Scientists have made the world's first synthetic tree: a palm-sized duplication of the elegant process by which trees drink.

Known as "transpiration," the hydration process appears to require no biological energy. Scientists theorize that as evaporation occurs on the surface of a tree's leaves, the resulting drop in water pressure propels water from the earth and through their bodies. The same principle pulls oil through the wick of a candle.

Cornell University researchers modeled the water-transporting tissue, called "xylem," with fine networks of hydrogel-embedded capillaries. The hydrogel itself had nanometer-scale pores – the same material is used in contact lenses – that allowed water to evaporate, creating the necessary pressure differential.

The artificial tree proved capable of transporting water, raising the possibility of applying transpiration mechanisms to the heating systems of buildings or the cooling systems of computers.

"It would be nice if you could, in a building, put these passive elements that carry heat around very effectively from a solar collector on the roof, to deliver heat all the way down through the building," said study co-author Abraham Stroock in a press release. Then you could "recycle that fluid back up to the roof the same way trees do it – pulling it back up."

The study was published in Nature.

The transpiration of water at negative pressures in a synthetic tree [Nature]

Images: Above, a detail of water transpiring through the hydrogel; at right, the schematic. Courtesy of Tobias Wheeler.

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