Diffuse Fabry-Pérot Cavities from a Bifunctional Metal Mesh for Angle-Invariant Electrochromic Camouflage

Tungsten trioxide (WO3) is a widely studied electrochromic material, yet its monochromatic switching behavior limits its applicability in scenarios requiring dynamic color modulation. To address this limitation, integration with a Fabry-Pérot (F-P) optical cavity has emerged as an effective strategy for expanding color tunability while reducing viewing-angle dependence. In this work, a simplified F-P cavity is constructed using stainless-steel mesh (SSM) as a bifunctional reflector and electrode, with a sputtered WO3 film serving as the electrochromic spacer. This design enables continuous full-spectrum color modulation across the visible range through precise regulation of the WO3 layer thickness. Meanwhile, the microscale topological roughness of the SSM introduces diffuse light scattering, which synergistically couples with F-P interference to compensate for optical path variations at different viewing angles. As a result, angle-independent structural coloration is achieved over a broad viewing-angle range from 15 to 90°. Furthermore, benefiting from the high electrical conductivity and unique porous structure of the SSM, a 14 cm × 14 cm inverted flexible electrochromic device was successfully fabricated. The resulting device exhibits fast switching kinetics, excellent mechanical durability under repeated bending, and stable reversible multicolor performance, demonstrating a scalable and cost-effective platform for adaptive visible-light camouflage and energy-efficient reflective display applications.