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Driving oscillatory flow around an obstacle generates, due to inertial rectification, a steady ‘streaming’ flow that is useful in a host of microfluidic applications. While theory has focused largely on two-dimensional flows, streaming in many practical microfluidic devices is three-dimensional due to confinement. We develop a three-dimensional streaming theory around an obstacle in a microchannel with a Hele-Shaw-like geometry, where one dimension (depth) is much shorter than the other two dimensions. Utilizing inertial lubrication theory, we demonstrate that the time-averaged streaming flow has a three-dimensional structure. Notably, the flow reverses direction across the depth of the channel, which is a feature not observed in less confined streaming set-ups. This feature is confirmed by our experiments of streaming around a cylinder sandwiched in a microchannel. Our theory also predicts that the streaming velocity decays as the inverse cube of the distance from the cylinder, faster than that expected from previous two-dimensional approaches. We verify this velocity decay quantitatively using particle tracking measurements from experiments of streaming around cylinders with different aspect ratios at different driving frequencies.
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STRONG MICROSTREAMING FROM A PINNED OSCILLATING MEMBRANE AND APPLICATION TO GAS EXCHANGE
We present a novel configuration to generate strong acoustic streaming vortices by a pinned oscillating membrane in a microchannel, its characterizations via advanced measurement techniques, and initial studies in application by augmentation of gas exchange across a permeable membrane towards microfluidic artificial lung technology. The configuration is stable over time and does not create any obstruction in flow passages. For an audible- frequency 20 Vpp input to a piezo buzzer, streaming velocity was measured up to 47 mm/s. Mixing from helical flow patterns in the microchannel augments gas transfer rate across the membrane up to 3.4 times compared to no actuation, allowing larger channel dimensions (better facilitation of scale-up manufacturing) and reduced shear (more hemocompatible) in microchannel-based artificial lung systems.
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- Award ID(s):
- 1951051
- PAR ID:
- 10399252
- Date Published:
- Journal Name:
- 2023 IEEE Conference on Microelectromechanical systems
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
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