible Neural Interfaces Based on 3D PEDOT:PSS Micropillar Arrays

Multi-electrode arrays with 3D micropillars allow the recording of electrophys-iological signals in vitro with higher precision and signal-to-noise ratio than planar arrays. This is the result of the tight interaction between the 3D elec-trode and the cell membrane. Most 3D electrodes are manufactured on rigid substrates and their integration on flexible substrates is largely unexplored. Here, a straightforward approach is presented for fabricating soft inter-faces featuring 3D poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) micropillars on a soft flexible substrate made of polydimethyl-siloxane (PDMS). Large-area isotropic arrays of PEDOT:PSS micropillars with tailored geometric area, surface properties, and electrochemical characteris-tics are fabricated via a combination of soft-lithography and electrodeposi-tion. A 60% increase in capacitance is achieved for high density micropillars compared to planar electrodes and this is found to be correlated with the increased electroactive surface area. Furthermore, 3D PEDOT:PSS micro-pillars support adhesion, growth and differentiation of SH-SY5Y cells, and influence the direction of neurite outgrowth. Finally, by virtue of their elas-ticity, soft micropillars act as excellent anchoring loci for elongating neurites, facilitating their bending and twisting around the micropillar, increasing the number of contact points between the cells and the electrode, a key require-ment to obtain high performance neural interfaces.