Micromachined, silicon based electrode arrays for electrical stimulation of or recording from cerebral cortex

Previous work has indicated that electrical stimulation of the visual cortex via penetrating electrodes may be a viable approach to providing a functional visual sense for the blind. Key to this concept is the development of a three-dimensional microstructure that contains an array of electrodes intended to be inserted into the visual cortex. Such a structure has been created, with electrodes designed to penetrate 1.5 mm into the visual cortex. The array consists of 100 needles, each of which is 1.5 mm long and 0.08 mm on a side at its base. The needles, which emerge from a 0.2 mm thick, 4.2 mm×4.2 mm silicon substrate, have center to center spacings of 0.4 mm. The fabrication methodologies consist of preliminary shaping with a computer-controlled diamond dicing saw and final shaping and polishing with a two-step chemical etching process. Preliminary work to investigate the biocompatibility of these silicon structures in cortical tissues indicates that the cortex tolerates implantation and the materials used in the arrays very well