Bionic femtosecond laser manufacturing for impressionistic camouflage infrared display

Abstract White Cyphochilus insulanus beetles, exhibiting both environmental camouflage display and radiative cooling functions, serve as a good prototype for biomimetic fabrication. As inspired, this work presents a femtosecond (fs) laser-based biomimetic fabrication strategy that takes full use of the synthesized radiative cooling nanomaterials for a groundbreaking stimuli-responsive infrared (IR) impressionistic camouflage display. The proposed technique is capable of readily transforming various substrates (quartz glass and metals including Ti, Al, Zr, and W) into self-assembled porous networks (aerogels) consisting of oxygen-vacancy-rich oxide nanoparticles. Surprisingly, the emissions of all as-prepared porous particle-networks in the radiative-cooling long-wavelength infrared (LWIR) band are above 95%, with the SiO 2 aerogels reaching a maximum of 99.6%. Benefiting from the far-from-equilibrium thermodynamic kinetics, metastable phases of anatase TiO 2 , tetragonal zirconia (t-ZrO 2 ), and monoclinic WO 3 (Pc) are synthesizable, opening up opportunities for exploring their optical applications. Taking the low-temperature metastable phase WO 3 (Pc) as representative for systematic studies, it is found that (1) the ratio WO 3 (Pc) phase to that of room-temperature phase of WO 3 (P2 1 /n) can be tailored by modulation of processing parameters; (2) laser synthesized aerogels with hybrid phases of WO 3 (Pc) and WO 3 (P2 1 /n) have a brighter visible whiteness, higher visible/near-infrared (NIR) spectral selectivity than the natural prototype of white Cyphochilus insulanus beetles but with comparable LWIR emittance. White WO 3 aerogel in situ deposited during flexibly fs laser artistic patterning can blur the painting features due to its radiative cooling effect, allowing a colorful impressionistic IR display in the heating mode. What’s more, invisible painting features concealed by the white deposited WO 3 aerogel are clearly/faintly distinguishable by introducing external stimuli of a human hand and sample heating, respectively, catalyzing progress in optical encryption and selectively stimuli-responsive decryption display in the infrared band.