For years, scientists have talked up the potential of nano-technology, or devices such as microscopic robots. Now, a chemist at the University of Michigan has developed one of these itsy-bitsy items, a fiber-optic sensor that can monitor the chemical properties, such as acidity, inside a living cell without damaging it. The new sensor, one-thousandth the size of existing fiber-optic sensors, could also be used to test the effects of new drugs on single cells.
A manufacturing technique called near field photopolymerization, developed by Raoul Kopelman, professor of chemistry, makes the probe possible. The polymer tip that enters a cell is about 20 times the size of an average molecule. To make it, researchers shine a beam of light into one end of an optical-fiber probe that is coated with aluminum. Light emerges from a small opening in the far end of the probe, which rests in a solution of molecules called monomers. The light induces a chemical reaction between the monomers and the molecules on the end of the probe, which "grow" the polymer tip.