Miniature Planes Developed
To Sniff Out Biological Weapons

LONDON (Reuters) - U.S. defence scientists have developed small radio-controlled planes capable of ``sniffing out'' the presence of biological weapons, a British magazine reported on Wednesday. New Scientist said the aircraft, described by one of their developers as ``like little toy planes,'' are designed to fly low into danger zones looking for up to four suspected types of bacteria. As they patrol, air is forced into an on-board sampling chamber, creating a vortex in a pool of water, the magazine said. Every five minutes, water from this chamber is pumped over a sensor consisting of four optical fibres, each of which has a probe fixed to its core. Each probe is coated with an antibody to which the spores of a particular bacterium will bind if present in the water. The planes send out electronic signals, generated by a second set of fluorescent antibodies, if they find even minute quantities of the suspected bacteria. ``They're remote controlled, like little toy planes. They're cheap and they fly low, which is where you need to be,'' New Scientist quoted Frances Ligler of Washington's Naval Research Laboratory as saying. It said Ligler and her team had tested a plane, with a four metre (yard) wingspan and weighing 19 kg (42 lbs), using a harmless bacterium which they had sprayed into the air. Depending on the temperature, it took between five and 20 minutes for the plane to detect the bacterium.