A novel and simple process was proposed to fabricate a parylene-based platinum-black coated wire microelectrode for orbicularis oculi muscle electrical stimulation. Compared with conventional microelectrodes, wire microelectrodes would enable smaller wounds, increased ease of implantation, and improved cosmesis. Meanwhile, the circumferential electrode sites of this wire microelectrode fabricated by lift-off process would contribute to fully contact with tissue and reduction of electrode-tissue interface impedance. The width and the amount of electrode sites could be decided by the thickness and the amount of sacrificial layer, respectively. The platinum-black coatings were electroplated on electrode sites by applying a current pulse train in chloroplatinic acid solution with ultrasonic bath for further electrode-tissue interface impedance reduction and good mechanical stability of coatings. Electrode impedance at 1 kHz has been significantly reduced by 90%, and the cathodic charge storage capacity (CSCc) has been increased by 13 times. In addition, hematoxylin-eosin (HE) staining section of muscle demonstrated the good biocompatibility of this electroplated platinum-black. By applying a charge imbalanced biphasic stimulation waveform for orbicularis oculi muscle stimulation, the rabbits with facial paralysis rehabilitated the function of closing eyes. This kind of microelectrode will be promising for neuromuscular applications.

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 H 2 PtCl 6 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.

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