Insulation of Carbon Nanotube Yarn Electrodes for Intrafascicular Neural Stimulation and Recording

The peripheral neural interfaces have been obtained great interests in recent decades. Design of electrodes implies a trade-off between selectivity and invasiveness. The ideal electrodes should achieve high selectivity with small invasiveness. Intrafascicular electrodes show a superior advantage on selectivity in comparison with extraneural electrodes, but chronic implantation cannot be accomplished for intraneural implants. The aim of this study was to further explore an intrafascicular electrode based on Carbon nanotube (CNT) yarns showing excellent biocompatibility, mechanical flexibility as well as electrochemical characteristics, and to preliminarily testify that CNT yarn electrodes could be used for neural recording and stimulation. Here we explored two kinds of technologies to insulate CNT yarns, including Teflon and C-Parylene (PC) coating. Then the electrodes were implanted into the rats' tibial nerve, and the exposed part inside the nerve was considered as the recording and/or stimulation sites. We found that the impedance after PC coating did not increase dramatically as that for Teflon coating. Therefore, we finally chose PC material as insulation coating. The electrophysiological experimental results indicated that CNT yarn electrodes were allowed to record sensory activities while stimulating the distal end of the tibial nerve in rats. Hopefully our study will support the widespread applications of CNT yarn electrodes for further studies in neuroscience fields.