Inertial effects on flow rate spectrum of diffuser micropumps

This study develops a diffuser micropump and characterizes its output flow rates, such as the parabola shape on the frequency domain and the affecting factors. First, an equivalent circuit using electronic-hydraulic analogies was constructed. Flow rate analysis results were then compared to experimental results to verify the applicability of the circuit simulation. The operational frequency was 800 Hz for both cases and maximum flow rates were 0.078 and 0.075 mu l/s for simulation and experimental results, respectively. Maximum flow rate difference between simulation and experiment was 3.7%. The circuit was then utilized to analyze inertial effects of transferred fluid and system components on output flow rates. This work also explained why the flow rate spectrum has a parabolic shape. Analysis results demonstrated that without inertial effects, micropump flow rates are linearly proportional to operational frequency; otherwise flow rate spectrum has parabolic shape. The natural frequency of the actuator-membrane structure was identified using the finite element method to verify whether this parameter affects flow rate characteristics. Experimental and simulation results demonstrated that the frequency of the maximum pumping flow rate was 800 Hz and the first mode natural frequency of actuator-membrane structure was 91.4 kHz, suggesting that the structure natural frequencies of the actuator-membrane structure do not play any role in micropump operations.