Strain-Insensitive Elastic Surface Electromyographic (sEMG) Electrode for Efficient Recognition of Exercise Intensities

Abstract

Surface electromyography (sEMG) sensors are widely used in the fields of ergonomics, sports science, and medical research. However, current sEMG sensors cannot recognize the various exercise intensities efficiently because of the strain interference, low conductivity, and poor skin-conformability of their electrodes. Here, we present a highly conductive, strain-insensitive, and low electrode–skin impedance elastic sEMG electrode, which consists of a three-layered structure (polydimethylsiloxane/galinstan + polydimethylsiloxane/silver-coated nickel + polydimethylsiloxane). The bottom layer of the electrode consists of vertically conductive magnetic particle paths, which are insensitive to stretching strain, collect sEMG charge from human skin, and finally transfer it to processing circuits via an intermediate layer. Our skin-friendly electrode exhibits high conductivity (0.237 and 1.635 mΩ·cm resistivities in transverse and longitudinal directions, respectively), low electrode–skin impedance (47.23 kΩ at 150 Hz), excellent strain-insensitivity (10% change of electrode–skin impedance within the 0–25% strain range), high fatigue resistance (>1500 cycles), and good conformability with skin. During various exercise intensities, the signal-to-noise ratio (SNR) of our electrode increased by 22.53 dB, which is 206% and 330% more than that of traditional Ag/AgCl and copper electrode, respectively. The ability of our electrode to efficiently recognize various exercise intensities confirms its great application potential for the field of sports health.

Development and Characterization of Embroidery-Based Textile Electrodes for Surface EMG Detection

“…According to the number of lines of electrodes, the trend of fill < 3 lines < 1 line was followed. A previous study analyzing the effect of the electrode area on the impedance reported that the impedance decreased with increasing cross-sectional area, indicating an inversely proportional relationship [22,32]. This result was attributed to the area in contact with the skin also increasing due to the increase in the density and area of the conductive material in the electrode of the same size when the amount of conductive yarn was increased.…”

“…Generally, a higher skin-contact impedance leads to an increased impedance mismatch that reduces common-mode rejection and, hence the SNR (signal to noise ratio) [31,32]. Therefore, it is important to decrease and control the impedance to manufacture an electrode for bio-signals.…”

Application of Surface Electromyography in Exercise Fatigue: A Review

“…Electrical currents generated by muscle contractions can be monitored in the form of EMG signals and displayed on a computer ( Barszap et al, 2016 ). Bioelectricity is detectable when muscle contracts ( Tang et al, 2020 ). Electromyographic techniques are used in sports and rehabilitation accepted by researchers ( Cortez et al, 2017 ; Pakosz and Konieczny, 2020 ; Quittmann et al, 2020 ).…”

Liquid Metal Based Nano-Composites for Printable Stretchable Electronics

“…Researchers have found that liquid metals have characteristics relating to multiple external stimuli responses, such as temperature, mechanical force, chemical environment, electric field, dielectric field, magnetic field, and even light [ 5 ]. As a result of innovative design principles and processing methods, LM has successfully generated many application prospects, e.g., stretchable sensing systems [ 6 , 7 , 8 ], electrodes [ 9 , 10 ], actuators [ 11 , 12 ], thermoelectric wearables [ 13 ], and energy storage systems [ 14 , 15 ].…”