Magnetically Enhanced Marangoni Convection for Efficient Mass and Heat Transfer like a Self-Driving Liquid Conveyor Belt

Temperature gradient-induced Marangoni convection has attracted much attention for basic research and applications since it provides an effective means for mass and heat transfer through a liquid surface flow. Here the authors first propose a general principle to enhance such surface flow by hindering its transition to recirculation flow using an external field. They subsequently identify ferrofluid and use it validate the principle since its reduced magnetic susceptibility at higher temperatures will make the heated surface liquid stay on the surface by a thermomagnetic body force. Using a laser beam to create a heated local surface and a magnet beneath the ferrofluid to provide a vertical field, a high speed and long-range Marangoni flow is confirmed experimentally and further supported by computational fluid dynamics simulations. To demonstrate possible applications, the authors show a self-driving pipeless liquid conveyor belt that can efficiently transfer heat from a source to sink without external power. The demonstration of enhanced Marangoni convection opens new avenue to explore interfacial fluid dynamics and its wide applications.