Directional interfacial motion of liquids: Fundamentals, evaluations, and manipulation strategies

The Marangoni effect-often invoked to describe the so-called tears of wine-is in essence the mass transfer along an interface between two fluids due to a gradient of the surface tension. If, in addition, the system experiences a temperature dependence, the phenomenon is called thermocapillary migration. It is an interfacial phenomenon where chemistry, physics, and engineering intersect and has extensive application prospects in modern machinery. It can accelerate the spreading of liquids to enhance the condensation and heat transfer efficiency in condensation assemblies, contribute to the flow rate in open microfluidics, or manipulate tiny amounts of liquids in microelectromechanical systems. In tribo-systems, although lubricant migration contributes to wet rubbing surfaces, an unexpected migration might disrupt the flow, either partially or fully starve the contact area, and cause system failure. It is important not to inadvertently control the lubricants migration for advancing the design philosophy of modern mechanical components. Hence, this paper presents a comparative review of the fundamentals of interfacial motion of liquids, evaluation methodologies, and manipulation strategies in design. Of particular interest is the implementation of manipulation strategies for modern tribo-systems exposed to thermal gradients and establish general guidelines for the design of miniature rolling bearings, microfluidics, and condensation and heat-transfer devices.

Automated summary

The Marangoni effect is a mass transfer phenomenon that can accelerate liquid spreading, enhance condensation and heat transfer efficiency, and has applications in microelectromechanical systems.