Investigation of Secondary (Dean) Flows in Curved Microchannels and Application to Microparticle Sample Preparation

Exchanging the solution of microparticles from a complex source fluid to a target clean buffer is important for sample preparation in portable microfluidic and point-of-care diagnostic devices. Current portable solution exchange methods are often limited in throughput or have low efficiencies. In this thesis, a novel method involving inertial focusing of microparticles at the inner wall of a curved channel and secondary Dean flow-based exchange of their fluid is investigated. The fluid behavior in curved microchannels is thoroughly studied and the effects of radius of curvature, hydraulic diameter, width and height of the channel and viscosity of the fluid on the development of Dean vortices are investigated experimentally and numerically. A comprehensive correlation for estimating the average lateral Dean velocity of the fluid is also proposed. The outcomes of the fluidic study is then combined with inertial particle focusing to devise a microfluidic platform for exchanging the solution of 11 m and 19 m microparticles. This was achieved with an unprecedented flow rate of 1 mL/min and throughput of 10000 particle/s at high efficiencies. Additionally, the application of the device for isolation of cell surrogates from a bacterial solution is shown. This technology can be used as a portable micro-centrifuge for sample preparation in point-of-care devices.