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Patricia Jastrzebska-Perfec1 Georgios Spyropoulos1 Jennifer Gelinas1 Dion Khodagholy1

1, Columbia University, New York, New York, United States

Anisotropic conductive films, which consist of electrically conductive particles dispersed in nonconductive media, are increasingly being applied to establish high-density electrical bonds between electronic boards and chips. However, current anisotropic composites utilize metallic particles, often nickel and epoxy-based media, that require high thermocompression energy for bonding. Therefore, they have limited applicability in thin-film, conformable, and plastic-based devices that are used in bioelectronic applications. Furthermore, these materials are not biocompatible, significantly limiting their use in biological systems. We hypothesized that replacing the metallic particles with conducting polymer particles combined with a biocompatible nonconducting matrix would address this limitation. We developed a novel anisotropic conducting polymer (ACP) consisting of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) conducting polymer particles dispersed in a matrix of crosslinked chitosan (CS). To determine the permeability of PEDOT:PSS to CS, we characterized the resistances of thin CS-based films sandwiched with PEDOT:PSS and gold pads. We investigated the particle size, structure, density and distribution of pure PEDOT:PSS particles and PEDOT:PSS-coated CS particles. The anisotropy was defined by the ratio of horizontal and vertical impedance between interconnects. We benchmarked the anisotropy of the developed ACPs by geometrically varying an array of gold electrodes. The final ACP, which was created at 70°C with minimal pressure, yielded anisotropy of 105-106. The ACP was then used to maintain precise connections between a high density conformable implantable neural probe and back-end electronics. It enabled complete chronic in vivoimplantation of these electronics with minimal encapsulation layers, highlighting applicability for use in bioelectronic and clinical devices

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