Transport of free surface liquid films and drops by external ratchets and self-ratcheting mechanisms

TL;DR

This paper explores how external and self-induced ratchet mechanisms can be used to transport free surface liquid films and drops in microfluidic systems, highlighting analogies with particle ratchets and potential applications.

Contribution

It introduces the concept of using both external ratchet capacitors and harmonic substrate vibrations for liquid transport, and discusses their relation to Fokker-Planck equations.

Findings

Demonstrates transport of dielectric liquids via ratchet capacitors.

Shows drops can be moved using substrate vibrations.

Draws analogies between thin film equations and particle ratchets.

Abstract

We discuss the usage of ratchet mechanisms to transport a continuous phase in several micro-fluidic settings. In particular, we study the transport of a dielectric liquid in a heterogeneous ratchet capacitor that is periodically switched on and off. The second system consists of drops on a solid substrate that are transported by different types of harmonic substrate vibrations. We argue that the latter can be seen as a self-ratcheting process and discuss analogies between the employed class of thin film equations and Fokker-Planck equations for transport of discrete objects in a 'particle ratchet'.