Continuous Separation of Multiple Size Microparticles using Alternating Current Dielectrophoresis in Microfluidic Device with Acupuncture Needle Electrodes

The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.

Aptamer-Based DNA Materials for the Separation and Analysis of Biological Particles

DNA is a biological macromolecule that carries genetic information in organisms.It provides a series of predominant bio-logical advantages,such as sequence programmability,high biocompatibility,and low biotoxicity.As such,it is a unique polymer material that shows great potential for application in biological and medical fields.DNA aptamers are short DNA sequences with a specific ability of molecular recognition.With its discovery,the application prospect of DNA materials has broadened,especially for the separation and analysis of biological particles.In this review,the functions and characteristics of DNA aptamers are introduced,and the applications of DNA materials in cell/exosome separation and cancer detection are summarized.The application prospect and possible challenges of DNA materials are predicted.

Microfluidic separation of particles by synergistic effect of geometry-induced hydrodynamics and magnetic field

Microfluidic combined with magnetic field have been demonstrated to be the promising solutions for fast and low-damage particles separation.However,the difficulties in the precise layout of magnets and accurate prediction of particle trajectories lead to under and over separation of target particles.A novel particle separation lab-on-chip(LOC)prototype integrated with microstructures and micropolar arrays is designed and characterized.Meanwhile,a numerical model for the separation of magnetic particles by the synergistic effect of geometry-induced hydrodynamics and magnetic field is constructed.The effect of geometry and magnetic field layout on particle deflection is systematically analyzed to implement accurate prediction of particle trajectories.It is found that the separation efficiency of magnetic particles increased from 50.2%to 91.7%and decreased from 88.6%to 85.7%in the range of depth factors from 15µm to 27µm and width factors from 30µm to 60µm,respectively.In particular,the combined effect of the offset distance of permanent magnets and the distance from the main flow channel exhibits a significant difference from the conventional perception.Finally,the developed LOC prototype was generalized for extension to arbitrary systems.This work provides a new insight and robust method for the microfluidic separation of magnetic particles.

Effect of Joule heating on the electroosmotic microvortex and dielectrophoretic particle separation controlled by local electric field

Dielectrophoresis(DEP)technology has become important application of microfluidic technology to manipulate particles.By using a local modulating electric field to control the combination of electroosmotic microvortices and DEP,our group proposed a device using a direct current(DC)electric field to achieve continuous particle separation.In this paper,the influence of the Joule heating effect on the continuous separation of particles is analyzed.Results show that the Joule heating effect is caused by the local electric field,and the Joule heating effect caused by adjusting the modulating voltage is more significant than that by driving voltage.Moreover,a non-uniform temperature distribution exists in the channel due to the Joule heating effect,and the temperature is the highest at the midpoint of the modulating electrodes.The channel flux can be enhanced,and the enhancement of both the channel flux and temperature is more obvious for a stronger Joule heating effect.In addition,the ability of the vortices to trap particles is enhanced since a larger DEP force is exerted on the particles with the Joule heating effect;and the ability of the vortex to capture particles is stronger with a stronger Joule heating effect.The separation efficiency can also be increased because perfect separation is achieved at a higher channel flux.Parameter optimization of the separation device,such as the convective heat transfer coefficient of the channel wall,the length of modulating electrode,and the width of the channel,is performed.

Combining field-modulating electroosmotic vortex and insulating post to manipulate particles based on dielectrophoresis

The dielectrophoretic technology has been one of the most frequently applied microfluidic technologies to manipulate particles.The way of a combination of controlled electroosmotic micro-vortices and dielectrophoresis to manipulate particles of different sizes was proposed in our previous work.However,the thickness of the modulating electrode is neglected.In practice,when the thickness of the modulating electrode increases,the channel flux increases,while the ability of the vortex to capture the particles reduces.In this study,a new method combining the field-modulating electroosmotic vortex and the insulating post is proposed to improve the manipulating capability of the field-modulated electroosmotic vortex to particles.The results indicate that there are three great advantages as the insulating post is placed on the channel wall on the same side of the modulating electrode.First,the capturing ability of the vortex to particles is greater due to the reduction of channel flux and the squeezing effect.Second,the range of regulating channel flux to achieve the optimal separation is extended.Third,the separation efficiency improves since the perfect separation can be achieved at a higher flow rate.Furthermore,the effects of the location and the size of the insulating post on particle separation are analyzed in detail.The present work could provide the reference for the application of the DEP technology.

