Ultra-stretchable hydrogel thermocouples for intelligent wearables

Abstract

Stretchable temperature sensors are necessary to enable tactile interaction and thermoregulation in the human body and soft robots. These sensors should be conformably adhered to a deformable surface and maintain temperature perception accuracy when stretched. However, current mainstream stretchable temperature sensors based on thermistors suffer from inherently unstable sensing during stretching due to the mutual interference of resistance changes caused by temperature and mechanical deformations. Herein, we propose an ultra-stretchable hydrogel thermocouple that provides unaltered temperature sensing upon stretching. The ultra-stretchability of this thermocouple is achieved by constructing thermogalvanic hydrogels with dynamic crosslinked double networks. By connecting P-type and N-type thermogalvanic hydrogels, the thermocouple exhibits a high equivalent See-beck coefficient of 1.93 mV K−1 and a stable sensitivity even under a 100% tensile strain. The advantage of this ultra-stretchable thermocouple is demonstrated in a smart glove prototype, which enables haptic feedback. Our work provides a new strategy for stretchable temperature sensors and may promote the development of intelligent wearables.