Performance Characteristics of a Membrane Driven Variable Flow Rate Micro-Pump

A micropump was developed for a fluidic system that requires fluid transport in the 100+ μL/min flow range. The constraints on the design included the ability to control the flow rate over a reasonable range of flow rates, operate at fairly high pressure loads, and non-contact of the working fluid with the pump actuation system. The design was based on a displacement style pump, actuated by a piezoelectric element, with one-way polymer membrane check valves. The valves provided essentially zero backflow based on the elastic character of the material. Results are presented for three membrane thicknesses, three valve opening diameters, over a range of operating frequencies. The flow rate versus frequency curves show a characteristic trend with three regions of operation, the first a linear region at low frequencies, the second a region of decreasing slope resulting in a maximum flow rate regime and the third a region of reduced flow rate with increasing frequency. Results also show that a suction lift could be overcome with the micropump whose value depends on the valve size. The performance is compared to an ideal case indicating that larger diameter valves with thinner membranes obtain the best performance.