Shrinkage Dept.

Research updates on the quest to make really tiny things

by Dr. S.R. Sturzenbaum and Dr. A.J. Morgan

Scientists have long dreamed of creating microscopic swimmers capable of ferrying drugs to precise locations in a cell or helping assemble infinitesimal machines. Now Iranian physicists have proposed a simple design modeled on the slow-moving earthworm. Their â€nano-swimmer†would consist of three spheres connected in a row by two rods. When moving, the rods would contract in sequence-first the rear one, then the front; next they would expand in reverse order. This might sound inefficient for a fluid environment, but on the molecular scale, water acts much like molasses: it would actually grip the swimmer´s leading sphere as the rods contracted. As they expanded, the water would hold on to the back of the hind sphere, allowing the front of the machine to lurch forward-similar to a competitive swimmer pushing off the wall after a turn. One group is already trying to build a prototype from molecules that inch forward in response to light, says co-designer Ramin Golestanian of the Institute for Advanced Studies in Basic Sciences in Zanjan, Iran, but the first applications are still about 20 to 30 years away.