Name: fabricating high-viscosity droplets using microfluidic capillary device with phase-inversion co-flow structure
Uploaded: 2018-04-17T14:00:00.000+00:00
Duration: 8 min 2 s
Description: Watch this Scientific Journal Video about Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure at JoVE.com

Diese Arbeit wurde von der National Natural Science Foundation of China (Nr. 51420105006 und 51322501) unterstützt. Wir danken Daniel für seine hilfreiche Diskussion über die hohe Viskosität-Ideen.

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Soc. 100, 41-48 (2017).</li><li>Chen, H., Man, J., Li, Z., Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+generation+of+high-viscosity+droplets+by+surface-controlled+breakup+of+segment+flow.">Microfluidic generation of high-viscosity droplets by surface-controlled breakup of segment flow.</a> ACS Appl. Mater. Interfaces. 9, 21059-21064 (2017).</li><li>Man, J., Li, Z., Li, J., Chen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+inversion+of+slug+flow+on+step+surface+to+form+high+viscosity+droplets+in+microchannel.">Phase inversion of slug flow on step surface to form high viscosity droplets in microchannel.</a> Appl. Phys. Lett. 110, 181601 (2017).</li></ol>

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Das Phase-Inversion-Co-Flow-Gerät bietet eine einfache und geradlinig vorwärts Methode Monodisperse hochviskose Tröpfchen erzeugen. Dieses Gerät hat eine ähnliche Struktur gemeinsamen Co-Flow-Geräte, wie die grundlegende Co-Flow-Struktur besteht aus einem Innenrohr, eingefügt in das mittlere Rohr, die, das Ausfahrt von denen mit Auslass-Schlauch verbunden ist. Allerdings gibt es zwei Hauptunterschiede zwischen dem Phase-Inversion Co-Flow Gerät und gemeinsamen Co-Flow-Gerät zur Erzeugung von hoher Viskosität Tr?...

