UC Berkeley

Drawing inspiration from the panther chameleon's sophisticated color-adaptive abilities, we introduce a unified design framework for a new class of bio-inspired mechanochromic materials with tailored reflectivity across the electromagnetic spectrum. While structural coloration in nature relies on the mechanical adjustment of photonic crystal spacing, engineering such systems is often hindered by the barreling effect, the lateral bulging of bulk materials caused by Poisson's effect. To address this, we developed a mechanical metamaterial substrate optimized through a genetic algorithm and modeled it using Timoshenko beam theory to ensure a uniform strain field during deformation. The proposed system features a two-dimensional hexagonal lattice of composite dielectric nanopillars positioned on top of a micro-architected substrate fabricated via Multiphoton Lithography (MPL). The nanopillars consist of an MPL core coated with a high-refractive-index material to achieve complete optical band gaps. By dynamically adjusting the lattice constant through controlled, reversible elastic deformation, the reflected wavelengths can be shifted across broad spectral ranges. We demonstrate the scalability and robustness of this approach through three distinct structures tailored for the visible, mid-wave infrared (MWIR), and long-wave infrared (LWIR) regions. This methodology lays a foundation for scalable, reversible mechanochromic materials with significant potential for applications in adaptive camouflage, radiative thermal management, and wearable electronics.