Hydrodynamics Of Drops And Particles Driven By Marangoni And Diffusiophoretic Forces

Author

Subramaniam Chembai Ganesh, CUNY City CollegeFollow

Date of Award

2024

Document Type

Dissertation

Department

Chemical Engineering

First Advisor

Charles Maldarelli

Second Advisor

Joel Koplik

Third Advisor

Jeffrey Morris

Keywords

active Janus particles, Marangoni flow, self diffusiophoresis, thermocapillary migration, low Reynolds number hydrodynamics, drops and colloids

Abstract

This study investigates the hydrodynamics of particles and drops driven by forces generated by an asymmetrical physical and chemical surrounding environment. In the first part, a novel colloidal motor design driven by surface tension forces is proposed, utilizing an active Janus particle encapsulated in an immiscible liquid drop to form a compound drop/particle. Marangoni forces induced by asymmetric solute adsorption at the liquid-liquid interface of the drop propels the compound system. The propulsion speeds of the motor are analyzed for various relative sizes and configurations of the Janus particle and the encapsulating drop and the effects of varying the transport properties of the suspending and suspended fluid medium are examined. The system demonstrates the ability to generate higher velocities compared to traditional diffusiophoretic Janus particle-based motors. The second part focuses on the thermocapillary migration of spherical drops with stagnant caps of finite thermal conductivity which significantly influences the drop migration and surrounding hydrodynamics. An analytical model for heat conduction in the stagnant cap is developed, and the effects of interfacial stresses on the migration velocity are evaluated. Finally, the interaction between a spherical Janus motor driven by self-diffusiophoresis and an inert cargo particle is explored in an axisymmetric configuration within the Stokes regime. A stream function-based analog to the twin multipole approach is developed to study the dynamics of the motor and the cargo in different configurations. The effects of Janus cap size and particle size ratios on their interactions are investigated, revealing distinct regimes of contact and contactless towing/hovering. Taken together this investigation offers valuable insights into the complexities of motion driven by molecular and interfacial forces, with implications ranging from fundamental understanding to potential applications in commercial multiphase technologies.

Recommended Citation

Chembai Ganesh, Subramaniam, "Hydrodynamics Of Drops And Particles Driven By Marangoni And Diffusiophoretic Forces" (2024). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/1299