Controllable Size-Independent Three-Dimensional Inertial Focusing in High-Aspect-Ratio Asymmetric Serpentine Microchannels

Abstract

High-throughput three-dimensional (3D) focusing of cells is the key prerequisite for enabling accurate microfluidic cell detection and analysis. In this work, we develop a high-aspectratio asymmetric serpentine (HARAS) microchannel for single-line inertial focusing of particles and cells at the 3D center of the channel. The mechanism of 3D focusing is explored by numerical simulation, and the focusing performances of differently sized particles are characterized experimentally at different flow rates. The results demonstrate the outstanding 3D single-line focusing capability of our HARAS microchannel. In addition, the phenomena of size-independent and position-controllable focusing over wide flow rates are observed. Finally, the applicability of our HARAS microchannel for processing real biological cells is validated by the 3D single-line focusing of A549 cells and MCF-7 cells. Our work overcomes the issue of off-centered focusing of most previous works and provides new insights into the 3D focusing in inertial microfluidics. The proposed HARAS microchannel is extremely easy for mass production and may provide a stable, high-throughput, and position-controllable scheme for subsequent single-cell detection and analysis.

Fluid Elasticity-Enhanced Insulator-Based Dielectrophoresis for Sheath-Free Particle Focusing in Very Dilute Polymer Solutions

“…Microfluidic devices have been widely used to handle particles (either synthetic or biological) for chemical, biomedical, and environmental applications. − Focusing particles into a narrow stream is usually a necessary step in many of these devices such as a flow cytometer and a particle sorter. − Both externally imposed (e.g., acoustic, − electric, − magnetic, − etc.) and internally induced (e.g., inertial − and elastic − lift) forces have been utilized to move particles across streamlines for sheath-free focusing. Among these active and passive particle focusing methods, insulator-based dielectrophoresis (iDEP) − has received increasing interest because of its easy and robust operation in electrokinetic microfluidic devices that favor integration and automation for point-of-care technologies.…”

High-throughput adjustable deformability cytometry utilizing elasto-inertial focusing and virtual fluidic channel

“…Due to the curving of the serpentine microchannel, a Dean flow will be formed in the cross-section, which applies a F D on cells to modify their equilibrium positions and accelerate the focusing process. 32 The value of the F D can be estimated as: F D = 3π μU D d (ref. 33) (where μ is the fluid dynamic viscosity; and U D is the average velocity of secondary flow and can be expressed as U D = 1.8 × 10 −4 De 1.63 ).…”

“…Due to the curving of the serpentine microchannel, a Dean flow will be formed in the cross-section, which applies a F D on cells to modify their equilibrium positions and accelerate the focusing process. 32 The value of the F D can be estimated as: .63 ). 34 Under competing F L and F D , cells will equilibrate at two vertical positions in the symmetric serpentine microchannel at finite Reynolds numbers.…”

“…34 Under competing F L and F D , cells will equilibrate at two vertical positions in the symmetric serpentine microchannel at finite Reynolds numbers. 32 However, the multiplex focusing positions in the vertical direction will cause the heterogeneous deformation of cells. To address this issue, we further coupled the viscoelasticity effect with the inertial effect in the symmetric serpentine microchannel.…”

Lattice-Boltzmann Modelling for Inertial Particle Microfluidics Applications — A Tutorial Review

“…Ni et al [129] simulated, and experimentally verified, the focussing of particles in an asymmetric serpentine channel with high aspect ratio. The authors observed that the periodic turn of the Dean flow causes the particles to migrate in waves within the channel and promotes the 3D single line focusing of the particles.…”