SILICON-SUBSTRATE MICROELECTRODE ARRAYS FOR PARALLEL RECORDING OF NEURAL ACTIVITY IN PERIPHERAL AND CRANIAL NERVES

A new process for the fabrication of regeneration microelectrode array s for peripheral and cranial nerve applications is presented. This typ e of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafte r held fixed with respect to the microelectrodes. The process describe d is designed for compatibility with industry-standard CMOS or BiCMOS processes (it does not involve high-temperature process steps nor heav ily-doped etch-stop layers), and provides a thin membrane for the via holes, surrounded by a thick silicon supporting rim. Many basic questi ons remain regarding the optimum via hole and microelectrode geometrie s in terms of both biological and electrical performance of the implan ts, and therefore passive versions were fabricated as tools for addres sing these issues in on-going work. Versions of the devices were impla nted in the rat peroneal nerve and in the frog auditory nerve. In both cases, regeneration was verified histologically and it was observed t hat the regenerated nerves had reorganized into microfascicles contain ing both myelinated and unmyelinated axons and corresponding to the gr id pattern of the via holes. These microelectrode arrays were shown to allow the recording of action potential signals in both the periphera l and cranial nerve settings, from several microelectrodes in parallel .