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1
Debski, Pawel, Karolina Sklodowska, Jacek Michalski, Piotr Korczyk, Miroslaw Dolata und Slawomir Jakiela. „Continuous Recirculation of Microdroplets in a Closed Loop Tailored for Screening of Bacteria Cultures“. Micromachines 9, Nr. 9 (17.09.2018): 469. http://dx.doi.org/10.3390/mi9090469.
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Emerging microfluidic technology has introduced new precision controls over reaction conditions. Owing to the small amount of reagents, microfluidics significantly lowers the cost of carrying a single reaction. Moreover, in two-phase systems, each part of a dispersed fluid can be treated as an independent chemical reactor with a volume from femtoliters to microliters, increasing the throughput. In this work, we propose a microfluidic device that provides continuous recirculation of droplets in a closed loop, maintaining low consumption of oil phase, no cross-contamination, stabilized temperature, a constant condition of gas exchange, dynamic feedback control on droplet volume, and a real-time optical characterization of bacterial growth in a droplet. The channels (tubing) and junction cubes are made of Teflon fluorinated ethylene propylene (FEP) to ensure non-wetting conditions and to prevent the formation of biofilm, which is particularly crucial for biological experiments. We show the design and operation of a novel microfluidic loop with the circular motion of microdroplet reactors monitored with optical sensors and precision temperature controls. We have employed the proposed system for long term monitoring of bacterial growth during the antibiotic chloramphenicol treatment. The proposed system can find applications in a broad field of biomedical diagnostics and therapy.
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Steege, Tobias, Mathias Busek, Stefan Grünzner, Andrés Fabían Lasagni und Frank Sonntag. „Closed-loop control system for well-defined oxygen supply in micro-physiological systems“. Current Directions in Biomedical Engineering 3, Nr. 2 (07.09.2017): 363–66. http://dx.doi.org/10.1515/cdbme-2017-0075.
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AbstractTo improve cell vitality, sufficient oxygen supply is an important factor. A deficiency in oxygen is called Hypoxia and can influence for example tumor growth or inflammatory processes. Hypoxia assays are usually performed with the help of animal or static human cell culture models. The main disadvantage of these methods is that the results are hardly transferable to the human physiology. Microfluidic 3D cell cultivation systems for perfused hypoxia assays may overcome this issue since they can mimic the in-vivo situation in the human body much better. Such a Hypoxia-on-a-Chip system was recently developed. The chip system consists of several individually laser-structured layers which are bonded using a hot press or chemical treatment. Oxygen sensing spots are integrated into the system which can be monitored continuously with an optical sensor by means of fluorescence lifetime detection.Hereby presented is the developed hard- and software requiered to control the oxygen content within this microfluidic system. This system forms a closed-loop control system which is parameterized and evaluated.
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Wang, Ningquan, Ruxiu Liu, Norh Asmare, Chia-Heng Chu, Ozgun Civelekoglu und A. Fatih Sarioglu. „Closed-loop feedback control of microfluidic cell manipulation via deep-learning integrated sensor networks“. Lab on a Chip 21, Nr. 10 (2021): 1916–28. http://dx.doi.org/10.1039/d1lc00076d.
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4
Loutherback, K., P. A. Bulur und A. Dietz. „Process Development and Manufacturing: CLOSED MICROFLUIDIC SYSTEM FOR MANUFACTURING DENDRITIC CELL THERAPIES“. Cytotherapy 24, Nr. 5 (Mai 2022): S171—S172. http://dx.doi.org/10.1016/s1465-3249(22)00448-0.
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Loutherback, K., P. A. Bulur und A. Dietz. „Process Development and Manufacturing: CLOSED MICROFLUIDIC SYSTEM FOR MANUFACTURING DENDRITIC CELL THERAPIES“. Cytotherapy 24, Nr. 5 (Mai 2022): S171—S172. http://dx.doi.org/10.1016/s1465-3249(22)00448-0.
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6
Fu, Hai, Wen Zeng, Songjing Li und Shuai Yuan. „Electrical-detection droplet microfluidic closed-loop control system for precise droplet production“. Sensors and Actuators A: Physical 267 (November 2017): 142–49. http://dx.doi.org/10.1016/j.sna.2017.09.043.
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7
Hansen, J. S., J. T. Ottesen und A. Lemarchand. „Molecular dynamics simulations of valveless pumping in a closed microfluidic tube-system“. Molecular Simulation 31, Nr. 14-15 (Dezember 2005): 963–69. http://dx.doi.org/10.1080/08927020500419297.
