Modelling the electromagnetic separation of non-metallic particles from liquid metal flowing through a two-stage multichannel

A two-stage multichannel was designed to increase the efficiency of separating non-metallic particles from liquid metal flowing through an alternating magnetic field. Numerical method was developed to calculate the particle concentration and separation efficiency of a zinc melt containing dross particles and verified by the experimental results. The distribution of particle concentration and axial fluid velocity changed significantly due to the added walls in the sub-channel, resulting in an abrupt increase in the residence time of the inner bulk melt with high particle concentrations and a remarkable increase in particle separation efficiency when flowing through the single-channel to sub-channels. A multistage and multichannel arrangement is hence recommended for further increase in the separation efficiency of an electromagnetic separator

Separation of bacterial spores from flowing water in macro-scale cavities by ultrasonic standing waves

The separation of micron-sized bacterial spores (Bacillus cereus) from a steady flow of water through the use of ultrasonic standing waves is demonstrated. An ultrasonic resonator with cross-section of 0.0254 m x 0.0254 m has been designed with a flow inlet and outlet for a water stream that ensures laminar flow conditions into and out of the resonator section of the flow tube. A 0.01905-m diameter PZT-4, nominal 2-MHz transducer is used to generate ultrasonic standing waves in the resonator. The acoustic resonator is 0.0356 m from transducer face to the opposite reflector wall with the acoustic field in a direction orthogonal to the water flow direction. At fixed frequency excitation, spores are concentrated at the stable locations of the acoustic radiation force and trapped in the resonator region. The effect of the transducer voltage and frequency on the efficiency of spore capture in the resonator has been investigated. Successful separation of B. cereus spores from water with typical volume flow rates of 40-250 ml/min has been achieved with 15% efficiency in a single pass at 40 ml/min.Comment: 11 pages, 6 figure

MICROPARTICLE SAMPLING AND SEAPARATIONENABLED BY DROPLET MICROFLUIDICS

This work reports design, device fabrication, modeling and experimental results on newsampling and separation principles in which liquid is transported in a droplet form on a plannerhydrophobic surface with no moving parts. The presented particle sampler and separatorconstitute core units for the handheld lab-on-a-chip-based airborne particle monitoring system.For the airborne particle sampling, a novel method is developed by which the particles onthe solid surface are swept and sampled by electrowetting-actuated moving droplets. Theoreticalanalysis and experimental works along with microfabricated testing devices are carried out toinvestigate the underlying physics and to optimize the sampling conditions. The samplingconcepts are examined and proved on a solid surface and perforated filter membrane showinghigh sampling efficiencies.For the particle separation, a new separation scheme is developed in which the mixedparticles are separated within a mother droplet by traveling-wave dielectrophoresis (tw-DEP).Using the subsequent operation of droplet splitting by way of electrowetting, the separatedparticles can be isolated into each split droplet according to the DEP properties of the particles.This in-droplet separation is examined with many combinations of particles in microfabricateddevices. By investigating the particle behavior as function of the frequency of the traveling waveDEP signal, the separation efficiencies are optimized.The above microfluidic units constitute key components for upstream particle sampling anddownstream sample processing in the lab on a chip system, providing the following advantages:extremely small amount use of samples/reagents (2) no external pressure source required forfluidic operations, (3) simple design and fabrication since no mechanical moving structure

System Integration - A Major Step toward Lab on a Chip

Microfluidics holds great promise to revolutionize various areas of biological engineering, such as single cell analysis, environmental monitoring, regenerative medicine, and point-of-care diagnostics. Despite the fact that intensive efforts have been devoted into the field in the past decades, microfluidics has not yet been adopted widely. It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics. In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications. Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications

