A high-performance wearable thermoelectric generator with comprehensive optimization of thermal resistance and voltage boosting conversion

This paper develops a superhigh-performance wearable thermoelectric generator (WTEG) for harvesting body heat, achieving an output power density of 15.8 μW/cm2 in windless and moveless conditions, and 97.6 μW/cm2 for walking of 0.8 m/s. A novel WTEG configuration integrated with the porous sandwich substrate and direct-soldering Cu-foam heat sink is designed to significantly improve its flexibility and considerably reduce the thermal resistance at the cold/hot sides. A new compact low-voltage boosting converter is optimized to obtain a high conversion efficiency (such as >50%@100 mV) and allow low self-startup input voltage (20 mV) and stable output voltage. A semi-automatization manufacturing process of the self-powered wearable sensor system is also designed to integrate the WTEG module, energy management module, multi-sensor (including acceleration, temperature, humidity, heart rate, and blood oxygen) module, and Bluetooth module onto the flexible substrate. The experimental results indicate that the sandwich substrate increases WTEG performance by 25% and achieves about 40 mW/cm2 for the constant temperatures at the cold/hot sides with the temperature difference of 60 °C. When the cold side of WTEG is exposed to the ambient air, the Cu-foam heat sink enables a performance increase of 73.6% compared to that without a heat sink for the ambient temperature of 18 °C, which even reaches 302% under the wind speed of 2 m/s (obtaining 457.97 μW/cm2). It is interesting to find that the bending WTEG could significantly increase its performance by 45.6% (for the curvature radius of 20 mm) compared to the plane case due to the thermal condition improvement. For harvesting body heat, the performance of WTEG fixed on the forehead is better than that on the arm or shank. It achieves a superhigh average output power of 3.12 mW for walking at the ambient temperature of 18 °C, which could fully power the wearable multi-sensor health monitoring system continuously.