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8
Yafia, Mohamed, Amir M. Foudeh, Maryam Tabrizian und Homayoun Najjaran. „Low-Cost Graphene-Based Digital Microfluidic System“. Micromachines 11, Nr. 9 (22.09.2020): 880. http://dx.doi.org/10.3390/mi11090880.
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In this work, the laser-scribing technique was used as a low-cost, rapid and facile method for fabricating digital microfluidic (DMF) systems. Laser-scribed graphene (LSG) electrodes are directly synthesized on flexible substrates to pattern the DMF electrode arrays. This facilitates the DMF electrodes’ fabrication process by eliminating many microfabrication steps. An electrowetting test was performed to investigate the effectiveness of the LSG DMF electrodes in changing the contact angles of droplets. Different DMF operations were successfully performed using the proposed LSG DMF chips in both open and closed DMF systems. The quality and output resolution were examined to assess the performance of such patterned electrodes in the DMF systems. To verify the efficacy of the LSG DMF chips, a one-step direct assay for the detection of Legionellapneumophila deoxyribonucleic acid (DNA) was performed on the chip without the need for any washing step. The high specificity in distinguishing a single-nucleotide mismatch was achieved by detecting target DNA concentrations as low as 1 nM. Our findings suggest that the proposed rapid and easy fabrication method for LSG DMF electrodes offers a great platform for low-cost and easily accessible point-of-care diagnostic devices.
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Lim, Hyunjung, Jae Young Kim, Seunghee Choo, Changseok Lee, Byoung Joe Han, Chae Seung Lim und Jeonghun Nam. „Separation and Washing of Candida Cells from White Blood Cells Using Viscoelastic Microfluidics“. Micromachines 14, Nr. 4 (23.03.2023): 712. http://dx.doi.org/10.3390/mi14040712.
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An early and accurate diagnosis of Candida albicans is critical for the rapid antifungal treatment of candidemia, a mortal bloodstream infection. This study demonstrates viscoelastic microfluidic techniques for continuous separation, concentration, and subsequent washing of Candida cells in the blood. The total sample preparation system contains two-step microfluidic devices: a closed-loop separation and concentration device and a co-flow cell-washing device. To determine the flow conditions of the closed-loop device, such as the flow rate factor, a mixture of 4 and 13 μm particles was used. Candida cells were successfully separated from the white blood cells (WBCs) and concentrated by 74.6-fold in the sample reservoir of the closed-loop system at 800 μL/min with a flow rate factor of 3.3. In addition, the collected Candida cells were washed with washing buffer (deionized water) in the microchannels with an aspect ratio of 2 at a total flow rate of 100 μL/min. Finally, Candida cells at extremely low concentrations (Ct > 35) became detectable after the removal of WBCs, the additional buffer solution in the closed-loop system (Ct = 30.3 ± 1.3), and further removal of blood lysate and washing (Ct = 23.3 ± 1.6).
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Jang, Kihoon, Yan Xu, Yo Tanaka, Kae Sato, Kazuma Mawatari, Tomohiro Konno, Kazuhiko Ishihara und Takehiko Kitamori. „Single-cell attachment and culture method using a photochemical reaction in a closed microfluidic system“. Biomicrofluidics 4, Nr. 3 (September 2010): 032208. http://dx.doi.org/10.1063/1.3494287.
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Kim, Jeeyong, Hyunjung Lim, Hyunseul Jee, Seunghee Choo, Minji Yang, Sungha Park, Kyounghwa Lee, Hyoungsook Park, Chaeseung Lim und Jeonghun Nam. „High-Throughput Cell Concentration Using A Piezoelectric Pump in Closed-Loop Viscoelastic Microfluidics“. Micromachines 12, Nr. 6 (09.06.2021): 677. http://dx.doi.org/10.3390/mi12060677.
