Microparticle manipulation in viscoelastic flows inside curvilinear microchannels: a thorough fundamental study with application to simultaneous particle sorting and washing

Abstract

Separation and solution exchange of microparticles in non-Newtonian fluids are vital steps in biomedical applications. Dean drag and elastic forces in curved (and straight) microchannels lead to microparticle focusing in viscoelastic fluids such as Polyethylene oxide (PEO) in water. A thorough investigation of particle behavior in these fluids is still required to understand particle migration trends in curved microchannels. In this paper, we investigated the particle migration and their focusing behavior in a co-flow of viscoelastic fluids in curvilinear microchannels with different widths, heights, and radii of curvature. The effects of flow axial velocity, fluid viscoelasticity, and particle size was also studied using various concentrations of PEO in water. Particle lateral migration alongside the channel width was quantified under the effects of inertial lift, elastic, and Dean drag forces. In general, the introduction of fluid viscoelasticity in curved microchannels could enhance the focusing of microparticles. However, the dominance of the Dean drag force, and its opposition to elastic and inertial forces, would disrupt particles focusing at high axial velocities. A non-dimensional analysis was used to categorize the particle focusing behavior according to the strength of secondary vortices and the fluid viscoelasticity. We report on the channel blockage ratio, Dean number and Weissenberg number ranges within which particle focusing can be achieved in curvilinear microchannels. We also demonstrate a simultaneous duplex particle sorting and washing process in viscoelastic PEO solutions. The developed knowledge of particle and viscoelastic fluid dynamics could enable the design of future elasto-inertial particle washing and sorting devices.