The Elegance of Simplicity: A Cost-Effective Janus Membrane for All-Day Radiative Thermal Management Inspired by Complementary Photothermal Design

Abstract

Passive radiation control technology is expected to replace the traditional energy-intensive cooling and heating methods to achieve high energy efficiency and environmental protection. We discovered that polymer Nylon66 and MXene exhibit complementary, step‐like radiative emissivity profiles-analogous to the Yin (cooling) and Yang (heating) interplay depicted in the Tai Chi diagram-that. By integrating MXene with a porous Nylon66 membrane featuring a richly textured, coral‐like hierarchical architecture, adeptly address environments characterized by extreme thermal disparities. The Nylon66 side, with a solar absorptivity of 0.062 and a mid-infrared emissivity of 0.928, achieves sub‐ambient cooling of 14.8°C (day) and 1.7°C (night), while the MXene side, with a solar absorptivity of 0.845 and mid-infrared emissivity of 0.073, delivers warming of 36.4°C (day) and 0.5°C (night). Rapid switching by flipping the membrane (Δε=0.843) and MXene’s conductive electrothermal heating for external compensation further expand its applicability. Although the materials themselves are well‐known, our simplified, low‐cost fabrication approach achieves performance on par with more complex systems, offering significant potential for large‐scale production in space exploration, architecture, and personal thermal management.