Glassy Carbon μECoG Electrode Array for In-vivo Sensing and Stimulation

Abstract

Current neural-prosthetic devices fail to provide high-quality signals with good resolution for long periods of time. This is due to changes in the device-tissue interface, mostly in the form of device degradation and macrophage/microglia encapsulation. A novel material for neural interfaces, glassy carbon (GC) provides tunable stiffness and impedance, reducing mechanical strain on brain tissue and offering optimized charge injection capabilities. GC is often used in electrochemical reactions due to its high stability and resistance to corrosion. Holes were also integrated into the design to allow astrocytes to form around the device, securing it in place for stable recording locations. We present results from in-vivo testing of a fully customized neural device made of GC μECoG electrodes and metal traces, supported on a flexible, polyimide substrate. The devices were integrated into a custom PCB using a low profile connector. They were then implanted subdurally into the brains of rats. During implant, complex impedance was measured multiple times weekly as an indicator of changes in the tissue-device interface. Stimulation effectiveness was determined by testing for evoked potentials. Animals were implanted with electrodes for 5-6 weeks, after which the animals were sacrificed for histological analysis. Our results led us toward several design modifica- tions before we had a fully functioning device. We also found that the holes performed as hypothesized and allowed for astrocytes to anchor the device.