New Technologies of Combined Agglomeration-separationfor Wolframite Fines

The new technology of combined agglomeration-separation and conditions for treating wolframite fineswere discussed. A mixture of wolframite and four kinds of gangue fines (quartz , fluorite, garnet and calcite)can be separated by this new technology. At high feed grade (wolframite : gangue = 1: 1) , wolframite con-centrate obtained by sedimentation assays 6 1 . 22 % ￣ 68. 33 % WO_3 with a recovery of 84. 4 % ￣93. 4 %. Atlow feed grade (wolframite : gangue =1 : 5) , wolframite ocncentrate obtained by combined agglomeration-separation and low-intensity magnetic separation assays 51 . 5% WO_3 with a recovery of 92. 0%. The majorfactors influencing these processes are the dosage of reagents and magnetite used, the time and the speed of agitation.

A new method for particle manipulation by combination of dielectrophoresis and field-modulated electroosmotic vortex

A field-modulated electroosmotic flow （FMEOF） in a microchannel can be obtained by applying modulating electric fields in a direction perpendicular to the channel wall. Micro-vortexes are generated around the electrodes along with an EOF due to the surface charge on the modulated wall. When polarizable particles are suspended near the electrodes, they experience dielectrophoretic forces due to a non-uniform electric field. In this paper, micro-vortexes and dielectrophoretic forces are combined to achieve separation and trap different sized particles in a continuous flow. Numerical results indicate that by adjusting the driving electric field parallel to the channel wall and the modulating electric field, the ratio of dielectrophoretic and hydrodynamic forces can be altered. One type of particles can be trapped by micro-vortexes （negative dielectrophoresis （DEP））, and the other particles are transported to the downstream so that the particles are separated. The influence of the electrode length and the channel height on the trapping rate is investigated.

DEM simulation of particle flow and separation in a vibrating flip-flow screen

Vibrating flip-flow screens(VFFS)with stretchable polyurethane sieve mats have been widely used in screening fine-grained materials in recent years.In this work,the discrete element method(DEM)is used to study the screening process in VFFS to explain particle flow and separation behavior at the particle scale.Unlike traditional vibrating screens,for VFFS,the amplitude response of each point on the elastic sieve mat is different everywhere.This study measures the kinematics of the elastic sieve mat under different conditions such as different stretched lengths and material loads.To establish the elastic sieve mat model in a DEM simulation,the continuous elastic sieve mat is discretized into multiple units,and the displacement signal of each unit tested is analyzed by Fourier series.The Fourier series analysis results of each unit are used as the setting parameters for motion.In this way,the movement of the elastic sieve mat is approximately simulated,and a DEM model of VFFS is produced.Through the simulation,the flow and separation of different-sized particles in VFFS are studied,and the reasonability of the simulation is verified by a pilot-scale screening experiment.The present study demonstrates the potential of the DEM method for the analysis of screening processes in VFFS.

Recent progresses in dry gas polymeric filters

Filtration and membrane separation are popular methods in gas separation since they are cost and energy efficient. Despite to air filters, there are comparatively few studies on dry gas filters, particularly at industrial scale. In fact, major unsolved challenges such as high efficiency, low pressure drop, long-term stability, high-thermal and chemical stability and advanced physiochemical properties, are still remained. The aim of this review is to scrutinize the advanced scientific and technological practices (such as selection of appropriate polymeric materials and additives, nanotechnology, modification techniques and preparation methods) towards design and fabrication of an efficient filter media for solid particles removal from the natural gas flow. Recent progresses in solid particle separation mechanisms, modeling and simulation techniques and the effect of membrane fabrication methods on its performance, strategies for modification of filter media, current challenges and future perspective are discussed.

INTERFACIAL SEPARATION OF PARTICLES

This book is addressed to scientists and engineers working in pigment and filler production, environmental protection, bioengineering, mineral and metallugical engineering, food and beverage industry, and the chemical industry in general. The book describes various interfacial separation techniques and intends to promote theoretical understanding of these phenomena.

