Self-adaptive photochromism

Camouflage is critically important because it improves the survival ability of animals when facing predators1. Some organisms (e.g., chameleon, octopus) with an active camouflage ability exhibit a changeable appearance with switching of environments2-4. However, manmade active camouflage systems heavily rely on the integration of electronic devices, which encounters problems such as a complex structure, poor usability, and high cost5-7. In the current work, we report active camouflage as an intrinsic function of materials by proposing self-adaptive photochromism (SAP). The SAP materials were fabricated using donor-acceptor Stenhouse adducts (DASAs) as the negative photochromic phases and organic dyes as the fixed phases. Incident light with a specific wavelength induces linear-to-cyclic isomerization of DASAs, which generates an absorption gap at the wavelength and accordingly switches the color. The SAP materials are in the primary black state in the dark and spontaneously switch to another color upon triggering by transmitted and reflected light in the background. SAP films and coatings were fabricated by incorporating polycaprolactone and are applicable to a wide variety of surfaces. Our work reports SAP as a distinct intrinsic property of materials, guiding the development of source-free active camouflage and anticounterfeiting technology.