Pitcher plant inspires slippery surface

26 September 2011

The slick interior of the pitcher plant has inspired a highly slippery material possessing self-lubricating, self-cleaning and self-healing properties.

Dr Tak-Sing Wong, a 2010 Croucher postdoctoral fellow and his colleagues at Harvard University have applied the strategy of the plant to create a new material that repels just about any type of liquid and does so even under harsh conditions like high pressure and freezing temperatures.

The bio-inspired liquid repellence technology, described in the 22 September 2011 issue of the scientific journal Nature should find applications in biomedical fluid handling, fuel transport, and anti-fouling and anti-icing technologies. It could even lead to self-cleaning windows and improved optical devices.

“The effect is similar to when a car hydroplanes, the tires literally gliding on the water rather than the road,” says Wong. “In the case of the unlucky ants, the oil on the bottom of their feet will not stick to the slippery coating on the plant. It’s like oil floating on the surface of a puddle.”

Inspired by the pitcher plant’s elegant solution, Wong and his colleagues designed a strategy for creating slippery surfaces by infusing a nano/microstructured porous material with a lubricating fluid. Like the pitcher plant, these surfaces are slippery for insects, but also repel a wide variety of liquids including oil.

By contrast, current state-of-the-art liquid repellent surfaces have taken cues from a different member of the plant world. The leaves of the lotus resist water due to the tiny microtextures on the surface; droplets balance on the cushion of air on the tips of the surface and bead up.

However, this “lotus effect” does not work well for organic or complex liquids. And if the surface is scratched or subject to extreme conditions, liquid drops tend to stick to or sink into the textures rather than roll away.

“This new repellent fluid surface offers additional benefits, as it is intrinsically smooth and free of defects,” says Wong. “Even after we damage a sample by scraping it with a knife or blade, the surface repairs itself almost instantaneously and the repellent qualities remain, making the surface self-healing.” The surface can be made optically transparent, and is therefore ideal for optical applications and self-cleaning, clear surfaces.

Reference: T-S Wong et al, Nature, 2011, 477, 443 (DOI:10.1038/nature10447)

26 September 2011

                 
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