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Cell concentration is a critical process in biological assays and clinical diagnostics for the pre-treatment of extremely rare disease-related cells. The conventional technique for sample preconcentration and centrifugation has the limitations of a batch process requiring expensive and large equipment. Therefore, a high-throughput continuous cell concentration technique needs to be developed. However, in single-pass operation, the required concentration ratio is hard to achieve. In this study, we propose a closed-loop continuous cell concentration system using a viscoelastic non-Newtonian fluid. For miniaturized and integrated systems, two piezoelectric pumps were adopted. The pumping capability generated by a piezoelectric pump in a microfluidic channel was evaluated depending on the applied voltage, frequency, sample viscosity, and channel length. The concentration performance of the device was evaluated using 13 μm particles and white blood cells (WBCs) with different channel lengths and voltages. In the closed-loop system, the focused cells collected at the center outlet were sent back to the inlet, while the buffer solution was removed to the side outlets. Finally, to expand the clinical applicability of our closed-loop system, WBCs in lysed blood samples with 70% hematocrit and prostate cancer cells in urine samples were used. Using the closed-loop system, WBCs were concentrated by ~63.4 ± 0.8-fold within 20 min to a final volume of 160 μL using 10 mL of lysed blood sample with 70% hematocrit (~3 cP). In addition, prostate cancer cells in 10 mL urine samples were concentrated by ~64.1-fold within ~11 min due to low viscosity (~1 cP).
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Kim, Jeong, Hye Choi, Chul Kim, Hee Jin, Jae-sung Bae und Gyu Kim. „Enhancement of Virus Infection Using Dynamic Cell Culture in a Microchannel“. Micromachines 9, Nr. 10 (21.09.2018): 482. http://dx.doi.org/10.3390/mi9100482.
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With increasing interest in induced pluripotent stem cells (iPSCs) in the field of stem cell research, highly efficient infection of somatic cells with virus factors is gaining importance. This paper presents a method of employing microfluidic devices for dynamic cell culture and virus infection in a microchannel. The closed space in the microchannel provided a better environment for viruses to diffuse and contact cell surfaces to infect cells. The microfluidic devices were fabricated by photolithography and soft lithography. NIH/3T3 fibroblast cells were cultured in the microfluidic device in static and dynamic conditions and compared with the conventional culture method of using Petri dishes. Virus infection was evaluated using an enhanced green fluorescent protein virus as a model. Dynamic culture in the microchannel showed similar growth of cells to that in Petri dish culture, but the virus infection efficiency was four-times higher. The proposed dynamic culture system could be useful in iPSC research by providing efficient virus infection tools.
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Heuck, F., P. van der Ploeg und U. Staufer. „Deposition and structuring of Ag/AgCl electrodes inside a closed polymeric microfluidic system for electroosmotic pumping“. Microelectronic Engineering 88, Nr. 8 (August 2011): 1887–90. http://dx.doi.org/10.1016/j.mee.2011.01.058.
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Bohm, Sebastian, und Erich Runge. „Multiphysics simulation of fluid interface shapes in microfluidic systems driven by electrowetting on dielectrics“. Journal of Applied Physics 132, Nr. 22 (14.12.2022): 224702. http://dx.doi.org/10.1063/5.0110149.
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We present a highly efficient simulation method for the calculation of three-dimensional quasi-static interface shapes under the influence of electric fields. The method is especially useful for the simulation of microfluidic systems driven by electrowetting on dielectrics because it accounts automatically and inherently for the highly non-trivial interface shape in the vicinity of the triple-phase contact. In particular, the voltage independence of the local contact angle predicted based on analytical considerations is correctly reproduced in all our simulations. For the calculation of the shape of the interface, the geometry is triangulated and the mesh nodes are shifted until the system energy becomes minimal. The same mesh is also used to calculate the electric field using the boundary-element method. Therefore, only the surface of the geometry needs to be meshed, and no volume meshes are involved. The method can be used for the simulation of closed systems with a constant volume (e.g., droplet-based microfluidics) while preserving the volume very precisely as well as open systems (e.g., the liquid–air interface within micro-cavities or capillaries). Additional effects, such as the influence of gravitational forces, can easily be taken into account. In contrast to other efficient simulations, such as the volume-of-fluid, level-set, or phase-field methods, ideally, sharp interfaces are obtained. We calculate interface shapes for exemplary systems and compare with analytical as well as experimental results.
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Tremblay, Yannick D. N., Philippe Vogeleer, Mario Jacques und Josée Harel. „High-Throughput Microfluidic Method To Study Biofilm Formation and Host-Pathogen Interactions in Pathogenic Escherichia coli“. Applied and Environmental Microbiology 81, Nr. 8 (13.02.2015): 2827–40. http://dx.doi.org/10.1128/aem.04208-14.
