New device can weigh a single molecule

An international team including researchers in California says it has made the first-ever mechanical device that can weigh individual molecules one at a time. The new technology could eventually help doctors diagnose diseases, enable biologists to study viruses and probe the molecular machinery of cells and even allow scientists to better measure nanoparticles and air pollution, researchers at the California Institute of Technology who took part in the effort reported. The device, only a couple of microns (millionths of a meter) in size, consists of a tiny, vibrating bridge-like structure. When a particle or molecule lands on the bridge, researchers said, its mass changes the oscillating frequency of the bridge in a manner that reveals how much the particle weighs. "As each particle comes in, we can measure its mass," Caltech physics Professor Michael Roukes said. "Nobody's ever done this before." A description of the technology has been published in the online version of the journal Nature Nanotechnology.