Ultra-Low Energy Adaptive Personal Thermoregulation—A Kirigami-Enabled Electrochromic Wearable Variable Emittance (WeaVE) Device

Personal thermoregulation is of key importance for human skin temperature stabilization and personalized thermal comfort. However, a long-standing trade-off exists between tunable functionality, energy consumption, and wearability. Inspired by the mid-infrared electrochromic conductive polymers, we developed the first <b>ultra-efficient wearable variable-emittance device (WeaVE)</b>, enabling the tunable radiative heat transfer coefficient to fill the missing gap between thermoregulation energy efficiency and controllability.<br/><br/>WeaVE is an electrically driven, kirigami-enabled electrochromic thin-film device that can effectively tune the thermal radiation heat loss of the human body. The device can also maintain its cooling/heating state without energy input, thereby stabilizing the human body heat dissipation in response to varying ambient temperature with orders of magnitude less energy input compared to active devices or heating, ventilation, and air-conditioning (HVAC) systems. We also show that the kirigami design can achieve stretchability and conformal deformation under various modes of deformation and exhibits excellent mechanical stability after 1000 cycles. The integration of sensors and electronic control also enable programmable personalized thermoregulation. Our results show that <b>with less than 5.58 mJ/cm² energy input per switching, WeaVE provides 4.9 °C (8.8 °F) expansion of the thermal comfort zone, which is equivalent to a continuous power input of 33.9 W/m².</b> This is more than 1,000 times switching for a 1m² WeaVE with a typical smartphone battery, corresponding to months of usage. WeaVE provides an entirely new scheme to breaking the dilemma between conventional personal thermoregulation devices’ functionality and energy consumption and maintaining the wearability requirement simultaneously.