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ABSTRACTBiofilm formation and host-pathogen interactions are frequently studied using multiwell plates; however, these closed systems lack shear force, which is present at several sites in the host, such as the intestinal and urinary tracts. Recently, microfluidic systems that incorporate shear force and very small volumes have been developed to provide cell biology models that resemblein vivoconditions. Therefore, the objective of this study was to determine if the BioFlux 200 microfluidic system could be used to study host-pathogen interactions and biofilm formation by pathogenicEscherichia coli. Strains of various pathotypes were selected to establish the growth conditions for the formation of biofilms in the BioFlux 200 system on abiotic (glass) or biotic (eukaryotic-cell) surfaces. Biofilm formation on glass was observed for the majority of strains when they were grown in M9 medium at 30°C but not in RPMI medium at 37°C. In contrast, HRT-18 cell monolayers enhanced binding and, in most cases, biofilm formation by pathogenicE. coliin RPMI medium at 37°C. As a proof of principle, the biofilm-forming ability of a diffusely adherentE. colimutant strain lacking AIDA-I, a known mediator of attachment, was assessed in our models. In contrast to the parental strain, which formed a strong biofilm, the mutant formed a thin biofilm on glass or isolated clusters on HRT-18 monolayers. In conclusion, we describe a microfluidic method for high-throughput screening that could be used to identify novel factors involved inE. colibiofilm formation and host-pathogen interactions under shear force.
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Fan, Shangchun, Jinhao Sun, Weiwei Xing, Cheng Li und Dongxue Wang. „Design and Simulation of a Fused Silica Space Cell Culture and Observation Cavity with Microfluidic and Temperature Controlling“. Journal of Applied Mathematics 2013 (2013): 1–13. http://dx.doi.org/10.1155/2013/378253.
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We report a principle prototype of space animal cell perfusion culture and observation. Unlike previous work, our cell culture system cannot only realize microfluidic and temperature controlling, automatic observation, and recording but also meet an increasing cell culture at large scale operation and overcome shear force for animal cells. A key component in the system is ingenious structural fused silica cell culture cavity with the wedge-shaped connection. Finite volume method (FVM) is applied to calculate its multipoint flow field, pressure field, axial velocity, tangential velocity, and radial velocity. In order to provide appropriate flow rate, temperature, and shear force for space animal cell culture, a closed-loop microfluidic circuit and proportional, integrating, and differentiation (PID) algorithm are employed. This paper also illustrates system architecture and operating method of the principle prototype. The dynamic culture, autofocus observation, and recording of M763 cells are performed successfully within 72 h in the laboratory environment. This research can provide a reference for space flight mission that carries an apparatus with similar functions.
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Alrifaiy, Ahmed, und Kerstin Ramser. „How to integrate a micropipette into a closed microfluidic system: absorption spectra of an optically trapped erythrocyte“. Biomedical Optics Express 2, Nr. 8 (20.07.2011): 2299. http://dx.doi.org/10.1364/boe.2.002299.
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18
Guan, Yin, Baiyun Li und Lu Xing. „Numerical investigation of electrowetting-based droplet splitting in closed digital microfluidic system: Dynamics, mode, and satellite droplet“. Physics of Fluids 30, Nr. 11 (November 2018): 112001. http://dx.doi.org/10.1063/1.5049511.
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Kimura, Hiroshi, Hirokazu Takeyama, Kikuo Komori, Takatoki Yamamoto, Yasuyuki Sakai und Teruo Fujii. „Microfluidic Device with Integrated Glucose Sensor for Cell-Based Assay in Toxicology“. Journal of Robotics and Mechatronics 22, Nr. 5 (20.10.2010): 594–600. http://dx.doi.org/10.20965/jrm.2010.p0594.
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We have developed a cell-based assay platform using a microfluidic device integrating a glucose sensor into a cell culture device with closed-loop perfusion. Online measurement of cell kinetic change associated with cell status change was achieved by measuring glucose concentration change in the device with a cell exposed to a toxic material. The cell-based assay platform, which is integrated with a sensor and a perfusion system, was expected to improve measurement accuracy and efficiency, leading to the discovery of new tools in such wide-ranging fields as drug discovery, life sciences, and medical research.
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Bartsch de Torres, Heike, Christian Rensch, Torsten Thelemann, J. Müller und M. Hoffmann. „Fully Integrated Bridge-Type Anemometer in LTCC-Based Microfluidic Systems“. Advances in Science and Technology 54 (September 2008): 401–4. http://dx.doi.org/10.4028/www.scientific.net/ast.54.401.
