The passive particle separation method of elasto-inertial microfluidics have greatpotential in the field of physics, biology and chemistry. The objective of thisdegree project was to understand particle behavior in curved microchannels fornon-Newtonian fluids. This in order to optimize the separation of 1 µm and 2 µmparticles where the end goal is to create an efficient sample preparation method fordiagnosing sepsis. Fluorescent beads were spiked into PEO solutions of differentconcentrations and used in microfluidic PDMS-glass chips with various radii toexamine the influence of curvature and elasticity as well as the flow rate. Theresult indicated an independence of both curvature and elasticity. Reynoldsnumber and Dean number are dependent on the flow rate which results in atrade-off between a high and low flow rate. A low Reynolds number is not enoughto create Dean vortices that can be used to separate particles while a highReynolds number creates strong Dean vortices that can obstruct the focusing. Later, microfluidic silicon-glass chips were used to separate 1 µm and 2 µm beads.The 2 µm particles were able to focus in two different PEO concentrations whereasthe 1 µm particles did not have time to focus entirely. This makes it possible toseparate 2 µm particles along with some 1 µm particles towards one outlet whileleaving another outlet with only 1 µm particles. This is a promising start butfurther optimization is required before being applied to real bacteria separation. / Den passiva partikelseparationsmetoden elastisk tröghetsmikrofluidik har storapotential inom fysik, biologi och kemi. Målet med examensarbetet var att förståpartiklars förflyttning i krökta mikrokanaler för icke-newtonska vätskor. Dettagjordes för att optimera separering av 1 µm och 2 µm partiklar där slutmålet är attskapa en effektiv provberedningsmetod för att diagnostisera sepsis. Fluorescerandepartiklar tillsatta i PEO-l¨osningar av olika koncentrationer anv¨andes imikrofluidiska PDMS-glas chip med olika radier för att undersöka inverkan avkrökning och elasticitet samt flödeshastigheten. Resultatet indikerade ettoberoende av både krökning och elasticitet. Reynolds nummer och Deans nummerär beroende av flödeshastigheten vilket resulterar i en avvägning mellan en hög ochlåg flödeshastighet. Ett lågt Reynolds nummer är inte tillräckligt för att skapaDean virvlar vilket kan utnyttjas för att separera partiklar medan ett högtReynolds nummer framkallar starka Dean virvlar vilket kan hindra fokuseringen. Sedan användes mikrofluidiska kisel-glas chip för att separera 1 µm and 2 µmpartiklar. 2 µm partiklarna lyckades fokusera i två olika PEO-koncentrationermedan partiklarna av 1 µm inte fokuserade fullt ut. Detta gör det möjligt attseparera 2 µm partiklar tillsammans med ett antal 1 µm partiklar mot ett utloppsamtidigt som ett annat utlopp endast innehåller 1 µm partiklar. Det är enlovande start men ytterligare optimering krävs innan det kan tillämpas på faktiskbakterieseparation.

