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 non-invasive wet and dry contact electrodes are impractical to telehealth applications. Existing capacitive electromyography (cEMG) measurement systems presented by various research groups are typically designed with multi-stage analog front-end circuitry and complex data acquisition (DAQ) systems. This paper 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 data (MASq) signal processing techniques. The proposed flexible capacitive biomedical sensor can be insulated by porous and non-porous 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.