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Particle Manipulation Based on Optically Controlled Free Surface Hydrodynamics


  • S.N.V., S.D.G., T.B., and S.H. kindly acknowledge support by the German Research Foundation (DFG) through the Cluster of Excellence 259. M. Ewald and M. Biesalski gratefully acknowledge funding from the research initiative “Soft Control” within the LOEWE Program of the State of Hessen (Germany). S.N.V. and S.D.G performed the experiments and the analysis of the experimental data. T.B. did the Computational Fluid Dynamics simulations and helped with the interpretation of the experimental results. S.H. developed the concept of optically-controlled Marangoni tweezers based on photosensitive surfactants and helped with the interpretation of the experimental results. M.E. and M.B. were responsible for the synthesis and purification of the surfactant C4AzoOC4E2, as well as for the verification the chemical identity of this molecule.


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Microparticle manipulation: The photoisomerization of surfactants adsorbed at a gas–liquid interface drives a Marangoni flow that can be used for the trapping and manipulation of small particles. By switching the laser wavelength, a flow either into or away from the focal spot can be induced. The picture shows a microparticle trapped in the focal region by the inflow.