Frequency Tuning of Micro-beams using Electrostatic Pull-in
J.S. Burdess, A.J. Harris and S. Kafumbe
University of Newcastle, UK
micro cantilever, frequency tuning, pull-in, voltage control
The work reported shows how the frequency of vibration of simple beam structures can be changed significantly through the action of electrostatic pull-in. The application of a voltage between the beam and a supporting, but insulating, substrate will eventually cause the beam to become attached to the substrate. This changes the supporting conditions and thus the free length of the beam and thus its natural frequency.A theory, which is developed using variational methods, is described and this identifies three different stable states of static deflection.For the final state, it is shown that the change in the frequency of free vibration is proportional to applied voltage and that increases in frequency, of up to an order of magnitude greater than the initial frequency, can be achieved.
Micro-cantilevered beams, fabricated from gold using electro-deposition, are used to test the efficacy of this approach. An overview of the experiment is presented and it is shown how the dynamic characteristics of the beams, at different pull-in voltages, are derived from Laser Doppler vibrometry measurements. The results of the tests are presented and it is shown that the pull-in procedure provides a non destructive way of actively changing the natural frequency of a simple elastic structure
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Nanotech 2006 Conference Program Abstract