Single-Camera 3D PTV Methods for Evaporation-Driven Liquid Flows in Sessile Droplets
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The experimental characterization of liquid flows in sessile evaporating droplets is an important task for the fundamental understanding of the complex phenomena occurring in these apparently simple systems. The liquid flow induced by the droplet evaporation has a strong three-dimensional character and conventional visualization methods are typically difficult to apply. A more effective approach is to look inside the droplets from the substrate where the droplet lies and use single-camera 3D particle tracking velocimetry (PTV) methods to reconstruct the whole flow field. This paper discusses the implementation of an experimental setup for the quantitative characterization of the flow inside sessile evaporating droplets based on two single-camera 3D PTV methods: the Astigmatic Particle Tracking Velocimetry (APTV) and the General Defocusing Particle Tracking (GDPT). Exemplary results on different types of sessile evaporating droplets are reported and discussed. The presented approach is easy to implement, does not require special or costly equipment, and has the potential to become a standard tool for this type of experiments.
The authors acknowledge financial support by the Deutsche Forschungsgemeinschaft KA1808/22. MR acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 713683 (COFUNDfellowsDTU). AM acknowledges funding from the European Research Council (ERC-StG-2015 NanoPacks, grant agreement No. 678573).
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