Cellulose Acetate-Based Janus Membrane with Dual-Mode Switching for On-Demand Radiative Cooling and Solar Heating

Abstract Conventional static thermal management materials incur overcooling penalties in cold seasons. In this study, we develop a cellulose acetate-based Janus bilayer membrane that enables on-demand switching between radiative cooling and solar heating via mechanical flipping. Fabricated through a scalable non-solvent-induced phase separation and lamination strategy employing bio-renewable materials, the membrane integrates a BaSO4 cooling side (97.1% solar reflectance, 96.5% mid-infrared emissivity) and an activated carbon heating side (94.0% solar absorptance). multiscale simulationsMie scattering, finite-difference time-domain (FDTD), and COMSOL phase-field and heat-transfer modelingreveal the underlying mechanisms of resonant scattering and hierarchical light-trapping absorption. The dual-mode performance is systematically validated through outdoor ice-melting experiments and small-scale building model tests under real sunlight and xenon-lamp irradiation; in the latter, the two sides maintain a stable 12 °C temperature differential on the same roof. Durability tests confirm >95% optical retention after 1000 abrasion cycles and <4% loss after UV aging. EnergyPlus simulations covering all 34 provincial-level administrative divisions in China demonstrate average cooling and heating energy savings of 68.2% and 39.8%, respectively. This work offers a sustainable, durable, and practically viable solution for year-round building energy conservation.