Alteration in contact line dynamics through competition between thermocapillary and electrothermal effects

TL;DR

This paper investigates how thermocapillary and electrothermal forces influence contact line dynamics in a narrow channel, revealing how their interplay can be used to control flow behavior in microfluidic systems.

Contribution

It provides a detailed analysis of the competition between thermocapillary and electrothermal effects on interfacial dynamics in microchannels, highlighting control mechanisms for flow manipulation.

Findings

Electrothermal forces dominate when forces are of equal strength.

Wettability influences whether interfacial or electrothermal forces dominate.

Force interplay can be used to control capillary filling time.

Abstract

The contact line dynamics of a thermal field assisted flow configuration of two immiscible fluids is considered in a narrow thermofluidic pathway. The surfaces of the channel are wetted with predesigned wettabilities and interdigitated electrodes are mounted on the substrates to generate non-uniform electric field. In this study, the interplay of thermocapillary and electrothermal forces on interfacial dynamics are studied in detail. The former is caused by surface tension gradients while the latter results from gradients in permittivity and electrical conductivity. Our investigations reveal that the relative strength of interfacial forces and electrothermal forces and their interactions can be effectively used to control the capillary filling time as well as the flow dynamics. For same strength of thermocapillary and electrothermal forces (characterized by individual dimensionless numbers) electrothermal forces dominate over thermocapillary forces. However, interfacial forces at some wettabilities dominate over electrothermal forces and set the fluid motion toward the entry of the channel.