Die Generation der Tröpfchen wird eine Schlüsseltechnologie in einer Vielzahl von Anwendungen, z. B. Drug-Delivery, Materialsynthese, 3D Bioprinting, Zelle Assays und Food engineering1,2,3,4 , 5 , 6. Co fließen mikrofluidischen Geräte mit t-Kreuzung7,8,1,9, oder Fluss-Fokussierung10,11 Strukturen sind weit verbreitet, Monodisperse zu generieren einzigen Emulsion Tröpfchen. Auswahl von viskoser dauerphase erleichtert die Bildung von Tröpfchen12, und die Viskosität der kontinuierlichen und verteilten Flüssigkeiten sind häufig unter 0,1 Pas in Tröpfchen Mikrofluidik13. Jedoch kann in vielen Anwendungen die dispersen Phase eine Viskosität mehrere hundert Mal höher als die des Wassers, wie Glycerin14, Lösungen mit Nanopartikeln15, Proteine16oder Polymere17 haben , 18 , 19, es ist zwar schwierig, Monodisperse Tropfen direkt von hochviskosen Flüssigkeiten in einem Stall tropft Regime11 in mikrofluidischen Geräten, insbesondere für Flüssigkeiten mit einer Viskosität η > 1 Pa·s14 zu erreichen ,17,18,19. Darüber hinaus wurde berichteten13,18 , dass typische mikrofluidischen Methoden zur Tropfenbildung Flüssigkeiten mit relativ niedrigen Viskosität und moderate Grenzflächenspannung einheitliche Tröpfchen in einer stabilen tropfenden bilden erfordern Regime.
Für dispergierte Phase mit einer Viskosität etwas größer als 0,1 Pas, gibt es mehrere mögliche Ansätze zur Erleichterung der Tropfenbildung mit typischen t-Kreuzung, Co-Flow oder Flow-Fokussierung mikrofluidischen Geräte: (1) Abnahme der Viskosität der dispersen Phase in eine flüchtige Lösungsmittel11,20verdünnen; (2) verringern Sie das Verhältnis verteilt, kontinuierliche Viskosität durch die Erhöhung der Viskosität der kontinuierlichen Phase1,11; (3) verringern Sie die Durchflussmenge der dispersen Phase auf einen extrem niedrigen Wert, wobei ein hoher kontinuierlicher zerstreut Flow Rate Verhältnis 14,19. Diese Ansätze sind jedoch nicht für Flüssigkeiten mit viel höherer Viskosität, praktisch, wie sie die Produktionsrate deutlich senken werden, während dramatisch erhöhen den Verbrauch das flüchtige Lösungsmittel oder die kontinuierliche Phase. Darüber hinaus wurde berichtet, dass einige hohe Viskosität Polymerlösungen mit η > 1 Pa·s noch nicht in Tröpfchen mit17,19genannten Ansätze brechen oben.
Es gibt auch mehrere verbesserte Designs von mikrofluidischen Geräten, die eine dritte Phase der Flüssigkeit in das System einzuführen, die die Erzeugung von hoher Viskosität Tröpfchen erleichtert. Innovationen gehören: Bläschen eingeführt, um eine sprühvolumen Fadenabschneiden in Tröpfchen21, eine nicht mischbaren Geschäftsplanungen Flüssigkeit mit moderaten Viskosität, als die mittlere Phase zwischen der Dipsersed-Phase und der kontinuierlichen Phase18, eingeführt und Mikroreaktoren eingeführt, um hochviskose Tröpfchen aus zwei dünnflüssigen Vorstufen21,22,23zu generieren. Jedoch wie ein flüssiger beteiligt ist, das System wird immer komplizierter und die Geräte funktionieren in der Regel in einem viel engeren Fluss Regime als die typische Geräte zur Erzeugung von einzelnen Emulsion Tröpfchen.
Monodisperse generieren, die Tropfen direkt aus eine hochviskose Flüssigkeit mit η > 1 Pa·s, Oberfläche-kontrollierten Phase-Inversion Methoden wurden untersucht,24. Wie die Generation von dünnflüssigen Tröpfchen viel einfacher als die von hoher Viskosität Tröpfchen12, längliche dünnflüssiges Tröpfchen in einer kontinuierlichen Phase hoher Viskosität entstehen zunächst mit einer typischen Co-Flow-Struktur, und dann sind Due abgewrackt zur Veränderung der Oberfläche Benetzbarkeit flussabwärts der Co-Flow Struktur. Das freigegebene dünnflüssiges Fluid kapselt umgekehrt die nachgelagerte hochviskose Flüssigkeit in Tröpfchen so dass Phase Inversion abgeschlossen ist. Nach der Phase Inversion Mechanismus können Monodisperse hochviskose Tröpfchen erzeugt werden, basierend auf einem typischen Co-Flow-Gerät während die Ausfahrt von der Co-Flow-Gerät behandelt, um durch die niedrigviskose Flüssigkeit benetzt werden und dann mit einem größeren Rohr24 verbunden ist ,25.

