Thermally Driven Imbibition and Drainage Induced by Terraced Nanostructures

TL;DR

This paper uncovers how thermally driven Brownian ratchet mechanisms, enabled by asymmetric nanostructures, can induce liquid displacement in nanoscale channels, challenging traditional wetting force expectations.

Contribution

It introduces a theoretical and simulation-based analysis of thermally driven liquid movement using nanostructured surfaces, providing analytical models for controlling wetting processes.

Findings

Thermal fluctuations can drive liquid displacement against capillary forces.

Asymmetric nanostructures enable directional control of wetting dynamics.

Analytical solutions predict displacement rates in nanoscale systems.

Abstract

Theoretical analysis and fully atomistic molecular dynamics simulations reveal a Brownian ratchet mechanism by which thermal fluctuations drive the net displacement of immiscible liquids confined in channels or pores with micro- or nanoscale dimensions. The thermally-driven displacement is induced by surface nanostructures with directional asymmetry and can occur against the direction of action of wetting or capillary forces. Mean displacement rates in molecular dynamics simulations are predicted via analytical solution of a Smoluchowski diffusion equation for the position probability density. The proposed physical mechanisms and derived analytical expressions can be applied to engineer surface nanostructures for controlling the dynamics of diverse wetting processes such as capillary filling, wicking, and imbibition in micro- or nanoscale systems.