Helicopter turboshaft engines may ingest large amounts of foreign particles (most commonly sand/dust), which can cause significant compressor blade damage and even engine failure. In many helicopters, this issue is mitigated by separating the particles from the intake airstream. An effective device for engine air-particle separation is the vortex tube separator (VTS), which uses centrifugal forces in a vortical flow to radially filter foreign particles from a duct with an annular exit. Dozens or hundreds of these devices are linked together on a shared manifold known as a VTS array. There is a distinct lack of scientific literature regarding these arrays, which likely feature significantly more complex flowfields than singular VTSs due to aerodynamic interactions between the devices. The research presented in this dissertation identifies and explains flow features unique to arrays by means of an experimental investigation downstream of various VTS configurations in a wind tunnel. Mean PIV flowfields reveal that the VTS array rapidly generates a strong central recirculation zone while a single VTS does not, implying the existence of axial flow gradients within associated separators that could affect filtration efficiency. The key factor here is the global swirl intensity, which is increased in array flows due to high angular momentum contributions from separators that are radially distant from the duct center. A preliminary momentum integral model is constructed to predict the onset of recirculation in VTS flows. Analysis is then extended to the unsteady flowfield, where it is shown that VTS-generated turbulence contains only low levels of anisotropy. Spectral proper orthogonal decomposition is conducted on the array flow; it reveals the existence of low-frequency harmonic behavior composed of back-and-forth pumping motions downstream of the central VTS. Additionally, a unique precession motion is found in the same region at a slightly higher frequency. Similar precessing vortex cores have been shown to reduce separation efficiency in other cyclone separators. Both of these coherent structures may be associated with the central recirculation zone and may interfere with VTS array filtration given their timescales relative to potential particle relaxation timescales. This dissertation opens the door for future experimental and computational studies of fluid and particle dynamics in VTS flows with the goal of improving VTS array-specific design philosophies. / Doctor of Philosophy / Vortex tube separators (VTSs) help protect helicopter engines by filtering harmful particles (sand, dust, snow, ash, sea spray, etc.) they would otherwise ingest. This is done by creating a vortex in which centrifugal forces eject particles outwards, separating them from the main airstream. These devices are effective when dozens are grouped together into VTS arrays, but little is understood of the complex air and particle dynamics that result from the many interacting vortices both in and around such arrays. This dissertation describes an early effort to study these aerodynamics and open the door for subsequent particle dynamics research. A laser-based measurement technique called particle image velocimetry is used to determine flow velocities downstream of a VTS array placed in a wind tunnel. When velocities are averaged together over time, they reveal a central recirculation zone (a known feature of intensely swirling flows) downstream of the VTS array that vanishes when only a single separator in the array is active. A mathematical model is developed to predict such recirculation. It demonstrates that a VTS array comprises many separators that are far from the center of the duct they are contained within, and these contribute greatly to the overall swirl intensity. Other data analysis techniques are used to investigate the instantaneous velocity flowfield, which differs significantly from averaged quantities. One such technique is spectral proper orthogonal decomposition, which extracts so-called "coherent structures" from the flow - correlated high-energy motions that exist at certain frequencies and may not be visible in the raw data. This analysis finds two interesting structures at the very center of the duct, possibly associated with the recirculation zone: a back-and-forth pumping motion at a very low frequency (and some of its harmonic frequencies), and a "precessing" (unsteadily rotating) vortex at a slightly higher frequency. These motions, as well as the central recirculation zone itself, are impactful because they may affect the filtration process within the VTS upstream of where they were measured. Such effects will be investigated in future experiments and, if confirmed, may influence the design of VTS arrays.

No description available.

