Implanted electronic circuitry must function reliably for the lifetime of the recipient. Experience in the pacemaker industry suggests that hermetic packaging of electronic components is needed to achieve such reliability. The goal of this project is to develop hermetic packaging techniques that can be used to protect the electronic circuitry needed for telemetry and powering of microelectrodes, as might be used in the central nervous system, and macroelectrodes, such as cuff or intramuscular electrodes for peripheral prostheses. Compared to cardiac pacemakers, the required packages are 100 to 1,000 times smaller in volume and require a greater number of feedthroughs. Research has demonstrated that feedthroughs can be fabricated on planar silicon substrates at a linear density of a feedthrough every 4 microns using batch fabrication techniques. Several of these feedthroughs can be tied in parallel if a low resistance path is required. A glass capsule has been anodically bonded to the silicon base to produce a microhermetic package. In-vitro testing of these packages at accelerated temperatures suggests that they will function reliably at body temperature for over 40 years. Hermetic packages for specific neural prosthesis applications will now be designed and developed. The mean-time-to-failure for the packages will be determined by accelerated testing. In-vivo testing of the packages will be conducted using hermetic packages that include a telemetry system and moisture sensors to permit monitoring of package integrity in an animal model. Based on the results of accelerated and in-vivo testing, failure mechanisms for hermetic seals will be studied. New materials and process methods will be devised to eliminate these failures. The investigators will also cooperate with other neural prosthesis investigators to develop complete implant systems for specific applications utilizing either micro or macroelectrodes.
