This dainty-looking floral display is actually a field of thousands of hardy carbon nanotubes–carbon atoms arranged in tough cylinders, each just 20 to 30 nanometers in diameter. Each petal consists of horizontal nanotubes and each center, of vertical ones. The daisies demonstrate a new nanofabrication technique devised by Pulickel Ajayan, Ganapathiraman Ramanath, and their colleagues at Rensselaer Polytechnic Institute in Troy, N.Y. The process is the first to control nanotube growth on silica in three dimensions, the team reports in the April 4 Nature.
In the new process, the scientists use traditional chip-making techniques to pattern silica–silicon dioxide–on a silicon surface. The Rensselaer team took advantage of carbon nanotubes’ ability to grow perpendicular to silica surfaces but not at all on silicon. For each flower, carbon nanotubes grow from the top and sides of a disk of silica. The technique might prove useful in making filtration membranes or microscopic mechanical devices that rely on nanotubes, says Ajayan.