Bioinspired sweating with temperature sensitive hydrogel to passively dissipate heat from high-end wearable electronics

Highlights: • A "sweating skin" made from hydrogel is proposed to cool wearable electronics. • 27 °C extra cooling performance is achieved for 1555.5 W/m² power. • Reliable for harsh environment and sweating-replenish cycles. • The cooling mechanisms are studied for phase-change and diffusion limited regions. -- Abstract: Thermal issues limit the application and development of electronic technique. In this work, temperature-sensitive poly (N-isopropylacrylamide) (PNIPA) hydrogel is used to dissipate heat for high-heat-flux thermal management (1555.5 W/m²) of uneven hotspots in virtual reality (VR) device by mimicking the phenomenon of biological sweating. This bioinspired method has an excellent heat dissipation effect, which significantly reduces the temperatures of the VR chips and the external surface. In addition, the heat transfer coefficient produced by hydrogel perspiration is more than twice that of the natural convection and radiation, resulting in a significant increase in cooling effect, and it can operate efficiently even in an environment with a relative humidity of 1. The heat dissipation control mechanism of this cooling method under different heat flux and the key factors under different mechanisms are analyzed. Besides, the hydrogel exhibited excellent stability. After 450 h of high-temperature and high-humidity (90 °C, 85%RH) aging tests and 60 cycles of fatigue tests, hydrogels still maintained a high water content and good swelling properties. The research results suggest that bio-inspired sweat cooling method is an effective and stable thermal management technology for VR devices, which indicates a new approach to address the obstacles of thermal management for development and application of electronic devices and even other heating objects.