Chinese researchers say a new material inspired by the way cactus spines pull moisture from desert air can clean oil from water.

Copying the shape of cactus spines that harvest water by pulling it down to their bases, they used conical copper needles to separate tiny oil drops from dirty water, the scientists in Beijing reported in the journal Nature Communications.

The researchers say they were inspired by the discovery that conical needles of the "bunny ear" cactus, Optunia microdasys, can collect water from the air as it coalesces on the needles, driving the moisture to the spine base by the interaction between the shape of the spine and the surface tension of the water droplet.

Synthetic spines can separate and collect oil droplets out of water in the same way, the researchers said, adding they've created a synthetic "cactus skin" of needles that do exactly that.

"We fabricated needle arrays. Each conical needle in the array is a little oil collection device. The arrays can collect micron-sized oil droplets from water continuously and effectively," research leader Lei Jiang said.

In tests the microscopic bed of nails could separate around 99 percent of mixed with water, the researchers said.

Experts hailed the experimental findings.

"This excellent piece of work provides a perfect example of first describing an interesting biological system and then taking it one step further by solving an engineering problem," Joanna Aizenberg of Harvard University told the BBC. "It shows not only how we can learn from Nature but also how to apply that knowledge in bio-inspired design."