Slip flow over structured surfaces with entrapped microbubbles

TL;DR

This study uses lattice Boltzmann simulations to investigate how microbubbles on structured surfaces affect slip in microfluidic flows, revealing that bubble deformation and increased shear can reduce slip, contrary to some experimental findings.

Contribution

It introduces a two-phase lattice Boltzmann simulation approach to analyze bubble deformation effects on slip in microchannels with structured surfaces.

Findings

Bubble presence can cause negative slip due to increased roughness.

Slip decreases with higher shear rates, opposing some experimental results.

Deformation of bubbles influences slip behavior in microfluidic flows.

Abstract

On hydrophobic surfaces, roughness may lead to a transition to a superhydrophobic state, where gas bubbles at the surface can have a strong impact on a detected slip. We present two-phase lattice Boltzmann simulations of a Couette flow over structured surfaces with attached gas bubbles. Even though the bubbles add slippery surfaces to the channel, they can cause negative slip to appear due to the increased roughness. The simulation method used allows the bubbles to deform due to viscous stresses. We find a decrease of the detected slip with increasing shear rate which is in contrast to some recent experimental results implicating that bubble deformation cannot account for these experiments. Possible applications of bubble surfaces in microfluidic devices are discussed.