Fine particle separation is a grand challenge in the mining and mineral processing industry. The industry standard process, froth flotation, is extremely robust and adaptable; however, it is inefficient for particles less than 20 microns. Owing to this limitation, some mining sectors, such as coal, opt to discard the ultrafine particles to waste impoundments as the costs to recover and dewater these materials are prohibitive. The Hydrophilic Hydrophobic Process (HHS) is one alternative to flotation that uses a recyclable solvent, rather than air bubbles, to selectively recover fine hydrophobic particles. Prior laboratory, proof-of-concept, and demonstration-scale testing has shown that the HHS process is extremely efficient, having no effective size limitation. The purpose of this research was to continue the development and improvement of the HHS process, through the design, construction, and testing of a mobile pilot plant. The pilot plant would in turn be used to demonstrate the robustness of the HHS process through a systemic study of multiple coal sources and ranks. In addition, the pilot plant would serve as a testbed for inquiry-based process intensification, the development and evaluation of design criteria for the various unit operation. Through the course of this research, a 50 lb./hr. (product rate) pilot plant was constructed and commissioned. Initial investigations focused on the shakedown and design of key unit operations, including the agglomeration and de-emulsification (i.e. Morganizing) steps. Studies showed that the initial design of these units, namely pump induced mixing in agglomeration and packed bed emulsification in the Morganizer, were not adequate to meet production demands, and as such, these stages were redesigned after appropriate fundamental evaluations. After implementing the design changes, the pilot plant was successfully operated over a 7-month period, routinely producing bituminous products with less than6% ash and less than 10% moisture as well as anthracite products with less than 3% ash and less than 4% moisture. This study also evaluated a new approach to de-emulsification using a jig based Morganizer in place of the standard oscillating column Morganizer. The jig utilizes a pulsing mechanism to move liquid to break up agglomerates versus the mechanical disk stack. Preliminary results showed that the jig Morganizer was comparable to the oscillating unit at more than half the size. This new design provides a pathway for reduced cost, footprint, and improved scalability. Lastly, this study evaluated both the HHS process and dual-scan X-ray based particle sorting as means of increasing the REE content of coal-based materials. Data from a pilot-scale x-ray sorter showed the unit was capable of preconcentrating REEs to over 300 ppm, while data from the HHS similarly showed the process was capable of REE recoveries of 85-90% and of preconcentrating REEs above 300 ppm. Altogether, these results indicate That both of these technologies are capable of efficiently and cost effectively preconcentrate REEs from wastes streams at operating coal preparation plants. / Doctor of Philosophy / The mining sector has traditionally been a large producer of waste, with the vast majority of this waste being ultrafine particles that are unable to be recovered using conventional technologies. These particles are often disposed of in large surface impoundments, which are an environmental and social liability in many mining districts. This study has evaluated a novel method of fine particle separation, the hydrophobic-hydrophilic separation (HHS) process. The HHS process uses a recyclable oil to selectively agglomerate fine particles, which are subsequently dispersed and recovered. The oil is then filtered and recycled within the process creating an approach that is both efficient and environmentally friendly. In this study, a mobile pilot HHS plant was constructed and tested, with the results showing that the HHS can effectively recover fine carbon from waste coals, thus turning an environmental liability into a potential value stream for high-end applications. In addition, the study showed that the process can be further improved to reduce costs while improving overall efficiency. Overall, this study has provided the data needed to further commercialize the HHS process. If widely deployed, the HHS process has the potential to both reduce the current amount of waste fines being generated and reclaim the existing impoundments.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

<div> <div> <div> <p>Microfluidics is a new and emerging field that has applications in a myriad of microfluidic industrial applications such as biochemical engineering, analytical processing, biomedical engineering and separation of cells. Microfluidics operations are carried out in microfluidic chips, and the traditional method of fabrication is carried out in a cleanroom. However, this fabrication method is very costly and also requires professional trained personnel. In this thesis, a low-cost fabrication platform was developed based on soft-lithography technique developed to fabricate the microfluidic devices with resolution at microscale. This fabrication method is advantageous and novel because it is able to achieve the microscale fabrication capability with simple steps and lower-level laboratory configuration. In the developed fabrication platform, an array of ultraviolet light was illuminated onto a photoresist film that has a negative photomask with a microfluidic design on it. The photoresist film is then developed, and a silicon polymer of polydimethylsiloxane (PDMS) is chosen to be the material for the device. In this work, the performance and resolution of the fabrication system was evaluated using scanning electron microscopy (SEM), polymer resolution test and light intensity analysis. </p> <p>Based on the success of the development of microfluidics fabrication platform, various experiment of mixing and separation was conducted and studied because the utilization of the microfluidic device for mixing and separation is very valuable in biomedical and chemical engineering. Although there are a lot of applications reported, the precise separation and mixing at microscale still meet some difficulties. Mixing in micromixers is extremely time-consuming and requires very long microchannels due to laminar flow and low Reynolds number. Particle separation is also hard to be achieved because the size of micron bioparticles is very small and thus the force is not strong enough to manipulate their motion. The integration of magnetic field is an active method to strengthen both mixing and separation that has been widely applied in the biomedical industry overcome these difficulties because of its compatibility with organic particles. However, most magnetic mixing and separation use bulky permanent magnets that leave a large footprint or electromagnets that generate harmful Joule heat to organic and bio-particles. In this work, microscale magnet made of a mixture of neodymium powder and polydimethylsiloxane was developed and integrated into microfluidic system to achieve both rapid mixing of ferrofluids and separation of microparticles. Systematic experiments were conducted to discuss the effect of various parameters on the performance of magnetic mixing and separation of microparticles. It was found that channel geometry, flow filed, and magnetic properties will affect the transport phenomena of ferrofluid and microparticles, and thus mixing and separation efficiency. These findings are of great significance for the high throughput sorting of cancer cells and its mixing between drug for therapy treatment.</p></div></div></div>

