1,670 research outputs found
Recommended from our members
Simulation of droplet-based microfluidic lab-on-a-chip applications
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Miniaturization of biological and chemical assays in lab-on-a-chip systems is a highly topical field of research. Droplet-based microfluidic chips are types of these miniaturized systems. They expand the capability of assays with special features that are unreached by traditional workflows. In particular, small sample volumes, independent separated reaction units, high throughput, automation and parallelization of assays are prominent features of droplet-based microfluidic devices. Full custom centric design of droplet-based microfluidic lab-on-a-chip technology implicates a high system integration level and design complexity. Therefore advanced development methodologies are needed, comparable with the methods in electronic design automation. Our design and simulation toolkit meets these requirements for an agile and low-risk development of custom lab-on-a-chip devices. The system simulation approach enables a fast and precise prediction of complex microfluidic networks. This fact is confirmed by reference and benchmark
experiments. The results show that the simulation correctly reproduces the experimental measurements.The German BMBF and the EU in the projects DiNaMiD, signature 0315591B and NoE Photonics4Life, Grant Agreement number: 224014
Yield Enhancement of Digital Microfluidics-Based Biochips Using Space Redundancy and Local Reconfiguration
As microfluidics-based biochips become more complex, manufacturing yield will
have significant influence on production volume and product cost. We propose an
interstitial redundancy approach to enhance the yield of biochips that are
based on droplet-based microfluidics. In this design method, spare cells are
placed in the interstitial sites within the microfluidic array, and they
replace neighboring faulty cells via local reconfiguration. The proposed design
method is evaluated using a set of concurrent real-life bioassays.Comment: Submitted on behalf of EDAA (http://www.edaa.com/
Bottom-up assembly of functional intracellular synthetic organelles by droplet-based microfluidics
Bottom-up synthetic biology has directed most efforts toward the construction of artificial compartmentalized systems that recreate living cell functions in their mechanical, morphological, or metabolic characteristics. However, bottom-up synthetic biology also offers great potential to study subcellular structures like organelles. Because of their intricate and complex structure, these key elements of eukaryotic life forms remain poorly understood. Here, the controlled assembly of lipid enclosed, organelle-like architectures is explored by droplet-based microfluidics. Three types of giant unilamellar vesicles (GUVs)-based synthetic organelles (SOs) functioning within natural living cells are procedured: (A) synthetic peroxisomes supporting cellular stress-management, mimicking an organelle innate to the host cell by using analogous enzymatic modules; (B) synthetic endoplasmic reticulum (ER) as intracellular light-responsive calcium stores involved in intercellular calcium signalling, mimicking an organelle innate to the host cell but utilizing a fundamentally different mechanism; and (C) synthetic magnetosomes providing eukaryotic cells with a magnetotactic sense, mimicking an organelle that is not natural to the host cell but transplanting its functionality from other branches of the phylogenetic tree. Microfluidic assembly of functional SOs paves the way for high-throughput generation of versatile intracellular structures implantable into living cells. This in-droplet SO design may support or expand cellular functionalities in translational nanomedicine
Dynamics of soft interfaces in droplet-based microfluidics
Diese Doktorarbeit untersucht die verschiedenen dynamischen Prozesse, welche sich an
der TropfenoberflĂ€che abspielen, und der Methoden, die fĂŒr deren Untersuchung verwendet
wurden. Das Ziel dieser Arbeit ist es, die entscheidenden Eigenschaften, die einen Einfluss auf
das mechanische Verhalten der GrenzflÀche haben, zu identifizieren. Wir verwenden die hydrodynamisch
erzwungene Deformation eines Tropfens in einem Mikrokanal, um die mechanischen
Eigenschaften der OberflÀche zu untersuchen. Diese Methode wird auf drei verschiedene
FĂ€lle angewendet.
