Wearable electronic devices have attracted more and more attention due to their flexibility, portability and biocompatibility, which can be applied to electronic skin, health monitoring, artificial intelligence, soft robots etc.. Different from traditional rigid sensors, flexible sensors not only meet the requirements of high sensitivity and fatigue resistance, but also have the characteristics of large deformation, stretching and even self-powered. However, these battery-powered sensors need to be recharged frequently, which is not ideal for monitoring human activity over long periods of time. Thus, developing a flexible self-powered sensor will provide greater feasibility for wearable devices to be used for human movement and health monitoring. Hydrogel strain sensors combining the advantages of thermoelectric voltage and high sensitivity of self-powered wearable strain sensors have become hot topics from interdisciplinary fields.
Prof. Wei Zeng's group (Institute of Chemical Engineering, Guangdong Academy of Sciences) recently reported a wearable self-powered human motion sensor made from highly stretchable quasi-solid state hydrogel, which shows 2800% elongation at break and good strain sensitivity (GF=4, when the strain is 200%). Further, the hydrogel-based sensor can harvest the human body heat and generate a thermovoltage to drive the sensor directly, which exhibits an impressive gigantic Seebeck coefficient of approximate 11.5 mV K-1 at ambient temperature. At the temperature difference of 40 oC, the maximum output power density reached 94.38 mW m-2 and the thermoelectric figure of merit reached 0.087. The self-powered sensor can also monitor a variety of motion patterns including finger, wrist, knee bending and even human voice, showing high repeatability and sensitivity. And it is expected to be applied in intelligent medical treatment, wearable electronics, national defense technology and other fields.
The research work has been published in Nano Energy, a top international Energy journal. The work has been partially supported by National Natural Science Foundation of China and the GDAS Project of Science and Technology Development.
Paper information: Chen, J., Zhang, L., Tu, Y., Zhang, Q., Peng, F., Zeng, W.,...& Tao, X. (2021). Wearable self-powered human motion sensors based on highly stretchable quasi-solid state hydrogel. Nano Energy, 106272.