The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels

Mohammadi, Mahshid; Sharp, Kendra V.

doi:10.1115/1.4029033

Cited by 18 publications

(30 citation statements)

References 31 publications

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“…Few study was performed to investigate bubble dislodgment in complex capillary network. The network structures reported in literatures for the investigation into bubble flow behavior are mainly single straight channels 6,13,16 , Y-type or U type channels 3,[19][20][21] . A single channel cannot simulate the flow conditions of bubble lodgment in complex capillary network.…”

Section: Introductionmentioning

confidence: 99%

Bubble Dislodgment in a Capillary Network with Microscopic Multichannels and Multibifurcation Features

et al. 2019

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Bubble lodgment in complex capillary network is a common issue in many industrial and biological processes. Research work reported in literature only investigated bubble dislodgement in single channels, and did not consider the effect of network complexity on the dislodgement. This paper focuses on the pressure required to dislodge single bubble from a microscopic capillary network, and investigates what factors affecting the dislodging pressure, to facilitate the precise control of bubble flows in porous media. A capillary network with multi-bifurcation and smoothly-changed diameter is designed to closely mimic the structure of the physiological vascular networks. Over 600 bubble dislodgement experiments have been conducted to understand the effect of network structure, channel dimensions, and bubble length on the dislodging pressure. The results indicate that network structure is a dominant factor affecting the dislodging pressure, and dislodging pressure increases with the increase in network complexity. The effect of bubble length on the dislodging pressure depends on bubble length. When the bubble length is less than a certain value, which is around 2 mm in this study, the dislodging pressure increases significantly with the decrease of bubble length. Once the bubble length is larger than 2 mm, the dislodging pressure is independent of bubble length. A model has been proposed to explain the bubble dislodgement in complex capillary networks. The impact of network structure on the bubble dislodging pressure is characterized by a parameter cj. The model indicates that the dislodging pressure is the function of bubble length, channel dimension and network structure. The analysis of model parameters and shows that parameter cj, rather than the channel size dominates the dislodging pressure for bubbles with length greater than 2 mm, and the increase rate of the dislodging pressure is significantly affected by both channel size and parameter cj.

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Section: Introductionmentioning

confidence: 99%

Bubble Dislodgment in a Capillary Network with Microscopic Multichannels and Multibifurcation Features

et al. 2019

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“…Moving above the low bubble mobility region and into the high bubble mobility region, the faster associated liquid velocities provide sufficient pressure field across the bubble to overcome the pinning forces resisting movement 9 in both PEO-coated and uncoated conditions, negating the effect of the coating for this purpose. Bubbles continue to move down channels in both conditions until the system achieves a channel clearance resulting in adequately low-pressure drop that allows remaining bubbles to be stationary in the channels.…”

Section: Discussionmentioning

confidence: 97%

“…3 Obstruction by gas bubbles is a common multiphase problem for liquid phase, microscale-based devices. [4][5][6][7][8][9] For both hollow fiber and microchannel hemodialysis, stationary bubbles within channels and manifolds reduce filtration surface area, create stagnant regions, and disturb flow distribution through the microchannel array. Consequently, filtration performance decreases and blood damage can occur in high shear zones created around bubbles or during prolonged contact of a stagnant blood pool with the walls of a microdevice.…”

Section: Introductionmentioning

confidence: 99%

“…Bubbles arise during normal setup and operation of hemodialysis systems. [9][10][11][12][13] Bubbles can form in-device, when dialysate is heated and when applying negative pressure on the dialysate compartment for ultrafiltration. (12) In the blood compartment, bubbles form when high blood flow and small-sized needles combine to create unsteady flow regions.…”

Section: Introductionmentioning

confidence: 99%

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Effect of PEO coating on bubble behavior within a polycarbonate microchannel array: A model for hemodialysis

et al. 2015

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Obstruction of fluid flow by stationary bubbles in a microchannel hemodialyzer decreases filtration performance and increases damage to blood cells through flow maldistribution. A polyethylene oxide (PEO)-polybutadiene (PB)-polyethylene oxide surface modification, previously shown to reduce protein fouling and water/air contact angle in polycarbonate microchannel hemodialyzers, can improve microchannel wettability and may reduce bubble stagnation by lessening the resistive forces that compete with fluid flow. In this study, the effect of the PEO-PB-PEO coating on bubble retention in a microchannel array was investigated. Polycarbonate microchannel surfaces were coated with PEO-PB-PEO triblock polymer via radiolytic grafting. Channel obstruction was measured for coated and uncoated microchannels after injecting a short stream of air bubbles into the device under average nominal water velocities of 0.9 to 7.2 cm/s in the channels. The presence of the PEO coating reduced obstruction of microchannels by stationary bubbles within the range of 1.8 to 3.6 cm/s, average nominal velocity. Numerical simulations based on the lattice Boltzmann method indicate that beneficial effects may be due to the maintenance of a lubricating, thin liquid film around the bubble. The determined effective range of the PEO coating for bubble management serves as an important design constraint. These findings serve to validate the multiutility of the PEO-PB-PEO coating (bubble lubrication, biocompatibility, and therapeutic loading). © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 941-948, 2016.

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“…At the microscale, gas bubble obstruction becomes an increasing challenge as interfacial energies begin to dominate inertial forces [6][7][8][9][10][11]. Small fabrication defects such as machining burrs or slight misalignments are relatively large in the application of microchannel processes [12].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Microchannel Hemodialyzers Using Residence Time Distribution Analysis

Coblyn¹,

Truszkowska²

2016

J Flow Chem

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Microchannel-based hemodialysis has a potential to improve survival rates and quality of life for end-stage renal disease patients compared to conventional hemodialysis technology. Characterization of hydrodynamic behavior in microchannel geometries is necessary for improving flow uniformity, a critical challenge in realizing a commercial device. A test loop was developed for measuring the impulse response of a tracer dye injected into a dialyzer test article for the purpose of developing residence time distributions (RTD) to characterize lamina design. RTD variance tended to lower for designs that are more dominated, volume-wise, by the microchannel array versus the headers. RTD results also emphasize how defect issues can significantly impact a microchannel device via discrepancies between conceptual and operational devices. A multisegmented CFD model, developed for pairing with the impulse response test loop and dialyzer, showed good agreement between visual observation of the tracer in simulations and experiments, and the shape and peak of the output profiles.

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The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels

Cited by 18 publications

References 31 publications

Bubble Dislodgment in a Capillary Network with Microscopic Multichannels and Multibifurcation Features

Bubble Dislodgment in a Capillary Network with Microscopic Multichannels and Multibifurcation Features

Effect of PEO coating on bubble behavior within a polycarbonate microchannel array: A model for hemodialysis

Characterization of Microchannel Hemodialyzers Using Residence Time Distribution Analysis

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