Fabrication and Investigation of Conducting Polymer Micro and Nano Structures for Bioelectronics Applications

Conducting polymers (CPs), especially poly(3,4-ethylenedioxythiophthene) (PEDOT) and poly(pyrrole) (PPy), are ideal materials for bioelectronics devices because of their biocompatibility, mechanical properties that are similar to those of biological structures, their ability to transduce signals through both ionic and electronic conductivity, and their facile and versatile fabrication routes. CPs have been shown to improve the electrical performance of neural recording/stimulation electrodes, deliver compounds to suppress unfavorable biological reactive responses, and enhance axon regeneration. CP structures have also been shown to create stable biocompatible actuators in the form of micro-robots and other controllable structures. However, much remains to be investigated with regard to CP micro and nano structures, especially those intended for bioelectronics applications. The purpose of this dissertation is to expand upon this knowledge with five novel investigations comprised of (1) explicitly determining the relationship between electrochemical deposition parameters and the resulting surface structure of PEDOT and PPy films doped with poly(styrene-sulfonate) (PSS), (2) investigating and comparing the ion exchange behavior and impact on surface roughness of PEDOT and PPy nanotubes as a function of voltage driven actuation, (3) fabrication of PPy microcups (MCs) with customizable geometries, and an investigation of the resulting electrode performance and drug release capabilities, (4) equivalent circuit modeling of PPy MCs electrodes to investigate the dependence of electrode impedance on the properties of the CP/electrolyte interface, and (5) development of a novel deposition methodology to create customizable linear and non-linear roughness gradients of PPy films for axon guidance applications. It was found that for both PEDOT and PPy, the surface topography (especially surface roughness) can be controlled through careful selection of deposition time and current/potential during electrochemical deposition. This allows for the tuning of the resultant impedance and charge storage capacity of bioelectronics devices. It also allows for controllable fabrication of novel CP structures including microcups and nanofibers. These structures were employed for the sustained release of dexamethasone, and an in-depth study of the actuation behavior of both CPs. Finally, a novel fabrication route allows for the reproducible deposition of nanostructured PPy gradients with arbitrary shapes for future applications in controlling nerve regeneration behavior.Biomedical Engineering, Department o