Ph.D. Dissertation Defense - Sajad Kafashi

June 13, 2017 - 11:00 AM
Duke 324
Department of Mechanical Engineering and Engineering Science, 704-687-8253

Instrumentation, Techniques, and Evaluation of ePTV for Particle Manipulation Studies Using Micro-Scale Oscillators

A need for dynamic micro-particle manipulation is the ability to gently position fragile particles, for instance biological particles like blood cells, stem cells, neurons, pancreatic β cells, DNA, chromosomes, proteins and viruses, for repeated measurement without perturbing their behavior. An oscillating fiber will induce vortices in a slurry of particles, subsequently the vortex force created by oscillation traps the particles located at these steady streaming micro-eddies. If multiple oscillatory fibers are placed inside the slurry, depending on frequency and timing of oscillation this method can be used for contact-free particle shepherding and sorting and for transporting particles from one fiber location to another. Due to the complicated dynamics of particles traveling in the fluid and the presence of noise, and significant number of particles, the commercial PIV softwares were not able to track individual particle paths. To enhance identification and tracking of individual particles a novel encoded-particle tracking velocimetry (ePTV) technique is developed and used in the experiments to track the particle trajectories. A parametric mathematical model and Monte Carlo statistical study of the encoding is presented in this dissertation. Two types of oscillation mechanism are used in the experimental component of this study, a PZT flexure-based macro-probe driven at frequencies around 250 Hz and higher frequency dynamic-absorber, quartz-based, micro-probes driven at frequencies around 32 kHz. A comprehensive theoretical, experimental, and FEM study of the dynamic frequency response behavior of micro-probes is presented in this study.