Elasto-inertial microparticle focusing in straight microchannels: A numerical parametric investigation

Abstract

Elasto-inertial microfluidic particle separation has attracted attention in biotechnological applications due to its passive nature and enhanced versatility compared to inertial systems. Developing a robust elasto-inertial sorting device can be facilitated with numerical simulation. In this study, a numerical parametric investigation was undertaken to study elasto-inertial focusing of microparticles in a straight microchannel. Our goal was to develop an approach that could be both accurate and easily implementable on the commercial solvers. We simulated the flow field using the Carreau model. The resulting elastic lift force was implemented based on an approximation of the Oldroyd-B model. Results were verified and validated against experimental measurements by us and others. A parametric study was conducted to investigate elasto-inertial particle focusing considering the important non-dimensional numbers such as the Reynolds number (Re), the Deborah number (De), dimensionless channel length (L), and blockage ratio (β). Based on this investigation, the commonly used design threshold, that is, De·L·β2=1, for particle focusing was modified and a new threshold was proposed De·Re0.2·L·β2=5. This reduced particle dispersion throughout the width of the channel from ∼20% to ∼3%. Based on this analysis and the new thresholding scheme, an empirical non-dimensional correlation was developed to predict elasto-inertial particle dispersion in straight square cross-sectional microchannels. Using this new correlation, variation in predicted dispersion was reduced from ∼15% to less than ∼5%. Our model can be used to optimize the design of elasto-inertial microfluidic particle sorters to improve experimental outcomes.