Radiative Cooling and Solar Heating Janus Films for Personal Thermal Management

Hot and cold seasonal temperature fluctuations pose a serious public health threat. Radiative thermal management has been shown to be an effective method for personal thermal management. However, the currently available materials cannot maintain human thermal comfort against the hot and cold seasonal temperature fluctuations, such as heating in cold weather or cooling in hot weather. Here, a Janus film that integrates the two opposite requirements of heating and cooling into one functional dual-mode film is fabricated. In cooling mode, the Al backing and embedded silicon dioxide (SiO2) microparticle can achieve a high solar reflectivity (∼0.85) and high IR emissivity (∼0.95) to induce a temperature drop of ∼2 °C. In contrast, the embedded carbon nanotubes (CNTs) can improve solar absorption (∼0.95) and induce a temperature increase of ∼7 °C. Owing to its radiative cooling and solar heating capability and compatibility with large-scale production, this Janus film is promising to bring new insights into the design of the next-generation functional textiles.