{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:2272"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:2272","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Readout of diagnostic assays on a centrifugal microfluidic platform","abstract":"This thesis presents the technical achievements towards establishing a
novel centrifugal microfluidic platform for multiplexed immunoassays
in the field of point-of-care applications. Multiplexing of immunoassays
is here defined as the detection of a set of different antigen
species from a given sample in a single channel.
Mixing as one of the crucial microfluidic unit operation is drastically
accelerated by two novel fluidic concepts. First, magnetic beads
confined in a mixing chamber are periodically deflected by a set of
permanent magnets aligned at spatially fixed positions. The resulting
relative motion of the beads with respect to the liquid induces advection.
In the second concept, without magnetic beads, the disk is spun with
periodic changes in the sense of rotation (shake-mode) where inertia
effects induce stirring of the liquids. As a result, both strategies speedup
mixing from about 10 minutes for mere diffusion to the 1-second
range. In several developed disk-based assays, shake-mode mixing
could proof to be a robust and versatile microfluidic tool.
Multiplexing of immunoassays on the centrifugal microfluidic platform
is technically implemented in two formats: as bead-based, or microarray-
based assays.
Bead-tagging in the multiplexed immunoassay scheme is implemented
by integrated quantum dots, or organic dyes. Here, a succesfully
implemented Hepatitis-A assay demonstrates the performance of the
approach with quantum dots as bead-tag.
A theoretical modeling of the bead-aggregation process in microfluidic
channels accompanied by experimental investigations resulted in a
microfluidic disk design, which allowed the successful conduction of
bead-based immunoassays.
Microarrays as an alternative to bead-based multiplexed immunoassays
are implemented and evaluated implementing a BSA assay on
the centrifugal microfluidic platform in three ways: on a rigid polymer
disk featuring microfluidic channels structures, on a PDMS lid, which
completely covers a lab-on-a-disk, or on a slide-based microfluidic chip
attached to a rotor (applied for patent). Beneficial in all cases are the
reduced sample and reagent consumption, the accelerated processing,
and the well controlled environmental settings along the complete
procedure.
The colorimetric absorbance readout as common scheme for metabolic
assays are implemented on the microfluidic centrifual system whereas
the optical path length through the detection cell as limiting factor is
drastically extended by monolithically incorporated V-grooves (applied
for patent). The performance of the simple and rugged concept is
successfully demonstrated on a modular setup to measure the concentration
of glucose (CV = 4%), hemoglobin (CV = 3%), and alcohol
(CV = 4%) in human whole blood.
The measurement of the hematocrit as an important marker for
medical diagnostics is transferred to the centrifugal microfluidic platform.
Here, a radially aligned dead end channel is first bubble-free
primed with blood. Here, trapping of gas upon priming is reliably
avoided by capillary wicking, which is solely promoted along
predetermined edges of the channel (applied for patent). After a
sedimentation step, the hematocrit is read out by visual inspection with
a disk-imprinted scale. As a result, an overall CV of 5% over the whole
physiological-pathological range is achieved.
A desktop-sized actuation and readout device for metabolic assays on
the centrifugal platform is conceptually designed; a demonstrator
device is assembled.
A designed and constructed test and development stand to accurately
visualize the propagation of fluids and the flow patterning in
micronchannels on fast spinning disks constitutes the experimental base
for this work and related ones.","abstract_html":"This thesis presents the technical achievements towards establishing a <br>novel centrifugal microfluidic platform for multiplexed immunoassays <br>in the field of point-of-care applications. Multiplexing of immunoassays <br>is here defined as the detection of a set of different antigen <br>species from a given sample in a single channel. <br>Mixing as one of the crucial microfluidic unit operation is drastically <br>accelerated by two novel fluidic concepts. First, magnetic beads <br>confined in a mixing chamber are periodically deflected by a set of <br>permanent magnets aligned at spatially fixed positions. The resulting <br>relative motion of the beads with respect to the liquid induces advection. <br>In the second concept, without magnetic beads, the disk is spun with <br>periodic changes in the sense of rotation (shake-mode) where inertia <br>effects induce stirring of the liquids. As a result, both strategies speedup <br>mixing from about 10 minutes for mere diffusion to the 1-second <br>range. In several developed disk-based assays, shake-mode mixing <br>could proof to be a robust and versatile microfluidic tool. <br>Multiplexing of immunoassays on the centrifugal microfluidic platform <br>is technically implemented in two formats: as bead-based, or microarray- <br>based assays. <br>Bead-tagging in the multiplexed immunoassay scheme is implemented <br>by integrated quantum dots, or organic dyes. Here, a succesfully <br>implemented Hepatitis-A assay demonstrates the performance of the <br>approach with quantum dots as bead-tag. <br>A theoretical modeling of the bead-aggregation process in microfluidic <br>channels accompanied by experimental investigations resulted in a <br>microfluidic disk design, which allowed the successful conduction of <br>bead-based immunoassays. <br>Microarrays as an alternative to bead-based multiplexed immunoassays <br>are implemented and evaluated implementing a BSA assay on <br>the centrifugal microfluidic platform in three ways: on a rigid polymer <br>disk featuring microfluidic channels structures, on a PDMS lid, which <br>completely covers a lab-on-a-disk, or on a slide-based microfluidic chip <br>attached to a rotor (applied for patent). Beneficial in all cases are the <br>reduced sample and reagent consumption, the accelerated processing, <br>and the well controlled environmental settings along the complete <br>procedure. <br>The colorimetric absorbance readout as common scheme for metabolic <br>assays are implemented on the microfluidic centrifual system whereas <br>the optical path length through the detection cell as limiting factor is <br>drastically extended by monolithically incorporated V-grooves (applied <br>for patent). The performance of the simple and rugged concept is <br>successfully demonstrated on a modular setup to measure the concentration <br>of glucose (CV = 4%), hemoglobin (CV = 3%), and alcohol <br>(CV = 4%) in human whole blood. <br>The measurement of the hematocrit as an important marker for <br>medical diagnostics is transferred to the centrifugal microfluidic platform. <br>Here, a radially aligned dead end channel is first bubble-free <br>primed with blood. Here, trapping of gas upon priming is reliably <br>avoided by capillary wicking, which is solely promoted along <br>predetermined edges of the channel (applied for patent). After a <br>sedimentation step, the hematocrit is read out by visual inspection with <br>a disk-imprinted scale. As a result, an overall CV of 5% over the whole <br>physiological-pathological range is achieved. <br>A desktop-sized actuation and readout device for metabolic assays on <br>the centrifugal platform is conceptually designed; a demonstrator <br>device is assembled. <br>A designed and constructed test and development stand to accurately <br>visualize the propagation of fluids and the flow patterning in <br>micronchannels on fast spinning disks constitutes the experimental base <br>for this work and related ones.","abstract_has_math":false,"creators":["Grumann, Markus"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Zengerle, Roland"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:40Z","subjects":["Mikrosystemtechnik","Diagnostik","zentrifugal","blood","centrifuga l, diagnostics","disk"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/2272","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Zengerle, Roland"]},{"key":"dc:creator","label":"Author","values":["Grumann, Markus"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Mikrosystemtechnik","Diagnostik","zentrifugal","blood","centrifuga l, diagnostics","disk"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This thesis presents the technical achievements towards establishing a
novel centrifugal microfluidic platform for multiplexed immunoassays
in the field of point-of-care applications. Multiplexing of immunoassays
is here defined as the detection of a set of different antigen
species from a given sample in a single channel.
Mixing as one of the crucial microfluidic unit operation is drastically
accelerated by two novel fluidic concepts. First, magnetic beads
confined in a mixing chamber are periodically deflected by a set of
permanent magnets aligned at spatially fixed positions. The resulting
relative motion of the beads with respect to the liquid induces advection.
In the second concept, without magnetic beads, the disk is spun with
periodic changes in the sense of rotation (shake-mode) where inertia
effects induce stirring of the liquids. As a result, both strategies speedup
mixing from about 10 minutes for mere diffusion to the 1-second
range. In several developed disk-based assays, shake-mode mixing
could proof to be a robust and versatile microfluidic tool.
Multiplexing of immunoassays on the centrifugal microfluidic platform
is technically implemented in two formats: as bead-based, or microarray-
based assays.
Bead-tagging in the multiplexed immunoassay scheme is implemented
by integrated quantum dots, or organic dyes. Here, a succesfully
implemented Hepatitis-A assay demonstrates the performance of the
approach with quantum dots as bead-tag.
A theoretical modeling of the bead-aggregation process in microfluidic
channels accompanied by experimental investigations resulted in a
microfluidic disk design, which allowed the successful conduction of
bead-based immunoassays.
Microarrays as an alternative to bead-based multiplexed immunoassays
are implemented and evaluated implementing a BSA assay on
the centrifugal microfluidic platform in three ways: on a rigid polymer
disk featuring microfluidic channels structures, on a PDMS lid, which
completely covers a lab-on-a-disk, or on a slide-based microfluidic chip
attached to a rotor (applied for patent). Beneficial in all cases are the
reduced sample and reagent consumption, the accelerated processing,
and the well controlled environmental settings along the complete
procedure.
