Technique For Separation Of Particles Research Articles

Molecular-Induced Steric Shape Separation of Nano Geometries

The separation of specific-shaped nanoparticles from particle mixtures is important for the construction of particle domains with shape-specific characteristics. On the other hand, shape-based particle separation techniques have not received as much attention as size-based techniques. The shape separation effect of molecule-coated nanoparticles is primarily dependent on short-range steric interaction. The surfactant’s geometrical arrangement determines the position of the nanoparticle’s various crystallographic facets; this also determines how the various shapes are organized throughout the nanoparticle self-assembly process. In addition to smooth surfaces with a fixed droplet contact line and a stable environment, the self-assembled shape separation effect has been observed on surfaces with wettability stripe patterns and fluctuating environments where the droplet contact line behaves stick–slip-like during the evaporation process. The shape separation of spheres and rods is strongly influenced by steric interactions. Since shape-dependent transport properties exist in such nano-crystalline domains, it is important to understand the shape separation effect.

Biological particle separation techniques based on microfluidics

Biological particle separation techniques based on microfluidics

Review: Impact of microfluidic cell and particle separation techniques on microplastic removal strategies

This review highlights the growing concern regarding the proliferation of microplastics (MPs) in aquatic ecosystems and their potential impact on both the environment and human health. Despite current efforts, a considerable number of MPs remain untreated due to their small size. Conventional identification and treatment methods are summarized pointing to the current limitations. Emerging technologies in microfluidics and nanotechnology are presented as potential solutions for the removal of MPs from aquatic environments. These novel technologies, which are currently being used for the development of novel point of care (PoC) diagnostic devices, can take advantage of the size and density similarities between MPs and commonly separated particles in microfluidics applications such as cells, making them promising candidates for MPs separation and recovery in wastewater treatment plants.This review evaluates the limitations of current MPs separation and recovery technologies in water treatment plants and laboratories and compares them with the promising capabilities of microfluidics and nanotechnology, providing valuable insights into future strategies for combating MPs pollution.

Optical sorting by trajectory tracking with high sensitivity near the exceptional points

Exceptional points (EPs) in non-Hermitian systems embody abundant new physics and trigger various novel applications. In the optical force system, the motion of a particle near its equilibrium position is determined by the optical force stiffness matrix (OFSM), which is inherently non-Hermitian when the particle is illuminated by vortex beams. In this study, by exploiting the rapid variations in eigenvalues and the characteristics of particle motion near EPs of the OFSM, we propose a method to sort particles with subtle differences in their radii or refractive indices based on their trajectories in air. We demonstrate that the trajectory of a particle with parameters slightly larger than those corresponding to certain EPs closely resembles an ellipse. The increase in the major axis of the ellipse can be several orders of magnitude larger than the increase in particle radius. Furthermore, even a slight change in the refractive index can not only significantly alter the size of the ellipse but also rotate its orientation angle. Hence, particles with subtle differences can be distinguished by observing the significant disparities in their trajectories. This approach holds promise as a technique for the precise separation of micro and nanoscale particles.

Numerical modeling reveals improved organelle separation for dielectrophoretic ratchet migration.

Organelle size varies with normal and abnormal cell function. Thus, size-based particle separation techniques are key to assessing the properties of organelle subpopulations differing in size. Recently, insulator-based dielectrophoresis (iDEP) has gained significant interest as a technique to manipulate sub-micrometer-sized particles enabling the assessment of organelle subpopulations. Based on iDEP, we recently reported a ratchet device that successfully demonstrated size-based particle fractionation in combination with continuous flow sample injection. Here, we used a numerical model to optimize the performance with flow rates a factor of three higher than previously and increased the channel volume to improve throughput. We evaluated the amplitude and duration of applied low-frequency DC-biased AC potentials improving separation efficiency. A separation efficiency of nearly 0.99 was achieved with the optimization of key parameters-improved from 0.80 in previous studies (Ortiz et al. Electrophoresis, 2022;43;1283-1296)-demonstrating that fine-tuning the periodical driving forces initiating the ratchet migration under continuous flow conditions can significantly improve the fractionation of organelles of different sizes.

Influence of the filter grain morphology on separation efficiency in dielectrophoretic filtration.

