Multiphysics-based Fluidic Manipulation of Particles: An Experimental and Numerical Study




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Noninvasive manipulation of various bioparticles, such as cells, enables their use as the building blocks to construct complex bioscaffold for tissue engineering, which has the potential to transform the basic research in biology/biomedicine as well as the clinical treatment of some intractable diseases. This dissertation aims at exploiting neural stem cells (NSCs) impregnated with superparamagnetic iron oxide nanoparticles (SPIONs), to develop an effective cure for spinal cord injury (SCI). In SCI patients, long distance axonal connections are lost because most axons in the adult mammalian central nervous system fail to regenerate after injury. Using an external magnetic field, the SPIONs labeled NSCs will spontaneously self-assemble into structured lattices along a virtual axis defined by the field flux lines, thereby forming a scaffold to guide the directional regrowth of axons. In the first part of this work, in vitro experiments were conducted to (1) establish the procedures for SPIONs impregnation and (2) to evaluate the toxicity of SPIONs and the morphology and proliferation of the two-dimensional (2D) and three-dimensional (3D) bioscaffold self-assembled by SPIONs labeled 3T3 cells and NSCs. The experimental data proves the efficacy of the proposed approach in fabricating injectable and alignable bioscaffold for neural tissue engineering, and also prepare the context for the fundamental study of external-field-driven particle manipulation. In the second part of this work, a multiphysics numerical framework was formulated to investigate the aggregation kinetics and pattern formation of particles in a fluid medium. In view of the similarities between electrostatic and magnetostatic fields, both electric and magnetic driving mechanisms, dielectrophoresis (DEP) and magnetophoresis (MAP) were considered. The arbitrary Lagrangian-Eulerian (ALE) method coupled with Maxwell stress Tensor (MST) approach was applied to solve the particle-fluid-field interaction problem, in which the motion of the particles (both translation and rotation), the flow field and the external electric/magnetic field are closely coupled. The insights gained from the experimental and theoretical studies of this work will help to advance the fundamental understanding of externally-driven field-particle interactions and the particle self-assembly process. This work also provides a potential tool to further medical treatment of SCI and other regenerative diseases in a noninvasive manner.



field-particle interactions, dielectrophoresis, magnetophoresis