The colorimetric absorbance readout as common scheme for metabolic
assays are implemented on the microfluidic centrifual system whereas
the optical path length through the detection cell as limiting factor is
drastically extended by monolithically incorporated V-grooves (applied
for patent). The performance of the simple and rugged concept is
successfully demonstrated on a modular setup to measure the concentration
of glucose (CV = 4%), hemoglobin (CV = 3%), and alcohol
(CV = 4%) in human whole blood.
The measurement of the hematocrit as an important marker for
medical diagnostics is transferred to the centrifugal microfluidic platform.
Here, a radially aligned dead end channel is first bubble-free
primed with blood. Here, trapping of gas upon priming is reliably
avoided by capillary wicking, which is solely promoted along
predetermined edges of the channel (applied for patent). After a
sedimentation step, the hematocrit is read out by visual inspection with
a disk-imprinted scale. As a result, an overall CV of 5% over the whole
physiological-pathological range is achieved.
A desktop-sized actuation and readout device for metabolic assays on
the centrifugal platform is conceptually designed; a demonstrator
device is assembled.
A designed and constructed test and development stand to accurately
visualize the propagation of fluids and the flow patterning in
micronchannels on fast spinning disks constitutes the experimental base
for this work and related ones.","Die vorliegende Arbeit beschreibt die Konzepte zur Etablierung
parallelisierter immunologischer Tests an einer Probe in
mikrofluidischen Kanälen (Multiplexing) auf einer zentrifugalen
Plattform.
Vermischen von Flüssigkeiten als wesentlicher fluidischer Prozessschritt
ist über zwei einfache und zuverlässige Konzepte auf der
rotierenden Scheibe etabliert. Im ersten werden paramagnetische
Polymerkugeln (Beads), die sich in einer Mischkammer auf der Scheibe
befinden, bei Rotation der Scheibe über ortsfeste Permanentmagnete
periodisch ausgelenkt, wobei die Relativbewegung der Beads
gegenüber dem Fluid das Mischen drastisch beschleunigt. Im zweiten
wird die mikrofluidische Scheibe nicht mit konstanter Frequenz rotiert,
sondern unter sich periodisch änderndem Drehsinn (Shake-Mode), was
aufgrund von Trägheitseffekten zum Laminieren der zu mischenden
Flüssigkeiten führt. Beide Wege reduzieren jeweils die Mischzeiten von
der 10-Minuten- in die 1-Sekunden-Skala.
Multiplexing immunologischer Tests auf der zentrifugalen mikrofluidischen
Plattform ist technisch über codierte Beads als Festphase
und über Mikroarrays implementiert. Die Codierung der Beads wurde
dabei über Nano-Kristallite, die in die Polymerkugeln eingequollen
sind, wie auch durch Farbstoffe in den Beads erreicht. Die
Leistungsfähigkeit des Bead-basierten Konzeptes wurde über die
Etablierung eines Hepatitis-A Assays nachgewiesen.
Die theoretische Modellierung des Aufstauens der Polymerkugeln in
der Messkammer in Form einer möglichst periodischen Monolage dient
der Optimierung des mikrofluidischen Designs mit dem nachfolgend
die Durchführung bead-basierter Tests erfolgreich demonstriert werden
konnte.
Mikroarrays sind auf der zentrifugalen mikrofluidischen Plattform in
drei Varianten implementiert und durch einen BSA-Assay: gedruckt in
eine scheiben-basierten Reaktionskammer, auf den korrespondierenden
Deckel aus PDMS, oder auf einen Standard-Kunststoffträger, der
zusammen mit einem mikrofluidischen PDMS-Chip über einen
separaten Rotor prozessiert wird.
Zusätzlich konnten kolorimetrische Tests auf der zentrifugalen
mikrofluidischen Plattform etabliert werden. Hier wurde die Länge des
optischen Weges durch die Messkammer - als limitierender Faktor der
Miniaturisierung bei senkrechter Durchstrahlung - durch die Integration
von V-Nuten als optische Reflektionselemente von der Dicke
der rotierenden Scheibe entkoppelt. Die erfolgreiche Implementierung
der Konzentrationsmesung von Glukose (VK = 4%), Hämoglobin
(VK = 3%) und Alkohol (VK = 4%) in menschlichem Vollblut
demonstriert dabei die Einfachheit und Zuverlässigkeit des neuartigen
Konzepts.
Ein Gerät zur Prozessierung und zum Auslesen von scheibenbasierten,
kolorimetrischen Tests wurde im Rahmen dieser Arbeit
entworfen und ein Demonstrator aufgebaut.
