Date post: | 26-Jul-2015 |
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Micro-Electro-Mechanical System
ELECTROSTATICALLY ACTUATED CANTILEVER BEAM
By-Vedavyas P.Burli
Introduction
• Elastic cantilever beam is an elementary structure in MEMS design.
• The electro mechanics interface to solve the coupled equations for the structural deformation and the electric field. Such structures are frequently tested by means of a low frequency capacitance voltage sweep.
• The bending of a beam due to electrostatic forces.
Model definition
• The dimensions of the beam are: Length: 300 μm; Width: 20 μm; and Thickness 2 μm.
• The beam is made of polysilicon with a Young’s modulus, E, of 153 GPa, and a Poisson’s ratio, ν, of 0.23.,
• It is fixed at one end but is otherwise free to move.
• The polysilicon is assumed to be heavily doped, so that electric field penetration into the structure can be neglected.
Result and discussion • There is positive feedback
between the electrostatic forces and the deformation of the cantilever beam.
• This action, in turn, increases the forces. At a certain voltage the electrostatic forces overcome the stress forces, the system becomes unstable, and the gap collapse
References • R.K. Gupta, Electrostatic Pull-In Structure Design for In-Situ Mechanical
Property Measurements of Microelectromechanical Systems (MEMS), Ph.D. thesis, MIT, 1997.
• Methodologies.V Vardhan K.J.Vinoy,S.Gopalkrishnan,Wiley.Smart Material systems and MEMS design and development
• Model gallery,COMSOL Multiphysics 4.3