Time–Temperature Integrating Optical Sensors Based on Gradient Colloidal Crystals

Manipulation-free and autonomous recording of temperature states for extended periods time is increasing importance food spoilage battery safety assessment. An optical readout preferred low-tech visual inspection. Here, a concept time–temperature integrators based on colloidal crystals introduced. Two unique features in this class advanced materials are combined: 1) the film-formation kinetics can be controlled by orders magnitude mixtures particles with distinct glass transition temperatures. 2) A gradual variation particle mixture along linear gradient crystal enables local readout. Tailor-made latex identical size but different temperatures provide homogenous photonic stopband. The disappearance opalescence directly related to ratio exposure combination. This sensing material adjusted report intermediate short excessive events, which makes it specifically suitable long-term tracing threshold applications.