Micro marbles make nano rings

Scientists are searching for faster, cheaper ways of making useful nanoscale objects than today's chipmaking techniques. Chemical methods are proving particularly fruitful.

Researchers from Basf Corporation, the University of Ulm and the Technical University of Chemnitz in Germany have devised a relatively simple way to make precisely-sized nanoscale rings en mass from many different materials including polymers and ceramics.

These tiny rings can be used to make materials that bend, or refract, light backwards. Negative refraction materials can be used to focus light down to smaller areas than are possible using ordinary lenses. The rings could eventually be used in powerful microscopes and equipment capable of making very fast computer chips.

The method yields rings with outer diameters of 150 to 400 nanometers, and inner diameters of 50 to 150 nanometers. A nanometer is one millionth of a millimeter.

To make the rings the researchers formed glass spheres 1.1 microns in diameter, put the spheres in ethanol and used a centrifuge to pack the particles into a tight, orderly crystal. They immersed the crystal in a liquid containing liquid plastic or ceramic and a solvent, and evaporated the solvent to leave liquid ring material in the spaces immediately surrounding the point where the spheres touch. They solidified the ring material, dissolved the spheres with hydrofluoric acid vapor, then dispersed the resulting rings in ethanol.

The work appeared in the March 15, 2005 issue of Angewandte Chemie International Edition (The Preparation of Mesoscopic Rings in Colloidal Crystal Templates).