Making devices that operate at room temperature and atmospheric pressure is a challenge in many areas of science, with many sensitive pieces of equipment only working at cryogenic temperatures or under vacuum conditions. However, physicists at Berkeley in the US have now built a nanoelectromechanical system (NEMS) that can detect mass with attogram (10-18 g) resolution under ambient conditions1.

The NEMS approach uses electric currents to drive and detect the motion of tiny mechanical structures such as beams and cantilevers. In the Berkeley device, Alex Zettl and co-workers suspend a carbon nanotube across a trench in a silicon-based substrate and connect it to source and drain electrodes on either side of the trench.

Zettl and colleagues monitor how the current through the nanotube varies as signals of different frequency are applied to the drain and a gate electrode at the bottom of the trench. They find that the device has a fundamental frequency of 1.3 GHz, which is a record for a NEMS device. Moreover, when a small amount of iron is deposited onto the nanotube, the resonance frequency changes significantly, so the device could be used as a highly sensitive mass detector.