Imaging of flow patterns with molecular rotors

Molecular rotors are fluorescent molecules used as non-mechanical microviscosity sensors with high spatial and temporal resolution. They form twisted intramolecular charge transfer (TICT) states, and once photoexcited they return to their ground states following one of two de-excitation pathways: nonradiative intramolecular rotation or fluorescence emission. A recent discovery has shown an increase in the shearing rate of a viscous solvent containing molecular rotors leads to an increasing quantum yield, and new research was conducted to better understand this phenomena. Viscous solvents containing molecular rotors were injected into different chamber geometries, with flow rates were controlled by a syringe pump. Collimated LEDs provided the light source necessary to photoexcite fluorescent molecules. A biomedical imaging software was used to analyze images, and the analysis shows a good visual match with CFD patterns, and thereby manifests promising signs for the use of molecular rotors as highly sensitive shear stress imaging and flow pattern sensors.