Available Technology
New Slippery Liquid-Infused Porous Surface (SLIPS) technology offers pressure-stable, self-healing anti-adhesive and anti-fouling surfaces
Technology:
Liquid-repellency
Markets Addressed
Liquid-repellency is critical to the functionality and robustness of many commercial and industrial products and processes including weather-resistant machines and apparel, non-stick and anti-fouling surfaces for consumer products and life sciences equipment, and moisture-repellent surfaces for electronics and devices used in energy and filtration. Current liquid-repellent technologies, such as bioinspired nanopatterned surfaces, have met success in several such areas of application, but these technologies generally suffer from low-durability, complicated and expensive fabrication techniques, and limited utility in a small, specific set of environmental conditions.
The Slippery Liquid-Infused Porous Surface (SLIPS) technology, developed by Dr. Aizenberg’ team, produces liquid-repellant, low-friction surfaces that offer unprecedented pressure-stability, omniphobicity, and impact-resistance. This technology overcomes many of the deficiencies seen in previous technologies and has a broad spectrum of potential commercial and industrial applications including:
- Anti-icing coatings for buildings, aircraft, and refrigeration units
- Anti-fogging coating for windshields, mirrors
- Anti-fouling surfaces for lenses, medical devices
- Anti-coagulant treatments for blood-carrying devices
- Anti-adhesive surfaces for general stain-resistance
- Surface treatments for weather-resistant apparel, solar panels
- Reduced-drag industrial/commercial piping for energy-efficient pumping
- Low-drag, self-healing surfaces for water/air vehicles
Innovations and Advantages
Slippery Liquid-Infused Porous Surfaces (SLIPS) are manufactured by wicking a chemically-inert, high-density liquid coating onto a roughened solid surface featuring micro and nanoscale topographies. The excellent liquid repellency and the self-healing property of the surface are attributed to the ultra-smoothness of the surface of the wicking liquid, which is capable to recover its original shape upon external deformation. The absence of any defects or roughness on such a surface will ensure the absence of the pinning points for a sliding liquid, thus reducing the hysteresis and rendering it nearly friction-free and slippery.
Omniphobicity – The superior liquid-repellency of SLIPS arises from differences in surface energy and density between a given liquid and the liquid-repellent coating. Using a carefully selected, nano-structured solid substrate and a suitable high-density, low surface energy liquid-repellent coating, a surface can be manufactured to repel a wide range of liquids of varying surface tensions, from hydrocarbons such as crude oil and ethanol to viscous fluids and suspensions such as blood (Figure 1).
Figure 1. Crude oil completely wicked from SLIPS without leaving a stain
Self-Healing – Many existing liquid-repellent surfaces rely upon nanostructured or atomically smooth surfaces to resist the penetration of liquids. Once damaged, however, these surfaces permanently lose their repellent capabilities, permit liquid droplet pinning and surface wetting, and cannot be self-repaired. SLIPS is able to maintain liquid-repellency after damaging surface impacts and recover full function.
Pressure-stability – SLIPS have been shown to maintain their liquid-repellency properties under pressures as high as 675 atm. This allows SLIPS to be used both in normal atmospheric conditions and in hazardous conditions such as those seen in underground oil extraction and deep earth exploration.
Optical Transparency – By matching the refractive index of the liquid-repellent coating to the refractive index of the solid nanostructured substrate, SLIPS can be made optically transparent. Furthermore, SLIPS designed for optical transparency will be resistant to scratching and fouling due to the aforementioned self-healing and anti-adhesive properties. In general, currently used non-liquid-infused nanostructured surfaces are not optically transparent, and atomically smooth surfaces, though they can be designed for optical transparency, are not self-healing.
Anti-coagulant – Blood clotting on synthetic biocompatible surfaces is well-recognized problem in medicine. Clotting agents are activated when proteins begin adhering to a synthetic surface, promoting platelet adhesion and life-threatening thrombosis. SLIPS is highly resistant to protein absorption and can thus minimize the incidence of blood clotting if used as the active surface of medical devices such as catheter tubes, stents, and various blood carrying tubes.
Anti-fogging and Anti-icing - Because of its superior liquid-repellent properties, SLIPS is resistant to the accumulation of liquid to due moisture condensation or high-pressure droplet impact under a broad variety of environmental conditions, including extreme temperatures. This property is useful in situations where accumulated liquids can freeze on the surface of a device or mechanism and adversely affects it performance.
Self-cleaning - Due to its anti-adhesive and liquid-repellent properties, SLIPS can be ‘self-cleaned’ of dust particles and other fouling substance using an appropriate low-density liquid (Figure 2).
Figure 2. SLIPS self-cleaning carbon dust with a droplet of ethanol
Additional Information
Publication: “Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity.” Nature 477 (2011) 443-447.
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Inventor(s):
Aizenberg, Joanna
Aizenberg, Michael
Kang, Sung Hoon
Kim, Philseok
Tang, Kam Yan
Wong, Tak Sing
Categories:
For further information, please contact:
Laura Brass, Director of Business Development
(617) 495-3067
Reference Harvard Case #3983