Plant technology used to create super-repellent material

Harvard scientists have adopted plant technology to create a material that repels just about any type of liquid, including blood and oil.

The new technology, described in the 22 September issue of Nature, is of particular significance because it also works under high pressures and freezing temperatures.

‘Inspired by the pitcher plant, we developed a new coating that outperforms its natural and synthetic counterparts and provides a simple and versatile solution for liquid and solid repellency,’ said Harvard’s Joanna Aizenberg.

The researchers anticipate that it may be possible for the discovery, for which they are seeking a patent, to be used for fuel- and water-transport pipes, and medical tubing (such as catheters and blood-transfusion systems), which are sensitive to drag and pressure.

Other potential applications include self-cleaning windows and surfaces that resist bacteria and other types of fouling (such as the build-up that forms on ship hulls). The technology may also find applications in ice-resistant materials and may lead to anti-sticking surfaces that repel fingerprints or graffiti.

The bio-inspired surface technology has been dubbed ‘SLIPS’ (Slippery Liquid-Infused Porous Surfaces).

Current advanced repellent surfaces have taken their cues from the lotus plant. The leaves of the lotus plant 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.

The so-called lotus effect, however, does not work well for organic or complex liquids and the technology is costly and difficult to manufacture.

The pitcher plant locks in a water layer, creating a slick coating on the top. In short, the fluid itself then becomes the repellent surface.

‘The effect is similar to when a car hydroplanes — the tyres are literally on the water rather than the road,’ said lead author Tak-Sing Wong, a postdoctoral fellow in the Aizenberg Lab.

‘In the case of 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,’ he said.