26 September 2011
An unwary insect 
that finds itself on the rim of a pitcher plant doesn't have long to live. Not only do the pitcher plants (Nepenthes) have deep cavities to trap their prey, but the rims of these cavities are exceptionally slippery - and their biology has just inspired a scientist at Harvard University to develop a new material so slippery that no liquid can stick to it. The result could be cleaner surgical instruments, walls that are impervious to graffiti, car windscreens that can't ice up, and much more.
The rims of Nepenthes, called the peristomes, have a series of complex adaptations that cause insects to aquaplane along the surface and fall into the pitcher. Researchers at Cambridge University looked at the peristomes under a microscope, in order to understand just how they were so slippery.
Science journalist Ed Yong describes their findings: "[The peristome] is lined with cells that overlap one another, creating a series of step-like ridges and troughs. The plant secretes nectar onto this uneven surface. The troughs collect the nectar, and the ridges hold it in place, preventing it from draining away. The result is an extremely smooth, stable and slippery surface that repels the oils on the feet of insects." By capturing these insects, the plants gain an additional source of nitrogen, allowing them to thrive in nutrient-poor soils.
Tak-Sing Wong has mimicked the Nepenthes peristomes to create a new synthetic material which is ten times as slippery as the next most slippery synthetic.
His surfaces "are made of either stacks of tiny posts, each a thousand times thinner than a human hair, or a random network of similarly thin fibres. These provide a rough structure, which Wong filled with a lubricant, just as the pitcher plant saturates its rough cells with nectar. The lubricant mixes with neither water nor oils, and it barely evaporates," explains Yong.
Find out more and see the vidoes of the slippery surface in action at Discover Magazine.
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