Design of a Micro-Pump via Simulation

The following section is a summary of a paper submitted to ASME [56]. The research was done with Ali Beskok of CFM, Brown University. It is included to demonstrate that the ALE component of has been used as a conceptual design tool. The goal of this project was to produce a potential design for a pump that can be fabricated in micro-dimensions.

The performance of the micro-pump is evaluated as a function of the Reynolds number and the geometric parameters. The volumetric flow rate is shown to increase as a function of the Reynolds number. However, the efficiency of the micro-pump decreases with increased Reynolds number, due to the increased leakage effects.

Micro-pump systems, delivering volumetric flow rates in the order of $10^{-8} \sim 10^{-12} m^3/s$ can be used in many bio-fluidic, drug delivery, mixing and flow control applications. Most of the micro-pump systems are actuated by a vibrating membrane in a chamber with hanging-beam-type (Cantilever beam) inlet and exit micro-valves [57], [58], [59]. These are uni-directional micro-pumps, since the Cantilever-type micro-valves only open in a preferred flow direction.

  

Figure 5.15: Sketch of the micro-pump operating between two micro-channel systems. Inlet and exit valves open and close periodicly with maximum gap of gmax=0.125L and minimum gap of gmin=0.025L.

In this study, we present a bi-directional (reversible) micro-pump utilizing a vibrating membrane and piston-type (moving) inlet and exit valves (See figure 5.15). Since the inlet and the exit valves are simple micro-pistons, oscillating in between open and closed positions with a prescribed motion, it is possible to control the performance of the micro-pump with control of the micro-valves. The design is flexible, so that the pumping direction can be easily reversed. This design has the advantage of reversibility, yet it can maintain its performance for relatively high Reynolds number applications.