A fully self-powered wearable monitoring system with systematically optimized flexible thermoelectric generator

Abstract

Wearable electronics for personal healthcare and environment awareness are attracting more and more attentions and gaining wide market acceptance. Wearable monitoring system with continuous energy supply is necessary and still faces great challenge at present. Flexible thermoelectric generator (f-TEG) is competitive and promising energy solution due to its advantage of continuously harvesting energy from body heat under any condition. Up to now, energy efficiency of f-TEG at normal temperature is low and design of energy supply for wearable electronics is unthoughtful, which limit its practical applications. Here, we propose a systematic optimization method for designing f-TEG, which takes multi-objective optimization of power density, material consumption and power matching with wearable electronics into considerations. We optimize the number of thermoelectric grains, the fill factor and the series-parallel connection mode of f-TEG to achieve high energy efficiency and implement power matching with wearable sensory system. By this method, we develop a high-efficient f-TEG utilizing bismuth telluride grains assembled on flexible polyimide substrate. The f-TEG exhibits excellent power performance with power density of 3.5 µW/cm2 and 12.3 µW/g, and a boosted output voltage of 2.8–3.3 V at body temperature in motionless and windless condition. Furthermore, a self-powered wearable multisensory bracelet incorporating the f-TEG with multisensory system, tailor-designed intelligent power management and data display is developed, which allows continuously and simultaneously monitoring temperature, humidity, and activity of human body, entirely powered by human body heat. The f-TEG can be competent as a continuous and green energy supply for wearable monitoring system.