Abstract
Flow cytometry is a technique for the analysis of cells and particles by coupling a sheath flow assisted focusing microfluidic device to an optical or electrical reader. In this context, polymer solutions can be employed to drive particle and cell focusing on the centreline of simple straight microfluidic channels. However, the change of the focusing efficiency due to polydispersity, which is a rule rather than the exception across cell populations, has not been extensively studied yet. In this work, the effect of particle polydispersity on the viscoelastic focusing in a straight cylindrical microchannel was studied by preparing two particle suspensions, containing different concentrations of particles with average diameters of 10,upmu hbox {m}, 15,upmu hbox {m} and 20,upmu hbox {m}, suspended in three solutions of polyethylene oxide with mass concentrations of 0.1 wt%, 0.25 wt% and 0.5 wt%. When the fluid explored the constant-viscosity region of the rheological curve, up to 95% of the particles were aligned on the channel centreline. When the fluid explored the shear-thinning region of the rheological curve, centreline focusing efficiency decreased, with the highest value of aligned particles being of 60%. For both mixtures, it was also observed that the fraction of aligned particles in a polydisperse system was not equivalent to that derived from the estimate of independent experiments with monodisperse particles.
Highlights
Flow cytometry is a technique for the analysis of cells and particles, by direct interrogation with an optical or electrical source (Erickson and Li 2004)
A suspension of flowing cells or particles is surrounded by two sheath flows which enable the focusing of the cells or the particles along the centreline of a microfluidic channel, achieving the so-called 3D focusing
To achieve 3D focusing in microfluidic devices, several sheath flows or more complicated channel designs are required, which eventually increases the complexity and costs of the system
Summary
Flow cytometry is a technique for the analysis of cells and particles, by direct interrogation with an optical or electrical source (Erickson and Li 2004). Despite being around since the 1960s, flow cytometry devices have been adopted for clinical analysis only in the last 30 years (Brown and Wittwer 2000). Technological advancements transformed a substantially bulky instrument into a more compact. This article is part of the topical collection “Particle motion in non-Newtonian microfluidics” guest edited by Xiangchun Xuan and Gaetano D’Avino.
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