We electroplated Pt black on the Pt microelectrodes to improve the quality of their recording. The Pt black plating solution contained 3% hexachloroplatinic acid hydrate (520896-5G, Sigma-Aldrich, USA), 0.025% HCl (4090-4400, DAEJUNG, South Korea), and 0.025% lead acetate (316512-5G, Sigma-Aldrich, USA) in deionized water17 (link). The tip of the neural probe was immersed in the plating solution with a reference electrode (Ag/AgCl wire) and a counter electrode (Pt wire). The Pt microelectrodes were electroplated selectively by applying the electrical potential (–0.2 V, 35 s) through a potentiostat (PalmSens3, PalmSens, Netherlands).
To measure the impedance of the Pt black microelectrodes, we immersed the tip of the neural probe in 0.1 M phosphate-buffered saline solution (21-040-CV, CORNING, USA) with the reference electrode (CHI 151, CH Instruments, Inc., Austin, TX, USA). The impedances of the 16 microelectrodes were measured by a frequency sweep mode (10 Hz–10 kHz) using an impedance analyzer (nanoZ, Neuralynx, Bozeman, Montana, USA).
To measure the impedance of the Pt black microelectrodes, we immersed the tip of the neural probe in 0.1 M phosphate-buffered saline solution (21-040-CV, CORNING, USA) with the reference electrode (CHI 151, CH Instruments, Inc., Austin, TX, USA). The impedances of the 16 microelectrodes were measured by a frequency sweep mode (10 Hz–10 kHz) using an impedance analyzer (nanoZ, Neuralynx, Bozeman, Montana, USA).