Coupled Vibration and Stability Analysis of a Circular Diaphragm in an Electrostatically Actuated Micro Pump

Micro pumps play a significant role in various electromechanical structures especially biomechanical devices where fluid delivery in micro scale is the essential requirement. These pumps are basically composed of three parts: moving part excited by an actuation mechanism, fluid chamber, and flow channel (valves). This paper investigates the free vibration of a circular diaphragm in an electrostatically actuated micro pump. Fluid chamber is cylindrical with rigid circumferential wall and covered by the deformable diaphragm. Bottom surface has a central outlet and an annular rigid section. Complete liquid-structure interaction between the elastic diaphragm and working fluid is adopted considering the time-variant fluidinduced pressure (linear Bernoulli equation) and kinematic compatibility in the boundaries. The governing equation for the lateral deflection of the diaphragm is derived using assumed-modes method. It is seen that higher modes frequencies are less affected by the coupling effect. Effect of material properties onthe natural frequencies of the coupled system is also investigated. Moreover, the change in the natural frequency of the system by the application of a bias DC voltage is depicted. Dynamic behavior of the diaphragm is depicted in case of DC and AC voltage excitations and pull-in conditions are investigated.

Keywords:

Micro pump , Coupled vibration , Electrostatic force , pull-in instability