Electrode insertion success, with focus on geometric and material considerations

Current Micro Electrode Arrays used in the field of neural prosthetics are typically composed of an electrode plus structural support. These chronically implanted combinations can cause persistent scarring which can extend out to 250μm in radius from a typical 15μm width silicon shank. This scarring, along with localized neuronal death and gliosis, makes detecting neuronal activity very difficult and can decrease the overall performance of an electrode. The goal of our study was to analyze different electrode designs, focusing on material selection and their geometric stability, which reduce or eliminate scarring and gliosis effects. This project specifically focused on the design consideration needed to develop an electrode that would successfully insert into the brain within certain failure conditions. Using previously acquired data of carbon fiber electrode insertions (Patel et al. 2015) an experimental model was developed to predict the insertion success of different electrode materials and geometries. Once our model for electrode development and failure analysis was complete, we then moved to the development of a brain phantom that mimics the brain’s elastic modulus and replicates previous carbon fiber insertion tests. Once the brain phantom was validated with reference values, insertion experiments with different electrode materials were conducted. We completed a full analysis on insertion performance and characterized the best electrode designs using simple geometries for the greatest insertion success. Our future work will consist of electrode support structure analysis for softer electrode materials and in vivo brain insertion experiments for further validation.