Als erstes verfolgen wir die zeitliche Entwicklung einer GrenzflÀchenverformung, um die
Dynamik der Tensidadsorption an einer OberflÀche zu untersuchen. Dabei kalibrieren wir
die Tropfenverformung als Funktion von TropfengröĂe und OberflĂ€chenspannung. Diese
Technik wird auf den Fall eines perfluorierten Tensids, welches von industriellem und wissenschaftlichem
Interesse ist, angewendet. Wir zeigen die Möglichkeit von Messungen der
dynamischen OberflÀchenspannung auf Zeitskalen von zehn Millisekunden und gewinnen daraus
kinetische Eigenschaften der MolekĂŒle. Wir vergleichen die Dynamik, welche mit der
klassischen Pendant-Drop-Methode gemessen werden kann mit denen der Mikrofluidik. Es
zeigt sich, dass die Adsorption fĂŒr den Pendant Drop von der Di usion begrenzt wird, wĂ€hrend
in der Mikrofluidik die Anbindung an die OberflÀche der langsamere Prozess ist. Der Unterschied
entsteht durch das Flussprofil in der Mikrofluidik, welches konvektiven Transport
induziert.
Danach untersuchen wir die Verformung unter verschiedenen rÀumlichen BeschrÀnkungen
im mikrofluidischen Kanal. Die Tropfenverformung wird mit einer zweidimensionalen
numerischen Simulationen und mit einem dreidimensionalen Modell eines Rotationsellipsoids
verglichen. In beiden FĂ€llen wird eine qualitative Ăbereinstimmung festgestellt, jedoch
existieren auch spĂŒrbare Abweichungen vom Experiment. Die Abweichungen vom zweidimensionalen
Modell ist erklÀrbar mit dem sinkenden Einfluss der viskosen Spannungen mit
der Kanalhöhe, hervorgerufen durch BeitrĂ€ge von Deformationen auĂerhalb der Beobachtungsebene,
welche von dem Modell nicht wiedergegeben werden. Die Abweichungen vom
dreidimensionalen Modell kommen von den rÀumlichen BeschrÀnkungen, welche die Tropfenform
von einem Rotationsellipsoid abweichend verformt. Die Untersuchung zeigt die Schwierigkeiten bei der Beschreibung von viskosen KrĂ€fte fĂŒr Abmessungen, die zu groĂ sind um als
zweidimensional betrachtet zu werden, aber wo die Wechselwirkungen mit den KanalwÀnden
nicht vernachlÀssigbar sind. Wir diskutieren ebenfalls den Fall der trÀgen Relaxation des
Tropfens bei Reynoldszahlen von Re 10, fĂŒr welchen Oszillationen der TropfenoberflĂ€che
beobachtet werden. Wir zeigen, dass die Oszillationen als hydrodynamische Analogie zu einer
hookeschen Feder beschrieben werden können, wobei die OberflÀchenspannung als Federkonstante
fungiert und die DĂ€mpfung durch die ViskositĂ€t der FlĂŒssigkeit bestimmt wird. Die
Methode liefert korrekte Ergebnisse sowohl fĂŒr reine GrenzflĂ€chen als auch fĂŒr GrenzflĂ€chen
mit Tensiden, was zu einer zusĂ€tzliche Möglichkeit fĂŒhrt, die OberflĂ€chenspannung aus der
Frequenz der Verformungen zu bestimmen. Die viskose Relaxation wurde auch hierbei von
den KanalwÀnden beeinflusst.
Als letztes wenden wir die Methode der mikrofluidischen Tensiometrie auf die Kinetik
einer Polymerisationsreaktion auf der TropfenoberflÀche an. Der Einfluss der Reagenzkonzentration
auf die Reaktionszeit wird untersucht, ebenso wie der E ekt der Gegenwart von TensidmolekĂŒlen.
Erste Ergebnisse dieser Untersuchung zeigen, dass die Deformation einer
komplexen GrenzflÀche nicht mehr allein durch die OberflÀchenspannung beschrieben werden
kann. Vielmehr muss die Beschreibung der mechanischen Eigenschaften der GrenzflÀche
notwendigerweise die Entstehung der ViskoelastizitÀt an der OberflÀche mit in Betracht ziehen.
