Tunable micromechanical oscillator

The movement of tiny cantilevers is important in many kinds of devices, including scanning probe microscopes, magnetometers, filters for telecommunications, and mass sensors. Applications are somewhat limited, however, because cantilevers oscillate at or near a single characteristic resonant frequency. Now, though, a group of researchers at Cornell University has built a cantilever that is tunable from 9.6 kHz all the way to 37 kHz. They used a scanning tunneling microscope probe, excited by a piezoelectric motor, to set a thin cantilever vibrating. In the figure, the probe comes in from the left and down at a 45° angle. The probe also played a second role: By moving along the length of the cantilever (which was clamped at one end), it changed the resonant frequency of the cantilever, much as one can adjust the frequency of a violin string by fingering it at various places. The Cornell scientists believe that their concept of combining a local drive force with a constraint will find many applications in microelectromechanical systems. They are currently working to extend this oscillator into the MHz region. (M. Zalalutdinov et al., Appl. Phys. Lett. 77, 3287, 2000 http://dx.doi.org/10.1063/1.1326035 .)