MICROFLUIDIC PARTICLE AND CELL MANIPULATION USING RESERVOIR-BASED DIELECTROPHORESIS

Controlled manipulation of synthetic particles and biological cells from a complex mixture is important to a wide range of applications in biology, environmental monitoring, and pharmaceutical industry. In the past two decades microfluidics has evolved to be a very useful tool for particle and cell manipulations in miniaturized devices. A variety of force fields have been demonstrated to control particle and cell motions in microfluidic devices, among which electrokinetic techniques are most often used. However, to date, studies of electrokinetic transport phenomena have been primarily confined within the area of microchannels. Very few works have addressed the electrokinetic particle motion at the reservoir-microchannel junction which acts as the interface between the macro (i.e., reservoir) and the micro (i.e., microchannel) worlds in real microfluidic devices. This Dissertation is dedicated to the study of electrokinetic transport and manipulation of particles and cells at the reservoir-microchannel junction of a microfluidic device using a combined experimental, theoretical, and numerical analysis. First, we performed a fundamental study of particles undergoing electrokinetic motion at the reservoir-microchannel junction. The effects of AC electric field, DC electric field, and particle size on the electrokinetic motion of particles passing through the junction were studied. A two-dimensional numerical model using COMSOL 3.5a was developed to investigate and understand the particle motion through the junction. It was found that particles can be continuously focused and even trapped at the reservoir-microchannel junction due to the effect of reservoir-based dielectrophoresis (rDEP). The electrokinetic particle focusing increases with the increase in AC electric field and particle size but decreases with the increase in DC electric field. It was also found that larger particles can be trapped at lower electric fields compared to smaller counterparts. Next, we utilized rDEP to continuously separate particles with different sizes at the reservoir-microchannel junction. The separation process utilized the inherent electric field gradients formed at the junction due to the size difference between the reservoir and the microchannel. It was observed, that the separation efficiency was reduced by inter-particle interactions when particles with small size differences were separated. The effect of enhanced electrokinetic flow on the separation efficiency was investigated experimentally and was observed to have a favorable effect. We also utilized rDEP approach to separate particles based on surface charge. Same sized particles with difference in surface charge were separated inside the microfluidic reservoir. The streaming particles interacted with the trapped particles and reduced the separation efficiency. The influences from the undesired particle trapping have been found through experiments to decrease with a reduced AC field frequency. Then, we demonstrated a continuous microfluidic separation of live yeast cells from dead cells using rDEP. Because the membrane of a cell gets distorted when it loses its viability, a higher exchange of ions results from such viability loss. The increased membrane conductivity of dead cells leads to a different Claussius-Mossoti factor from that of live cells, which enables their selective trapping and continuous separation based on cell viability. A two-shell numerical model was developed to account for the varying conductivities of different cell layers, the results of which agree reasonably with the experimental observations. We also used rDEP to implement a continuous concentration and separation of particles/cells in a stacked microfluidics device. This device has multiple layers and multiple microchannels on each layer so that the throughput can be significantly increased as compared to a single channel/single layer device. Finally, we compared the two-dimensional and three-dimensional particle focusing and trapping at the reservoir-microchannel junction using rDEP. We observed that the inherent electric field gradients in both the horizontal and vertical planes of the junction can be utilized if the reservoir is created right at the reservoir-microchannel junction. Three-dimensional rDEP utilizes the additional electric field gradient in the depth wise direction and thus can produce three-dimensional focusing. The electric field required to trap particles is also considerably lower in three-dimensional rDEP as compared to the two-dimensional rDEP, which thus considerably reduces the non-desired effects of Joule heating. A three-dimensional numerical model which accounted for the entire microfluidic device was also developed to predict particle trajectories

Investigation of Ultrasonic Wave Scattering Effects using Computational Methods

Advances in computational power and expanded access to computing clusters has made mathematical modeling of complex wave effects possible. We have used multi-core and cluster computing to implement analytical and numerical models of ultrasonic wave scattering in fluid and solid media (acoustic and elastic waves). We begin by implementing complicated analytical equations that describe the force upon spheres immersed in inviscid and viscous fluids due to an incident plane wave. Two real-world applications of acoustic force upon spheres are investigated using the mathematical formulations: emboli removal from cardiopulmonary bypass circuits using traveling waves and the micromanipulation of algal cells with standing waves to aid in biomass processing for algae biofuels. We then move on to consider wave scattering situations where analytical models do not exist: scattering of acoustic waves from multiple scatterers in fluids and Lamb wave scattering in solids. We use a numerical method called finite integration technique (FIT) to simulate wave behavior in three dimensions. The 3D simulations provide insight into experimental results for situations where 2D simulations would not be sufficient. The diverse set of scattering situations explored in this work show the broad applicability of the underlying principles and the computational tools that we have developed. Overall, our work shows that the movement towards better availability of large computational resources is opening up new ways to investigate complicated physics phenomena

Methodologies, technologies and strategies for acoustic streaming based Acoustofluidics

Acoustofluidics offers contact-free manipulation of particles and fluids, enabling their uses in various life sciences, such as for biological and medical applications. Recently, there have been extensive studies on acoustic streaming-based acoustofluidics, which are formed inside a liquid agitated by leaky surface acoustic waves (SAWs) through applying radio frequency signals to interdigital transducers (IDTs) on a piezoelectric substrate. This paper aims to describe acoustic streaming-based acoustofluidics and provide readers with an unbiased perspective to determine which IDT structural designs and techniques are most suitable for their research. This review, first, qualitatively and quantitatively introduces underlying physics of acoustic streaming. Then, it comprehensively discusses the fundamental designs of IDT technology for generating various types of acoustic streaming phenomena. Acoustic streaming-related methodologies and the corresponding biomedical applications are highlighted and discussed, according to either standing surface acoustic waves or traveling surface acoustic waves generated, and also sessile droplets or continuous fluids used. Traveling SAW-based acoustofluidics generate various physical phenomena including mixing, concentration, rotation, pumping, jetting, nebulization/atomization, and droplet generation, as well as mixing and concentration of liquid in a channel/chamber. Standing SAWs induce streaming for digital and continuous acoustofluidics, which can be used for mixing, sorting, and trapping in a channel/chamber. Key challenges, future developments, and directions for acoustic streaming-based acoustofluidics are finally discussed

MICROFLUIDIC APPROACHES FOR DISEASED CELL SEPARATION FROM BLOOD

Ph.DDOCTOR OF PHILOSOPH

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals

On-Chip Magnetic Bead and Nanoparticle Separation in Compound Droplet EWOD

A novel technique to manipulate, transport and separate magnetic beads and super-paramagnetic nanoparticles in compound droplets on open chip digital microfluidic platform using electrowetting on dielectric has been presented. Magnetic particles added in water-oil based compound droplet are used. The magnetic properties of particles and electrowetting forces are utilized to cause particle separation using magnetic and electric fields. This paper demonstrates magnetic particle concentration and separation in an open digital microfluidic platform using compound droplets. It provides a new paradigm to enhance liquid manipulation using compound droplets on lab-on-chip platforms