Flexible and Stretchable Dry Active Electrodes with PDMS and Silver Flakes for Bio-potentials Sensing Systems

Flexible and stretchable dry active electrodes for multi bio-potentials sensing based on Ag flakes / polydimethylsiloxane (PDMS) electrically conductive composite (ECC) are developed and characterized. The proposed dry active electrode consists of soft substrate, electrode, and simple circuits with an amplifier and a capacitor. The soft substrate is made of silicone with a molding process, while the electrode is fabricated by bar coating the ECC on the patterned substrate. Furthermore, circuits interconnect, soldering of chip and other components, and connection with flexible PCB (FPC) are all implemented with ECC directly, which simplifies the fabrication process. A portable bio-potential sensing system is also designed and implemented to work with the proposed electrodes. Various experiments were carried out to verify the proposed electrodes as well as the whole sensing system. The connectivity and proper functionality of the electrodes and cables remain stable during the stretching test. The system and the sensors yield good signal quality for multiple bio-potentials. Compared with conventional Ag/AgCl wet passive electrodes in electrocardiogram (ECG) sensing, the proposed dry active electrodes showed comparable noise floor and less sensitivity to power line interferences and motion artifacts. In electroencephalogram (EEG) sensing, the observed alpha rhythm was 12.66 dB higher than the baseline in the eye-close state. The proposed sensors exhibited potential applications in wearable systems in the electromyogram (EMG) grip force measurement and classification test. Overall, the proposed sensors could provide better comforts during long-time wearing according to its better matching modulus with skin and can meet the requirements of high quality multi bio-potential sensing.