From metastable colloidal crystalline arrays to fast responsive mechanochromic photonic gels: An organic gel for deformation-based display panels

An efficient and straightforward method is developed to prepare a mechanochromic photonic gel by fixing the metastable SiO₂ colloidal crystalline array (CCA) in the mixture of ethylene glycol (EG) and poly(ethylene glycol) methacrylate (PEGMA) through photopolymerization. Thanks to the recent fabrication of solvent-wrapped, metastable CCA, a high volume fraction of EG (46%) is introduced to the photonic gel before particle assembly, but not by swelling after polymerization, which leads to a more deformable composite than most reported opal gels. Compared to traditional photonic gels, this opal gel not only has improved mechanochromic sensitivity to weak external force and extended color tuning range from red to blue (Δλ = 150 nm), but also possesses fast and reversible response in millisecond level (20-200 ms), repeatable reflection signals in cycling and fatigue tests, and good resolution in response to localized deformation, which renders it an ideal deformation-based photonic display screen. A new trigger system is designed to solve the large deformation causing color fading in conventional mechanochromic gels and brilliant red, green, and blue (RGB) pixels can be conveniently manipulated by 'pushing' operations. A mechanochromic photonic gel is prepared by fixing metastable SiO₂ colloidal crystalline array in the mixture of EG and PEGMA through photopolymerization. Compared to traditional opal gels, it has improved mechanochromic sensitivity, a broad color tuning range, fast response, repeatable reflection signals in cycling and fatigue tests, and good resolution for localized deformation, which makes it a good deformation-based photonic display panel with controllable RGB pixels.