Parylene-based implantable Pt-black coated flexible 3-D hemispherical microelectrode arrays for improved neural interfaces

In implantable medical systems, low-impedance electrode-tissue interface is important for maintaining signal quality for recording and effective charge transfer for stimulation. In this paper, we propose a novel hemispherical biocompatible and flexible microelectrode arrays (MEAs) which were fabricated by the process of micro electrical mechanical system (MEMS). Compared with conventional planar microelectrodes, the interface impedance of hemispherical microelectrodes decreased due to their increased surface area. Parylene C thin film with good biocompatibility and flexibility was chemical vapor deposited as packaging material for decreasing nerve tissue damage. Pt-black coatings were electroplated by applying current pulses in H2PtCl6 solution on electrode sites for the further decrease of interface impedance. Moreover, the geometrical and electrical properties of these MEAs were demonstrated by using a scanning electron microscope (SEM) and an electrochemical workstation. Experimental results showed that the interface impedance decreased by about 34% compared with conventional planar microelectrodes, and significantly decreased by 84% with Pt-black coatings on electrode sites compared with those uncoated microelectrodes.