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

A composite film material which combines CsPbBr3 perovskite nanocrystals with 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 aqueous medium. CsPbBr3 nanocrystal-Hyflon films immersed in aqueous solutions showed a stable luminescence over at least 4 months and exhibited a fully reversible pronounced temperature sensitivity of 1.2% K-1 between 20 and 80 ºC. 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.