Recovery of noble materials from waste is essential for industries around the globe. Dielectrophoretic (DEP) filtration, an electrically switchable particle separation technique, can be applied to tackle this challenge. It is highly selective regarding particle size, material or shape. Expanding the scope of DEP towards high throughput and improving the trapping efficiency are vital to make DEP a viable robust alternative to conventional separation methods. DEP filtration works by selective immobilisation of particles in a porous medium by the action of an inhomogeneous electric field. The field inhomogeneity comes from scattering an electric field at the phase boundary between the particle suspension and the filter surface. In this article, we show how the filter structure affects the DEP separation. We study fixed bed filters of three different grain types and find that the morphology of the grains highly influences the DEP filter efficiency. Specifically, grains with irregular surface structure and high perceived angularity show high separation efficiency. We believe these insights into the design of DEP filtration will pave the way towards its application in, for example, the recovery of valuable materials from electronic waste dust.

Size Distribution, Elemental Composition and Morphology of Nanoparticles Separated from Respirable Coal Mine Dust

Nanoparticles, defined as particles with one dimension below 100 nm, contribute little to the total mass concentration in respirable coal mine dust (RCMD) toxicological studies, but they could have a considerable part in the adverse health effects by RCMD inhalation. It has been shown that inhaled nanoparticles can penetrate deep into the lung and could plausibly contribute to acute and chronic pulmonary diseases by triggering oxidative stress formation and inducing inflammation. RCMD nanoparticles from samples collected in an underground mine in the United States were analyzed by a particle separation technique, field-flow fractionation (FFF), for size, morphology, and elemental composition. Two sub-techniques, asymmetrical flow field-flow fractionation (AsFlFFF), and sedimentation field-flow fractionation (SdFFF) were used to increase the detection size range. Nanoparticles with a size range between 25–400 nm were detected. Fractions were collected throughout the size distribution and were analyzed by electron microscopy and inductively-coupled plasma mass spectrometry (ICP-MS). Electron micrographs showed the presence of carbonaceous particles, mineral particles, diesel particles, and aggregates. Major and trace elements such as Si and Ca were detected in high abundance in all fractions. Other metals included Mg, Fe, Al, Cs, and Pb. Higher relative concentrations of Cs and Pb were observed at the size range below 30 nm. The data suggests that nanoparticles in RCMD can be highly reactive, either as a result of their size or their potential to carry toxins such as transition and heavy metals. To the best of the authors’ knowledge, this is the first data on the size, morphology, and composition of RCMD nanoparticles with a size below 100 nm.

Utilizing bifurcations to separate particles in spiral inertial microfluidics

Particles suspended in fluid flow through a closed duct can focus to specific stable locations in the duct cross section due to hydrodynamic forces arising from the inertia of the disturbed fluid. Such particle focusing is exploited in biomedical and industrial technologies to separate particles by size. In curved ducts, the particle focusing is a result of balance between two dominant forces on the particle: (i) inertial lift arising from small inertia of the fluid and (ii) drag arising from cross-sectional vortices induced by the centrifugal force on the fluid. Bifurcations of particle equilibria take place as the bend radius of the curved duct varies. By using the mathematical model of Harding et al. [J. Fluid Mech. 875, 1–43 (2019)], we illustrate via numerical simulations that these bifurcations can be leveraged in a spiral duct to achieve a large separation between different sized neutrally buoyant particles and identify a separation mechanism, not previously reported, which exploits the transient focusing of smaller particles near saddle points. We demonstrate this for similar sized particles, as well as particles that have a large difference in size, using spiral ducts with a square cross section. The novel formalism of using bifurcations to manipulate particle focusing can be applied more broadly to different geometries in inertial microfluidics, which may open new avenues in particle separation techniques.

Diagnostic Role of Serum Protein Electrophoresis

Introduction: Electrophoresis is a technique for separation of different charged particles. It is based on movementof charged particles through a solution when subjected to an electrical field. Since proteins are negatively chargedat pH 8.6, subjecting them to electrical field will push protein particles towards anode.Materials and Methods: Place of Study: This study was carried out in the Department of Pathology,RampurhatGovernment Medical College & Hospital, Birbhum, West Bengal, India.Period of Study: Study was conducted from January 2020 to March 2022.Study Design: ProspectiveAge Group: 1st decade to 8th decadeControl Group: 10 male and 10 female healthy persons of every decade were chosen as control groups.Result: Cellulose acetate electrophoresis of 150 symptomatic patients performed. Major diseases diagnosed wereMultiple Myeloma(24 cases), Chronic inflammatory disease (15 cases),HIV (13cases), Hematological malignancy(10cases), solid malignancy (10 cases), tuberculosis (7 cases) with some Miscellaneous conditions.Among the 28 Monoclonal Gammopathy cases studied(100%),the most common case was Multiple Myeloma(24 cases, 85.71%) followed by 2 cases of Solitary Plasmacytoma(7.15%) and 1 case of Monoclonal Gammopathy ofundetermined significance( MGUS) (3.57%) and 1 case of Smoldering Myeloma (3.57%).

