Designing auxetic pattern with elastic photonic crystals for ultrasensitive mechanochromism

Abstract

In the lower layer of the chameleon skin, guanine nanocrystals in the form of particles are regularly arranged in a non-closed packaged, face-centered cubic structure, and the regular arrangement reflects external light of a specific wavelength through constructive interference, resulting in color. Similar to the chameleon, when inelastic colloidal particles form a non-closed lattice structure in an elastic medium, immediate discoloration is possible according to mechanical deformation. However, due to the inherent characteristics of the crystal material, the resonance wavelength mobility relative to the strain is fixed as Poisson's ratio, which limits the achievement of high sensitivity. In this thesis, showed high discoloration characteristics even at low strain using hierarchical cutting patterns. Since the deformation leading to the deformation of the cutting area in the expansion of the auxetic surface with a hierarchical cut surface is the deformation of the cutting area, the deformation rate can be maximized locally. Based on this, the pattern skeleton uses a urethane polymer material with a relatively large elastic modulus and a torsional deformation, and uses a low elastic colloidal photonic crystal to maximize the local strain in the elastic photonic crystal region even at a small strain. The auxetic pattern with elastic photonic crystals designed through this study can potentially be applied to fields requiring high sensitivity, such as aging diagnosis of cars, airplanes, ships, and old buildings.