Four-state electrochromic smart devices for dynamic environmental adaptive camouflage with synergistic thermal–electromagnetic energy management

Abstract

Electrochromic smart devices with dynamic multispectral modulation and thermal management are critical for the adaptive camouflage of electronic equipment. Our work presents a Prussian blue (PB)-based electrochromic smart window that enables four color switching (blue/green/yellow/transparent) for dynamic adaptive camouflage covering sea, sky, and desert environments. A polyacrylic acid hydrogel (PAAH)–electrolyte-assembled quasi-solid-state electrochromic device (ECD) achieves synergistic optical–thermal–electromagnetic management. The device exhibits 55.99% optical contrast at 472 nm and 37.74% optical contrast at 1106 nm by a voltage-controlled Fe²⁺/Fe³⁺ redox reaction in the PB layers. Coupled with an Li⁺-doped PAAH, the ECD exhibits electromagnetic interference shielding performance above 40 dB in the X-band (8.2–12.4 GHz) due to the constructed ion–polymer conductive networks. An ECD was also designed to be a prototype device of smart window, which exhibits the feasibility for energy reuse. The designed ECDs realize multifunctional environmental adaptive camouflage, which integrates dynamic optical camouflage, electromagnetic interference shielding, thermal management, and energy reuse into a single platform, providing a paradigm for next-generation electrochromic smart windows.