Deterministic Lateral Displacement Microfluidic Chip for Minicell Purification.

Deterministic lateral displacement (DLD) is a well-known microfluidic technique for particle separation with high potential for integration into bioreactors for therapeutic applications. Separation is based on the interaction of suspended particles in a liquid flowing through an array of microposts under low Reynolds conditions. This technique has been used previously to separate living cells of different sizes but similar shapes. Here, we present a DLD microchip to separate rod-shaped bacterial cells up to 10 µm from submicron spherical minicells. We designed two microchips with 50 and 25 µm cylindrical posts and spacing of 15 and 2.5 µm, respectively. Soft lithography was used to fabricate polydimethylsiloxane (PDMS) chips, which were assessed at different flow rates for their separation potential. The results showed negligible shear effect on the separation efficiency for both designs. However, the higher flow rates resulted in faster separation. We optimized the geometrical parameters including the shape, size, angle and critical radii of the posts and the width and depth of the channel as well as the number of arrays to achieve separation efficiency as high as 75.5% on a single-stage separation. These results pave the way for high-throughput separation and purification modules with the potential of direct integration into bioreactors.

In-Cell Labeling Coupled to Direct Analysis of Extracellular Vesicles in the Conditioned Medium to Study Extracellular Vesicles Secretion with Minimum Sample Processing and Particle Loss.

Extracellular vesicles (EVs) are involved in a multitude of physiological functions and play important roles in health and disease. The largest proportion of studies on EVs is based on the analysis and characterization of EVs secreted in the cell culture medium. These studies remain challenging due to the small size of the EV particles, a lack of universal EV markers, and sample loss or technical artifacts that are often associated with EV labeling for single particle tracking and/or separation techniques. To address these problems, we characterized and validated a method for in-cell EV labeling with fluorescent lipids coupled with direct analysis of lipid-labeled EVs in the conditioned medium by imaging flow cytometry (IFC). This approach significantly reduces sample processing and loss compared to established methods for EV separation and labeling in vitro, resulting in improved detection of quantitative changes in EV secretion and subpopulations compared to protocols that rely on EV separation by size-exclusion chromatography and ultracentrifugation. Our optimized protocol for in-cell EV labeling and analysis of the conditioned medium reduces EV sample processing and loss, and is well-suited for cell biology studies that focus on modulation of EV secretion by cells in culture.

Particle Separation through Diverging Nanochannels via Diffusiophoresis and Diffusioosmosis

Colloid separation from dilute solutions is of significant relevance in a multitude of technological applications. Here we use numerical simulations to investigate a recently proposed particle separation technique based on diffusiophoresis. Diffusiophoresis refers to the chemotactic migration of particles induced by local chemical gradients that allows for efficient particle manipulation. It can act in a cooperating or competing manner with respect to fluid advection, and is usually accompanied by diffusioosmosis that refers to the bulk flow adjacent to a solid surface. We consider a microfluidic setup with cocurrent flow in two horizontal channels connected by vertical diverging nanochannels, where the top flow contains suspended colloidal particles and solute at a low concentration and the bottom flow contains solute at a higher concentration. We analyze the fluid, solute, and particle dynamics to show that the particle motion is driven into the diverging nanochannels under the combined influence of fluid advection and diffusiophoresis, the latter arising due to the imposed solute gradient. Selective separation and characterization of the particles based on their size and surface charge can be achieved, whose efficiency can be improved by controlling the diffusiophoretic mobility of the particle, solute P\'eclet number, and imposed solute gradient. Diffusioosmosis can enhance or inhibit the diffusiophoretic separation, depending on the surface charge of the solid surfaces.

Progress of Microfluidic Continuous Separation Techniques for Micro-/Nanoscale Bioparticles.

