Multi-bioinspired flexible thermal emitters for all-day radiative cooling and wearable self-powered thermoelectric generation

Passive radiative cooling technology provides an energy-efficient solution to reduce cooling costs and alleviate greenhouse gas emissions. However, a significant challenge lies in compatibility between the dual-band optical characteristics (solar and mid-infrared bands) of radiative cooler (RC) and their applicability in various scenarios. Drawing inspiration from biological thermoregulation mechanisms, we developed flexible thermal emitters with a multi-scale structure. This bioinspired RC effectively scatters and reflects photons within the solar spectral range while enhancing emission in the mid-infrared region, resulting in a remarkable cooling performance of 7.3 °C during the day and 10.2 °C at night. Furthermore, we integrated the RC into a homemade flexible circular thermoelectric generator (C-TEG). This radiative cooling-based C-TEG (RC-C-TEG) boasts a high area ratio (α=2.7), surpassing the output performance of traditional RC-TEG (α=1) by 150%. When affixed to the human body, RC-C-TEG simultaneously harvests sustainable thermal energy from the cold space and the human body, achieving a power density of 143 mW/m2. Overall, the flexible metamaterial with multiscale structure, inspired by multiple biomimetics in this work, opens up new avenues for advanced all-day radiative cooling. The RC-C-TEG demonstrates significant potential in providing an uninterrupted power supply for wearable electronics.