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A thick film anemometer for in situ control of the flow rate in fluidic systems was designed, manufactured and characterized. The sensor is integrated in a retention modulus consisting of Low Temperature Cofired Ceramics (LTCC). These materials allow the cost-effective realisation of fluidic microsystems with integrated electronics. The challenge of the work is to design an anemometer under the exclusive use of thick film technologies. The necessity to trim resistors causes the external use of relevant pastes. Therefore, the use inside of a closed fluidic system requires the leak of process gases and, at the same time, a maximal heat-insulating of the sensor element from the substrate. Free-standing elements necessitate the control of stress due to shrinking mismatch, TCE mismatch, density gradients and deformation during the lamination. In the presented solution, embossed flue channels prevent blow forming on a free-standing bridge. The anemometer has a linear sensor characteristic for flow rates up to 0.1 ml/min. The layout guarantees that the fluid gets only in contact with the basic ceramic material, which is compatible with a wide range of biological substances. Therefore the sensor is applicable in contact with cell fluids or PCRreagents.
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Nouri, Abdelmounaim, Maria L. Rodgers, Daniel L. Bolnick, Rebecca Carrier, Kathryn Milligan-Myhre, Samuel Scarpino und Natalie C. Steinel. „Microfluidic gut-on chip system for reproducing the microbiome-immune cells interaction in Threespine Stickleback“. Journal of Immunology 208, Nr. 1_Supplement (01.05.2022): 116.05. http://dx.doi.org/10.4049/jimmunol.208.supp.116.05.
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Abstract The development of in vitro models that mimic the immunological, mechanical, and structural properties of the gut, as well as its crucial microbial symbionts, facilitate the real-time assessment of host-microbiome interactions. Here, we describe our development of a threespine stickleback fish “gut-on-chip” biomimetic microdevice which will co-culture complex microbial communities with mucus-secreting intestinal epithelia and leukocytes. This chip was fabricated using soft lithography with liquid PDMS and consists of a middle channel coated with extracellular matrix (ECM) compounds separating two microfluidic side channels. After temperature cure, PDMS is bound on a glass slide by plasma activation, forming a closed microenvironment where cells can be grown. We have successfully isolated and independently cultured stickleback intestinal epithelial cells and leukocytes and evaluated their tolerance to various components of ECM. Our results show that fibrinogen is more suitable for culturing intestinal leukocytes compared to collagen-1 or gelatin. Leukocyte viability is more sustainable after stimulation with LPS-B5 compared to unstimulated. Unlike immune cells, stickleback epithelial cells do not survive on fibrinogen and show better viability on the collagen-1 coated medium. This study establishes the unique culture conditions necessary for teleost microfluidic gut-on-a-chip and will advance our understanding of the host-microbiome interactions in this non-model system. Supported by Gordon and Betty More Foundation, SASI Symbiosis Model Systems #9323
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Heidt, Benjamin, Renato Rogosic, Nils Leoné, Eduardo Brás, Thomas Cleij, Jules Harings, Hanne Diliën, Kasper Eersels und Bart van Grinsven. „Topographical Vacuum Sealing of 3D-Printed Multiplanar Microfluidic Structures“. Biosensors 11, Nr. 10 (15.10.2021): 395. http://dx.doi.org/10.3390/bios11100395.
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We demonstrate a novel way of creating three-dimensional microfluidic channels capable of following complex topographies. To this end, substrates with open channels and different geometries were 3D-printed, and the open channels were consecutively closed with a thermoplastic using a low-resolution vacuum-forming approach. This process allows the sealing of channels that are located on the surface of complex multiplanar topographies, as the thermoplastic aligns with the surface-shape (the macrostructure) of the substrate, while the microchannels remain mostly free of thermoplastic as their small channel size resists thermoplastic inflow. This new process was analyzed for its capability to consistently close different substrate geometries, which showed reliable sealing of angles >90°. Furthermore, the thermoplastic intrusion into channels of different widths was quantified, showing a linear effect of channel width and percentage of thermoplastic intrusion; ranging from 43.76% for large channels with 2 mm width to only 5.33% for channels with 500 µm channel width. The challenging sealing of substrate ‘valleys’, which are created when two large protrusions are adjacent to each other, was investigated and the correlation between protrusion distance and height is shown. Lastly, we present three application examples: a serpentine mixer with channels spun around a cuboid, increasing the usable surface area; a cuvette-inspired flow cell for a 2-MXP biosensor based on molecular imprinted polymers, fitting inside a standard UV/Vis-Spectrophotometer; and an adapter system that can be manufactured by one-sided injection molding and is self-sealed before usage. These examples demonstrate how this novel technology can be used to easily adapt microfluidic circuits for application in biosensor platforms.
