Alteration in contact line dynamics of fluid-fluid interfaces in narrow confinements through competition between thermocapillary and electrothermal effects

Abstract

The paper reports the results of our numerical investigation on contact line dynamics of a thermal field assisted flow configuration of two immiscible fluids 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 a non-uniform electric field. In this study, the interplay of thermocapillary and electrothermal forces on interfacial dynamics are considered. The former is caused by temperature-induced surface tension gradients while the latter is originated from the temperature-induced 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 flow dynamics. For the same strength of thermocapillary and electrothermal forces (characterized by individual dimensionless numbers), electrothermal effects dominate over thermocapillary effects. However, interfacial forces dominate over electrothermal forces at certain wettabilities (characterized by the imposed contact angle on the surfaces), and depending on the direction of the interfacial forces, the contact line travels toward the entry or exit of the channel.