Nature Chem. doi:10.1038/nchem.113 (2009)

Tiny tubes grow spontaneously when small crystals of an inorganic solid are dunked in a solution of an organic ion. The effect could be exploited to build networks of miniature pipes that direct and control fluids.

Leroy Cronin and his colleagues at the University of Glasgow, UK, filmed tubes sprouting at up to 13 micrometres a second; some reached lengths of several centimetres.

The tubes grew from polyoxometalate (POM) crystals in solutions of phenanthridinium-based ions. The dissolving crystals first mingle with the ions to form a membrane, which subsequently bursts, squirting out POM that forms tube walls on contact with more organic ions.

The tubes can be bent with an electric field or the judicious use of obstacles. Their diameters can be customized by altering the concentration of organic ions.