Carnivorous plant inspires new super-slippery material
By Ben Coxworth
September 23, 2011
Who doesn't like carnivorous plants? They eat pesky bugs, they look like something out of Flash Gordon, and now it turns out that one of them has inspired a new type of liquid-repellent surface. The inspirational flora is the pitcher plant, which is shaped like - well, like a water pitcher, or perhaps a wide-end-up trumpet. When insects step onto its slippery inner surface, they lose their footing and fall down into a pool of collected rainwater in its base, where they are digested. Scientists from Harvard University's School of Engineering and Applied Sciences (SEAS) have copied the structure of that inner surface and come up with a material that resists not only most liquids, but also ice and bacteria, and it does so under a wide range of conditions.
The secret of the pitcher plant's surface lies in the fact that it does take in a small amount of water, which it keeps in a thin layer on the very outside. In the same way that car tires can hydroplane on an only slightly-wet road, this layer of liquid keeps the oil on insect feet from making secure contact with the plant's actual surface.
The SEAS researchers copied this concept, by infusing an unnamed nanostructured porous material with a lubricating fluid. The resulting technology is known as SLIPS, which stands for Slippery Liquid-Infused Porous Surfaces.
Previous experiments with liquid-repellent surfaces have replicated the surface of the lotus leaf, the microtextured surface of which creates a cushion of air that causes water to bead up. According to SEAS, however, man-made versions of this surface don't perform well with organic or complex liquids, they're expensive to create, they don't stand up to physical damage or extreme conditions, and the liquid droplets tend to soak in instead of rolling away.
On the other hand, besides shrugging off the previously-mentioned substances, SLIPS is said to be inexpensive, self-healing, and able to work in high pressure environments, humid conditions, and freezing temperatures. Possible applications include self-cleaning windows, anti-fouling coatings for ships' hulls, ice- and graffiti-resistant products, and low-friction linings for pipelines and medical tubing.
SEAS is presently in the process of seeking a patent for the technology.
The research was published yesterday in the journal Nature.