Integrated electrode and high density feedthrough system for chip-scale implantable devices.

High density feedthroughs have been developed which allow for the integration of chip-scale features and electrode arrays with up to 1141 stimulating sites to be located on a single implantable package. This layered technology displays hermetic properties and can be produced from as little as two laminated 200 μm thick alumina sheets. It can also be expanded to a greater number of layers to allow flexible routing to integrated electronics. The microelectrodes, which are produced from sintered platinum (Pt) particulate, have high charge injection capacity as a result of a porous surface morphology. Despite their inherent porosity the electrodes are electrically stable following more than 1.8 billion stimulation pulses delivered at clinically relevant levels. The ceramic-Pt constructs are also shown to have acceptable biological properties, causing no cell growth inhibition using standard leachant assays and support neural cell survival and differentiation under both passive conditions and active electrical stimulation.