"A magnetically driven acoustic streaming micropump using a flexible PCB actuator"
A magnetically driven acoustic streaming micropump using a flexible PCB actuator
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This thesis is concerned with the phenomenon known as acoustic streaming, which describes a net flow that arises from the attenuation of acoustic waves, either in the bulk of the fluid or near a solid boundary, and investigates, if this effect can be used as a driving mechanism in a microfluidic pump, with the goal of a simple and cost effective setup. Boundary layer driven acoustic streaming was found to be promising for the implementation as a micropump, where one wall of the fluid channel is made of a flexible material and should support a flexural travelling wave. The study consists of an elaboration of the theoretical basis that is necessary when considering fluid dynamics, including a detailed review of the governing equations and dimensionless numbers that are useful when investigating acoustic streaming. Perturbation theory is introduced to the governing equations and is implemented using the commercial finite element software COMSOL Multiphysics for a numerical analysis of the effect. This approach helps reducing the computational effort and a comprehensive study of the influences on the generated mean flow is carried out. A comparison of this approach with the results of a time-dependent simulation of the full Navier-Stokes equations is provided, to proof the feasibility of the perturbation approach. The proposed design of the micropump utilizes a flexible printed circuit board (PCB) as an oscillating channel wall; the motion is magnetically actuated via Lorentz forces acting on the current-carrying traces in a magnetic field. The approach with the flexible PCB makes the manufacturing process simple and would keep costs down in a mass production. The fluid channel itself is printed with a 3D-printer. Finally, experimental results of this setup are presented, where particle tracking velocimetry (PTV) was used for the evaluation of the flow velocity, and a comparison with the theoretical results is made.