Novel Neural Interface for Vision Prosthesis Electrodes: Improving Electrical and Mechanical Properties through Layering

The rationale for this research is to address the problem of long-term function of neural interfaces. The approach followed is surface modification of traditional electrode materials using electrically conducting polymers and biological factors with the aim of establishing a functional neural interface between stimulating electrode and neural tissue. Polypyrrole films can be relatively flexible but have insufficient electrochemical stability to be used in long-term neuroprosthetic implants. Polyethylene dioxythiophene films have good electrochemical stability but are very difficult to handle and are subject to failure by brittle fracture. The specific aim of this study was to evaluate layering of different conductive polymers for optimization of film properties. Layering of the films was shown to produce composite materials with properties superior to those of the individual components. Conductivity of the layered film was between that of each film alone and mechanical stability was similar to the more flexible PPy films. Neurite outgrowth was improved on the layered film. These layered films show promise as conductive coatings for electrodes.