Advancing Bipolar Electrochemistry for Targeted Deposition of Biocompatible Polymers in Electrolyte-Free Solutions via Finite Element Modeling

Abstract

The spatially controlled, template-free, deposition of electroactive and biocompatible materials on 3D objects is of great interest for wireless cell stimulation intended for diverse applications ranging from electroceuticals to advanced sensor development. Bipolar electrochemistry provides the possibility of depositing electrically conducting polymers controlled through the (shaped) electric field distribution. A second advantage is that electrochemistry can be performed in electrolyte-free media potentially removing the “interfering” effect of added electrolyte. Here, poly(3,4-ethylenedioxythiophene) (PEDOT) films have been deposited on bipolar electrodes directly in ultrapure water. Significantly, the deposition patterns cannot be fully explained using a linear change in the solution-phase potential, which is a common assumption for bipolar electrochemical systems. 3D finite element modeling and diffusive mass transport considerations have been combined to map the electric field distribution in this very low conductivity medium and demonstrate that homogenous rather than heterogeneous electron transfer is likely to play an important role in polymer deposition. Moreover, modeling predictions were compared to electrochemical impedance and cyclic voltammetry results and non-linear behaviours qualitatively matched, through film capacitances, and deposition patterns. The proposed framework opens up significant opportunities for the template-free deposition of various electroactive materials on bipolar electrodes in low-conductivity solutions.