A microassembled low-profile three-dimensional microelectrode array for neural prosthesis applications

This paper describes the design and microassembly process of a low-profile 3-D microelectrode array for mapping the functional organization of targeted areas of the central nervous system and for possible application in neural prostheses. The array consists of multiple planar complimentary metal-oxide-semiconductor stimulating probes and 3-D assembly components. Parylene-encapsulated gold beams supported by etch-stopped silicon braces allow the backends of the probes to be folded over to reduce the height of the array above the cortical surface. A process permitting parylene to be used at wafer level with bulk-silicon wet release has been reported. Spacers are used to fix the microassembled probes in position and are equipped with interlocking structures to facilitate the assembly process and increase yield. Four-probe 256-site 3-D arrays operate from 5 V with an average per-channel power dissipation of 97 mu W at full range stimulation with pulse widths of 100 mu s at 500-Hz frequency. Thirty-two sites can be stimulated simultaneously with maximum currents of 127 mu A and a current resolution of 1 mu A. The microassembly techniques allow a variety of 3-D microstructures to be created from planar components.