Application of SU-8 as the insulator toward a novel planar microelectrode array for extracellular neural recording

In this research work the design and prototyping of novel planar microelectrode arrays that utilize SU-8 as the insulating material is presented. The microelectrode arrays are fabricated as a key component of an extracellular neural recording system comprising a full customized CMOS analog neural signal readout ASIC for neural signal processing and an 8 by 8 microelectrode array for acquiring the action potentials by means of capacitive coupling. The prototyped multi-channel mixed signal fully-customized CMOS biosensor analog front-end serves as the neural signal readout circuitry, which is comprised of analog signal buffers, high gain amplifier and control/interface. The concept of using epoxy-based photoresist SU-8 as the insulator instead of the conventional silicon nitride or silicon dioxide is due to the existence of nonuniformities and pinholes in the nitride layer. This pinhole free biocompatible SU-8 greatly improves the performance of the insulation layer and provides an approach for the construction of low cost disposable microelectrode arrays.