Diese Erkenntnis erö net neue Möglichkeiten, mit Hilfe von Mikrofluidik die mechanischen
Eigenschaften von komplexen GrenzflÀchen, wie zum Beispiel kolloidbesetzte GrenzflÀchen
oder Membranen, zu charakterisieren
Development of Gel Droplet Microfluidic System for High Throughput Microbial Screening
Over the last few decades, droplet based microfluidics has received great attention and it is growing rapidly with interdisciplinary fields, such as biomedical, physics, chemical engineering, tissue engineering and even therapeutic area. Droplet based microfluidics offers uncountable potential in its applications ranging from a developing analytical system to precise controlling of the content inside the droplet. One of the most highlighted advantages of droplet based microfluidics is the capability of cell screening in high throughput manner, which results in significant reductions in cost and discovering new medicine or curing technology
Nowadays, culturing encapsulated cell in 3D environment has been required and performed. Although conventional 2D culturing has simplicity of platform but because 3D environment has the capability of providing high throughput biological assays and an environment similar to native biological complexes, it was chosen for this study. Furthermore, the field of biomedical or biomaterials prefer to improve that 3D environment to be much closer to genuine systems. From this respect, hydrogels have been proven and replaced as a useful platform for 3D cell culture applications in microfluidics and cell laden hydrogel droplet is one of the most popular application with their flexibility similar to natural tissue and mild gelation method. In this thesis, we studied two different types of hydrogel droplets and developed a strategy for the microbial co-culture platform from the âplatformâ perspective. This thesis focuses on the microfabrication to pattern silicon wafer ii mold for the mass production and creating polydimethylsiloxane (PDMS) devices. With this transparent hydrophobic material, hydrogel droplet generation, on-chip cross linking and manipulation could be possible
Multiplexed combinatorial drug screening using droplet-based microfluidics
The therapy of most cancers has greatly benefited from the use of targeted drugs. However, their effects are often short-lived since many tumors develop resistance against these drugs. Resistance of tumor cells against drugs can be adaptive or acquired and is often caused by genetic or non-genetic heterogeneity between tumor cells. A potential solution to overcome drug resistance is the use of drug combinations addressing multiple targets at once.
Finding potent drug combinations against heterogeneous tumors is challenging. One reason is the high number of possible combinations. Another reason is the possibility of inter-patient heterogeneity in drug responses, making patient tailored treatments necessary. These require screens on patient material, which would drastically benefit from miniaturization, as it is the case in droplet-based microfluidics. However, drug screens in droplets against primary tumor cells have so far only been performed at a modest chemical complexity (55 treatment conditions) and with low content readouts.
In this thesis we aimed at developing a droplet-based microfluidic workflow that allows the generation of high numbers of drug combinations in picolitre-sized droplets and their multiplexed analysis. To this end, we have established a pipeline to produce up to 420 drug combinations in droplets. We were able to significantly increase the number of possible combinations by building a microfluidic setup that comprises valve and micro-titer plate based injection of drugs into microfluidic devices for droplet generation
Furthermore, we integrated a DNA-based barcoding approach to encode each treatment condition, enabling their multiplexed analyses since all droplets can be stored and processed together, which highly increases the throughput. With the established approach we can perform barcoding of each cellsâ transcriptome according to the drugs it was exposed to in the droplet. Thereby, the effects of drug combinations on gene expression can be studied in a highly multiplexed way using RNA-Sequencing.
