Radiation‐Based 3D Dual‐Mode Thermal Management Devices: Advances in Active/Passive Switching for Energy‐Saving Applications

Radiation-based energy-saving strategies, including solar heating (SH) and radiative cooling (RC), have emerged as sustainable solutions that operate without an external energy input. SH relies on broadband solar absorbers to capture solar radiation, whereas RC employs selective emitters with high solar reflectance and strong thermal emissivity in the atmospheric transparent window regime. Despite their potential, single-mode SH or RC devices lack adaptability under dynamic environmental conditions. To overcome these limitations, dual-mode devices that integrate both SH and RC have been proposed. However, 2D film-type dual-mode devices have limited tunability and environmental adaptability. This perspective paper highlights the development of 3D dual-mode thermal management devices that exploit structural deformations-axial loading, flipping, and bending-for reversible switching between SH and RC. Active devices enable dynamically adaptive control, whereas passive devices achieve zero-energy operation. Overall, 3D dual-mode devices represent a promising platform for sustainable energy savings. This paper reviews the recent advances in this field, classifies the devices according to the deformation mode, and discusses existing challenges and future opportunities. Thus, it serves as a comprehensive guide for researchers and industry professionals, inspiring future innovations and contributing to sustainable thermal regulation strategies.