Cross-stream migration characteristics of a deformable droplet in a non-isothermal Poiseuille Flow through Microfluidic Channel

TL;DR

This study investigates how temperature gradients and flow influence the movement of deformable droplets in microchannels, combining analytical and numerical methods to understand and control droplet trajectories.

Contribution

It introduces a combined analytical and numerical framework to analyze droplet migration under thermal and flow effects, including Marangoni stresses and wall effects.

Findings

Temperature gradients can direct droplet migration.

Marangoni stress determines droplet stationary points.

Wall effects and thermal convection influence droplet paths.

Abstract

The migration characteristics of a suspended deformable droplet in a parallel plate microchannel is studied, both analytically and numerically, under the combined influence of a constant temperature gradient in the transverse direction and an imposed pressure driven flow. Any predefined transverse position in the micro channel can be attained by the droplet depending on the applied temperature gradient in the cross-stream direction or how small the droplet is with respect to the channel width. For the analytical solution, an asymptotic approach is used, where we neglect any effect of inertia or thermal convection of the fluid in either of the phases. To obtain a numerical solution, we use the conservative level set method. Variation of temperature in the flow field causes a jump in the tangential component of stress at the droplet interface. This jump in stress component, which is the thermal Marangoni stress, is an important factor that controls the trajectory of the droplet. The direction of cross-stream migration of the droplet is decided by the magnitude of the critical Marangoni stress, corresponding to which the droplet remains stationary. In order to analyze practical microfluidic setup, we do numerical simulations where we consider wall effects as well as the effect of thermal convection and finite shape deformation on the cross-stream migration of the droplet.