Novel silk hydrogel-based material for wearable energy harvesting and sensing mountaineers’ activities

Wearable sensors are being widely utilized to monitor athletes’ physiological conditions during sports performance, especially when activities are performed in extreme weather conditions, such as skiing, snowboarding, mountain biking, bicycle motocrossing, and rock climbing. Extreme weather conditions, e.g., cold temperatures, call for stable wearable self-power sensors whose properties and functionality are independent of the external temperature. In this work, we present a novel flexible composite material based on silk-glycerol hydrogel, whose temperature-independent mechanical and triboelectric properties are used for the realization of stable wearable self-power sensors. The proposed hydrogel shows good mechanical (minimum stretchability of around 130% and Young’s Modulus of about 0.08 MPa) and triboelectric properties (maximum current output of 12.5 nA) independent of the temperature up to $- 20 ^{\circ}\mathrm{C}$. Moreover, the developed triboelectric nanogenerator (TENG) yields a linear relationship between the current and the applied compressive force up to 35 N, demonstrating the possibility to realize hydrogel-based TENG devices to be used as bio-mechanical sensors for wearable applications.