Electrothermally modulated contact line dynamics of a binary fluid in a patterned fluidic environment

Abstract

In this paper, we depict the 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 investigation, based on the free-energy-based phase field formalism, reveals 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 the interfacial tension and the driving electrothermal force. An interplay of these 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 the contact line pinning. Alteration in the position of the ribs between the electrode pairs changes the electric field strength and thereby the bulk ACET forces across the contact line. Furthermore, by suitable arrangement of these ribs, various intricate shapes of the liquid front can be achieved over a short distance, which can have significant implications on the morphological control of microscale flow.