Alternating current driven interfacial dynamics of a binary fluid in a patterned fluidic environment modulated by electrothermal effects

TL;DR

This study explores how alternating current electrothermal forces influence the movement and shape of two immiscible fluids in a microchannel with patterned ribs, revealing how geometric and wetting properties control interfacial dynamics.

Contribution

It introduces a phase field model to analyze the combined effects of electrothermal forces and surface patterning on fluid interface behavior in microchannels.

Findings

Rib patterning significantly affects contact line motion.

Electric field modulation alters interfacial tension and flow.

Complex liquid front shapes can be achieved through rib arrangement.

Abstract

In this paper, we depict interfacial electro-thermo-chemical-hydrodynamics of two immiscible fluids in a microchannel with substrates patterned by ribs. The motion of the binary fluids is set by an alternating current electrothermal (ACET) mechanism. Our investigations, based on free-energy-based phase field formalism, reveal that the capillary filling dynamics and the contact line motion are strong functions of the wetting characteristics and geometric parameters of the patterned ribs. Modulation of these parameters alters the surface energy over the rib surface, which, in turn, facilitates the interaction between interfacial tension and driving electrothermal forces. The competition between two forces may speed up or slow down the fluid-fluid-solid contact line motion over the rib surface. At the edges of the ribs, the interface can halt for a sufficiently long time owing to contact line pinning. Alteration in positions of the rib between the electrode pairs changes the electric field strength and thereby bulk ACET forces across the contact line. Further, by suitable arrangement of the ribs, various intricate shapes of the liquid front can be achieved over a short distance, which can have significant implications in the morphological control of microscale flows.