Superconfinement tailors fluid flow at microscales

Setu, Siti Aminah; Dullens, Roel P. A.; Hernández–Machado, A.; Pagonabarraga, Ignacio; Aarts, Dirk G. A. L.; Ledesma‐Aguilar, Rodrigo

doi:10.1038/ncomms8297

Cited by 17 publications

(13 citation statements)

References 40 publications

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“…Finally, experimental systems consisting of colloid-polymer mixtures are known to phase separate into colloid-rich and colloid-poor domains, with an interface width that is of order 1 µm (Aarts et al 2004;Setu et al 2015), much larger than the typical value for molecular fluids. Such a system can potentially be exploited to realise the different contact line slip regimes discussed here experimentally.…”

Section: Discussionmentioning

confidence: 99%

Moving contact line dynamics: from diffuse to sharp interfaces

2015

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We reconcile two scaling laws that have been proposed in the literature for the slip length associated with a moving contact line in diffuse interface models, by demonstrating each to apply in a different regime of the ratio of the microscopic interfacial width $l$ and the macroscopic diffusive length $l_D= (M\eta)^{1/2}$, where $\eta$ is the fluid viscosity and $M$ the mobility governing intermolecular diffusion. For small $l_D/l$ we find a diffuse interface regime in which the slip length scales as $\xi \sim(l_Dl)^{1/2}$. For larger $l_D/l>1$ we find a sharp interface regime in which the slip length depends only on the diffusive length, $\xi \sim l_D \sim (M\eta)^{1/2}$, and therefore only on the macroscopic variables $\eta$ and $M$, independent of the microscopic interfacial width $l$. We also give evidence that modifying the microscopic interfacial terms in the model's free energy functional appears to affect the value of the slip length only the diffuse interface regime, consistent with the slip length depending only on macroscopic variables in the sharp interface regime. Finally, we demonstrate the dependence of the dynamic contact angle on the capillary number to be in excellent agreement with the theoretical prediction of \cite{Cox1986}, provided we allow the slip length to be rescaled by a dimensionless prefactor. This prefactor appears to converge to unity in the sharp interface limit, but is smaller in the diffuse interface limit. The excellent agreement of results obtained using three independent numerical methods, across several decades of the relevant dimensionless variables, demonstrates our findings to be free of numerical artifacts.Comment: 24 pages, 5 figure

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Section: Discussionmentioning

confidence: 99%

Moving contact line dynamics: from diffuse to sharp interfaces

2015

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“…When the liquid is only partially wetting, however, a critical plate velocity is needed for the liquid to coat the substrate [9,[27][28][29]. In the re-130 verse process of forced wetting transition in advancing contact lines, air is entrained, but at much higher contact line velocities [30][31][32][33][34][35][36][37]. Below the wetting transition, the contact line moves with the same velocity as the interface tip.…”

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confidence: 99%

“…Most existing microfluidic bubble generators rely on flow channels with ge-225 ometric constrictions [49][50][51][52] or an external cross-flow [53][54][55][56] to initiate bubble pinch-off [57][58][59]. Recently, it has been shown that "superconfinement" can trigger a jet instability from a moving interface in the absence of geometric features, but through a mechanism that relies on thermal fluctuations 230 in systems with ultralow surface tension [36]. Our experiments demonstrate that pinch-off will occur in smooth, uniform capillaries as a result of wettability-mediated contact line motion.…”

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confidence: 99%

Forced Wetting Transition and Bubble Pinch-Off in a Capillary Tube

et al. 2018

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Immiscible fluid-fluid displacement in partial wetting continues to challenge our microscopic and macroscopic descriptions. Here, we study the displacement of a viscous fluid by a less viscous fluid in a circular capillary tube in the partial wetting regime. In contrast with the classic results for complete wetting, we show that the presence of a moving contact line induces a wetting transition at a critical capillary number that is contact angle dependent. At small displacement rates, the fluid-fluid interface deforms slightly from its equilibrium state and moves downstream at a constant velocity, without changing its shape. As the displacement rate increases, however, a wetting transition occurs: the interface becomes unstable and forms a finger that advances along the axis of the tube, leaving the contact line behind, separated from the meniscus by a macroscopic film of the viscous fluid on the tube wall. We describe the dewetting of the entrained film, and show that it universally leads to bubble pinch-off, therefore demonstrating that the hydrodynamics of contact line motion generate bubbles in microfluidic devices, even in the absence of geometric constraints.

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“…This gives the advantage to easily incorporate complex physical phenomena in the algorithm, ranging from phase behavior, multiphase flows to chemical interactions between the fluid and the surrounding solid surfaces. Moreover, it avoids the need to track the time evolution of the interface between different phases [45], which makes it ideal to study problems involving the time evolution of fluid-fluid 100 interfaces [46,47].…”

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Capillary filling and Haines jump dynamics using free energy Lattice Boltzmann simulations

Zacharoudiou

Boek

2016

Advances in Water Resources

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We investigate numerically the dynamics of capillary filling and Haines jump events using free energy Lattice Boltzmann (LB) simulations. Both processes are potentially important multi-phase pore-scale flow processes for geological CO 2 sequestration and oil recovery. We first focus on capillary filling and demonstrate that the numerical method can capture the correct dynamics in the limit of long times for both high and low viscosity ratios, i.e. the method gives the correct scaling for the length of the penetrating fluid column as a function of time.Examining further the early times of capillary filling, three consecutive length vs. time regimes have been observed, in agreement with available experimental work in the literature. In addition, we carry out simulations of Haines jump events in idealised and realistic rock pore geometries. We observe that the Haines jump events are cooperative, non-local and associated with both drainage and imbibition dynamics. Our observations show that the pore filling dynamics is controlled by the Ohnesorge number, associated with the balance between viscous forces and inertial / surface tension forces. Using this concept, we are able to identify the type of pore filling dynamics that will occur.

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Superconfinement tailors fluid flow at microscales

Cited by 17 publications

References 40 publications

Moving contact line dynamics: from diffuse to sharp interfaces

Moving contact line dynamics: from diffuse to sharp interfaces

Forced Wetting Transition and Bubble Pinch-Off in a Capillary Tube

Capillary filling and Haines jump dynamics using free energy Lattice Boltzmann simulations

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