Film dynamics and lubricant depletion by droplets moving on lubricated surfaces

Abstract

Lubricated surfaces have shown promise in numerous applications where impinging foreign droplets must be removed easily; however, before they can be widely adopted, the problem of lubricant depletion, which eventually leads to decreased performance, must be solved. Despite recent progress, a quantitative mechanistic explanation for lubricant depletion is still lacking. Here, we first explained the shape of a droplet on a lubricated surface by balancing the Laplace pressures across interfaces. We then showed that the lubricant film thicknesses beneath, behind, and wrapping around a moving droplet change dynamically with droplet's speed---analogous to the classical Landau-Levich-Derjaguin problem. The interconnected lubricant dynamics results in the growth of the wetting ridge around the droplet, which is the dominant source of lubricant depletion. We then developed an analytic expression for the maximum amount of lubricant that can be depleted by a single droplet. Counter-intuitively, faster moving droplets subjected to higher driving forces deplete less lubricant than their slower moving counterparts. The insights developed in this work will inform future work and the design of longer-lasting lubricated surfaces.

References in corpus (4)

• Condensation on Slippery Asymmetric Bumps
• Oleoplaning droplets on lubricated surfaces
• Direct measurements of air layer profiles under impacting droplets using high-speed color interferometry
• Levitation of a drop over a moving surface

Cited by in corpus (9)

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• Deformation and relaxation of viscous thin films under bouncing drops
• Cloaking Transition of Droplets on Lubricated Brushes
• Lubrication effects on droplet manipulation by electrowetting-on-dielectric (EWOD)
• Droplets on Lubricated Surfaces: The slow dynamics of skirt formation
• Enhanced Water Nucleation and Growth Based on Microdroplet Mobility on Lubricant-Infused Surfaces
• Dynamics of Droplets Moving on Lubricated Polymer Brushes
• Water under the Ridge: Evaporation, Translation, Crumpling and Encapsulation of a Water Droplet atop a Liquid Polymeric Film
• Dynamics of Thin Lubricant Films upon Liquid Contact on Slippery Surfaces