<table><tbody><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>8240</td><td>Square - Miniature Hollow Glass Tubing, I.D.=0.4mm, OD=0.8mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>CV2033</td><td>Round - Miniature Hollow Glass Tubing, I.D.=0.2mm, O.D.=0.33mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>CV1017</td><td>Round - Miniature Hollow Glass Tubing, I.D.=0.1mm, O.D.=0.17mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>Q14606</td><td>Square - Miniature Hollow Glass Tubing, I.D.=1.05mm+0.1/-0, OD=1.5mm</td></tr><tr><td>Standard Glass Capillaries</td><td>WPI</td><td>1B100-6</td><td>Round - Glass Tubing, I.D.=0.58mm, O.D.=1.00mm</td></tr><tr><td>Glycerol</td><td>Sinopharm Chemical Reagent Beijing</td><td>10010618</td><td></td></tr><tr><td>Paraffin Liquid</td><td>Sinopharm Chemical Reagent Beijing</td><td>30139828</td><td></td></tr><tr><td>Poly(vinyl alcohol), PVA-124</td><td>Sinopharm Chemical Reagent Beijing</td><td>30153084</td><td></td></tr><tr><td>Span 80</td><td>Sigma-Aldrich</td><td>85548</td><td></td></tr><tr><td>Starch</td><td>Sigma-Aldrich</td><td>S9765</td><td></td></tr><tr><td>Trichloro(octadecyl)silane</td><td>Sigma-Aldrich</td><td>104817</td><td></td></tr><tr><td>Toluidine Blue O</td><td>Sigma-Aldrich</td><td>T3260</td><td></td></tr><tr><td>Honey</td><td></td><td></td><td>Chaste tree honey, common food product purchased from supermarket</td></tr><tr><td>DEVCON 5 Minute Epoxy</td><td>ITW&amp;nbsp;</td><td></td><td>Epoxy glue</td></tr><tr><td>Blunt Tip Stainless Steel Dispensing Needles (Luer Lock)</td><td>Suzhou Lanbo Needle, China</td><td>LTA820050</td><td>20G x 1/2&quot;&amp;nbsp;</td></tr><tr><td>Tungsten/Carbide Scriber</td><td>Ullman</td><td>1830</td><td>For cutting glass tubing</td></tr><tr><td>Microscope Slides</td><td>Sail Brand</td><td>7101</td><td>76.2 mm x 25.4 mm, Thickness 1 - 1.2 mm</td></tr><tr><td>Polyethylene Tubing</td><td>Scientific Commodities</td><td>BB31695-PE/5</td><td>I.D. = 0.86 mm, O.D. = 1.32 mm</td></tr><tr><td>Syringe Pumps</td><td>Longer Pump, China</td><td>LSP01-1A</td><td>3 pumps needed for the experiments</td></tr></tbody></table>

fabricating high-viscosity droplets using microfluidic capillary device with phase-inversion co-flow structure

Die Generation der Monodisperse Tropfen mit hoher Viskosität seit jeher eine Herausforderung in Tröpfchen Mikrofluidik. Hier zeigen wir ein Phase-Inversion Co-Flow Gerät um einheitlich hoher Viskosität Tröpfchen in eine niedrigviskose Flüssigkeit zu erzeugen. Das mikrofluidischen Kapillare Gerät hat eine gemeinsame Co-Flow-Struktur mit seinen Ausgang zu einem breiteren Schlauch anschließen. Längliche Tröpfchen der niedrigviskosen Flüssigkeit werden zunächst durch die hochviskose Flüssigkeit in der Co-Flow Struktur gekapselt. Wie die länglichen dünnflüssiges Tröpfchen durch den Ausgang die behandelt wird fließen, durch die niedrigviskose Flüssigkeit benetzt werden, wird Phase Inversion dann durch die Adhäsion der niedrigen Viskosität Tropfen an der Spitze der Ausfahrt induziert die Ergebnisse in die anschließende inverse Kapselung von hochviskosen Flüssigkeiten. Die Größe der resultierenden hochviskose Tröpfchen kann durch Ändern der Preis Verhältnis der niedrigviskosen Flüssigkeit, hochviskose Flüssigkeit. Wir zeigen einige typische Beispiele für die Erzeugung von hoher Viskosität Tröpfchen mit einer Viskosität bis 11,9 Pas, wie Glycerin, Honig, Stärke und Polymer-Lösung. Die Methode bietet einen einfachen und unkomplizierten Ansatz um Monodisperse hochviskose Tröpfchen erzeugen, die in einer Vielzahl von Tröpfchen-basierten Anwendungen wie Materialsynthese, Drug-Delivery, Zelle Assay, Bioengineering und Lebensmitteln verwendet werden dürfen Technik.

Eine mikrofluidischen Kapillare Gerät mit einer Phase-Inversion, Co-Flow Struktur wurde entwickelt, um Monodisperse wässrigen hochviskose Tröpfchen, erzeugen, wie in Figur 1Adargestellt. In Abbildung 1, war die hochviskosen wässrige Phase Glycerin hat eine Viskosität ηw = 1,4 Pas; dünnflüssiges Öl-Phase wurde flüssiges Paraffin, hat eine Viskosität ηo = 0,029 Pas; die Oberfläch...

Watch this Scientific Journal Video about Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure at JoVE.com

Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

Herstellung von hoher Viskosität Tröpfchen mit mikrofluidischen Kapillare Gerät mit Phase-Inversion Co-Flow Struktur

Eine Phase-Inversion-Co-Flow-Gerät zeigt um Monodisperse hochviskose Tröpfchen über 1 Pas zu erzeugen, die schwierig, in Tröpfchen Mikrofluidik zu verwirklichen ist.

