Electrode characterization for use in a Regenerative Peripheral Nerve Interface

Abstract

The Regenerative Peripheral Nerve Interface (RPNI) has the capacity to provide fine motor control and sensory feedback to advanced robotic limbs by interfacing directly with the residual extremity of an amputee. RPNI electrodes must provide high fidelity stimulation and recording capability without compromising biological integrity at the electrode-tissue interface. To identify an optimal electrode for utilization with the RPNI, multiple electrode types were characterized in vitro and in vivo. Electrochemical impedance spectroscopy, cyclic voltammetry, and in vivo electromyography (EMG) were performed. All electrodes demonstrated favorable performance. The platinum (Pt) needle and pacemaker lead exhibited lower impedance and higher charge storage capacity values during in vitro testing. Electrophysiological testing revealed that at threshold stimulation, the Pt needle and stainless steel (SS) pad electrodes recorded a larger signal of interest relative to the other experimental electrodes, while the SS pad, flexible microwire, and pacemaker lead demonstrated a larger relative signal at maximal stimulation. Several electrodes which exhibited favorable performance were identified for use in the RPNI.