Die Bestimmung des Hämatokrit-Wertes von Blut über einen
Sedimentationsprozess ist auf der zentrifugalen Plattform implementiert,
wobei das Auslesen mit dem Auge ohne optische Hilfsmittel
möglich ist. Der fluidische Messkanal folgt der Form einer
konventionellen Glaskapillare, weist jedoch nur einen Einlass auf. Die
vollständige und blasenfreie Befüllung über Kapillarkräfte lässt sich
durch eine geeignete Kanalgeometrie erreichen. Mit einem VK von 5%
über den relevanten physiologisch-pathologischen Bereich lassen sich
damit Hämatokrit-Messungen einfach und präzise durchführen.
Alle mikrofluidischen Experimente wurden auf einem optischen
Messplatz durchgeführt, dessen Entwurf und Aufbau Teil der
vorliegenden Arbeit ist. Hier lassen sich Flüssigkeiten in Kanälen
(laterale Abmessungen im my-m-Bereich) auf einer schnell rotierenden
Scheibe beobachten."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Readout of diagnostic assays on a centrifugal microfluidic platform","Auslesestrategien für diagnostische Tests auf einer zentrifugalen mikrofluidischen Plattform"]}]}],"canonical_facts":{"dc:contributor":["Zengerle, Roland"],"dc:creator":["Grumann, Markus"],"dc:description.abstract":["This thesis presents the technical achievements towards establishing a
novel centrifugal microfluidic platform for multiplexed immunoassays
in the field of point-of-care applications. Multiplexing of immunoassays
is here defined as the detection of a set of different antigen
species from a given sample in a single channel.
Mixing as one of the crucial microfluidic unit operation is drastically
accelerated by two novel fluidic concepts. First, magnetic beads
confined in a mixing chamber are periodically deflected by a set of
permanent magnets aligned at spatially fixed positions. The resulting
relative motion of the beads with respect to the liquid induces advection.
In the second concept, without magnetic beads, the disk is spun with
periodic changes in the sense of rotation (shake-mode) where inertia
effects induce stirring of the liquids. As a result, both strategies speedup
mixing from about 10 minutes for mere diffusion to the 1-second
range. In several developed disk-based assays, shake-mode mixing
could proof to be a robust and versatile microfluidic tool.
Multiplexing of immunoassays on the centrifugal microfluidic platform
is technically implemented in two formats: as bead-based, or microarray-
based assays.
Bead-tagging in the multiplexed immunoassay scheme is implemented
by integrated quantum dots, or organic dyes. Here, a succesfully
implemented Hepatitis-A assay demonstrates the performance of the
approach with quantum dots as bead-tag.
A theoretical modeling of the bead-aggregation process in microfluidic
channels accompanied by experimental investigations resulted in a
microfluidic disk design, which allowed the successful conduction of
bead-based immunoassays.
Microarrays as an alternative to bead-based multiplexed immunoassays
are implemented and evaluated implementing a BSA assay on
the centrifugal microfluidic platform in three ways: on a rigid polymer
disk featuring microfluidic channels structures, on a PDMS lid, which
completely covers a lab-on-a-disk, or on a slide-based microfluidic chip
attached to a rotor (applied for patent). Beneficial in all cases are the
reduced sample and reagent consumption, the accelerated processing,
and the well controlled environmental settings along the complete
procedure.
The colorimetric absorbance readout as common scheme for metabolic
assays are implemented on the microfluidic centrifual system whereas
the optical path length through the detection cell as limiting factor is
drastically extended by monolithically incorporated V-grooves (applied
for patent). The performance of the simple and rugged concept is
successfully demonstrated on a modular setup to measure the concentration
of glucose (CV = 4%), hemoglobin (CV = 3%), and alcohol
(CV = 4%) in human whole blood.
The measurement of the hematocrit as an important marker for
medical diagnostics is transferred to the centrifugal microfluidic platform.
Here, a radially aligned dead end channel is first bubble-free
primed with blood. Here, trapping of gas upon priming is reliably
avoided by capillary wicking, which is solely promoted along
predetermined edges of the channel (applied for patent). After a
sedimentation step, the hematocrit is read out by visual inspection with
a disk-imprinted scale. As a result, an overall CV of 5% over the whole
physiological-pathological range is achieved.
A desktop-sized actuation and readout device for metabolic assays on
the centrifugal platform is conceptually designed; a demonstrator
device is assembled.
A designed and constructed test and development stand to accurately
visualize the propagation of fluids and the flow patterning in
micronchannels on fast spinning disks constitutes the experimental base
for this work and related ones.","Die vorliegende Arbeit beschreibt die Konzepte zur Etablierung
parallelisierter immunologischer Tests an einer Probe in
mikrofluidischen Kanälen (Multiplexing) auf einer zentrifugalen
Plattform.