No description available.

This thesis focuses on fundamental aspects of microfluidic systems and applies relevant findings to innovative designs for advanced particle manipulation applications. Computational Fluid Dynamics (CFD) is adopted for fluid modeling, based on the Finite Volume method. The accuracy of the solutions obtained is confirmed by grid sensitivity analysis and by comparisons with experimental work. Curved microchannel features and the induced Dean flow are studied through a parametric space exploration and simulations. The Lagrange-Euler coupling method – Surface Marker Point methodology – is applied to simulate large-size particles (of comparable size to the channel). Through this simulation approach, all the forces on such particles are directly derived through solving the governing equations and the influence of these particles on the flow is considered in a fully coupled manner. A new approach – the Frozen Flow & Flow Correction Coefficient method – is developed, making trans-relaxation-time simulations possible and improving computational efficiency significantly, for 3D simulations of arbitrary shape and size microparticles in complicated microfluidic channels. Detailed comparisons between simulation results and experiments involving particle sedimentation and particle equilibrium position have been conducted for methodology validation. Mechanisms of hydrodynamic particle manipulation are then studied, including hydrodynamic focusing and separation. It is found that the Tubular Pinch effect, Dean flow and the Radial Pressure Gradient effect interact to yield two distinct particle separation mechanisms. For advanced applications, particle focusing, non-magnetic and magnetic separation for neutrally buoyant particles are proposed, based on newly gained insight on the above-mentioned mechanisms. Appropriate channel designs have been proposed both for particle focusing and size-based particle separation, while the vertical-magnetic-Dean separation scheme is highlighted for magnetic separation. Finally, a new integrated system is proposed, that combines the above novel designs into a device-like ensemble. It promises to offer functionality for biomaterial separation and detection, including different types of cells, antigens and biomarkers.

Active membranes with switchable pores that are based on hydrogels can be used to measure the cell size distribution in blood samples. The system investigated in the present research is based on a polyethylene terephthalate (PET) membrane that is surface polymerized with poly (N-isopropyl acrylamide) (PNiPAAm) to form active pores of arbitrary geometry. The PET membrane provides the functionality of a backbone for mechanical rigidity, while the soft PNiPAAm hydrogel forms the active pores. Modeling and simulation of the active hydrogel behavior proved to adequately predict the opening and closing of the pores under application of an activating stimulus, e.g. temperature. The applied model is called Temperature-Expansion-Model and uses the analogy of thermal expansion to model the volume swelling of hydrogels. The Normalized Extended Temperature-Expansion-Model can englobe arbitrary hydrogels and large geometric displacements. Studies of pore opening - performed by using commercial finite element tools - show good agreement of the experimentally measured shape change of active pores. Based on these studies, the particulate fluid flow through the switchable pores is analyzed. Through application of a membrane process, i.e. a given variation of applied pressure and switching stimulus for the hydrogel, the size profile of the blocking particles can be measured directly using the flux difference under constant pressure. This allows the measurement of the cell size distribution in blood samples, e.g. to detect circulating tumor cells or anomalies in the distribution that hint to anemia.