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On the multi-dimensional microparticle fractionation in a sharp-corner serpentine microchannel

Blahout, Sebastian (2022)
On the multi-dimensional microparticle fractionation in a sharp-corner serpentine microchannel.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00021566
Ph.D. Thesis, Primary publication, Publisher's Version

Abstract

In this thesis, the multi-dimensional fractionation of particles smaller than 10μm with respect to their size and density is investigated inside a sharp-corner serpentine microchannel by means of experimental as well as numerical methods. The motivation for research on multi-dimensional particle fractionation methods is twofold. First, particles with highly specified characteristics are the basis for various products of several different industries. Second, due to environmental or sustainability requirements, particles with defined properties are targeted to be extracted from a bulk quantity. Passive microfluidic approaches have a large potential to provide such fractionation methods, due to their simplicity and parallelizability. One of these approaches is fractionation in sharp-corner serpentine microchannels. This approach is investigated in the present thesis. Long-exposure measurements are performed to investigate the general behavior of particles of several sizes and different densities at various bulk Reynolds numbers (chapter 4). Besides the confirmation of the high potential of the used method to fractionate micron sized particles with regard to their size, the results also reveal the potential to fractionate particles solely with regard to their density. Furthermore, it is demonstrated that the used method is suitable to focus sub-micron particles on distinct trajectories. The reconstruction of three-dimensional particle distributions additionally reveals that micron particles with different sizes and densities not only move on trajectories that are spatially separated in-plane, but also out-of-plane (chapter 5). Astigmatism Particle Tracking Velocimetry measurements also enable to determine a size fractionation performance of nearly 100%. To surpass qualitative descriptions of the force contributions that are relevant for the particle motion inside a serpentine microchannel, numerical simulations are performed (chapter 6). A detailed evaluation of the simulation results reveals that the contributions of the shear-gradient force and depending on the particle size also the drag force are dominant for the motion of a particle inside a serpentine loop under the investigated conditions. Moreover, a new extension of micro Particle Image Velocimetry is presented that provides the opportunity to measure the bulk dynamics of both phases of a suspension flow simultaneously (chapter 7). For this, a labelling procedure is used to create suspension particles with a ring-shaped particle image. A comparison with Gaussian and plateau-shaped particle images showed the superior characteristics of such ring-shaped particle images with respect to measurement accuracy.

Item Type: Ph.D. Thesis
Erschienen: 2022
Creators: Blahout, Sebastian
Type of entry: Primary publication
Title: On the multi-dimensional microparticle fractionation in a sharp-corner serpentine microchannel
Language: English
Referees: Hussong, Prof. Dr. Jeanette ; Cierpka, Prof. Dr. Christian
Date: 2022
Place of Publication: Darmstadt
Collation: xxvii, 135 Seiten
Refereed: 13 April 2022
DOI: 10.26083/tuprints-00021566
URL / URN: https://tuprints.ulb.tu-darmstadt.de/21566
Abstract:

In this thesis, the multi-dimensional fractionation of particles smaller than 10μm with respect to their size and density is investigated inside a sharp-corner serpentine microchannel by means of experimental as well as numerical methods. The motivation for research on multi-dimensional particle fractionation methods is twofold. First, particles with highly specified characteristics are the basis for various products of several different industries. Second, due to environmental or sustainability requirements, particles with defined properties are targeted to be extracted from a bulk quantity. Passive microfluidic approaches have a large potential to provide such fractionation methods, due to their simplicity and parallelizability. One of these approaches is fractionation in sharp-corner serpentine microchannels. This approach is investigated in the present thesis. Long-exposure measurements are performed to investigate the general behavior of particles of several sizes and different densities at various bulk Reynolds numbers (chapter 4). Besides the confirmation of the high potential of the used method to fractionate micron sized particles with regard to their size, the results also reveal the potential to fractionate particles solely with regard to their density. Furthermore, it is demonstrated that the used method is suitable to focus sub-micron particles on distinct trajectories. The reconstruction of three-dimensional particle distributions additionally reveals that micron particles with different sizes and densities not only move on trajectories that are spatially separated in-plane, but also out-of-plane (chapter 5). Astigmatism Particle Tracking Velocimetry measurements also enable to determine a size fractionation performance of nearly 100%. To surpass qualitative descriptions of the force contributions that are relevant for the particle motion inside a serpentine microchannel, numerical simulations are performed (chapter 6). A detailed evaluation of the simulation results reveals that the contributions of the shear-gradient force and depending on the particle size also the drag force are dominant for the motion of a particle inside a serpentine loop under the investigated conditions. Moreover, a new extension of micro Particle Image Velocimetry is presented that provides the opportunity to measure the bulk dynamics of both phases of a suspension flow simultaneously (chapter 7). For this, a labelling procedure is used to create suspension particles with a ring-shaped particle image. A comparison with Gaussian and plateau-shaped particle images showed the superior characteristics of such ring-shaped particle images with respect to measurement accuracy.