Vermischen von Flüssigkeiten als wesentlicher fluidischer Prozessschritt
ist über zwei einfache und zuverlässige Konzepte auf der
rotierenden Scheibe etabliert. Im ersten werden paramagnetische
Polymerkugeln (Beads), die sich in einer Mischkammer auf der Scheibe
befinden, bei Rotation der Scheibe über ortsfeste Permanentmagnete
periodisch ausgelenkt, wobei die Relativbewegung der Beads
gegenüber dem Fluid das Mischen drastisch beschleunigt. Im zweiten
wird die mikrofluidische Scheibe nicht mit konstanter Frequenz rotiert,
sondern unter sich periodisch änderndem Drehsinn (Shake-Mode), was
aufgrund von Trägheitseffekten zum Laminieren der zu mischenden
Flüssigkeiten führt. Beide Wege reduzieren jeweils die Mischzeiten von
der 10-Minuten- in die 1-Sekunden-Skala.
Multiplexing immunologischer Tests auf der zentrifugalen mikrofluidischen
Plattform ist technisch über codierte Beads als Festphase
und über Mikroarrays implementiert. Die Codierung der Beads wurde
dabei über Nano-Kristallite, die in die Polymerkugeln eingequollen
sind, wie auch durch Farbstoffe in den Beads erreicht. Die
Leistungsfähigkeit des Bead-basierten Konzeptes wurde über die
Etablierung eines Hepatitis-A Assays nachgewiesen.
Die theoretische Modellierung des Aufstauens der Polymerkugeln in
der Messkammer in Form einer möglichst periodischen Monolage dient
der Optimierung des mikrofluidischen Designs mit dem nachfolgend
die Durchführung bead-basierter Tests erfolgreich demonstriert werden
konnte.
Mikroarrays sind auf der zentrifugalen mikrofluidischen Plattform in
drei Varianten implementiert und durch einen BSA-Assay: gedruckt in
eine scheiben-basierten Reaktionskammer, auf den korrespondierenden
Deckel aus PDMS, oder auf einen Standard-Kunststoffträger, der
zusammen mit einem mikrofluidischen PDMS-Chip über einen
separaten Rotor prozessiert wird.
Zusätzlich konnten kolorimetrische Tests auf der zentrifugalen
mikrofluidischen Plattform etabliert werden. Hier wurde die Länge des
optischen Weges durch die Messkammer - als limitierender Faktor der
Miniaturisierung bei senkrechter Durchstrahlung - durch die Integration
von V-Nuten als optische Reflektionselemente von der Dicke
der rotierenden Scheibe entkoppelt. Die erfolgreiche Implementierung
der Konzentrationsmesung von Glukose (VK = 4%), Hämoglobin
(VK = 3%) und Alkohol (VK = 4%) in menschlichem Vollblut
demonstriert dabei die Einfachheit und Zuverlässigkeit des neuartigen
Konzepts.
Ein Gerät zur Prozessierung und zum Auslesen von scheibenbasierten,
kolorimetrischen Tests wurde im Rahmen dieser Arbeit
entworfen und ein Demonstrator aufgebaut.
Die Bestimmung des Hämatokrit-Wertes von Blut über einen
Sedimentationsprozess ist auf der zentrifugalen Plattform implementiert,
wobei das Auslesen mit dem Auge ohne optische Hilfsmittel
möglich ist. Der fluidische Messkanal folgt der Form einer
konventionellen Glaskapillare, weist jedoch nur einen Einlass auf. Die
vollständige und blasenfreie Befüllung über Kapillarkräfte lässt sich
durch eine geeignete Kanalgeometrie erreichen. Mit einem VK von 5%
über den relevanten physiologisch-pathologischen Bereich lassen sich
damit Hämatokrit-Messungen einfach und präzise durchführen.
Alle mikrofluidischen Experimente wurden auf einem optischen
Messplatz durchgeführt, dessen Entwurf und Aufbau Teil der
vorliegenden Arbeit ist. Hier lassen sich Flüssigkeiten in Kanälen
(laterale Abmessungen im my-m-Bereich) auf einer schnell rotierenden
Scheibe beobachten."],"dc:format.medium":["application/pdf"],"dc:subject":["Mikrosystemtechnik","Diagnostik","zentrifugal","blood","centrifuga l, diagnostics","disk"],"dc:title":["Readout of diagnostic assays on a centrifugal microfluidic platform","Auslesestrategien für diagnostische Tests auf einer zentrifugalen mikrofluidischen Plattform"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:40Z"}