Calibration-Free Travel Time After Photobleaching Velocimetry

In interfacial science, there is an increasing need to measure flow velocity fields at interfaces with ultrahigh spatial and temporal resolution to study transport phenomena. Although laser-induced fluorescence photobleaching anemometry (LIFPA) has achieved nanoscopic resolution for flow measurement, it requires pre-calibration, which is unavailable for unknown flows. We present a novel, calibration-free travel time after photobleaching velocimeter (TTAPV) which can both measure fluid flow velocity and satisfy the long-anticipated need of calibration for LIFPA.