A Versatile and Wireless Multichannel Capacitive EMG Measurement System for Digital Healthcare

Transforming existing electromyography (EMG) measurement system into portable and wearable devices is key to fuel the revolution of digital healthcare and rehabilitation. Conventional EMG measurement systems that rely on invasive needle electrodes and noninvasive wet and dry contact electrodes are impractical to telehealth applications. Existing capacitive EMG (cEMG) measurement systems presented by various research groups are typically designed with multistage analog front-end circuitry and complex data acquisition (DAQ) systems. This article proposed a simple and versatile multichannel wireless cEMG measurement system. It consists of flexible cEMG biomedical sensors, a low-noise wireless DAQ module, and a moving average of the squared (MASq) data signal processing techniques. The proposed flexible capacitive biomedical sensor can be insulated by porous and nonporous materials. Only two electrodes are needed to acquire raw EMG signals while achieving low-common-mode noise. Overall, the system achieves a high-mean pulse signal-to-noise ratio (PSNR) of 13.6 (polyimide film) and 8.3 (micropore). It recorded a linear correlation between the mean root-mean-square (RMS) of the MASq data and muscle strength with a step size of 1 kg. The total power consumption of this system is 41 mW with five EMG input channels, averaging 8 mW each. This low-noise and low-power consumption characteristic is ideal for battery-based wearable devices.