Surface electromyography (sEMG) plays an important role in the daily practice of clinical hand function rehabilitation. The materials and design of current typical clinical sEMG electrodes make it difficult to provide a stable electrode-skin interface for adequate long-term, high-quality data. Therefore, conformal, soft, breathable, wireless epidermal sEMG sensor systems have great potential in clinical rehabilitation. 

A research group led by YANG Hongbo from the Suzhou Institute of Biomedical Engineering and Technology (SIBET) of the Chinese Academy of Sciences, together with CHENG Huanyu from the Pennsylvania State University, has jointly demonstrated a stretchable epidermal sEMG sensor array system with optimized materials and structural strategies for hand gesture recognition and hand function rehabilitation. 

The optimized serpentine structures, with improved stretchability and fill ratio, provide lower impedance and high quality sEMG signals. Compared to traditional serpentine design, the signal-to-noise ratio of the new sensor has been increased from 18.89 dB to 29.15 dB, greatly improving the quality of the sEMG acquisition.  

The easy-to-use air-hole design makes the sensor six times more breathable, further ensuring its stable and long-term contact with the skin for recording, according to the researchers. 

In addition, the sensors, integrated with a customized flexible wireless data acquisition system, achieved real-time eight-channel sEMG monitoring. 

Combined with the CNN-based algorithm, this new sensor system also realized monitoring in seven hand gestures automatically and reliably, with an accuracy of 81.02%.  

"The low-cost yet high-performance epidermal sEMG sensor system demonstrated its conceptual feasibility in quantitatively evaluating the hand of stroke patients and facilitating human-robot collaboration in hand rehabilitation through proof-of-concept clinical testing," said YANG Hongbo. 

The results, titled "Conformal, stretchable, breathable, wireless epidermal surface electromyography sensor system for hand gesture recognition and rehabilitation of stroke hand function," were published in Materials & Design. 

This study was supported by the National Key R&D Program of China, and the National Natural Science Foundation of China, etc. 

The schematic illustrating the conformal, soft, breathable, wireless epidermal sEMG sensor system and application for hand gesture recognition rehabilitation of stroke hand function. (Image by SIBET)

Mechanical and electronic characterization of epidermal sEMG sensors system. (Image by SIBET)