Study Of Mechanical Behaviors Of Electrostatically Actuated Microstructures

As an important driving force in Micro Electromechanical System (MEMS), the electrostatic force is widely applied to such microdevices as micromirror, micropump, micromotor, microgyro, microforceps, moicroresonator, and RF switch et al. Although some electrostatically driven MEMS products have been commercialized, the related design theoretics cannot satisfy the devising demands yet. So the method of trial and error, which resulted in low eligible products ratio and low reliability, is the primary technology reason which slows down the step of research and industrialization of the products. Based on the theories of electrostatic field, elastic force, structure dynamics and hydrodynamics, the problems of electrostatic force, statics and dynamics in several typical electrostatically driven microstructures are lucubrated with the aid of compute simulation to achieve the systemic analysis and design. An electrostatically-driven micro-acceleration switch with obvious threshold characteristic is devised, a model of which is established and emulated. The work done in this paper not only has an important academic significance in promoting the study of the theory of microstructures driven by electrostatic force, but also has an instructive significance in improving the design level of electrically actuated microdevices .On the basis of the parallel-plate capacitance theory and the virtual displacement principle, the model for calculating electrostatic force of several typical microstructures is educed. The effect of fringe field on the electrostatic force is discussed. The precision of different models of electrostatic force is analyzed. So the appropriate domain of electrostatic force of infinite parallel-plate is obtained to provide a theoretic basis for the statics and dynamics research of structures.A distributing hypothesis of electric field between the EFM tip and the sample surface is put forward. Based on the hypothesis, an analytic model is set up to calculate the electrostatic force of the tip. The results from the model are consistent not only with those from such numerical means as equivalent charge and FEM, but also (consistent) with the experimental results.The phenomenon of pull-in or snap-down is analyzed, which results from the coupling between the elastic force of microstructure and the electrostatic force. Based on the small deflection theory, a numerical procedure and an analytical formula, by which the pull-in deflection is obtained, are presented to calculate the deflection of microbeam driven by electrostatic force. The rationality is analyzed by using small deflection theory to calculate the deflection of microstructures.Based on the small deflection theory, the differential equation of axis-symmetrically circular laminate driven by electrostatic force is established and calculated through the weighted residual method of Galerkin. With the differential equation established, the pull-in deflection is obtained to be 1/3 of the initial gap. Based on the torque equilibrium principle, the dominating equation of micromirror is established and computed to analyze the effect of air-film damp on the response speed of micromirror.Based on the analytical model established to calculate the electrostatic force of tip, the deflection of EFM tip is acquired. The effect of the structural parameters of EFM tip on the deflection of the tip is analyzed. The pull-in deflection of EFM tip is obtained to...