Simulation-based Analysis of 3d Flow inside a Micropump with Passive Valves

It is expected that chemical, biological and environmental applications of microdevices will increase with new developments in micromachining techniques. In this work, a micropump design that utilizes passive valves and an actuated diaphragm is presented. The flow rate is controlled by the deflection and the frequency of the diaphragm’s displacement. Passive valves are used for directing the flow. Poiseuille flow analogy is used to generate the equivalent pressure drop and flow rate via modifying the viscosity in the valve-channel in order to replace the variation of the channel width due to valve movement. Overall flow in the micropump is governed by three-dimensional time-dependent Navier Stokes equations. Deformation of the domain due to moving boundaries that coincide with the diaphragm motion is handled with the arbitrary LagrangianEulerian method. Flow rate, hydraulic power and the efficiency of the micropump are obtained with respect to driving frequency and displacement of the diaphragm. INTRODUCTION Micropumps are in demand for a vast range of applications such as surgical operations [1], fuel delivery [2], electronic cooling of microdevices [3] and bio-chemical sensors and actuators [4]. Micropump designs vary with respect to their operation conditions and performance expectations [5]. Especially for liquids, viscous forces dominate the flow in micro scales limiting the transduction mechanisms that can be used in micropumps. In general, micropumps can be classified into two categories based on the principles of actuation that result in a net flow: (1) mechanical displacement pumps that utilize an actuated diaphragm or a similar moving part to generate pressure difference, and (2) dynamic pumps that utilize an electric or magnetic field, and ultrasonic waves on a boundary to generate an external force to move the fluid [5,6,7]. Mechanical reciprocating positive-displacement pumps, in general, consist of a diaphragm membrane or a piston, and at least one or two check valves or nozzle-diffuser type passive-components to move and direct the flow. High flow rates are obtained only with the application of large voltages to piezoelectricmaterial drivers. A few drawbacks of these mechanical pumps include complexity of the design, and unsteady flow rates. Producing controllable steady flows with mechanical micropumps remains somewhat a challenge. Electrically conducting and magnetic fluids can be forced to flow by means of an external electric or magnetic field. However, the emerging electric currents in the fluid may not suitable for many applications. Here, we present a micropump design composed of a dome-shaped diaphragm and two passive valves, which are attached to the inlet and exit of the pump as shown in Fig. 1. Circular diaphragm is placed at