Alternative Abstract:
Alternative abstract Language

In dieser Arbeit wird die mehrdimensionale Fraktionierung von Partikeln kleiner als 10μm hinsichtlich ihrer Größe und Dichte in einem Serpentinen-Mikrokanal mittels experimenteller und numerischer Methoden untersucht. Die Erforschung mehrdimensionaler Partikel-Fraktionierungsmethoden wird durch zwei Anwendungsgebiete motiviert. Zum einen bilden Partikel mit hochspezifischen Eigenschaften die Basis für verschiedene technische Produkte. Zum anderen bedingen Anforderungen des Umweltschutzes und der Nachhaltigkeit, die Extraktion von Partikeln mit definierten Eigenschaften aus verschiedensten Substanzen. Passive, mikrofluidische Fraktionierungs-Ansätze haben hierzu aufgrund ihrer Einfachheit und Parallelisierbarkeit ein großes Potenzial. Einer dieser Ansätze, die Fraktionierung in Serpentinen-Mikrokanälen, wird in dieser Arbeit untersucht. Dazu werden Messungen mittels Langzeit-Belichtung durchgeführt, um das Verhalten von Partikeln unterschiedlicher Größe und Dichte bei diversen Bulk-Reynoldszahlen zu untersuchen (Kapitel 4). Die Ergebnisse bestätigen das große Potenzial der verwendeten Methode zur Größenfraktionierung von Mikro-Partikeln. Außerdem werden Möglichkeiten aufgezeigt, Partikel ausschließlich aufgrund ihrer Dichte zu fraktionieren. Es wird ebenfalls gezeigt, dass die verwendete Methode geeignet ist, um Submikro-Partikel auf definierten Trajektorien zu fokussieren. Die Rekonstruktion dreidimensionaler Partikelverteilungen zeigt darüber hinaus, dass sich Mikro-Partikel mit unterschiedlichen Größen und Dichten nicht nur innerhalb einer Ebene auf räumlich getrennten Bahnen, sondern auch auf unterschiedlichen Höhenpositionen bewegen (Kapitel 5). Die dabei eingesetzte Astigmatism Particle Tracking Velocimetry ermöglicht es, einen Trenngrad von nahezu 100% für die Größenfraktionierung zu bestimmen. Um das qualitative Verständnis des die Partikel-Bewegung bestimmenden Kräftegleichgewichtes zu erweitern, werden numerische Simulationen durchgeführt (Kapitel 6). Die detaillierte Auswertung der Simulationsergebnisse zeigt, dass für die untersuchten Bedingungen Schergradienten und je nach Partikelgröße auch Widerstandskräfte die Partikelbewegung innerhalb einer Serpentine dominieren. Außerdem wird eine neue Erweiterung der micro Particle Image Velocimetry vorgestellt. Diese ermöglicht die simultane Bestimmung der Dynamik beider Phasen einer Suspensions-Strömung (Kapitel 7). Dazu wird ein Labelling-Verfahren verwendet, um Suspensions-Partikel mit ringförmigem Partikelbild zu erzeugen. Ein Vergleich mit Gauß’schen- und plateauförmigen Partikelbildern zeigt die überlegenen Eigenschaften ringförmiger Partikelbilder hinsichtlich der Messgenauigkeit.

German
Status: Publisher's Version
URN: urn:nbn:de:tuda-tuprints-215663
Classification DDC: 600 Technology, medicine, applied sciences > 620 Engineering and machine engineering
Divisions: 16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Fluid Mechanics and Aerodynamics (SLA)
Date Deposited: 08 Jul 2022 11:41
Last Modified: 11 Jul 2022 06:29
PPN:
Referees: Hussong, Prof. Dr. Jeanette ; Cierpka, Prof. Dr. Christian
Refereed / Verteidigung / mdl. Prüfung: 13 April 2022
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