Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
Committee Chair/Advisor
Dr. Xiangchun Xuan
Committee Member
Dr. Rodrigo Martinez-Duarte
Committee Member
Dr. Zhen Li
Committee Member
Dr. Yuhao Xu
Abstract
Innovations in microfabrication over the past three decades have enabled the development of microfluidic devices with intricate channel geometry. Microfluidic platforms offer controlled manipulation of fluids and particles by leveraging the internally induced and/or externally imposed force field(s). The demand for compact microchannel geometry has turned the attention toward curved microchannels with significantly reduced footprints. However, most of the previous studies in curved microchannels have been limited to particle migration in Newtonian fluids. The influence of fluid rheology has remained largely unexplored.
In the first part of this dissertation, we present a systematic experimental study on the influences of fluid inertia, elasticity and shear thinning on particle migration in pressure-driven flow of polymer solutions through curved microchannels. The typical flow-induced force dynamics is transformed due to the curvature-driven Dean vortices and fluid rheological effects, each of which can alter the particle equilibrium position(s). Specifically, in a spiral microchannel, particles equilibrate towards the outer half of the spiral in polymer-based non-Newtonian fluids, contrasting the inner half focusing in a Newtonian fluid. The introduction of fluid elasticity or shear thinning reduces the threshold Reynolds number required to achieve particle focusing. In a serpentine microchannel, particles migrate toward the center regardless of the fluid rheology due to the alternating curvature. Each of the fluid rheological effects alone is found to accelerate this centerline particle focusing while the combination of fluid elasticity and shear thinning may yield multiple equilibrium particle positions.
In the second part of this dissertation, we study the particle migration in DC electric field-driven flow of polymer solutions through curved microchannels. The channel curvature induced non-uniform electric field creates a dielectrophoretic force, which couples with the fluid rheology-induced hydrodynamic force to affect the particle dynamics. In a serpentine microchannel, the alternating nature of the dielectrophoretic force yields a single-line particle stream at the center in a Newtonian fluid. Introducing elasticity lowers the threshold electric field required to achieve this centerline focusing. In contrast, particles in a shear-thinning fluid exhibit wall focusing, which gets defocused in a viscoelastic and shear thinning fluid. In a spiral microchannel, the unchanging direction of the dielectrophoretic force directs particles towards the outer wall in a Newtonian fluid. Introducing elasticity shifts the particle focusing position closer to the outer wall while at a lowered threshold electric field. In contrast, fluid shear thinning pushes particles toward either wall like in the serpentine microchannel.
Recommended Citation
Raut, Sanskruti Ramesh, "Particle Migration in Non-Newtonian Fluid Flows Through Curved Microchannels" (2025). All Dissertations. 4125.
https://open.clemson.edu/all_dissertations/4125