Extremely sensitive mechanochromic photonic crystals with broad tuning range of photonic bandgap and fast responsive speed for high-resolution multicolor display applications

Mechanochromic photonic crystals (MPCs) that can change their colors under pressures are highly desired. However, the poor sensitivity of MPCs (including the limited tuning range of photonic bandgap and responsive speed) and stability restrict their practical applications. Here, extremely sensitive MPCs film with outstanding optical performances was fabricated through the self-assembly of the silica particles into di(ethylene glycol) ethyl ether acrylate (DEGEEA) and fixing the ordered structures by photopolymerization. The strong electrostatic repulsion between the particles was experimentally proved to be the key for the self-assembly of silica particles in nonpolar DEGEEA, ruling out the solvation force as the driving force. Compared with the conventional MPCs, the as-fabricated MPCs exhibit significant improvements in optical performances, including broad tuning range of photonic bandgap (362 nm), high sensitivity (7.55 nm/kPa), fast responsive speed (7.0 nm/ms), long-lasting usability (>2 months), wide working temperature range (−20 to100 ℃) and excellent reversibility (>1000 times) in cycling test. Based on these characteristics, the MPCs can be used for display applications with high-resolution (up to 5.0-µm resolution) and full colors. This work provides new insight for the self-assembly of colloids and will extend the applications of MPCs in sensitive sensors, multicolor displays, and smart windows.