Dynamics of Capillary-Driven Flow in Open Microchannels

Yang, Die; Krasowska, Marta; Priest, Craig; Popescu, M. N.; Ralston, John

doi:10.1021/jp2065826

Cited by 128 publications

(167 citation statements)

References 52 publications

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“…We find that fits to the numerical solution of the exact differential equation describing capillary rise, neglecting the fingers, up to the point where the fingers reach the ends of the channels can describe the rise of the central meniscus of the liquid in both of these cases. We also find that the friction in the openchannel case is consistent with a non-rigidified liquid-air interface rather than for a rigidified boundary as recently reported for imbibition into horizontally mounted open microchannels (Yang et al, 2011).…”

Section: Introductionsupporting

confidence: 89%

“…However, Girardo et al (2012) found that fingers do not seem to induce appreciable extra dissipation in the early stage of microcapillary imbibitions in horizontally mounted smooth microchannels. It is also of note that the fitted values of the viscous coefficient a for the open channels are a factor 2 and 3 lower (for the 400 µm and 600 µm wide open channels) than would be expected for a rigidified liquid-air boundary, as required by Yang et al (2011) to explain the dynamics of capillary flow in their horizontally mounted open narrow microchannels. This indicates that a non-rigidified liquid-air interface best represents the flow in our lower aspect ratio channels.…”

Section: Resultsmentioning

confidence: 78%

“…W, the aspect ratio function  o ()1. It should be noted that alternative, but equivalent Fourier series solutions for the flow in an open rectangular exist, such as that in Baret et al (2007) and Yang et al (2011).…”

Section: Viscous Terms and Interpolation Formulaementioning

confidence: 99%

“…These advances are leading to studies with microfluidic (e.g. Yang et al, 2011) and nanofluidic capillaries widths of a few tens of nm (Han et al, 2006) or with depths as small as 6 nm (Oh et al, 2009). Whilst non-constant channel cross sections have been a focus of study experimentally and theoretically (Legait, 1983;Staples andShaffer, 2002, Reysatt et al, 2008;Liou et al, 2009), increased solid-liquid contact area, and hence increased capillary pull can be achieved using a range of in-channel structures.…”

Section: Introductionmentioning

confidence: 99%

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Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Ouali

McHale

Javed

et al. 2013

Microfluid Nanofluid

149

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The spontaneous capillary-driven filling of microchannels is important for a wide range of applications. These channels are often rectangular in cross-section, can be closed or open, and horizontal or vertically orientated. In this work, we develop the theory for capillary imbibition and rise in channels of rectangular cross-section, taking into account rigidified and non-rigidified boundary conditions for the liquid-air interfaces and the effects of surface topography assuming Wenzel or Cassie-Baxter states. We provide simple interpolation formulae for the viscous friction associated with flow through rectangular cross-section channels as a function of aspect ratio. We derive a dimensionless cross-over time, T c , below which the exact numerical solution can be approximated by the Bousanquet solution and above which by the visco-gravitational solution. For capillary rise heights significantly below the equilibrium height, this cross-over time is T c  (3X e /2) 2/3 and has an associated dimensionless crossover rise height X c  (3X e /2) 1/3 , where X e =1/G is the dimensionless equilibrium rise height and G is a dimensionless form of the acceleration due to gravity. We also show from wetting considerations that for rectangular channels, fingers of a wetting liquid can be expected to imbibe in advance of the main meniscus along the corners of the channel walls. We test the theory via capillary rise experiments using polydimethylsiloxane oils of viscosity 96.0, 48.0, 19.2 and 4.8 mPa s within a range of closed square tubes and open rectangular cross-section channels with SU-8 walls. We show that the capillary rise heights can be fitted using the exact numerical solution and that these are similar to fits using the analytical visco-gravitational solution. The viscous friction contribution was found to be slightly higher than predicted by theory assuming a non-rigidified liquid-air boundary, but far below that for a rigidified boundary, which was recently reported for imbibition into horizontally mounted open microchannels. In these experiments we also observed fingers of liquid spreading along the internal edges of the channels in advance of the main body of liquid consistent with wetting expectations. We briefly discuss the implications of these observations for the design of microfluidic systems.

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Section: Introductionsupporting

confidence: 89%

Section: Resultsmentioning

confidence: 78%

Section: Viscous Terms and Interpolation Formulaementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Ouali

McHale

Javed

et al. 2013

Microfluid Nanofluid

149

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show abstract

“…Particularly, for channel width below the water capillary length (i.e., 2.7 mm), the interfacial shear stress increases as the channel size decreases. Investigating the speed of the advancing meniscus flooding an open hydrophilic channel, Yang et al 30 found a good agreement between experimental data and theoretical predictions when a no-slip boundary condition was assumed at the liquid-air interface.…”

Section: Introductionmentioning

confidence: 89%

Evidence of slippage breakdown for a superhydrophobic microchannel

Bolognesi¹,

Cottin-Bizonne²,

Pirat³

2014

Physics of Fluids

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A full characterization of the water flow past a silicon superhydrophobic surface with longitudinal micro-grooves enclosed in a microfluidic device is presented. Fluorescence microscopy images of the flow seeded with fluorescent passive tracers were digitally processed to measure both the velocity field and the position and shape of the liquid-air interfaces at the superhydrophobic surface. The simultaneous access to the meniscus and velocity profiles allows us to put under a strict test the no-shear boundary condition at the liquid-air interface. Surprisingly, our measurements show that air pockets in the surface cavities can sustain non-zero interfacial shear stresses, thereby hampering the friction reduction capabilities of the surface. The effects of the meniscus position and shape as well as of the liquid-air interfacial friction on the surface performances are separately assessed and quantified.

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Introduction

2016

Open Microfluidics

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Dynamics of Capillary-Driven Flow in Open Microchannels

Cited by 128 publications

References 52 publications

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Evidence of slippage breakdown for a superhydrophobic microchannel

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