Nonlinear dynamics of electrostatically actuated micro-pumps with thermal effects and filled fluids

As an important component of micromechanical electronics system, micro-pumps have been wide application in chemical, medical and biological fields. Reciprocating displacement micro-pumps composed of a closed pump chamber and an elastic diaphragm. Its fluctuating flow rate is proportional to the vibration amplitudes of the elastic diaphragm. Therefore, in this paper nonlinear vibration behavior of electrostatically actuated micro-pumps is investigated. The influences of mid-plane stretching effect, thermal effect and couple stress are simultaneously considered. An approximate solution of nonlinear resonant frequency is obtained by using the multiple scales method. Results show that without the effect of mid-plane stretching, the system shows a litter softening behavior. If taking the mid-plane stretching effect into account, the system exhibits significant stiffening behavior. Couple stress and negative temperature change decrease the stiffening behavior of the system. This indicates the couple stress reduces the effect of mid-plane stretching. In addition, either increasing applied voltages (AC and DC voltages) or decreasing inner diameter of the micro-pump will extend the useful operating frequency range of the micro-pump. Finally, the useful operating frequency range of the micro-pump is also strongly dependent of properties of fluids inside it.