Thermoregulatory clothing with temperature-adaptive multimodal body heat regulation To adapt to the fluctuating and extreme temperature, temperature-adaptive clothing with both heating and cooling capability uses metalized polyethylene as actuator for multimodal body thermal regulation via radiation, convection, and sweat evaporation. The clothing with rectangular openwork in its front and back sides is knitted using traditional yarns, and the openwork is covered by the actuators. Polyethylene (PE), with simple and long C–C bonds along its main chain (Figure 1D), presents a much higher linear thermal expansion ratio than typical textile materials (e.g., nylon and polyester) (Figure S1). We hypothesize the PE film can be used as a temperature-responsive actuator. To amplify the thermal expansion property of the PE film, we design a bilayer structure by depositing a metal layer (i.e., copper-Cu in this work) onto the PE film (Figure S2). In this structure, the copper layer is regarded as the temperature-inert material, as its thermal expansion ratio (∼10−4)26 is much smaller than that of the PE film (∼10−3). In a hot environment, the PE film in the lower layer would expand, but the metal layer in the upper layer would expand little. Due to the thermal-induced mechanical mismatch, the heterogeneous bilayer actuator would bend towards the ambient (Figure 1C and Video S1). In this process, the textile with the actuators can directly transmit the infrared body radiation into the ambient and simultaneously enhances the air convection and sweat evaporation, thereby enhancing the body-heat dissipation for cooling effects (Figure 1E). Thermoregulatory clothing is not only essential to personal thermal comfort but also highly desirable for indoor building energy savings. The heating, ventilation, and air-conditioning (HVAC) system of a building accounts for over 50% of total building energy use. Thermoregulatory clothing that can decrease the heating set point (e.g., 21.5°C) by 2°C or increase the cooling set point (e.g., 24.5°C) by 2°C would lead to about 12.5% heating or 17.5% cooling building energy savings, respectively, which obeys the sustainability concept