Nonlinear behavior in elastic coupled inertial microfluidics

The ability to precisely control and manipulate particles and fluid flow is one of the key goals of microfluidics. To achieve this goal, it is necessary to gain an understanding of the physical phenomena governing microfluidic flows. Inertial microfluidics makes use of unique phenomena that are accessible in microscale structured channels. Due to the difficulty of the fluid dynamics associated with these systems, the underlying physics needs to be better understood. Though current studies mostly use Newtonian fluids, it is important to note that the biological solutions are usually non-Newtonian. However, of the few reports that have exmained non-Newtonian fluids, most were found to use microscale flowrates. This project aims to determine the mechanism of particle focusing in non-Newtonian solutions at relatively high flow rates to address real-life clinical applications (e.g. plasma separation from blood, and cancer cell separation from blood). In this thesis, new straight and spiral microchannels with rectangular, trapezoidal and complex cross sections were designed and fabricated. To place the elasto-inertial effects into context, fluid-induced forces present in particulate flow are investigated. The effects of solution viscoelasticity, particle size and particle to channel size ratio are examined. This study improves understanding of particle focusing manipulation in viscoelastic fluids using both straight and spiral microchannels