76th Annual Meeting of the APS Division of Fluid Dynamics (November 19, 2023 — November 21, 2023)

V0077: Light-driven Marangoni flows

Authors
  • Xichen Liang, Department of Chemical Engineering, University of California, Santa Barbara
  • Kseniia Karnaukh, Department of Chemistry, University of California, Santa Barbara
  • Lei Zhao, Department of Mechanical Engineering, University of California, Santa Barbara
  • Serena Seshadri, Department of Chemistry, University of California, Santa Barbara
  • Austin DuBose, Department of Chemistry, University of California, Santa Barbara
  • Sophia Bailey, Department of Chemistry, University of California, Santa Barbara
  • Qixuan Cao, Department of Physics, University of California, Santa Barbara
  • Marielle Cooper, Department of Mechanical Engineering, University of California, Santa Barbara
  • Hao Xu, Department of Mechanical Engineering, University of California, Santa Barbara
  • Michael Haggmark, Department of Chemical Engineering, University of California, Santa Barbara
  • Matthew Helgeson, Department of Chemical Engineering, University of California, Santa Barbara
  • Michael Gordon, Department of Chemical Engineering, University of California, Santa Barbara
  • Paolo Luzzatto-Fegiz, Department of Mechanical Engineering, University of California, Santa Barbara
  • Javier Read de Alaniz, Department of Chemistry, University of California, Santa Barbara
  • Yangying Zhu, Department of Mechanical Engineering, University of California, Santa Barbara
DOI: https://doi.org/10.1103/APS.DFD.2023.GFM.V0077

Fast and programmable transport of liquid droplets on a solid substrate is desirable in microfluidic, thermal, biomedical, and energy devices. Past research has focused on designing substrates with asymmetric structures or gradient wettability where droplet behaviors are passively controlled, or by applying external electric, thermal, magnetic, or acoustic stimuli that either require the fabrication of electrodes or a strong applied field. In this work, we demonstrate tunable and programmable droplet motion on liquid-infused surfaces (LIS) and inside solid-surface capillary channels using low-intensity light and photo-responsive surfactants. When illuminated by the light of appropriate wavelengths, the surfactants can reversibly change their molecular conformation thereby tuning interfacial tensions in a multi-phase fluid system. This generates a Marangoni flow that drives droplet motions. The method demonstrated in this study serves as a simple and exciting new approach for the dynamic manipulation of droplets for microfluidic, thermal, and water harvesting devices.

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