Particle focusing and separation in curved microchannels using elasto-inertial microfluidics

Abstract: The passive particle separation method of elasto-inertial microfluidics have greatpotential in the field of physics, biology and chemistry. The objective of thisdegree project was to understand particle behavior in curved microchannels fornon-Newtonian fluids. This in order to optimize the separation of 1 µm and 2 µmparticles where the end goal is to create an efficient sample preparation method fordiagnosing sepsis. Fluorescent beads were spiked into PEO solutions of differentconcentrations and used in microfluidic PDMS-glass chips with various radii toexamine the influence of curvature and elasticity as well as the flow rate. Theresult indicated an independence of both curvature and elasticity. Reynoldsnumber and Dean number are dependent on the flow rate which results in atrade-off between a high and low flow rate. A low Reynolds number is not enoughto create Dean vortices that can be used to separate particles while a highReynolds number creates strong Dean vortices that can obstruct the focusing. Later, microfluidic silicon-glass chips were used to separate 1 µm and 2 µm beads.The 2 µm particles were able to focus in two different PEO concentrations whereasthe 1 µm particles did not have time to focus entirely. This makes it possible toseparate 2 µm particles along with some 1 µm particles towards one outlet whileleaving another outlet with only 1 µm particles. This is a promising start butfurther optimization is required before being applied to real bacteria separation.