Amorphous Silicon Carbide Neural Interface Devices

Microelectrode arrays (MEAs) are used in acquisition of neural activity for restoring communication and controlling movement of paralyzed or prosthetic limbs. In addition, neuroscientists need reliable recording probes, which can provide large numbers of unit activity with high signal-to-noise ratio (SNR) over long periods. Compared to brain surface electrodes, penetrating intracortical MEAs offer higher resolution of neural activity at the scale of single neurons to enhance neural signal decoding. Of significant interest to neural engineers is the development of MEAs with a high number of recording sites, reduced foreign body response, longer shanks from 2 mm to 1 cm for shallow and deep recording, respectively. Laminar silicon- based probes partially overcome the limitation of the high number of recording sites by increasing the number of recording channels along the shank to allow recording from different depths along one cortical column. Despite the success in increasing the number of recording channels, current silicon-based intracortical MEAs, exhibit degraded performance 3-6 months after implantation. To improve the longevity of MEAs, our group is investigating the use of a novel material, amorphous silicon carbide (a-SiC), as a substrate for neural probe fabrication. This dielectric material has the required mechanical and electrical properties (high stiffness and resistivity), chemical inertness, and compatible with thin-film fabrication methods for MEA applications. Using a-SiC, we have developed ultramicroelectrode arrays (UMEAs) with 16 to 32 electrode sites with scalable shank dimensions ranging from 500 μm to 2 mm for shallow and up to 10 mm for deep recording. We hypothesized that a-SiC based MEAs will provide electrochemical stability and enable reliable neural recording and stimulation. Our ultimate goal was to develop high density (a-SiC)-based UMEAs (increased number of electrode channels per unit area) and high spatial selectivity for neural recording and stimulation while maintaining ultramicroelectrode dimensions. This dissertation addresses the fabrication and development of these devices.