Dual-Mode Stretchable Emitter with Programmable Emissivity and Air Permeability.

Materials with anisotropic emission characteristics have attracted considerable attention for thermal management. Although many dual-mode emitters have been developed for this purpose in the form of textiles, multilayer films, and photonic structures, multiple functionalities are essential for their versatile applications. Herein, a highly stretchable dual-mode emitter with programmable emissivity and air permeability is presented. The emitter comprises a planar GeSbTe (GST) cavity on one side of a perforated elastomer substrate and an infrared-reflecting metal layer on the other side. With a laser-induced phase transition from amorphous to crystalline GST, the emitter exhibits a large emissivity difference of 0.52 between both sides. The dual-mode emitter remains highly stable without mechanical failure after repeated stretching cycles to a strain of 50%. This air-permeable and stretchable emitter can be attached to any curved surface, including the human body. The GST-side emissivity can be programmed into an arbitrary emissivity pattern using a spatially modulated laser beam, ultimately enabling the printing of mutually independent visible and thermal images in a single emitter. This study provides a promising structure for multispectral optical security as well as thermal management.