Substance transfer behavior controlled by droplet internal circulation

Internal flow can be induced by the external flow around a droplet. In the present work, the three-dimensional flow pattern and dynamic characteristics of the internal vortex of adhered droplet were demonstrated firstly, and then the substance transfer behavior within the droplet dominated by the internal circulation was revealed by adopting two systems, namely fluorescence reaction and suspended particle capture, and combining with an interface reaction model developed. It was found that the internal circulation could not only transfer the reactants from the inside onto the surface of the droplet quickly, but also carry the particles captured on the droplet surface into the vortex core rapidly in a vortex manner, which could improve the reaction rate and control the capture process. This work uniquely demonstrates fundamental insights into the internal flow pattern of adhered droplet and promotes an understanding of the multiphase droplet-based mass transfer mechanism and particle capture process.