Drop transport and positioning on lubricant-impregnated surfaces

Abstract

We demonstrate the transport and positioning of water droplets on macro-patterned lubricant-impregnated surfaces. The macro-patterning produces menisci features in the impregnating liquid layer which interact with a droplet via a capillary mechanism similar to the Cheerios effect. These interactions control the droplet motion and positioning on an otherwise completely slippery surface. We present experimental results using a V-shape channel geometry as a model system. The interaction between deformations on the lubricant layer induced by the droplet and the underlying V-shape geometry leads to both local and global equilibrium positions for the droplet within the channel. We present a mathematical model to quantify the transition from local equilibrium states to the global equilibrium state and show that the latter can be described on the basis of a force balance along the apparent contact line of the droplet. We highlight possible applications where lubricated macro-patterned surfaces can be used to control the motion and localisation of droplets.

Slippery Lubricant‐Infused Surfaces: Properties and Emerging Applications

“…[81] A similar patterned V-shaped surface also allowed for the positioning and movement of droplets based on capillary interactions. [82] Recently, we investigated the capability of different liquids to displace the lubricant from higher surface energy regions and showed that both high and low surface tension liquids can replace it, thereby forming droplets sharply following underlying surface (1) is coated with photoresist (2), irradiated through a photomask, and developed to create the surface pattern (3). Vapor-phase fluoro silanization used to create fluorinated surface functionalities at the exposed surface regions (4); the protected surface regions remain nonfunctionalized after removal of the photoresist (5).…”

Guided droplet transport on synthetic slippery surfaces inspired by a pitcher plant

“…Lubricated topographies, however, would be able to overcome such shortcomings thanks to the pinning introduced by the feature and the droplet's tendency to adhere to the lubricating liquid (whilst being completely mobile). Furthermore, directed motion on lubricated topographies could be created with a vanishingly small tilt of the surface [5,6,[11][12][13][14]22].…”

“…The surfaces were rendered superhydrophobic with a nanoparticle based coating (Glaco Mirror Coat Soft 99 Co.). They were subsequently immersed in a bath of silicone oil (Sigma-Aldrich, 20cSt) and withdrawn vertically at a controlled rate of 1 mms −1 to create a uniform lubricant layer of thickness, t ≈ 13 µm [13].…”

“…Both SLIPS and LIS are modelled on the peristome surface of the Nepenthes trap in that they are preferentially wetted by a film of lubricating liquid that repels foreign liquids (immiscible to the lubricating liquid) [5,6]. Since their conception, these surfaces have often out-performed their conventional superhydrophobic counterparts in terms of their liquid-shedding abilities [5,6,[11][12][13]. However, the lack of drop-solid interaction on these surfaces also means that controlling the motion of liquid droplets is inherently difficult [11,14].…”

“…In doing so, we decipher the mechanism by which prey is guided into the pitcher plant trap, and also provide a means of generating pathways that can control and guide the motion of droplets on slippery, synthetic surfaces. reported the formation of a meniscus due to the distortion to the lubricant layer by a step when the lubricant thickness is comparable to the step height [13]. Here, we assume the shape of the lubricating liquid roughly follows the shape of the macroscopic feature, since the thickness of the lubricating layer is orders of magnitude smaller than the size of the feature.…”