Hydrodynamic focusing and interdistance control of particle-laden flow for microflow cytometry (original) (raw)
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A Novel Hydrodynamic Focusing Microdevice for Flow Cytometry Applications
Iranian Journal of Science and Technology: Transactions of Mechanical Engineering
Hydrodynamic focusing is one of the most utilized techniques in microfluidics. Its applications have been employed in a wide variety of biological analyses including on-chip flow cytometry, single molecule detection, and laminar mixers. In the present study, a new hydrodynamic focusing microdevice for flow cytometry applications is presented and numerically investigated. In the proposed microdevice, the sample fluid is compressed both in vertical and horizontal directions simultaneously by radial sheath flows injected within flow cytometer through one ring. The microdevice configuration is optimized and effective parameters on stream distribution are investigated. In addition, in order to observe hydrodynamic focusing phenomena, particles trajectories are studied. Moreover, results of the proposed model are compared with the previous one in order to verify that the performance of the present model is more efficient.
Universally applicable three-dimensional hydrodynamic microfluidic flow focusing
Lab on a Chip, 2013
We have demonstrated a microfluidic device that can not only achieve three-dimensional flow focusing but also confine particles to the center stream along the channel. The device has a sample channel of smaller height and two sheath flow channels of greater height, merged into the downstream main channel where 3D focusing effects occur. We have demonstrated that both beads and cells in our device display significantly lower CVs in velocity and position distributions as well as reduced probability of coincidental events than they do in conventional 2D-confined microfluidic channels. The improved particle confinement in the microfluidic channel is highly desirable for microfluidic flow cytometers and in fluorescence-activated cell sorting (FACS). We have also reported a novel method to measure the velocity of each individual particle in the microfluidic channel. The method is compatible with the flow cytometer setup and requires no sophisticated visualization equipment. The principles and methods of device design and characterization can be applicable to many types of microfluidic systems.
Particle Focusing in Staged Inertial Microfluidic Devices for Flow Cytometry
Analytical Chemistry, 2010
Microfluidic inertial focusing has been demonstrated to be an effective method for passively positioning microparticles and cells without the assistance of sheath fluid. Because inertial focusing produces well-defined lateral equilibrium particle positions in addition to highly regulated interparticle spacing, its value in flow cytometry has been suggested. Particle focusing occurs in straight channels and can be manipulated through cross sectional channel geometry by the introduction of curvature. Here, we present a staged channel design consisting of both curved and straight sections that combine to order particles into a single streamline with longitudinal spacing. We have evaluated the performance of these staged inertial focusing channels using standard flow cytometry methods that make use of calibration microspheres. Our analysis has determined the measurement precision and resolution, as a function of flow velocity and particle concentration that is provided by these channels. These devices were found to operate with increasing effectiveness at higher flow rates and particle concentrations, within the examined ranges, which is ideal for high throughput analysis. Further, the prototype flow cytometer equipped with an inertial focusing microchannel matched the resolution provided by a commercial hydrodynamic focusing flow cytometer. Most notably, our analysis indicates that the inertial focusing channels virtually eliminated particle coincidence at the analysis point. These properties suggest a potentially significant role for inertial focusing in the development of inexpensive flow cytometry-based diagnostics and in applications requiring the analysis of high particle concentrations.
Microflow Cytometers with Integrated Hydrodynamic Focusing
Sensors, 2013
This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex) principle. The sample-A suspension of micro particles or blood cells-is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.
Passive Dielectrophoretic Focusing of Particles and Cells in Ratchet Microchannels
Micromachines, 2020
Focusing particles into a tight stream is critical for many microfluidic particle-handling devices such as flow cytometers and particle sorters. This work presents a fundamental study of the passive focusing of polystyrene particles in ratchet microchannels via direct current dielectrophoresis (DC DEP). We demonstrate using both experiments and simulation that particles achieve better focusing in a symmetric ratchet microchannel than in an asymmetric one, regardless of the particle movement direction in the latter. The particle focusing ratio, which is defined as the microchannel width over the particle stream width, is found to increase with an increase in particle size or electric field in the symmetric ratchet microchannel. Moreover, it exhibits an almost linear correlation with the number of ratchets, which can be explained by a theoretical formula that is obtained from a scaling analysis. In addition, we have demonstrated a DC dielectrophoretic focusing of yeast cells in the sy...
