Slippery Slope of Liquid Repellency
Unwanted contact between liquids and solids can create a variety of problems in everything from biomedical devices to fuel tankers. In response, a number of liquid repellent surfaces have been developed to help mitigate these issues, but with limited success. Some researchers at Harvard, inspired by the the slippery surface of the carnivorous Nepenthes pitcher plant, have developed a new liquid-repellent surface technology that is transparent, self-healing, and can repel blood, oil, and brine, among other things.
The Slippery Liquid-Infused Porous Surface (SLIPS) combines a lubricated film on a porous solid using nano/microstructured substrates. The team says the technology can easily scale, because just about any porous material and a variety of liquids can be used in its manufacture. According to the Harvard website:
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.
The team published its initial findings in Nature last September.
Among the applications the team envisions: crude oil and biofuel transport; ice-resistant coatings operating in refrigerated environments; stain-resistant coatings for optical surfaces such as solar cells and night-vision devices; anti-biofouling coatings for medical devices or marine vessels; medical tubing; and even pest barriers. The material can even repel graffiti.
I’ve posted some SLIPS demo videos below: