Composite Films of CsPbBr3 Perovskite Nanocrystals in a Hydrophobic Fluoropolymer for Temperature Imaging in Digital Microfluidics

A composite film material that combines CsPbBr₃ perovskite nanocrystals with a Hyflon AD 60 fluoropolymer was developed and utilized for high-resolution optical temperature imaging. It exhibited bright luminescence and, most importantly, long-term stability in an aqueous medium. CsPbBr₃ nanocrystal-Hyflon films immersed in aqueous solutions showed stable luminescence over at least 4 months and exhibited a fully reversible pronounced temperature sensitivity of 1.2% K^-1 between 20 and 80 °C. They were incorporated into a digital microfluidic (electrowetting on dielectric) platform and were used for spatially resolved temperature measurements during droplet movements. Thermal mapping with a CsPbBr₃ nanocrystal-Hyflon sensing layer in a room temperature environment (22.0 °C) revealed an increase in local temperatures of up to 40.2 °C upon voltage-driven droplet manipulations in a digital microfluidic system, corresponding to a local temperature change of up to 18.2 °C.