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion ...

fabricating-high-viscosity-droplets-using-microfluidic-capillary

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10.2K Aufrufe.  University of Science and Technology Beijing. Eine Phase-Inversion-Co-Flow-Gerät zeigt um Monodisperse hochviskose Tröpfchen über 1 Pas zu erzeugen, die schwierig, in Tröpfchen Mikrofluidik zu verwirklichen ist.

Serie: Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

Fluorescence detection methods for microfluidic droplet platforms

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints.1
In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation.2-4 Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented.
Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

Fluoreszenz-Nachweisverfahren für Mikrofluidik-Tropfen-Plattformen

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that ...

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Biotechnik

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

High-Throughput-Einzel-Zell-und Multiple-Zelle Mikroverkapselung

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal microfluidic device. W/O microdroplets have recently been used in powerful methods that enable miniaturized chemical experiments. Therefore, developing a versatile method to yield monodisperse W/O microdroplets is needed. We have developed a method for generating monodisperse W/O microdroplets based on a capillary-based centrifugal axisymmetric co-flowing microfluidic device. We succeeded in controlling the size of microdroplets by adjusting the capillary orifice. Our method requires equipment that is easier-to-use than with other microfluidic techniques, requires only a small volume (0.1-1 &#181;l) of sample solution for encapsulation, and enables the production of hundreds of thousands number of W/O microdroplets per second. We expect this method will assist biological studies that require precious biological samples by conserving the volume of the samples for rapid quantitative analysis biochemical and biological studies.

Here, we demonstrate a simple production method for size-controllable, monodisperse, water-in-oil (W/O) microdroplets using a capillary-based centrifugal microfluidic device. This method requires only a small sample volume and enables high-yield production. We expect this method will be useful for rapid biochemical and cellular analyses.

Kapillar-basierten Kreisel Mikrofluidik-Vorrichtung zur Größe steuerbare Bildung von monodispersen Mikrotröpfchen

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

Ingenieurwesen

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Größe-gesteuerte Poly (Ethylenglycol) Diacrylate Tröpfchen über Semi-3-dimensionale fließen mit Schwerpunkt mikrofluidischen Geräte-Generation

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

High Speed Droplet-based Delivery System for Passive Pumping in Microfluidic Devices

A novel microfluidic system has been developed that uses the phenomenon of passive pumping along with a user controlled droplet based fluid delivery system. Passive pumping is the phenomenon by which surface tension induced pressure differences drive fluid movement in closed channels. The automated fluid delivery system consists of a set of voltage controlled valves with micro-nozzles connected to a fluid reservoir and a control system. These voltage controlled valves offer a volumetrically precise way to deliver fluid droplets to the inlet of a microfluidic device in a high frequency manner. Based on the  dimensions demonstrated in the current study example, the system is capable of flowing 4 milliliters per minute (through a 2.2mm by 260um cross-sectional channel). Based on these same channel dimensions, fluid exchange of a point inside the channel can be achieved in as little as eight milliseconds. It is observed that there is interplay between momentum of the system (imparted by a combination of the droplets created by the valves and the fluid velocity in the channel), and the surface tension of the liquid. Where momentum provides velocity to the fluid flow (or vice-versa), equilibration of surface tension at the inlet provides a sudden stop to any flow. This sudden stop allows the user to control the flow characteristics of the channel and opens the door for a variety of biological applications, ranging anywhere from reagent delivery to drug-cell studies. It is also observed that when nozzles are aimed at the inlet at shallow angles, the droplet momentum can cause additional interesting fluid phenomena, such as mixing of multiple droplets in the inlet.

A novel microfluidic system has been developed using the phenomenon of passive pumping and a user controlled fluid delivery system. This microfluidic system has the potential to be used in a wide variety of biological applications given its low cost, ease of use, volumetric precision, high speed, repeatability and automation.

