Fabrication of All-Silicon Carbide Neural Interfaces

Abstract

A significant and recognized problem in implantable neural recording and stimulation probes is operational lifetime. It is well known that both electrophysiological recording and, to a lesser extent, stimulation probes suffer severe performance degradation over periods ranging from months to a few years. Performance degradation of implantable probes arises due to a number of factors, including systemic host response, glial scarring, cellular responses to non-inert materials and, importantly, probe material degradation and delamination. SiC has superior chemical inertness and molecule barrier properties that result in insulation endurance for long term applications in bodily fluids. We present a microfabrication process that employs both insulating and conducting silicon carbide thin films to produce a novel type of implantable neural probes which present no heterogenous material interfaces to the biological environment. The exterior of our devices is composed of seamless transitions between doped and insulating SiC, completely encapsulating metal traces necessary to reduce track resistivity. The fabrication process is specifically designed such that the only interfaces presented to the extracellular fluid are made entirely from SiC, thus rendering these arrays very resistant to long-term delamination and interface failure. This process presents an important path towards neural implants for truly chronic applications; the fabrication method can be used for other neural probes.