ÌÇÐÄVlog

An air pollution monitor small enough to wear on the wrist could be built using a new technique developed by physicists at the University of Birmingham. The device could alert asthmatics to traffic fumes that trigger attacks.

Richard Palmer, who is leading the project and who suffers from asthma, said: "We would like to build a nano-nose. If you were walking down the road and you wanted to avoid a particular exhaust gas, it could warn you of its presence.

"We are trying to construct nanostructures just a few atoms across using a bottom-up technique - a sort of atomic Lego," Professor Palmer said.

His researchers create clusters of about 500 atoms floating freely in a gas, then select them by their mass and spray them onto a surface. Using this technique, they can build up minute structures.

The number of atoms in each cluster affects the way in which the cluster behaves. Professor Palmer's team can therefore tune the physical characteristics of each cluster to detect particular gas molecules.

However, there is a danger that the characteristics of each cluster will be lost if the clusters are brought too close together and merge. "The real challenge is in creating materials that replicate the properties of one cluster throughout the whole assembly," Professor Palmer said. "To achieve this we need to locate each cluster exactly. We do this by giving each cluster enough energy to take one atom from the substrate, creating a defect that traps the cluster."

Professor Palmer intends to publish details of his technique shortly.