High‐Throughput Inertial Focusing of Micrometer‐ and Sub‐Micrometer‐Sized Particles Separation

Abstract

The ability to study individual bacteria or subcellular organelles using inertial microfluidics is still nascent. This is due, in no small part, to the significant challenges associated with concentrating and separating specific sizes of micrometer and sub‐micrometer bioparticles in a microfluidic format. In this study, using a rigid polymeric microfluidic network with optimized microchannel geometry dimensions, it is demonstrated that 2 µm, and even sub‐micrometer, particles can be continuously and accurately focused to stable equilibrium positions. Suspensions have been processed at flow rates up to 1400 µL min−1 in an ultrashort 4 mm working channel length. A wide range of suspension concentrations—from 0.01 to 1 v/v%—have been systematically investigated, with yields greater than 97%, demonstrating the potential of this technology for large‐scale implementation. Additionally, the ability of this chip to separate micrometer‐ and sub‐micrometer‐sized particles and to focus bioparticles (cyanobacteria) has been demonstrated. This study pushes the microfluidic inertial focusing particle range down to sub‐micrometer length scales, enabling novel routes for investigation of individual microorganisms and subcellular organelles.

Dean flow assisted single cell and bead encapsulation for high performance single cell expression profiling

“…The balance of drag force and lift force dictated the equilibrium positions of the particles on the channel cross section 14 . Inertial microfluidics predicted that particles are more likely to occupy a single equilibrium position in a curvilinear channel when [21][22][23][24][25] designs of spiral channels would be sufficient to focus beads, but for cells, we added serpentine channels 15 at the outlet of the spiral channel as an additional focusing mechanism, as shown in Figure 1a. In the asymmetrical semicircle serpentine channel, cells were simultaneously subjected to both viscous drag force ( D F ) and centrifugal force ( C F ), and the equilibrium position of cells depends on the balance of the two forces 15,27 .…”

Rapid separation and identification of beer spoilage bacteria by inertial microfluidics and MALDI-TOF mass spectrometry

“…Considerable literature has recently grown around the theme of microfluidics as an efficient strategy for cell separation. [24][25][26][27][28][29][30][31] Generally, microfluidics is defined as the precise control and manipulation of fluid through microchannels. 32 These miniaturised devices have multiple practical applications, including particle/cell separation, 33 fluid mixing, 34 and droplet generation.…”

Study of Local Inertial Focusing Conditions for Spherical Particles in Asymmetric Serpentines

“…The achievement of proper inertial focusing conditions can then be inferred from the values of these dimensionless constants and variables with respect to known specific inequalities or diagrams both deduced from experimental and/or numerical data. The main purpose of these studies is to gather information provided by the experimental conditions to produce state diagrams which outline the focusing conditions of particles in a succinct manner; the outcome of the experiment can in principle be deduced according to the position or parcel that the associated dimensionless constants in a given experiment occupy in a state diagram [1,[36][37][38][39][40]. A well stablished criterion to characterize inertial focusing in straight channels is based on the use of two dimensionless constants, namely, the particle confinement ratio λ = a/D h , where a is the particle diameter and D h = 2wh/(w + h) is the hydraulic diameter of the channel, where w and h are the width and height of the channel; and the particle Reynolds number Re p = λ 2 Re C , where Re C = ρU Max D h /µ is the channel Reynolds number, ρ is the density of the fluid, U Max the maximum velocity of the flow in the channel and µ is the fluid viscosity.…”

“…If secondary flows are strong enough, the position and the stability of the particles' focusing positions may be influenced by the drag induced by the Dean flow. Aiming at finding a parameter to characterize particle focusing conditions in curved channels, some authors proposed the use of a ratio between lift forces and the drag caused by Dean flows, the inertial force ratio, R F = F L /F D [1,36,40]. The value of this ratio should, in principle, be useful to predict the outcome of the interaction between inertial lift and Dean drag forces on the particles' equilibrium positions in a curved channel; no change in the focusing positions (F L F D ), the positions are modified (F L ≈ F D ) or stable trajectories are completely destroyed by Dean flows (F L F D ).…”

“…Additionally, it is believed that Dean drag may allow faster focusing than in straight channels because it aids particles in sweeping the section of the fluidic channel to find their focusing position faster [36]. Due to the dependence of Dean drag and inertial lift to particle size, inertial focusing in curved channels enables unique particle size-dependent equilibrium positions which can be used for passive selective positioning and sorting [2,21,39,40,[45][46][47][48].…”