Interfacial slip on rough, patterned and soft surfaces: A review of experiments and simulations

Abstract

Advancements in the fabrication of microfluidic and nanofluidic devices and the study of liquids in confined geometries rely on understanding the boundary conditions for the flow of liquids at solid surfaces. Over the past ten years, a large number of research groups have turned to investigating flow boundary conditions, and the occurrence of interfacial slip has become increasingly well-accepted and understood. While the dependence of slip on surface wettability is fairly well understood, the effect of other surface modifications that affect surface roughness, structure and compliance, on interfacial slip is still under intense investigation. In this paper we review investigations published in the past ten years on boundary conditions for flow on complex surfaces, by which we mean rough and structured surfaces, surfaces decorated with chemical patterns, grafted with polymer layers, with adsorbed nanobubbles, and superhydrophobic surfaces. The review is divided in two interconnected parts, the first dedicated to physical experiments and the second to computational experiments on interfacial slip of simple (Newtonian) liquids on these complex surfaces. Our work is intended as an entry-level review for researchers moving into the field of interfacial slip, and as an indication of outstanding problems that need to be addressed for the field to reach full maturity.

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

“…There have been previous NEMD, 74 and experimental investigations, 75 ('shear banding') in liquid systems composed of more structured molecules are known to occur for more normal lubricant liquid like systems, [34][35][36]85,86 so this feature appears to be generic to the liquid state under these conditions.…”

The Translational and Rotational Dynamics of a Colloid Moving Along the Air-Liquid Interface of a Thin Film

“…This contact line singularity due to no-slip can be removed by the inclusion of several physicochemical hydrodynamic effects 23 : (i) Inclusion of slip at the contact line by a Navier slip condition, (ii) the introduction of intermolecular (disjoining pressure) forces in the fluid in the vicinity of the contact line which can lead to precursor films ahead of the macroscopic contact line, (iii) modelling the contact line motion as a thermally activated process using molecular kinetic theory in which progression of the contact angle is in steps that overcome energetic barriers and (iv) the inclusion of evaporation and condensation of liquid at the contact line, allowing the liquid to move over an existing thin layer. Here, the Navier slip model is used as experiments have revealed the presence of small slip coefficients (order 1–10 nm) in the motion of liquids over solid surfaces which are smooth on the scale of order tens of nanometers or smaller 24–27 . Brenner et al .…”

Brushes of semiflexible polymers in equilibrium and under flow in a super-hydrophobic regime

“…Polymer brushes were studied intensely in equilibrium and non-equilibrium conditions [8,11,12] by computer simulations and theory [13]. However, the vast majority of work was devoted to fully flexible polymer chains.…”