Scalable and durable Janus thermal cloak for all-season passive thermal regulation

Global climate change and high energy costs pose urgent demands in the development of low-cost, passive thermal-regulation technologies. Despite intensive efforts invested, high-efficacy, all-season temperature regulation on real-world objects has not yet been achieved through truly passive, reliable structures. We propose and experimentally realize a Janus thermal cloak (JTC) composed of an all-ceramic, radiative-cooling phononic metafabric facing the sky and a photon-recycling foil facing indoor space. The phononic metafabric, which supports broadband hyperbolic phonon polaritons (HPhPs) and strong scattering of phonon transport, shows outstanding resilience under harsh thermal, mechanical, and corrosive environments. Field tests on electric vehicles (EVs) show that the JTC realizes daytime sub-ambient cooling by 8.0 degrees C degrees C (by 27.7 degrees C degrees C compared with non-covered EVs) in summer and nighttime supra-ambient warming by 6.8 degrees C degrees C in winter. The JTC does not involve dynamic phase change or moving parts and thus is promising toward practical applications in buildings, vehicles, and extraterrestrial environments.