Investigation of viscoelastic focusing of particles and cells in a zigzag microchannel
Electrophoresis , 2021
Microfluidic particle focusing has been a vital prerequisite step in sample preparation for downstream particle separation, counting, detection, or analysis, and has attracted broad applications in biomedical and chemical areas. Besides all the active and passive focusing methods in Newtonian fluids, particle focusing in viscoelastic fluids has been attracting increasing interest because of its advantages induced by intrinsic fluid property. However, to achieve a well-defined focusing position, there is a need to extend channel lengths when focusing micrometer-sized or sub-microsized particles, which would result in the size increase of the microfluidic devices. This work investigated the sheathless viscoelastic focusing of particles and cells in a zigzag microfluidic channel. Benefit from the zigzag structure of the channel, the channel length and the footprint of the device can be reduced without sacrificing the focusing performance. In this work, the viscoelastic focusing, including the focusing of 10 μm polystyrene particles, 5 μm polystyrene particles, 5 μm magnetic particles, white blood cells (WBCs), red blood cells (RBCs), and cancer cells, were all demonstrated. Moreover, magnetophoretic separation of magnetic and nonmagnetic particles after viscoelastic pre-focusing was shown. This focusing technique has the potential to be used in a range of biomedical applications.
Effect of Microchannel Sizes on 3D Hydrodynamic Focusing of a Microflow Cytometer
Hydrodynamic focusing is an important method used in microfluidics cell sorting devices. A design of flow cytometer has been developed and simulated using COMSOL Multyphysics software. The device is capable of creating a self-aligned stream by manipulating the flow rate, Q in both sheath channel. The objective of this research is to study the effect of channel size variation on the fluid flow in the micro flow cytometer device. The flow rate ratio Qs/Qi is applied in order find the best flow rate ratio value between sheath channel and sample channel. Simulated results showed that when Qs is smaller than Qi, the stream size is bigger and the length of the stream is longer. However, Qs is equal to Qi, the stream becomes smaller and the length of the stream is shorter. Similary, when Qs is bigger than Qi, the stream becomes smaller and shorter. The results showed that fluid flow is better when the size of the channel is bigger.
Hydrodynamic focusing is an important method used in microfluidics cell sorting devices. It is a technique that allows two sheath fluids to conflow at different velocities to obtain the focusing of sample fluid. The objective of hydrodynamic focusing is to make sure the particle arrives one by one at detection source. Simulation is done using COMSOL Multyphysics software to observe particle trajectories in micro flow cytometer with circular and rectangular cross-section. The density and sizes of the particles is similar to protein particles properties. Normal inflow velocity fot sheath channel is 800µm/s and normal inflow velocity for sample channel is 150µm/s. At The beginning of the experiment, circular flow cytometer was expected to have better hydrodynamic focusing effect and better particle trajectories. However, after the simulation is done the results show that particle trajectories in rectangular channel are better. Reduce channel height is one of the factor that enables particle to focus in the middle of the channel for the rectangular shape channel device.
Field-free particle focusing in microfluidic plugs
Biomicrofluidics, 2012
Particle concentration is a key unit operation in biochemical assays. Although there are many techniques for particle concentration in continuous-phase microfluidics, relatively few are available in multiphase (plug-based) microfluidics. Existing approaches generally require external electric or magnetic fields together with charged or magnetized particles. This paper reports a passive technique for particle concentration in water-in-oil plugs which relies on the interaction between particle sedimentation and the recirculating vortices inherent to plug flow in a cylindrical capillary. This interaction can be quantified using the Shields parameter (h), a dimensionless ratio of a particle's drag force to its gravitational force, which scales with plug velocity. Three regimes of particle behavior are identified. When h is less than the movement threshold (region I), particles sediment to the bottom of the plug where the internal vortices subsequently concentrate the particles at the rear of the plug. We demonstrate highly efficient concentration ($100%) of 38 lm glass beads in 500 lm diameter plugs traveling at velocities up to 5 mm/s. As h is increased beyond the movement threshold (region II), particles are suspended in well-defined circulation zones which begin at the rear of the plug. The length of the zone scales linearly with plug velocity, and at sufficiently large h, it spans the length of the plug (region III). A second effect, attributed to the co-rotating vortices at the rear cap, causes particle aggregation in the cap, regardless of flow velocity. Region I is useful for concentrating/collecting particles, while the latter two are useful for mixing the beads with the solution. Therefore, the two key steps of a bead-based assay, concentration and resuspension, can be achieved simply by changing the plug velocity. By exploiting an interaction of sedimentation and recirculation unique to multiphase flow, this simple technique achieves particle concentration without on-chip components, and could therefore be applied to a range of heterogeneous screening assays in discrete nl plugs. V