Electrical Impedance Spectroscopy of Radiofrequency Electrodes for Functional Electrical Stimulation in Patients with Spinal Cord Injury

Functional electrical stimulation (FES) is a technology utilized to attempt to restore motor control in patients affected with paralysis, usually through techniques like intraspinal microstimulation (ISMS). FES uses a surface electrode to delivery extremely small to the target muscles that stimulate their movement and improve signaling within the neighboring nerves. This project sought to measure the impedance of an electrode used for FES in order to characterize other neural structures involved in the electrical impulse transmission process, either through the use of components added to the electrode or through the combination of multiple impedance readings. The electrode used in the present study was composed of 15 microelectrodes, which were fully characterized through electrochemical impedance spectroscopy to analyze the impedance profile with change in frequency. The data points obtained from the microelectrodes were then averaged in order to obtain a larger picture of the impedance of the general electrode. As expected, the impedance of the microelectrodes decreased as frequency increased. The average impedance of a microelectrode at a frequency of 1 kHz was found to be 50 k, although high variance in the data requires further testing to be done to verify the validity of the values that were found.