Wearable Body Temperature Sensing with Autonomous Self-Regulated Joule Heating and Passive Cooling for Healthcare Applications

Innovative solutions for efficient temperature monitoring and thermal management are crucial in the field of wearable electronics and smart textiles, necessitating materials that exhibit superior sensitivity, adaptability, and environmental compatibility. The positive temperature coefficient (PTC) effect observed in conductive polymer composites (CPCs) holds significant promise due to its wide materials selection and ability to offer enhanced sensitivity. However, traditional CPCs have relatively high PTC temperatures and are often unsuitable for bodily healthcare devices. This study introduces a novel approach leveraging the synergistic effect of an eco-friendly fatty acids, namely lauric acid (LA), with flexible styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomer (TPE) as a matrix and graphene nanoplatelets as a conductive filler. The composite film demonstrates exceptional temperature responsiveness at body-relevant temperatures (35-40°C) with a PTC intensity reaching an unprecedented four orders of magnitude, set apart by its fine-tuning ability across a remarkable detecting temperature interval (Maximum temperature coefficient of resistance (TCR): 471.4% °C^-1). This advancement is facilitated through a carefully engineered morphology, wherein the distribution of LA significantly influences the conductive network’s reformation within the composite, with the in-situ optical microspore used to reveal the reformation of the conductive network structure. The flexible composite film showcases unparalleled adaptability for body temperature sensing and autonomous self-regulated Joule heating and passive cooling. This presents a substantial leap in material design for health monitoring and thermotherapy devices, while simultaneously addressing environmental concerns by incorporating biodegradable LA. This study not only highlights a novel material with exceptional low-temperature detection capabilities but also paves the way for future developments in eco-friendly, highly sensitive, and flexible sensors for wearable technology.