Continuous Microfluidic Particle Separation via Elasto-Inertial Pinched Flow Fractionation

Abstract

Many of the fluids encountered in chemical and biomedical applications exhibit non-Newtonian behavior. However, the majority of current particle separation methods have been demonstrated in Newtonian fluids only. This work presents an experimental study of continuous particle separation in viscoelastic solutions via a combined action of elastic and inertial lift forces, which we term elasto-inertial pinched flow fractionation (eiPFF). The parametric effects on eiPFF are systematically investigated in terms of dimensionless numbers. It is found that eiPFF offers much higher particle throughput and separation resolution than the traditional steric effects-based PFF. Moreover, eiPFF works most efficiently when the Reynolds number, Re, is of order 1 and hence fills perfectly into the gap of our recently proposed inertia-enhanced PFF (iPFF) technique (Anal. Chem. 2015, 87, 4560-4565) that favors Re of the order 10 or more. However, the particle separation via eiPFF does not increase monotonically with the elasticity number at higher polymer concentrations and is strongly affected by the aspect ratio of channel width to height, both of which have not been previously reported. More surprisingly, the elasto-inertial deflection of small particles can be even greater than that of large particles in a high-aspect-ratio channel for Re less than 1.

Particle manipulations in non-Newtonian microfluidics: A review

“…As the microchannel in Fig. 9c has a similar structure to that used in pinched flow fractionation (PFF) [122], Lu and Xuan [123] termed this separation technique elasto-inertial pinched flow fractionation (eiPFF). They performed a comprehensive study of multiple parametric effects on eiPFF in terms of dimensionless numbers including Re, Wi, El, AR and the sheath to particle flow rate ratio (Fig.…”

“…Lu and Xuan [129] applied the technique, eiPFF, which had been demonstrated effective for sizebased particle separation [123], to separate spherical and peanutshaped PS particles of nearly equal volume with a sheath-flow pre-focusing (Fig. 11a, top row).…”

Microfluidic co-flow of Newtonian and viscoelastic fluids for high-resolution separation of microparticles

“…23,25 Sheath flow of viscoelastic carrier medium has also been coupled with "pinched flow fractionation" mechanism for enhanced chromatographic particle separation. 31,32 Most of these works use sheath and sample fluids with the same rheological property, where particle migration is not influenced by the sheath/sample interface. Recently, the co-flow of Newtonian (sheath) and viscoelastic (sample) fluids is developed to effectively transfer particles from the viscoelastic streams into the Newtonian streams for particle/cell washing and separation.…”

Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion–contraction cavity arrays

“…Seo et al 24 investigated the elasto-migration of microparticles in a microscale pipe flow of viscoelastic fluids using a holographic technique, and evaluated the effects of blockage ratio, flow rate, and entry length on particle migration. Lu and Xuan 25 presented an experimental study of continuous particle separation in viscoelastic solutions via a combined action of elastic and inertial lift forces, which is termed as elasto-inertial pinched flow fractionation (eiPFF).…”