A tiny silicon disk can measure pollutants present in aqueous or gaseous environments, according to Oliver Brand and colleagues at Georgia Institute of Technology. One the disk is a cantilever microbalance that measures the mass of pollutant molecules. "When pollutant chemicals get adsorbed to the surface of the sensor, a frequency change of the vibrating microbalance provides a measure of the associated mass change," explains Brand. Such cantilever microbalances are not new. But, the team has now overcome the issue of how to dampen the cantilever's vibrations without loss of sensitivity, by designing a sensor array on to a silicon disk rather than using the conventional approach.
A sense of atmosphere