Sputtered iridium oxide modified flexible parylene microelectrodes array for electrical recording and stimulation of muscles

• A flexible parylene microelectrodes array modified by sputtered iridium oxide film (SIROF) for electrical recording and stimulation has been successfully fabricated.
• The SIROF markedly reduces the impedance and increases the charge storage capacity (CSC) of the microelectrode.
• The averaged thermal noise amplitude for SIROF recording sites is 3.83 ± 1.02 μV which is only 10.4% of the Au recording sites as 36.87 ± 21.39 μV.
• The maximum SNR of SIROF microelectrode and bare gold microelectrode could reach 29.27 dB and 0.47 dB, respectively.
• The preliminary animal experiments validated the feasibility of SIROF microelectrode in electrical stimulation based on the three-axis force responses and torque responses.

Here we report the flexible parylene microelectrodes array modified by sputtered iridium oxide film (SIROF) for electrical recording and stimulation of muscles. By using an optimal deposition condition of SIROF that the oxygen flow is 25 sccm and the sputtering pressure is 4.2 Pa, the SIROF modified flexible parylene microelectrodes are successfully fabricated. Combing with the advantages of parylene and SIROF, the microelectrodes show excited mechanical and electrochemical properties, which are capable of electrical recording and stimulation with remarkable performances. Based on experimental results and theoretical calculation, the averaged thermal noise amplitude for SIROF recording sites is 3.83 ± 1.02 μV which is only 10.4% of the Au recording sites as 36.87 ± 21.39 μV. These features increased the signal-to-noise ratios (SNR) of the recorded electromyography (EMG). The maximum SNR of SIROF microelectrode and bare gold microelectrode could reach 29.27 dB and 0.47 dB, respectively. Furthermore, the SIROF microelectrode could safely deliver the stimulation current as high as 400 μA which resulted a large charge injection capacity as 3.54 mC/cm2. The preliminary animal experiments also validated the feasibility of SIROF microelectrodes in electrical stimulation.