We applied the developed approach to run combinatorial drug screens in droplets and analysed the effects of in total 630 drug combinations on gene expression in
K562 cells. The low number of cells needed (max. 2 million cells) for such screens, could enable their application directly on tumor biopsies, thus paving the way for personalized therapy approaches. Since the established workflow is compatible with single cell readouts, we also envision its application to analyse drug resistances in heterogeneous tumor samples on the single cell level
Development of Gel Droplet Microfluidic System for High Throughput Microbial Screening
Over the last few decades, droplet based microfluidics has received great attention and it is growing rapidly with interdisciplinary fields, such as biomedical, physics, chemical engineering, tissue engineering and even therapeutic area. Droplet based microfluidics offers uncountable potential in its applications ranging from a developing analytical system to precise controlling of the content inside the droplet. One of the most highlighted advantages of droplet based microfluidics is the capability of cell screening in high throughput manner, which results in significant reductions in cost and discovering new medicine or curing technology
Nowadays, culturing encapsulated cell in 3D environment has been required and performed. Although conventional 2D culturing has simplicity of platform but because 3D environment has the capability of providing high throughput biological assays and an environment similar to native biological complexes, it was chosen for this study. Furthermore, the field of biomedical or biomaterials prefer to improve that 3D environment to be much closer to genuine systems. From this respect, hydrogels have been proven and replaced as a useful platform for 3D cell culture applications in microfluidics and cell laden hydrogel droplet is one of the most popular application with their flexibility similar to natural tissue and mild gelation method. In this thesis, we studied two different types of hydrogel droplets and developed a strategy for the microbial co-culture platform from the âplatformâ perspective. This thesis focuses on the microfabrication to pattern silicon wafer ii mold for the mass production and creating polydimethylsiloxane (PDMS) devices. With this transparent hydrophobic material, hydrogel droplet generation, on-chip cross linking and manipulation could be possible
Double emulsions with controlled morphology by microgel scaffolding
Double emulsions are valuable structures that consist of drops nested inside bigger drops; they can be formed with exquisite control through the use of droplet based microfluidics, allowing their size, composition, and monodispersity to be tailored. However, only little control can be exerted on the morphology of double emulsions in their equilibrium state, because they are deformable and subject to thermal fluctuations. To introduce such control, we use droplet based microfluidics to form oil in water in oil double emulsion drops and arrest their shape by loading them with monodisperse microgel particles. These particles push the inner oil drop to the edge of the aqueous shell drop such that the double emulsions adopt a uniform arrested, anisotropic shape. This approach circumvents the need for ultrafast polymerization or geometric confinement to lock such non spherical and anisotropic droplet morphologies. To demonstrate the utility of this technique, we apply it to synthesize anisotropic and non spherical polyacrylate polyacrylamide microparticles with controlled size and shap
Recommended from our members
Microfluidic droplet control by photothermal interfacial flow
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Droplet-based microfluidics is an emerging field that can perform a variety of discrete operation of
tiny amount of reagent or individual cell. Noncontact manipulation of droplets in a microfluidic platform can
be achieved by using the Marangoni convection due to a local temperature gradient given by the irradiation
of heating light. This method provides noncontact, selective and flexible manipulation for droplets flowing in
microfluidic network. Although the potential of this selective operation method of droplets was confirmed,
the driving force exerted on droplets has not been quantitatively obtained. In this study, we have developed a
measurement system of the temperature field around droplets during the manipulation by light irradiation
and evaluated the manipulation force. In O/W emulsion system with oleic acid and buffer solution, oleic acid
for droplet and buffer solution for continuous phase, the temperature distribution around the droplets was
measured by laser-induced fluorescence. From the balance of drag force and photo-induced Marangoni force,
the driving force was determined. From the results, we confirmed the applicability of the noncontact droplet
manipulation using the photothermal Marangoni effect
Droplet breakup driven by shear thinning solutions in a microfluidic T-Junction
Droplet-based microfluidics turned out to be an efficient and adjustable
platform for digital analysis, encapsulation of cells, drug formulation, and
polymerase chain reaction. Typically, for most biomedical applications, the
handling of complex, non-Newtonian fluids is involved, e.g. synovial and
salivary fluids, collagen, and gel scaffolds. In this study we investigate the
problem of droplet formation occurring in a microfluidic T-shaped junction,
when the continuous phase is made of shear thinning liquids. At first, we
review in detail the breakup process providing extensive, side-by-side
comparisons between Newtonian and non-Newtonian liquids over unexplored ranges
of flow conditions and viscous responses. The non-Newtonian liquid carrying the
droplets is made of Xanthan solutions, a stiff rod-like polysaccharide
displaying a marked shear thinning rheology. By defining an effective Capillary
number, a simple yet effective methodology is used to account for the
shear-dependent viscous response occurring at the breakup. The droplet size can
be predicted over a wide range of flow conditions simply by knowing the
rheology of the bulk continuous phase. Experimental results are complemented
with numerical simulations of purely shear thinning fluids using Lattice
Boltzmann models. The good agreement between the experimental and numerical
data confirm the validity of the proposed rescaling with the effective
Capillary number.Comment: Manuscript: 11 pages 5 figures, 65 References. Textual Supplemental
Material: 6 pages 3 figure. Video Supplemental Materials: 2 movie
- âŠ