MODELING AND SIMULATION OF ELECTROKINETIC MANIPULATION OF BIOLOGICAL PARTICLES

Thesis (Ph.D.), School of Mechanical and Materials Engineering, Washington State UniversityRecent experimental studies show that electrophoretic and dielectrophoretic these two electrokinetic forces can manipulate biological particles efficiently in micro/nanofluidic devices. Electrokinetic forces in those devices depend on various parameters related to properties of the particle, surrounding fluid and device. Therefore, to design an effective micro/nanofluidic platform for a specific manipulation, it is necessary to analyze the effect of the above parameters using mathematical models and numerical simulations. To reduce computational cost, a point based method or smaller domain or single particle is used in the conventional modeling and simulation. However, these methods produce erroneous results when particle and device sizes are comparable, and often ignore detail physics in the devices. To overcome the limitations of existing methods, two mathematical models and numerical algorithms have been developed considering presence of multiple particles in an actual device. The first model is based on distributed Lagrange multiplier based fictitious domain approach for flow field and motion of particles, and on a multi-domain method for electric potential. This model is suitable for those electrokinetic manipulation devices where dielectrophoretic force dominates. Dielectrophoretic force in this model is calculated using Maxwell stress tensor. The capability of the proposed model is demonstrated by simulating trajectories of two biological particles of different electrical properties. Next, based on this model a new microfluidic device was designed to improve the efficiency of continuous separation of particles. A hybrid and periodic truncated trapezoidal electrodes configuration has been suggested in that device to increase inter particle distance while applying dielectrophoretic force in two directions. The second mathematical model is developed based on Poisson-Nernst-Planck equations along with Navier-Stokes equations for fluid flow and on the Langevin equation for particle translocation. This model is suitable for electrophoretic manipulation of nanoparticles. Separation of nano-bioparticles through solid state nanopore has been studied using this model. Our numerical study suggests that membrane pore surface charge density is a more important parameter than pore diameter and length for particle separation through a nanopore.Department of Mechanical Engineerin