Novel wearable EMG sensors based on nanowire technology

Wearable electrodes made of silver nanowires (AgNWs) have demonstrated great potential for sensing a variety of physical and physiological signals. This paper aimed to study the feasibility of AgNWs electrodes for measuring surface electromyographic (sEMG) signals. One human subject was recruited and instructed to perform wrist extension repetitively or to produce no movement in the experiment. sEMG signals were collected from the right extensor digitorum communis of the human subject by an AgNWs electrode and a commercially available Ag/AgCl wet sEMG electrode, separately. The quality of recorded sEMG in time and frequency domains was compared between the two types of electrodes. The results showed that the sEMG signals recorded by the AgNW electrode were comparable with that by the Ag/AgCl electrode. Since the dry AgNWs electrodes are flexible, wearable, and potentially robust for daily use, novel AgNW-based EMG electrodes are promising for many biomedical applications, such as myoelectric control of artificial limbs.

1. Introduction

Surface electromyography (sEMG) is a technique for measuring electrical potentials generated by active motor units, comprising groups of muscle fibers [1]. sEMG can be detected by electrodes placed on the skin surface during muscle contractions, and have been used in various applications, such as diagnosis of neuromuscular disorders, evaluations of muscle fatigue, and control inputs for powered prosthetic/orthotic devices [2]–[5]. Two types of surface electrodes are commonly in use: wet and dry electrodes. Conventional silver/silver chloride (Ag/AgCI) wet electrode used electrolytic gel as a chemical interface between the skin and the conductive layer of electrode to measure good-quality sEMG signals. A dry electrode, on the other hand, measures sEMG signals via direct skin contact without gel. Commonly-used dry sEMG electrodes were made of noble metals (e.g. platinum, gold, or silver), carbon, or sintered Ag/AgCI [6].