Adaptive Particle Swarm Optimization Data Hiding for High Security Secret Image Sharing

The main aim of this work is to improve the security of data hiding forsecret image sharing. The privacy and security of digital information have becomea primary concern nowadays due to the enormous usage of digital technology.The security and the privacy of users’ images are ensured through reversible datahiding techniques. The efficiency of the existing data hiding techniques did notprovide optimum performance with multiple end nodes. These issues are solvedby using Separable Data Hiding and Adaptive Particle Swarm Optimization(SDHAPSO) algorithm to attain optimal performance. Image encryption, dataembedding, data extraction/image recovery are the main phases of the proposedapproach. DFT is generally used to extract the transform coefficient matrix fromthe original image. DFT coefficients are in float format, which assists in transforming the image to integral format using the round function. After obtainingthe encrypted image by data-hider, additional data embedding is formulated intohigh-frequency coefficients. The proposed SDHAPSO is mainly utilized for performance improvement through optimal pixel location selection within the imagefor secret bits concealment. In addition, the secret data embedding capacityenhancement is focused on image visual quality maintenance. Hence, it isobserved from the simulation results that the proposed SDHAPSO techniqueoffers high-level security outcomes with respect to higher PSNR, security level,lesser MSE and higher correlation than existing techniques. Hence, enhancedsensitive information protection is attained, which improves the overall systemperformance.

About One Discrete Mathematical Model of Perfect Fluid

In work, it is constructed a discrete mathematical model of motion of a perfect fluid. The fluid is represented as an ensemble of identical so-called liquid particles, which are in the form of extended geometrical objects: circles and spheres for two-dimensional and three-dimensional cases, respectively. The mechanism of interaction between the liquid particles on a binary level and on the level of the n-cluster is formulated. This mechanism has previously been found by the author as part of the mathematical modeling of turbulent fluid motion. In the turbulence model was derived and investigated the potential interaction of pairs of liquid particles, which contained a singularity of the branch point. Exactly, this is possible to build in this article discrete stochastic-deterministic model of an ideal fluid. The results of computational experiment to simulate various kinds of flows in two-dimensional and three-dimensional ensembles of liquid particles are presented. Modeling was carried out in the areas of quadratic or cubic form. On boundary of a region satisfies the condition of elastic reflection liquid particles. The flows with spontaneous separation of particles in a region, various kinds of eddy streams, with the quite unexpected statistical properties of an ensemble of particles characteristic for the Fermi-Pasta-Ulam effect were found. We build and study the flow in which the velocity of the particles is calibrated. It was possible using the appropriate flows of liquid particles of the ensemble to demonstrate the possibility to reproduce any prescribed image by manipulating the parameters of the interaction. Calculations of the flows were performed with using MATLAB software package according to the algorithms presented in this article.

NUMERICAL SIMULATION OF FINE PARTICLE SEPARATION IN A ROTATIONAL TUBE SEPARATOR

This paper presents a numerical analysis of gas-solid separation in a rotational tube separator. This separator which collects fine particles from gas in laminar flow is effective for fine particle separation. The separation efficiency and critical particle diameter of the separator were simulated using CFD package （FLUENT 6.0）. The simulation showed that separation efficiency can be significantly decreased due to the presence of turbulence. The simulation also showed that the Saffman lift force has little effect on the efficiency of this separator. The critical particle diameter of this tube separator was also calculated theoretically, Some experimental data were provided to validate the simulation results. Comparison between experimental results and simulation predictions on separation efficiency showed satisfactory agreement.

Numerical investigation of particle separation in Y-shaped bifurcating microchannels

In this study the Zweifach-Fung effect is investigated in a Y-shaped bifurcation when the clearance between the rigid spherical particle and the walls is small compared to both channel’s and particle’s radii.Single-and two-particle systems are studied using resolved computational fluid dynamics coupled to discrete element method to obtain a two-dimensional map of the initially positioned particles that would enter each child branch.In all cases,the path selection of the sphere depends on its two-dimensional positioning far from the bifurcation region in the parent channel.Increasing the flow rate ratio or decreasing the Reynolds number intensifies the Zweifach-Fung bifurcation effect in a single-particle system.Similarly,in two-particle systems where non-contact particle-particle interaction is present,decreasing the particle-to-particle distance reduces the bifurcation effect,while changing the Reynolds number has the same influence as in the single-particle systems.The results provide insight for optimizing the flow characteristics in bifurcating microchannels to separate the suspended particles.

