Bio-inspired hierarchical wrinkles for tunable infrared reflectance

Abstract

Wrinkles with large infrared emissivity regulation are attractive for thermal management. Here we present the design and preparation of hierarchical wrinkles (H-wrinkles) of POE-POE/Al, which exhibit a high reflectance modulation range from 0.60 to 0.16 upon mechanical actuation. The POE-POE/Al primary wrinkles (P-wrinkles) with optimum structure factors are prepared by hot-pressing. According to the FDTD calculation, the infrared absorption by plasma resonance in periodic structure mainly occurs at the troughs. Hierarchical troughs would further promote the infrared absorption by dual plasma resonance. Then sub-troughs via mechanical instability are introduced in the primary troughs according to prediction of theoretical analysis. When placed on a hot stage of 40°C, a temperature difference of ∼5.3°C is obtained for the H-wrinkles before and after a uniaxial stretching of 150%. Meanwhile, when being covered on the artificial skin, the H-wrinkles could achieve a dynamic temperature modulation of ∼1.4°C upon mechanical actuation. The study offers a strategy for preparation of the biomimetic wrinkles with high infrared modulation ability for applications in infrared camouflage and thermal management.