In the current state of the art in wearable technology, there is a limited array of biomonitoring devices available to record in-home biopotentials such as electromyography (EMG), a key metric in assessing motor function and motor activity. Of the devices available for commercial use, electrode types are often limited to conventional adhesive-based single-use wet electrodes, requiring users to place the electrodes individually. This work describes the development of EMG armbands with printed electrodes for the Bluetooth Electromyography Stroke Therapeutic (BEST) system, an in-home therapeutic system featuring a wearable muscle-sensing device and user-friendly mobile biofeedback application to improve the daily living of neuro-compromised individuals.
The armbands are developed via screen-printing and heat lamination techniques to embed Ag/AgCl electrodes onto the textile, allowing for accurate and efficient monitoring of muscle activity. We controlled electrode diameters and contact pressure with different armband sizes to find optimum conditions for higher signal quality. The integration of printed electrodes into the design of comfortable, wearable, and reusable EMG armbands represents a significant advancement in the field of human motion monitoring, providing a cost-effective and user-friendly solution for capturing and analyzing muscle activity. Furthermore, we fitted the technology with Bluetooth Low Energy protocols to enable high-fidelity 24-bit signal transmission in real time. The participant completed three repeating trials performing a 3-second isometric grip hold at 25%, 50% and 75% of their maximum voluntary contraction with electrodes overlying their flexor digitorum. The EMG signals were collected at the sample rate of 2000 Hz. The collected signals were filtered from 10 to 250 Hz, Hilbert transformed and rectified. The data was then smoothed using a sliding window of 600 samples with an overlap of 20 samples. The signal-to-noise ratio (SNR) was calculated for each pressure level to evaluate signal quality. The developed technology provided high-quality EMG signals capable of low-latency wireless signal transmission during the isometric grip task. When compared to traditional single-use wet electrodes, the SNR for each electrode type was not significantly different.
These findings suggest the armbands are capable of multi-use EMG signal collection. Further work will be done to evaluate their durability and robustness for application in various other sectors, including, but not limited to, sports performance analysis, rehabilitation, and gesture recognition. Upon further development of our proprietary biofeedback algorithm, we aim to provide multi-channel insights relating to muscle activation, communication, and imbalances, further allowing users to pinpoint areas of weakness that require additional focus during training and practice.
