Credit: © 2009 NPG

Nanoelectromechanical systems (NEMS) are used in applications as diverse as fundamental physics and biosensing. At the centre of any NEMS device is a small beam that vibrates with a natural frequency. A wide range of methods are used to make this beam start vibrating in the first instance, and to measure how the vibration frequency changes as, for example, molecules stick to it.

Existing actuation schemes for starting the vibrations can either be on-chip or external, but both approaches suffer from disadvantages, such as high levels of dissipation for the former and problems at high frequencies for the latter. Physicists at the Ludwig Maximilians University in Munich have now demonstrated a new approach to this task that avoids many of these disadvantages1.

Jörg Kotthaus and co-workers used gold electrodes to create an inhomogeneous electric field in the vicinity of their nanobeam, and then relied on the fact that any polarizable material — such as a nanobeam made of silicon nitride — will experience an attractive force that moves it towards the region of maximum field strength. If a second pair of electrodes is added, this dielectric gradient force can also be exploited to detect the motion of the nanobeams.