Capillary Filling in Open Rectangular Microchannels with a Spatially Varying Contact Angle

The dynamics of a fluid flow within an open capillary channel depend on the fluid's contact angle with the channel substrate, but determining the real value of the contact angle with the solid surface is an ominous problem in capillary microflows. The Lucas-Washburn law assumes a constant contact angle during the fluid motion; however, it is observed that the contact angle of the flowing liquid with the walls differs from its static (Young) value. Correlations for the dynamic contact angle have been proposed, and upon close inspection of Lucas-Washburn behavior in closed channels, a dynamic contact angle should be taken into account depending on the flow velocity. In this work, the dynamic contact angle in open-channel configurations is investigated using experimental data obtained with different liquids. It is shown that a dynamic contact angle must be taken into account in the early stages of the flow, i.e., at the beginning of the viscous regime when flow velocities are sufficiently high. Here, we found that amongst the different correlations for the dynamic contact angle, the Hamraoui correlation-presenting the dynamic contact angle in terms of a friction coefficient-reproduces the experimental results while other correlations overpredict the fluid velocity in open channels.

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“…The sensitivity of an open microflow in a rectangular channel has recently been pointed out by Chang et al 53 .…”

Section: Resultsmentioning

confidence: 91%

“…It is verified that at t = 0 (we neglect the evanescent inertial motion 53 ), z 0 = 0 and z = 0. For a long channel, z 0 becomes large and z 0 .…”

Section: Theoretical Approachmentioning

confidence: 83%

On the dynamic contact angle of capillary-driven microflows in open channels

Tokihiro

McManamen

Phan

et al. 2023

Preprint

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show abstract

“…The sensitivity of an open microflow in a rectangular channel has recently been pointed out by Chang et al…”

Section: Resultsmentioning

confidence: 93%

“…It is verified that at t = 0 (we neglect the evanescent inertial motion), z 0 = 0 and z = 0. For a long channel, z 0 becomes large and z → z 0 .…”

Section: Theoretical Approachmentioning

confidence: 84%

On the Dynamic Contact Angle of Capillary-Driven Microflows in Open Channels

Tokihiro,

McManamen,

Phan

et al. 2024

Langmuir

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The true value of the contact angle between a liquid and a solid is a thorny problem in capillary microfluidics. The Lucas−Washburn−Rideal (LWR) law assumes a constant contact angle during fluid penetration. However, recent experimental studies have shown lower liquid velocities than those predicted by the LWR equation, which are attributed to a velocity-dependent dynamic contact angle that is larger than its static value. Inspection of fluid penetration in closed channels has confirmed that a dynamic angle is needed in the LWR equation. In this work, the dynamic contact angle in an open-channel configuration is investigated using experimental data obtained with a range of liquids, aqueous and organic, and a PMMA substrate. We demonstrate that a dynamic contact angle must be used to explain the early stages of fluid penetration, i.e., at the start of the viscous regime, when flow velocities are sufficiently high. Moreover, the open-channel configuration, with its free surface, enhances the effect of the dynamic contact angle, making its inclusion even more important. We found that for the liquids in our study, the molecular-kinetic theory is the most accurate in predicting the effect of the dynamic contact angle on liquid penetration in open channels.

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Capillary Filling in Open Rectangular Microchannels with a Spatially Varying Contact Angle

Cited by 2 publications

References 61 publications

On the dynamic contact angle of capillary-driven microflows in open channels

On the dynamic contact angle of capillary-driven microflows in open channels

On the Dynamic Contact Angle of Capillary-Driven Microflows in Open Channels

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