Optimized thermal design for excellent wearable thermoelectric generator

The development of wearable thermoelectric generators (w-TEGs) toward lightweight, economical and high-power-generation performance can provide more opportunities for their application in self-powered wearable electronics. For existing w-TEGs, insight into the physical parameter coupling between the substrate and TE legs is lacking, which leads to inefficient utilization of the temperature difference and deterioration of the power generation performance. In this work, comprehensive thermal management of the heat collector, TE legs and heat radiator is carried out using finite element simulation. It is found that increasing the thermal conductivity of the substrates for heat collection and dissipation is conducive to reducing the optimal fill factor and substrate thickness and improving the power density, thus facilitating comfortable-to-wear, economical, and functional w-TEGs. Specifically, a laminated film with good flexibility prepared from polyimide (PI) film and graphene assembly film (GAF) acts as the substrate of w-TEG. The PI film compensates and enhances the mechanical strength of the laminated substrate. The GAF has high thermal conductivity, which reduces the in-plane and out-of-plane thermal resistance of the laminated substrate, thus contributing to the heat collection of the bottom substrate. The GAF also has high emissivity, which enhances the radiative heat transfer and facilitates the heat dissipation of the top substrate, which is cut into blocks without affecting the electrical path to ensure the overall flexibility of the w-TEG. When the w-TEG with the laminated substrate and a fill factor of 10% (four w-TEG units connected in series, 20 x 145 mm(2) in plane) is worn on the wrist for running (contact pressure: 0 kPa, wind speed: 3 m s(-1)), the optimal output voltage and power density reach 281.6 mV and 45.6 mu W cm(-2), respectively, which is one of the best results among recently reported heatsink-less w-TEGs. This work provides guidance for optimizing the output performance of w-TEG and accelerating the development of self-powered electronics.