Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging1. Inspirations from natural nonwetting structures2,3,4,5,6, particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air–liquid interface7,8,9. Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis9, failure under pressure10,11,12 and upon physical damage1,7,11, inability to self-heal and high production cost1,11. To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach—inspired by Nepenthes pitcher plants13—is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert ‘slippery’ interface. This surface outperforms its natural counterparts2,3,4,5,6 and state-of-the-art synthetic liquid-repellent surfaces8,9,14,15,16 in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1–1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments.
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T.-S.W. acknowledges funding support from the Croucher Foundation Postdoctoral Fellowship. We thank K. E. Martin for help with the drop impact test. We also thank J. C. Weaver and P. Allen for help in manuscript preparation. The work was supported partially by the AFOSR MURI award FA9550-09-1-0669-DOD35CAP (optical properties), and ARO MURI award W911NF-09-1-0476 (robustness and self-repair). We acknowledge the use of the facilities at the Harvard Center for Nanoscale Systems supported by the NSF under award ECS-0335765.
This movie demonstrates the liquid repellency of a SLIPS under extremely high pressure (˜675 atm) environment. As seen from the movie, a droplet of decane (˜ 4 µL) retains the ability to slide on the SLIPS when the surface is tilted less than 10 degrees relative to the horizontal plane.
This movie demonstrates the fast recovery of the liquid-repellent function of a SLIPS after critical physical damage. As seen from the movie, the crude oil droplet is pinned on a nanostructured superhydrophobic surface (without lubricating fluid), while the droplet maintains its mobility on the SLIPS. Extra-light crude oil (from Appalachian Basin, USA) was used as the test liquid for demonstration.
This movie demonstrates the excellent oil repellency of a SLIPS, as compared to other textured and non-textured surfaces. As seen from the movie, oils slide faster on the SLIPS leaving behind no noticeable oil, whereas oil stains are observed on the other surfaces. Light crude oil (from Louisiana, USA) was used as the test liquid for demonstration. This movie corresponds to Fig. 4a in the main text.
This movie demonstrates the excellent blood repellency of a SLIPS, as compared to other textured and non-textured surfaces. As seen from the movie, no noticeable blood is left on the SLIPS, whereas blood stains are observed on the other surfaces. Sheep blood (HemoStat Laboratories, CA) was used as the test fluid. This movie corresponds to Fig. 4b in the main text.
This movie demonstrates the excellent ice-repellency of a SLIPS, as compared to a nanostructured surface. As seen from the movie, an ice block (formed from a frozen water droplet of ˜100 µL at –4 °C and ˜45% relative humidity) slides on the SLIPS under the influence of gravity. In comparison, an ice block of the same volume remains strongly pinned on a superhydrophobic nanostructured surface without a lubricating layer. This movie corresponds to Fig. 4c in the main text.
This movie demonstrates the ability of a SLIPS to repel an insect and a highly viscous fluid (i.e., strawberry jam). As seen from the movie, a carpenter ant is unable to stay on our synthetic slippery surface—a direct mimicry on the insect-trapping capability of pitcher plants in nature. This movie corresponds to Fig. 4d in the main text.
This movie demonstrates the self-cleaning ability of a SLIPS. As seen from the movie, carbon dust is seeded onto the SLIPS and can be easily removed by sliding an ethanol droplet across the surface. This movie corresponds to Fig. S7a in the Supplementary Information.