Viscoelastic microfluidics: progress and challenges

The manipulation of cells and particles suspended in viscoelastic fluids in microchannels has drawn increasing attention,in part due to the ability for single-stream three-dimensional focusing in simple channel geometries.Improvement in the understanding of non-Newtonian effects on particle dynamics has led to expanding exploration of focusing and sorting particles and cells using viscoelastic microfluidics.Multiple factors,such as the driving forces arising from fluid elasticity and inertia,the effect of fluid rheology,the physical properties of particles and cells,and channel geometry,actively interact and compete together to govern the intricate migration behavior of particles and cells in microchannels.Here,we review the viscoelastic fluid physics and the hydrodynamic forces in such flows and identify three pairs of competing forces/effects that collectively govern viscoelastic migration.We discuss migration dynamics,focusing positions,numerical simulations,and recent progress in viscoelastic microfluidic applications as well as the remaining challenges.Finally,we hope that an improved understanding of viscoelastic flows in microfluidics can lead to increased sophistication of microfluidic platforms in clinical diagnostics and biomedical research.

Challenges in characterization of nanoplastics in the environment

Plastic pollution has been a legacy environment problems and more recently,the plastic particles,especially those ultrafine or small plastics particles,are widely recognized with increasing environmental and ecological impacts.Among small plastics,microplastics are intensively studied,whereas the physicochemical properties,environmental abundance,chemical states,bioavailability and toxicity toward organisms of nanoplastics are inadequately investigated.There are substantial difficulties in separation,visualization and chemical identification of nanoplastics due to their small sizes,relatively low concentrations and interferences from coexisting substances(e.g.,dyes or natural organic matters).Moreover,detection of polymers at nanoscale is largely hampered by the detection limit or sensitivity for existing spectral techniques such as Transformed Infrared Spectroscopy(FTIR)or Raman Spectroscopy.This article critically examined the current state of art techniques that are exclusively reported for nanoplastic characterization in environmental samples.Based on their operation principles,potential applications and limitations of these analytical techniques are carefully analyzed.

Numerical simulation of a dense solid particle flow inside a cyclone separator using the hybrid Euler-Lagrange approach

This paper presents a numerical simulation of the flow inside a cyclone separator at high particle loads. The gas and gas–particle flows were analyzed using a commercial computational fluid dynamics code. The turbulence effects inside the separator were modeled using the Reynolds stress model. The two phase gas–solid particles flow was modeled using a hybrid Euler–Lagrange approach, which accounts for the four-way coupling between phases. The simulations were performed for three inlet velocities of the gaseous phase and several cyclone mass particle loadings. Moreover, the influences of several submodel parameters on the calculated results were investigated. The obtained results were compared against experimental data collected at the in-house experimental rig. The cyclone pressure drop evaluated numerically underpredicts the measured values. The possible reason of this discrepancies was disused.

Stormwater treatment： examples of computational fluid dynamics modeling

Control of rainfall-runoff particulate matter （PM） and PM-bound chemical loads is challenging; in part due to the wide gradation of PM complex geometries of many unit operations and variable flow rates. Such challenges and the expense associated with resolving such challenges have led to the relatively common examination of a spectrum of unit operations and processes. This study applies the principles of computa- tional fluid dynamics （CFD） to predict the particle and pollutant clarification behavior of these systems subject to dilute multiphase flows, typical of rainfall-runoff, within computationally reasonable limits, to a scientifically acceptable degree of accuracy. The Navier-Stokes （NS） system of nonlinear partial differential equations for multi- phase hydrodynamics and separation of entrained particles are solved numerically over the unit operation control volume with the boundary and initial conditions defined and then solved numerically until the desired convergence criteria are met. Flow rates examined are scaled based on sizing of common unit operations such as hydrodynamic separators （HS）, wet basins, or filters, and are examined from 1 to 100 percent of the system maximum hydraulic operating flow rate. A standard turbulence model is used to resolve flow, and a discrete phase model （DPM） is utilized to examine the particle clarification response. CFD results closely follow physical model results across the entire range of flow rates. Post-processing the CFD predictions provides an in-depth insight into the mechanistic behavior of unit operations by means of three dimensional （3-D） hydraulic profiles and particle trajectories. Results demon- strate the role of scour in the rapid degradation of unit operations that are not maintained. Comparisons are provided between measured and CFD modeled results and a mass balance error is identified. CFD is arguably the most powerful tool available for our profession since continuous simulation modeling.