Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity

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Introduction

Most of current state-of-the-art superhydrophobic surfaces are based on the lotus leaf effect, where they owe their superhydrophobic nature to the composite air-solid-liquid interface (Cassie-Baxter model) which reduces solid-liquid contact area resulting in liquid repellency. This approach works well for liquid such as water, but not for liquid with small surface tensions such as most hydrocarbons. Wong et al has designed a new kind of liquid-repelling surface based on a completely different physical principle, inspired by the pitcher plant Nepenthes. The surface consists of a sponge-like material which is filled with a lubricating film that is smooth to the atomic level. Any liquid that is immiscible with the lubricating liquid can then easily be rolled off. Moreover, the surface, dubbed Slippery Liquid-Infused Porous Surfaces (SLIPS) can withstand high pressures and exhibit impressive self-repairing capabilities.

Results

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Figure 1. Design of SLIPS. a, Schematics showing the fabrication of a SLIPS by infiltrating a functionalized porous/textured solid with a low-surface- energy, chemically inert liquid to form a physically smooth and chemically homogeneous lubricating film on the surface of the substrate. b, Comparison of the stability and displacement of lubricating films on silanized and non-silanized textured epoxy substrates. Top panels show schematic side views; bottom panels show time-lapse optical images of top views. Dyed pentane was used to enhance visibility. c, Scanning electron micrographs showing the morphologies of porous/textured substrate materials: an epoxy-resin-based nanofabricated post array (left) and a Teflon-based porous nanofibre network (right). d, Optical micrographs demonstrating the mobility of a low-surface-tension liquid hydrocarbon—hexane (γA = 18.6 ±0.5 mN m-1, volume ~ 3.6 μl)—sliding on a SLIPS at a low angle (𝛼=3.00).

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References

1. T.S. Wong, S.H. Kang, S.K.Y. Tang, E.J. Smythe, B.D. Hatton, A. Grinthal & J. Aizenberg, "Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity", Nature 2011