Evaluation of a Body-Conforming Electrode for Functional Ultrasound Compatible Electrical Stimulation

Functional electrical stimulation (FES) is a neurorehabilitation modality that helps improve the size and strength of atrophied muscles after paralysis and reduce spasticity. However, FES causes muscle fatigue, and monitoring the patient's response to avert muscle fatigue caused by FES becomes imperative. Ultrasound (US) imaging can elucidate valuable information about muscle thickness, stiffness, force, and fatigue in the muscles. However, if the FES electrodes do not match the acoustic properties of the surrounding tissues, it could result in the interference with other electronic devices, potentially affecting both US imaging and the performance of the FES system. This study evaluates a specially designed body-conforming FES customized electrode that is intended to be compatible with US. The electrode is made with silver-nanowires/ Polydimethylsiloxane (AgNW/PDMS). The performance of the body-conforming customized FES electrode was demonstrated in parallel to that of the commercial hydrogel electrode. Moreover, compatibility with US was established through tests employing a 3.5 MHz single-element US transducer. The customized FES electrode exhibited a comparably minor variance (< 8%) relative to the commercial hydrogel electrode.