Design, modeling and fabrication of a constant flow pneumatic micropump

This paper characterizes a bi-directional pneumatic diaphragm micropump and presents a model for performance of an integrated fluidic capacitor. The fluidic capacitor is used to convert pulsatile flow into a nearly continuous flow stream. The pump was fabricated in acrylic using a CNC mill. The stroke volume of the pump is similar to 1 mu L. The pump is self-priming, bubble tolerant and insensitive to changes in head pressure and pneumatic pressure within its operating range. The pump achieves a maximum flow rate of 5 mL min(-1) against zero head pressure. With pneumatic pressure set to 40 kPa, the pump can provide flow at 2.6 mL min(-1) against a head pressure of 25 kPa. A nonlinear model for the capacitor was developed and compared with experimental results. The ratio of the time constant of the capacitor to the cycle time of the pump is shown to be an accurate indicator of capacitor performance and a useful design tool.