Feasibility Study for a Novel Micropump Design That Utilizes Shape Memory Alloy Diaphragm and Blood Flow

Abstract

Many different types of micropumps have been designed to pump a variety of fluids at the micro-liter level. Some of the major short-comings of these designs are leaks due to moving parts, lack of tolerance to bubbles, high operating voltages, structural complexity, slow response time, and insufficient pressure head. This research presents a novel design that utilizes a two-way shape memory alloy (SMA) diaphragm within the micropump. Heating of the SMA diaphragm is accomplished via resistive heating, while the cooling is accomplished with a novel method that utilizes blood flow. Blood is used as the cooling fluid since it is readily available in most medical applications, such as drug delivery or lab-on-a-chip (LOC). Additionally, with humans there is a constant supply of blood at a constant temperature. This study explains and illustrates how an SMA micropump operates. With the primary liquid flow in this application being blood, a detailed model of the non- Newtonian behaving blood is included. The hydrodynamics are numerically computed using the Lattice Boltzmann Method (LBM). Two different non-Newtonian blood models are presented. Phase changes in the shape memory alloy are computed using the Cosine Model. All of the thermal analysis is performed via finite volumes. Ultimately, this study shows that an SMA micropump is feasible when pumping fluids in the micro-liter range of flow. This work is a feasibility study and addresses iii operation parameters in a general sense. All of the design parameters are reasonable for a micro-liter micropump.