Flexible Dry Electrodes for EMG Acquisition within Lower Extremity Prosthetic Sockets

Acquisition of surface electromyography (sEMG) from a person with an amputated lower extremity (LE) during prosthesis-assisted walking remains a significant challenge due to the dynamic nature of the gait cycle. Current solutions to sEMG-based neural control of active LE prostheses involve a combination of customized electrodes, prosthetic sockets, and liners. These technologies are generally: (i) incompatible with a subject's existing prosthetic socket and liners; (ii) uncomfortable to use; and (iii) expensive. This paper presents a flexible dry electrode design for sEMG acquisition within LE prosthetic sockets which seeks to address these issues. Design criteria and corresponding design decisions are explained and a proposed flexible electrode prototype is presented. Performances of the proposed electrode and commercial Ag/AgCl electrodes are compared in seated subjects without amputations. Quantitative analyses suggest comparable signal qualities for the proposed novel electrode and commercial electrodes. The proposed electrode is demonstrated in a subject with a unilateral transtibial amputation wearing her own liner, socket, and the portable sEMG processing platform in a preliminary standing and level ground walking study. Qualitative analyses suggest the feasibility of real-time sEMG data collection from load-bearing, ambulatory subjects.