Mechanical and electrical stability of parylene-based platinum-black coated wire microelectrode for implantable applications

Abstract

In this paper, a parylene-based platinum-black coated wire microelectrode with multi-electrode sites for neuromuscular stimulation was fabricated. The electrodes with tunable electrode site position, quantity, and width will achieve multi-stimulation during functional electrical stimulation. The platinum-black coating was electroplated on electrode sites by applying a current pulse train in chloroplatinic acid solution (H2PtCl6) under ultrasonic bath, which contributed to achieve excellent mechanical and electrical stability of the microelectrode. After electroplating, the 90 % of impedance reduction and 13 times of cathodic charge storage capacity increase were achieved. Finally, the mechanical and electrochemical stability test, the passive soaking test, and the bending test were performed. The results showed that the platinum-black coated wire microelectrode had good stability after 5 min of ultrasonic vibration and 122 h of current pulses stimulation. After soaking in 0.9 % saline solution at 87 °C for 8 months, the average impedance at 1 kHz just increased by 1.6 kΩ. The bending test (with maximum bending angle of 90°) also showed that there was a little change in the electrochemical characteristics of the electrode. This parylene-based platinum-black coated wire microelectrode will be promising for facial prosthesis applications.