Separation of micro- and nano-sized biological particles, such as cells, proteins, and nucleotides, is at the heart of most biochemical sensing/analysis, including in vitro biosensing, diagnostics, drug development, proteomics, and genomics. However, most of the conventional particle separation techniques are based on membrane filtration techniques, whose efficiency is limited by membrane characteristics, such as pore size, porosity, surface charge density, or biocompatibility, which results in a reduction in the separation efficiency of bioparticles of various sizes and types. In addition, since other conventional separation methods, such as centrifugation, chromatography, and precipitation, are difficult to perform in a continuous manner, requiring multiple preparation steps with a relatively large minimum sample volume is necessary for stable bioprocessing. Recently, microfluidic engineering enables more efficient separation in a continuous flow with rapid processing of small volumes of rare biological samples, such as DNA, proteins, viruses, exosomes, and even cells. In this paper, we present a comprehensive review of the recent advances in microfluidic separation of micro-/nano-sized bioparticles by summarizing the physical principles behind the separation system and practical examples of biomedical applications.

A density-based threshold model for evaluating the separation of particles in heterogeneous mixtures with curvilinear microfluidic channels

Particle separation techniques play an important role in biomedical research. Inertial focusing based microfluidics using nonlinear channels is one of the promising label-free technologies for biological applications. The particle separation is achieved as a result of the combination of inertial lift force (FL) and Dean drag force (FD). Although the mathematical expressions of FL and FD have been well derived in prior studies, they are still complicated, which limits their popularity in practice. Recent studies modified these expressions through experiments and proposed a threshold model, which assumes that only particles larger than the threshold will be well focused. Although this threshold model has been used in recent studies, two varying versions of the threshold model (TM1 and TM2) prevents standardisation in practice. In addition, both models were developed with regular low-density particles and may not be applicable to samples with higher density or samples with irregular shapes. Here, we evaluated the threshold models with samples of different densities. Based on these evaluations, we derived a modified model (TM4), which additionally considers the factor of particle density to improve the accuracy of existing models. Our results demonstrated that TM4 could more reliably predict the sorting efficiency of samples within a wider density range.

Synthesis and characterization of elution behavior of nonspherical gold nanoparticles in asymmetrical flow field-flow fractionation (AsFlFFF)

Asymmetrical flow FFF (AsFlFFF) is a member of field-flow fractionation (FFF) and can provide the separation of particles with size from nano to microscale based on their hydrodynamic diameters with smaller particles being eluted earlier than larger ones. For spheres, if the AsFlFFF conditions are well optimized, the FFF theory allows prediction of the elution time for a given diameter. Herein, we aim to use the AsFlFFF channel to compare the elution behavior of the gold nanoparticles with three different morphologies and give a comprehensive depiction for the mechanism of their separation in AsFlFFF. Furthermore, the particles size obtained from AsFlFFF was compared with that obtained from other techniques such as transmission electron microscopy (TEM), and dynamic light scattering. In this study, gold nanospheres (GNS), gold nanotriangles (GNT), and gold nanorods (GNR) were synthesized. TEM data stated that the mean particle diameter and the edge length of GNS and GNT were 51 and 35 nm, respectively, and the length of GNR was 47 nm. Although, the diameter of GNS is close to the length of GNR, the elution time of GNS (4.45 min) was much longer than that of the GNR (3.70 min) at the same AsFlFFF conditions. Also, the elution time of GNT was longer than that of GNR, even though it has smaller size than GNR. This might be attributed to GNR reaching an equilibrium position that is farther away from the accumulation wall of the channel than GNS, resulting in earlier elution than GNS. The GNT particles are rather similar in shape to spheres, and may behave more closely to the spheres than GNR. It seem that AsFlFFF could be an analytical technique for particle size analysis and separation of nanoparticles of different shapes.

On magnetophoretic separation of blood cells using Halbach array of magnets

Magnetophoretic separation has gained much attention in recent years due to its easy application and low-cost fabrication compared to other active particle separation techniques. Due to the different properties of white blood cells (WBCs) and red blood cells (RBCs), it is possible to manipulate and separate them using a magnetic field. In this paper, a simple microfluidic device is proposed to fractionate WBCs and RBCs from whole blood using magnetophoretic force applied by Halbach array of three permanent magnets. Plasma streams containing WBCs and RBCs enter a simple microchip fabricated by PDMS. Permanent magnets apply positive and negative magnetophoretic forces to the RBCs and WBCs, respectively. Two cladding streams containing blood plasma are used to concentrate the cells in the magnetophoretic area. A wide range of inlet velocities and different distances of magnets from the channel (d) are investigated. It is demonstrated that the volume flow rate of core, and cladding streams, total flow rate and the distance between magnets and microchannel affect the separation efficiency individually. The results reveal that d = 0.1, 0.2, 0.3, 0.4, and 0.5 mm may lead to complete separation when core and cladding flow rates are 1 and 7 μl/h, respectively.

