TY - JOUR
T1 - Capillary-flow dynamics in open rectangular microchannels
AU - Kolliopoulos, Panayiotis
AU - Jochem, Krystopher S.
AU - Johnson, Daniel
AU - Suszynski, Wieslaw J.
AU - Francis, Lorraine F.
AU - Kumar, Satish
N1 - Publisher Copyright:
© The Author(s), 2021. Published by Cambridge University Press
PY - 2021
Y1 - 2021
N2 - Spontaneous capillary flow of liquids in narrow spaces plays a key role in a plethora of applications including lab-on-a-chip devices, heat pipes, propellant management devices in spacecrafts and flexible printed electronics manufacturing. In this work we use a combination of theory and experiment to examine capillary-flow dynamics in open rectangular microchannels, which are often found in these applications. Scanning electron microscopy and profilometry are used to highlight the complexity of the free-surface morphology. We develop a self-similar lubrication-theory-based model accounting for this complexity and compare model predictions to those from the widely used modified Lucas-Washburn model, as well as experimental observations over a wide range of channel aspect ratios and equilibrium contact angles. We demonstrate that for large the two model predictions are indistinguishable, whereas for smaller the lubrication-theory-based model agrees better with experiments. The lubrication-theory-based model is also shown to have better agreement with experiments at smaller, although as it fails to account for important axial curvature contributions to the free surface and the agreement worsens. Finally, we show that the lubrication-theory-based model also quantitatively predicts the dynamics of fingers that extend ahead of the meniscus. These findings elucidate the limitations of the modified Lucas-Washburn model and demonstrate the importance of accounting for the effects of complex free-surface morphology on capillary-flow dynamics in open rectangular microchannels.
AB - Spontaneous capillary flow of liquids in narrow spaces plays a key role in a plethora of applications including lab-on-a-chip devices, heat pipes, propellant management devices in spacecrafts and flexible printed electronics manufacturing. In this work we use a combination of theory and experiment to examine capillary-flow dynamics in open rectangular microchannels, which are often found in these applications. Scanning electron microscopy and profilometry are used to highlight the complexity of the free-surface morphology. We develop a self-similar lubrication-theory-based model accounting for this complexity and compare model predictions to those from the widely used modified Lucas-Washburn model, as well as experimental observations over a wide range of channel aspect ratios and equilibrium contact angles. We demonstrate that for large the two model predictions are indistinguishable, whereas for smaller the lubrication-theory-based model agrees better with experiments. The lubrication-theory-based model is also shown to have better agreement with experiments at smaller, although as it fails to account for important axial curvature contributions to the free surface and the agreement worsens. Finally, we show that the lubrication-theory-based model also quantitatively predicts the dynamics of fingers that extend ahead of the meniscus. These findings elucidate the limitations of the modified Lucas-Washburn model and demonstrate the importance of accounting for the effects of complex free-surface morphology on capillary-flow dynamics in open rectangular microchannels.
KW - Key words capillary flows
KW - lubrication theory
KW - microfluidics
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U2 - 10.1017/jfm.2020.986
DO - 10.1017/jfm.2020.986
M3 - Article
AN - SCOPUS:85100068808
SN - 0022-1120
VL - 911
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
M1 - A32
ER -