High Speed ​​Droplet-based Delivery System für Passive Pumping in Mikrofluidiksysteme

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Biologie

Double Emulsion Generation Using a Polydimethylsiloxane (PDMS) Co-axial Flow Focus Device

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 &#181;m to 50 &#181;m in diameter while using large channels that are robust against fouling and clogging.

Double Emulsion Generation Using a Polydimethylsiloxane PDMS Co-axial Flow Focus Device

Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 &#181;m.

Doppelemulsion Erstellung Mit einem Polydimethylsiloxan (PDMS) Co-Axial Flow Fokus Geräte-

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper ...

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Protocols are described for the fabrication of degradable thermoresponsive hydrogels based on hydrazone cross-linking of polymeric oligomers on the bulk scale, microscale, and nanoscale, the latter for preparation of both gel nanoparticles and nanofibers.

Herstellung von abbaubaren Thermoresponsive Hydrogele auf mehreren Längenskalen über reaktive Extrusion, Mikrofluidik, Selbstmontage und Elektrospinnen

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), ...

Glass-Based Devices to Generate Drops and Emulsions

In this manuscript, three different step-by-step protocols to generate highly monodisperse emulsion drops using glass-based microfluidics are described. The first device is built for the generation of simple drops driven by gravity. The second device is designed to generate emulsion drops in a coflowing scheme. The third device is an extension of the coflowing device with the addition of a third liquid that acts as an electric ground, allowing the formation of electrified drops that subsequently discharge. In this setup, two of the three liquids have an appreciable electrical conductivity. The third liquid mediates between these two and is a dielectric. A&#160;voltage difference applied between the two conducting liquids creates an electric field that couples with hydrodynamic stresses of the coflowing liquids, affecting the jet and drop formation process. The addition of the electric field provides a path to generate smaller drops than in simple coflow devices and for generating particles and fibers with a wide range of sizes.

Here, a protocol to manufacture glass-based microfluidic devices used for generating highly monodisperse emulsions with controlled drop size is presented.

Glasbasierte Geräte zur Erzeugung von Tropfen und Emulsionen

In this manuscript, three different step-by-step protocols to generate highly monodisperse emulsion drops using glass-based microfluidics are described. ...

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

Mehrstufige Höhenverstellbarem Lithografie für Valved Mehrschichtige Mikrofluidiksysteme

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

Aufbau einer mikrofluidischen Vorrichtung zur kombinatorischen Steckerherstellung

Bilayer Microfluidic Device for Combinatorial Plug Production

Droplet microfluidics is a versatile tool that allows the execution of a large number of reactions in chemically distinct nanoliter compartments. Such systems have been used to encapsulate a variety of biochemical reactions - from incubation of single cells to implementation of PCR reactions, from genomics to chemical synthesis. Coupling the microfluidic channels with regulatory valves allows control over their opening and closing, thereby enabling the rapid production of large-scale combinatorial libraries consisting of a population of droplets with unique compositions. In this paper, protocols for the fabrication and operation of a pressure-driven, PDMS-based bilayer microfluidic device that can be utilized to generate combinatorial libraries of water-in-oil emulsions called plugs are presented. By incorporating software programs and microfluidic hardware, the flow of desired fluids in the device can be controlled and manipulated to generate combinatorial plug libraries and to control the composition and quantity of constituent plug populations. These protocols will expedite the process of generating combinatorial screens, particularly to study drug response in cells from cancer patient biopsies.

Autor im Rampenlicht: Integration von computergestützten und experimentellen Ansätzen in der Präzisionsonkologie

The fabrication of a polydimethylsiloxane (PDMS)-based bilayer device for the production of combinatorial libraries in water-in-oil emulsions (plugs) is presented here. The necessary hardware and software required to automate plug production are detailed in the protocol, and the production of a quantitative library of fluorescent plugs is also demonstrated.

Zweischichtiges mikrofluidisches Gerät für die kombinatorische Steckerproduktion

Droplet microfluidics is a versatile tool that allows the execution of a large number of reactions in chemically distinct nanoliter compartments. Such ...

Herstellung von hoher Viskosität Tröpfchen mit mikrofluidischen Kapillare Gerät mit Phase-Inversion Co-Flow Struktur

Zusammenfassung

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