Polymeric C-shaped cuff electrode for recording of peripheral nerve signal

We reported a polyimide-based C-shaped neural interface electrode to record peripheral nerve signal from the rat sciatic nerve. The neural interface electrode consisted of four recording probes protruded from the C-shaped frame, and two reference electrode sites on the C-shaped frame. Thanks to the unique bendable protruding structure of the recording probes, electrode sites were able to adapt to and maintain close contact to the nerve without restricting nerve movement. Gold, gold-carbon nanotube (CNT) composite, and platinum were chosen as the electrode materials. The electrodes were characterized by electrochemical impedance spectroscopy (EIS) analysis in phosphate buffer solution (PBS) (pH 7.4). The results showed that the gold-CNT electrode (area of 8500 μm²) had an average impedance of 11.1 kΩ, approximately 15-fold and 3-fold lower than gold and platinum, respectively. An in vivo nerve signal recording test was also performed using the three electrodes. The magnitude of the compound nerve action potentials (CNAPs), the latency of the onset and the duration of the CNAPs were measured and analyzed under various stimulus currents. The results of the CNAPs magnitude and the signal-to-noise ratio (SNR) indicated a proportional relationship to the stimulus current beyond the threshold current of 0.3 mA. Our electrode has the capability to measure nerve signals less than 5 μV.