Stretchable thermoelectric generators (s-TEGs) have been considered as potential energy sources for self-powered wearable devices. However, their low performance is a large bottleneck for them to be used in practical applications. Korean researchers at Seoul National University report high-performance stretchable thermoelectric generators that can drive wireless, self-powered wearable devices by harvesting milliwatt-scale power merely from body-heat. The study appears in the journal ACS Energy Letters in May.

The researchers focused on the high internal resistance of s-TEGs, which is reversely proportional to its power generation capacity. High internal resistance in s-TEGs originates from the poor electrical contact at the interface, and low electrical conductivity of stretchable conductors. To solve each issue, two strategies were suggested in this work. First, functional interlayers that bridge discrete electromechanical properties at the rigid-soft interface were introduced into the platform using a scalable approach. Second, a solution-based welding method was applied to generate a highly conductive stretchable electrode based on a volumetrically connected network of 1-dimensional metal nanowires.

Such techniques effectively reduced the internal resistance of the s-TEG and greatly improved its power generation capacity. Among previously reported s-TEGs, the highest normalized power density of 1.48 μW·cm-2·K-2 was achieved in this work. Finally, the researchers demonstrated a wireless wearable rescue system powered by the high-performance s-TEG for people falling into cold water. 

Professor Hong said that "While low performance was considered to be a technical limitation in increasing the practicality of s-TEGs, the s-TEG developed in this work by reducing its internal resistance could generate milliwatt-scale power from body heat and operate wireless wearable devices without using any batteries". Also, professor Hong said, “This work will greatly contribute in the popularization and commercialization of battery-free self-powered wearable devices by providing a basis of s-TEG design”.

[Reference] H. Cho et al., (2023) “Milliwatt-scale body-heat harvesting using stretchable thermoelectric generators for fully untethered, self-sustainable wearables” ACS Energy Letters, https://doi.org/10.1021/acsenergylett.3c00243

[Main Author] Hyeon Cho (Seoul National University), Dongju Jang (Seoul National University), Byeongmoon Lee (Stanford University), Seungjun Chung (KU-KIST, Korea University), Yongtaek Hong (Seoul National University)

* Contact : Professor Yongtaek Hong (yongtaek@snu.ac.kr)