Abstract: According to the working principle of valveless micropumps, the theoretical analysis of membrane-fluid coupling vibration process is carried out and a non-linear coupling vibration equation is developed. The approximate solution is obtained by using Galerkin weighted minimum residual method. And the relations among the damping coefficient, the driving force, the natural frequency of membrane and the amplitude of membrane, phase difference, and the flow rate of valveless pumps are discussed. Theoretical analysis shows that when the damping coefficient is small, the amplitude increases near the first order natural frequency. With the increasing of damping coefficient, the resistance of fluid increases gradually on the membrane. At the same time, the amplitude decreases rapidly and phase difference tends to 90° faster with the increasing frequency. When the driving force is certain, the lower the first order frequency of the membrane is, the greater the amplitude can achieve in low frequency. As for the flow rate, it will reach the maximum value quickly in low frequency. Moreover, the greater the damping coefficient is, the lower the natural frequency of pump membrane is, the greater the driving force is, the flux will reach its maximum value more quickly.

Key words: Dynamic characteristics, Solid-liquid coupling, Valveless micropumps