Theory of Wetting-Induced Fluid Entrainment by Advancing Contact Lines on Dry Surfaces

Abstract

We report on the onset of fluid entrainment when a contact line is forced to advance over a dry solid of arbitrary wettability. We show that entrainment occurs at a critical advancing speed beyond which the balance between capillary, viscous, and contact-line forces sustaining the shape of the interface is no longer satisfied. Wetting couples to the hydrodynamics by setting both the morphology of the interface at small scales and the viscous friction of the front. We find that the critical deformation that the interface can sustain is controlled by the friction at the contact line and the viscosity contrast between the displacing and displaced fluids, leading to a rich variety of wetting-entrainment regimes. We discuss the potential use of our theory to measure contact-line forces using atomic force microscopy and to study entrainment under microfluidic conditions exploiting colloid-polymer fluids of ultralow surface tension.

Dynamic wetting failure in surfactant solutions

“…The solution families exhibit a limit point corresponding to the largest Ca, which is denoted as the critical capillary number Ca crit . Beyond this Ca crit value (Ca > Ca crit ), we are unable to find 2D steady-state solutions, suggesting that the system may develop transient or 3D flows leading to wetting failure Ledesma-Aguilar, Hernandez-Machado & Pagonabarraga 2013). For the 1D and hybrid models, Ca crit corresponds to a turning point in the solution paths that connects the stable (lower) and unstable (upper) branches of steady-state solutions.…”

Wetting failure of hydrophilic surfaces promoted by surface roughness

“…The stability of the thin liquid film climbing on an impact body, which is relevant to surface roughness, determines whether an air cavity will be created or not5619(as illustrated in Fig. 1).…”

“…We will also show how the promoting effect works based on the contact-line instability induced by the imbalance between the capillary driving force and viscous friction force810171924.…”

“…He observed the spreading of the silicone oil on both smooth and rough glass surfaces, and revealed complex spreading regimes in addition to the traditional regimes of spreading driven by capillarity and gravity. With further experimental and theoretical studies of the contact line dynamics on ideally smooth surfaces13141516171819, the influences of roughness on dynamic wetting have been explored recently, e.g., hemi-wicking of superhydrophilic spreading2021, coating limits on rough surfaces56, pinning potential by defects22, and topographically driven spreading232425. However, most present studies only consider one certain aspect such as superwetting limit2022232425, superhydrophobic limit26, and low capillary number limit2022232425.…”

Stabilizing Fluid-Fluid Displacements in Porous Media Through Wettability Alteration

“…Our knowledge and understanding of imbibition in this regime is much less complete, even in simple geometries like a straight capillary tube [44,45] or Hele-Shaw cell [46]. Experiments in transparent porousmedia cells illustrating the phenomenon of viscous fingering date back to the 1950s [47,48].…”