Can a Dynamic Contact Angle Be Understood in Terms of a Friction Coefficient?

Hamraoui, Ahmed; Thuresson, Krister; Nylander, Tommy; Yaminsky, Vassili

doi:10.1006/jcis.2000.6830

Cited by 111 publications

(115 citation statements)

References 30 publications

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“…In our experiments, θ d was 68 • for water, which agrees well with the experimental data obtained in quartz capillaries [20]. For ethanol, θ d was smaller than the dynamic contact angle for water which was in accordance with measurements made in glass capillaries with an inner radius of 0.295 mm [30]. The θ d for the 40% ethanol water mixture was 38 • , which was significantly smaller than θ d for both water and ethanol.…”

Section: Filling Kinetics Of Isopropanol Ethanol and 40% Ethanol Insupporting

confidence: 91%

Filling kinetics of liquids in nanochannels as narrow as 27 nm by capillary force

Han

Mondin

Hegelbach

et al. 2006

Journal of Colloid and Interface Science

108

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We report the filling kinetics of different liquids in nanofabricated capillaries with rectangular cross-section by capillary force. Three sets of channels with different geometry were employed for the experiments. The smallest dimension of the channel cross-section was respectively 27, 50, and 73 nm. Ethanol, isopropanol, water and binary mixtures of ethanol and water spontaneously filled nanochannels with inner walls exposing silanol groups. For all the liquids the position of the moving liquid meniscus was observed to be proportional to the square root of time, which is in accordance with the classical Washburn kinetics. The velocity of the meniscus decreased both with the dimension of the channel and the ratio between the surface tension and the viscosity. In the case of water, air-bubbles were spontaneously trapped as channels were filled. For a binary mixture of 40% ethanol and water, no trapping of air was observed anymore. The filling rate was higher than expected, which also corresponds to the dynamic contact angle for the mixture being lower than that of pure ethanol. Nanochannels and porous materials share many physicochemical properties, e.g., the comparable pores size and extremely high surface to volume ratio. These similarities suggest that our nanochannels could be used as an idealized model to study mass transport mechanisms in systems where surface phenomena dominate.

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Section: Filling Kinetics Of Isopropanol Ethanol and 40% Ethanol Insupporting

confidence: 91%

Filling kinetics of liquids in nanochannels as narrow as 27 nm by capillary force

Han

Mondin

Hegelbach

et al. 2006

Journal of Colloid and Interface Science

108

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“…(25) The assumptions in the approach in sections 2.1.2 and 2.1.3 taken to derive the capillary terms is that they include a quasi-equilibrium advancing state and this leads to the You g's l w equilibrium contact angle,  e . Many authors have questioned this and replaced the contact angle by either the advancing contact angle or the velocity dependent dynamic contact angle Hoff 's formula (Siebold et al, 2000;Chebbi, 2007) or molecular-kinetic theory (Hamraoui et al, 2000;Hamraoui and Nylander, 2002;Blake and de Coninck, 2004) or have considered a range of possible dynamic contact angle relationships (e.g. Popescu et al, 2008).…”

Section: Defining Equation and Its Assumptionsmentioning

confidence: 99%

“…However, a visco-gravitational solution for time as a function of meniscus position does exist for the equivalent of the LucasWashburn regime (e.g. Krotov and Rusanov, 1999;Hamraoui et al 2000, Hamraoui andNylander, 2002), including for liquid-liquid systems (Mumley et al, 1986). In these problems, the role of the shape and wetting state of the walls are critical.…”

Section: Introductionmentioning

confidence: 99%

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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“…If a velocity dependent, and hence time dependent, dynamic contact angle, θ=θ(t), is assumed a further defining equation relating the dynamic contact angle to the instantaneous speed and physical parameters is required 14,[20][21][22] . However, it is often assumed that the contact angle can be approximated to a constantθ=θ A (the advancing contact angle) and with this assumption eq.…”

Section: Theoretical Approachmentioning

confidence: 99%

Capillary Penetration into Inclined Circular Glass Tubes

et al. 2016

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The spontaneous penetration of a wetting liquid into a vertical tube against the force of gravity and the imbibition of the same liquid into a horizontal tube (or channel) are both driven by capillary forces and described by the same fundamental equations. However, there have been few experimental studies of the transition from one orientation to the other. We report systematic measurements of capillary penetration of polydimethylsiloxane oils of viscosities 9.6, 19.2 and 48.0 mPas into glass capillary tubes. We first report the effect of tube radii R between 140 µm and 675 µm on the dynamics of spontaneous imbibition We show that the data can be fitted using the exact numerical solution to the governing equations and that these are similar to fits using the analytical visco-gravitational approximation. However, larger diameter tubes show a rate of penetration slower than expected using an equilibrium contact angle and the known value of liquid viscosity. To account for the slowness, an increase in viscosity by a factor (η/ρ) scaling is needed. We show full agreement with theory requires the ratio R/κ

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Can a Dynamic Contact Angle Be Understood in Terms of a Friction Coefficient?

Cited by 111 publications

References 30 publications

Filling kinetics of liquids in nanochannels as narrow as 27 nm by capillary force

Filling kinetics of liquids in nanochannels as narrow as 27 nm by capillary force

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

Capillary Penetration into Inclined Circular Glass Tubes

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