Regulating Interpenetrating Network Gels to Create Anisotropic Photonic Crystals toward Ultrasensitive Mechanochromism

Colloid photonic crystals (CPCs) possess the ability to selectively and dynamically manipulate light reflection, which are pivotal and highly demanded for nano-optical sensors and various other applications. However, their optical performance, particularly response sensitivity, dynamic range, and color stability, is constrained by their typical isotropic structural characteristics. In this study, an anisotropic CPC with individually tunable vertical lattice constants was created by a reconstruction strategy. The essence of this reconstruction strategy lies in regulating the constrained swelling and oriented formation of an interpenetrating gel network within an isotropic CPC template. Compared to the conventional CPCs, the fabricated anisotropic CPCs exhibit superior mechanochromic performance featuring a higher sensitivity (10 nm/%), a larger response range (≥250 nm), and improved reflectivity stability. The advantages conferred by anisotropic shapes in CPCs not only manifest in their mechanochromic properties, but can also be extended to other PC materials with diverse response functions.