Particle Migration due to Viscoelasticity of the Suspending Liquid and Its Relevance in Microfluidic Devices

Abstract

The fast growth of microfluidic applications based on complex fluids is a result of the unique fluid dynamics of these systems, enabling the creation of devices for health care or biological and chemical analysis. Microchannels designed to focus, concentrate, or separate particles suspended in viscoelastic liquids are becoming common. The key fluid dynamical issue on which such devices work is viscoelasticity-induced lateral migration. This phenomenon was discovered in the 1960s in macroscopic channels and has received great attention within the microfluidic community in the past decade. This review presents the current understanding, both from experiments and theoretical analysis, of viscoelasticity-driven cross-flow migration. Examples of promising microfluidic applications show the unprecedented capabilities offered by such technology based on geometrically simple microchannels and rheologically complex liquids

Recent advances in direct current electrokinetic manipulation of particles for microfluidic applications

“…There are a few other research directions in the field that the author considers worthy of future intensive studies and are each explained below: Current studies on electrokinetic transport and manipulation of particles in microchannels have been focused mainly upon Newtonian fluids despite the fact that many of the chemical and biological fluids in microfluidic applications possess non‐Newtonian characteristics . There has been a growing interest in the understanding of fluid rheological effects (e.g., elasticity and shear thinning) on particle motion in both DC electroosmotic and pressure‐driven flows of non‐Newtonian fluids in microchannels. However, the majority of the studies on electrokinetic particle motion are purely theoretical , and experimental investigations are desperately lacking.…”

Particle manipulations in non-Newtonian microfluidics: A review

“…Another often used dimensionless number for viscoelastic effect is the Deborah number, De, which is defined as the ratio of the fluid relaxation time to the characteristic time of an experimental observation (or a numerical simulation) [15,16], t p , i.e.,…”

“…As a matter of fact, many of the real chemical (e.g., colloidal suspensions and polymer solutions) [9,10] and biological (e.g., blood, saliva and DNA solutions) [11,12] samples exhibit non-Newtonian characteristics such as shear thinning and viscoelasticity [13,14]. Hence, there has recently been an growing interest in the fundamental and application studies of microfluidic particle manipulations in non-Newtonian fluids [15,16].…”

“…The readers are suggested to refer to the review articles from Leal [32,33] and Brunn [34] as well as the book chapter from McKinley [35] for those early-date studies of particle motions in stationary non-Newtonian fluids and in non-Newtonian fluid flows through cylindrical pipes with a diameter of the order of few millimeters. The readers are also suggested to refer to the review articles from D'Avino & Maffettone [15] and D'Avino et al [16] for the recent advancements in the fundamental understanding (primarily numerical [e.g., 36-42]) of particle motions in non-Newtonian fluid flows through straight microchannels of various shapes.…”

Continuous sheath‐free separation of drug‐treated human fungal pathogen Cryptococcus neoformans by morphology in biocompatible polymer solutions

“…Figure B shows the inherently induced lift forces on a suspended cell in the flow of viscoelastic fluids through a straight rectangular microchannel. The elastic lift is a result of the normal stress difference over the channel cross‐section. It has been suggested in recent studies to be viewed as a combination of two opposing force components: one is the center‐directed elastic lift component, , due to fluid elasticity, and the other is the wall‐directed elastic lift component, , due to fluid elasticity and shear thinning.…”