Potential and Current Density Distributions at Electrodes Intended for Bipolar Patterning

Christian Ulrich, Olof Andersson, Leif Nyholm, Fredrik Björefors

This paper deals with the use of reaction gradients on bipolar electrodes for the patterning of electrode surfaces.More specifically, the potential and current density distributions in two setups containing bipolar electrodes were investigated to optimize and design specific gradient geometries. Comparisons with simulations based on simple conductivity models showed a good qualitative agreement, demonstrating that these models could be used to predict bipolar behavior in more complex setups. In conjunction with imaging surface plasmon resonance(iSPR) experiments, the reaction gradients on bipolar electrodes could further be visualized. It was, for example,found that the gradient in potential difference was approximately linearly distributed in the center of the bipolar electrode and that these potential differences could be determined using an ordinary Ag/AgCl reference electrode.The present results thus provide a better understanding of the processes relevant for bipolar patterning.This approach was finally used to generate a circular gradient region in a self-assembled monolayer, thereby showing the possibilities to create interesting substrates for biosensors and microarray applications.