Micro- and nanoscale fluid flow on chemical channels

TL;DR

This study investigates the dynamics of thin liquid films on chemical patterns at micro- and nanoscale, using simulations to understand flow behavior and control mechanisms relevant for lab-on-a-chip applications.

Contribution

It combines lattice-Boltzmann and molecular dynamics simulations to analyze flow on complex chemical patterns, focusing on junctions and flow control at microscopic scales.

Findings

Liquid films can be directed across complex patterns with small geometric variations.

Flow remains confined to chemical channels under certain force and volume conditions.

Pearling instabilities do not prevent continuous flow across the pattern.

Abstract

We study the time evolution and driven motion of thin liquid films lying on top of chemical patterns on a substrate. Lattice-Boltzmann and molecular dynamics methods are used for simulations of the flow of microscopic and nanoscopic films, respectively. Minimization of fluid surface area is used to examine the corresponding equilibrium free energy landscapes. The focus is on motion across patterns containing diverging and converging flow junctions, with an eye towards applications to lab-on-a-chip devices. Both open liquid-vapor systems driven by body forces and confined liquid-liquid systems driven by boundary motion are considered. As in earlier studies of flow on a linear chemical channel, we observe continuous motion of a connected liquid film across repeated copies of the pattern, despite the appearance of pearling instabilities of the interface. Provided that the strength of the driving force and the volume of liquid are not too large, the liquid is confined to the chemical channels and its motion can be directed by small variations in the geometry of the pattern.