Stretchable thermoelectric generators with enhanced output by infrared reflection for wearable application

The infrared reflection mechanism offered by reflective layer coated with Ag NWs facilitates infrared insulation between skin and hot side while reduces radiant heating of the cold side, promoting an increase in electrical output due to the increased temperature difference. This work represents the new perspectives into thermal transport mechanism and its effects on the thermoelectric output. • Infrared reflection mechanism establishes high temperature gradient for FTEG. • Wet-twisting technique enables transform CNT film into tightly structured yarn. • Performance of the stretching originates from thermoelectric loop structure. • Waterproof encapsulation facilitates the application in different environments. Flexible thermoelectric generators can directly convert body heat into electricity to power wearable electronics, which is recognized as a potential candidate for durable energy supply. Nevertheless, the parasitic heat loss and inadequate waterproofing have greatly limited its practical application. Here we propose a compliant engineering solution for encapsulated thermoelectric generators that ensures sufficient alignment of thermal gradient based on infrared reflection effect, which realized both the increased infrared radiation insulation at hot end and the reduced radiation heating of cold end. It contributes to a remarkable increase in temperature difference as compared to the unencapsulated one when subjected to a same heat source, presenting up to ∼35% increase in voltage output. Owing to waterproof encapsulation, this TE wristband is reliable in a variety of real-life activities such as running and swimming. Moreover, the design concepts of thermoelectric wristband described here can bring new inspiration for realizing body energy harvesting.