Oil spill-absorbing material inspired by cactus needles

When an oil spill occurs at sea, there are already a number of possible options for gathering the oil that floats in a layer on the water’s surface. Some of the oil also forms into tiny suspended droplets, however, which have proven much more difficult to gather. Now, Chinese scientists have developed what could be a solution – and it owes a debt to the humble cactus needle.

Although it may seem that the only purpose of cactus needles is to protect the plants from peoples’ bare feet, they also help provide the cacti with water. They do so by collecting moisture from the desert air, which forms into droplets and is carried to the base of each needle via surface tension. There, it can be absorbed through pores in the plant’s surface.

A team from the Chinese Academy of Sciences has recently taken that same principle, and applied it to a material that shows promise as a means of absorbing the oil spill droplets.

At first glance, the material appears to simply have a rough surface. Upon closer inspection, however, it can be seen that the surface actually consists of an array of tiny conical copper spikes. These spikes are affixed to a flexible synthetic substrate that is known for its tendency to absorb oil, but not water.

When the material is placed in oil-contaminated water in a lab, micron-sized droplets gather on the spikes and are then drawn to the substrate – just like the water droplets do on cactus needles. It’s reportedly able to remove up to 99 percent of the droplets from water samples, and it gathers oil continuously.

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