Femtosecond laser subtractive/additive-integrated biomimetic manufacturing for visible/infrared encryption and stimuli-responsive infrared decryption

Black wings of butterfly Ornithoptera goliath and infrared-band radiative cooling function of Rapala dioetas butterfly wings are associated with black pigment (e.g., melanin) and unique hierarchical micro/nanostructures, greatly stimulating biomimetic fabrication of functional photonic structures but mainly targeted to one prototype. Targeted at two-prototype integrated biomimetic fabrication from fully compositional/structural/functional aspects, femtosecond (fs) laser subtractive/additive-integrated hierarchical micro/nano-manufacturing technique is proposed in this work. This technique can one-step transfer refractory metals (e.g., W, Mo, Nb, Ta) into black non-stoichiometric oxide nanomaterials with abundant oxygen vacancies and simultaneously enable the realization of in situ quasi-controllable micro/nanoscale hierarchical aggregation and assembly, all displaying black color but with tunable infrared emission. Adjusting the scan interval for biomimetic manufacturing can tailor the structural oxidation degree, the emission in the long-wave infrared (LWIR) band while keeping the blackness of hierarchical aggregates, and the confined height between the covering quartz plate and the ablated sample. The blackening efficiency of this technique can reach ∼11.25 cm2·min-1, opening opportunities for high-throughput optical/thermal applications. Selectively patterned Chinese characters, Arabic numbers, and English letters are easily fabricable, which are intrinsically invisible-infrared dual-band encrypted but decryptable via static/dynamic environment stimuli (e.g., sample heating/cooling, introducing external hot/cold sources including human hands). The self-evolution from ‘orderless’ structuring to ‘ordered’ functionalization is validated for the proposed fs laser subtractive/additive-integrated biomimetic manufacturing, specifically from the synthesis of diverse black nanomaterials and the seemingly disordered micro/nano-aggregates to the ordered optical/thermal regulation capacities for a delicate modulation of information encryption and decryption, unveiling a new concept for future exploration and extension.