Passivated-electrode insulator-based dielectrophoretic separation of heterogeneous cell mixtures.

Rapid and accurate purification of various heterogeneous mixtures is a critical step for a multitude of molecular, chemical, and biological applications. Dielectrophoresis has shown to be a promising technique for particle separation due to its exploitation of the intrinsic electrical properties, simple fabrication, and low cost. Here, we present a geometrically novel dielectrophoretic channel design which utilizes an array of localized electric fields to separate a variety of unique particle mixtures into distinct populations. This label-free device incorporates multiple winding rows with several nonuniform structures on to sidewalls to produce high electric field gradients, enabling high locally generated dielectrophoretic forces. A balance between dielectrophoretic forces and Stokes' drag is used to effectively isolate each particle population. Mixtures of polystyrene beads (500nm and 2μm), breast cancer cells spiked in whole blood, and for the first time, neuron and satellite glial cells were used to study the separation capabilities of the design. We found that our device was able to rapidly separate unique particle populations with over 90% separation yields for each investigated mixture. The unique architecture of the device uses passivated-electrode insulator-based dielectrophoresis in an innovative microfluidic device to separate a variety of heterogeneous mixture without particle saturation in the channel.

Particle separation and alignment technique in microchannel flow by dielectrophoretic force using boxcar-type electrode

Particle separation and alignment technique in microchannel flow by dielectrophoretic force using boxcar-type electrode

Evaluation of acoustic-based particle separation methods

Purpose This paper aims to Separation and sorting of biological cells is desirable in many applications for analyzing cell properties, such as disease diagnostics, drugs delivery, chemical processing and therapeutics. Design/methodology/approach Acoustic energy-based bioparticle separation is a simple, viable, bio-compatible and contact-less technique using, which can separate the bioparticles based on their density and size, with-out labeling the sample particles. Findings Conventionally available bioparticle separation techniques as fluorescence and immunomagnetic may cause a serious threat to the life of the cells due to various compatibility issues. Moreover, they also require an extra pre-processing labeling step. Contrarily, label-free separation can be considered as an alternative solution to the traditional bio-particle separation methods, due to their simpler operating principles and lower cost constraints. Acoustic based particle separation methods have captured a lot of attention among the other reported label-free particle separation techniques because of the numerous advantages it offers. Practical implications This study tries to briefly cover the developments of different acoustic-based particle separation techniques over the years. Unlike the conventional surveys on general bioparticles separation, this study is focused particularly on the acoustic-based particle separation. The study would provide a comprehensive guide for the future researchers especially working in the field of the acoustics, in studying and designing the acoustic-based particle separation techniques. Originality/value The study insights a brief theory of different types of acoustic waves and their interaction with the bioparticles is considered, followed by acoustic-based particle separation devices reported till the date. The integration of acoustic-based separation techniques with other methods and with each other is also discussed. Finally, all major aspects like the approach, and productivity, etc., of the adopted acoustic particle separation methods are sketched in this article.

Simultaneous separation of carboxyl functionalized cellulose and egg albumin using ionic polyelectrolytes in an aqueous-organic multi-phase system

Harvesting microalgae is technically challenging due to the low concentration of biomass in the growth medium. Moreover, separation and harvesting of intracellular components from microalgae are equally challenging due to the complexity of the algal matrix. Separation of the valuable intracellular compounds from microalgae requires significant processing steps and can add to the cost of the final products. In this work, we report a novel technique for separation of cellulose particles (mimicking algal cells) and albumin (mimicking algal proteins) via selective interfacing of cationic polyelectrolyte to the surface of one component and migrating it to a hydrophobic organic solvent. In this work, two different systems were studied, a two-phase system consisting of water-organic solvent, and a three-phase system consisting of salt, polyethylene glycol, and an organic solvent. In the two-phase system, it was found that around ~75% of proteins can be retained in water phase while ~85% cellulose can be migrated into hexane phase at pH 4.5 and a polyelectrolyte concentration of 3% (w/w of the suspended particles) in a single unit operation. The efficiency of the migration in the three-phase was much lower since proteins dispersed in all the three phases. The results indicate the possibility of using the cationic polyelectrolyte-based two-phase technique to separate proteins from a mixture of cellulose and protein alluding the possibility of usage to separate cellulose-heavy microalgal debris from water-soluble components such as proteins from a disintegrated algal matrix.