High power output based on watch-strap-shaped body heat harvester using bulk thermoelectric materials

This paper reports on the high power output of a watch strap-shaped body heat harvester and presents the detailed analysis of its performance. The device is made up of bulk thermoelectric materials and contains an integrated heat sink. When the device is worn on the wrist, it generates an output power of 6.97 μW/cm² while the subject is walking. Theoretical analysis based on the human thermoregulatory model explains the high power output. Owing to the design of the body heat harvester, which can be adapted to conform to curved surfaces such as the skin and a screwed-down heat sink, an unprecedently low thermal contact resistance was achieved. Furthermore, the finned heat sink and high fill factor augmented the output power level. This research demonstrates the possibility of extracting body heat for operating wearable and/or implantable sensors made of bulk thermoelectric materials.