Wearable temperature sensors. (a) Schematic illustration for the preparation of a gold-doped silicon nanomembrane epidermal temperature sensor array. (b) Photographic images of temperature sensors attached to the skin below the nose and on the back. (c) The fractional resistance changes of gold-doped silicon sensors and conventional metal sensors over time during periods of rest and exercise. [(a)–(c)] Figure adapted from Ref. 21. Reproduced with permission from Sang et al., Adv. Mater. 34(4), 2105865 (2022). Copyright 2021 Authors, licensed under a Creative Commons Attribution (CC BY) license. (d) Schematic illustration of the wearable sensors for core body temperature estimation. (e) Labeled cross section schematic illustration of the device. (f) Comparison of estimated and measured core body temperatures under various ambient temperatures. [(d)–(f)] Figure adapted from Ref. 22. Reproduced with permission from Jeong et al., Sci. Adv. 7(20), eabg3092 (2021). Copyright 2021 Authors, licensed under a Creative Commons Attribution (CC BY) license.