Adhesive, mechanochromic structural color materials for large strain sensing and optical reflectors

Abstract

Chameleon-inspired mechanochromic photonic crystals (MPCs) are receiving growing attention owing to their unique ability to alter structural colors under external forces. Although MPCs have been extensively prepared, the low reflectance, small strain sensing range (<60%), limited wavelength tuning range (<200 nm), and lack of adhesive functions significantly limit their potential toward advanced applications. Here, a new type of MPC with a high reflectance (∼70%), a broad wavelength tuning range (305 nm), excellent adhesive properties, and capability to sense a large strain (180%) has been successfully fabricated by simply non-close-assembling polystyrene-silica core–shell particles into di(ethylene glycol)ethyl ether acrylate. The unique material and structural design, including the large refractive index contrast between the particles and acrylate, the large lattice distance, and the intense interactions between MPCs and substrates, is key to the above characteristics. By rationally combining these characteristics, bilayer MPC-based optical reflectors capable of outputting dual and dynamic photonic bandgaps have been realized, showing their potential for application in optical reflectors, photonic coatings, and wearable devices.