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Koenig, Leopold, Anja Patricia Ramme, Daniel Faust, Manuela Mayer, Tobias Flötke, Anna Gerhartl, Andreas Brachner et al. „A Human Stem Cell-Derived Brain-Liver Chip for Assessing Blood-Brain-Barrier Permeation of Pharmaceutical Drugs“. Cells 11, Nr. 20 (19.10.2022): 3295. http://dx.doi.org/10.3390/cells11203295.
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Significant advancements in the field of preclinical in vitro blood-brain barrier (BBB) models have been achieved in recent years, by developing monolayer-based culture systems towards complex multi-cellular assays. The coupling of those models with other relevant organoid systems to integrate the investigation of blood-brain barrier permeation in the larger picture of drug distribution and metabolization is still missing. Here, we report for the first time the combination of a human induced pluripotent stem cell (hiPSC)-derived blood-brain barrier model with a cortical brain and a liver spheroid model from the same donor in a closed microfluidic system (MPS). The two model compounds atenolol and propranolol were used to measure permeation at the blood–brain barrier and to assess metabolization. Both substances showed an in vivo-like permeation behavior and were metabolized in vitro. Therefore, the novel multi-organ system enabled not only the measurement of parent compound concentrations but also of metabolite distribution at the blood-brain barrier.
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Schmieder, Florian, Stefan Behrens, Nina Reustle, Nathalie Franke, Frank Sonntag, Jan Sradnick und Bernd Hohenstein. „A microphysiological system to investigate the pressure dependent filtration at an artificial glomerular kidney barrier“. Current Directions in Biomedical Engineering 5, Nr. 1 (01.09.2019): 389–91. http://dx.doi.org/10.1515/cdbme-2019-0098.
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AbstractChronic kidney disease (CKD) is a global health problem that affects around 11 to 13% of the world’s population and more than 18% of European citizens. Characteristic syndromes of CKD during all stages of the disease are proteinuria and ongoing glomerular dysfunction caused by cellular damages at the glomerular filtration barrier. While some rare cases of the disease are correlated to genetic depositions the majority of cases are caused by diabetes, glomerulosclerosis, high blood pressure and glomerulonephritis. Thus, recapitulating the interplay of high blood pressure and changes at the glomerular filtration barrier in vitro seems an adequate way to mimic CKD. Here we present a microphysiological system of the glomerular filter that is capable to simulate high blood pressure at the glomerular filtration barrier in vitro. It consists of a closed loop microfluidic circuit with an integrated pneumatically driven heart like micro pump that constantly circulates the cell culture media at the blood site of the glomerular barrier. The ThinCert™ insert could be reversibly integrated into a holder system that ensures the correct position of the insert within the microfluidic circuit. By using different modulations of the integrated pneumatic micro pump different physiological and pathophysiological conditions e.g. hypertonic stress, like in CKD, could be applied. The influence of hypertonic conditions on the filtration above the barrier was studied by changes of TEER values and measurement of the flux of fluorescent labelled albumin through the cellular barrier.
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Gómez, J. R., J. P. Escandón, C. G. Hernández, R. O. Vargas und D. A. Torres. „Multilayer analysis of immiscible power-law fluids under magnetohydrodynamic and pressure-driven effects in a microchannel“. Physica Scripta 96, Nr. 12 (18.11.2021): 125028. http://dx.doi.org/10.1088/1402-4896/ac37a0.
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Abstract In the present study, the combined magnetohydrodynamic and pressure-driven flow of multilayer immiscible fluids into a parallel flat plate microchannel is semi-analytically solved. Due to the handling of complex fluids in various microfluidic platform applications, the fluid transport reviewed here considers the power-law model. The movement of electrically conductive fluid layers is due to Lorentz forces that arise from the interaction between an electric current and a magnetic field. To find a solution for the flow field, the momentum equation and the rheological model for each fluid layer, together with the corresponding boundary conditions at the liquid-liquid and solid-liquid interfaces, are solved simultaneously through a closed system of nonlinear equations. The graphical results show the influence of the dimensionless parameters that arise from the mathematical modeling on the velocity profiles and flow rate. These are the magnetic parameters, the fluid layers thickness, the viscosity coefficients, the ratios between pressure forces and magnetic forces, and the flow behavior indexes. This theoretical work contributes to the design of microfluidic devices for flow-focusing tasks in chemical, clinical, and biological areas.
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Silverio, Vania, Miguel Amaral, João Gaspar, Susana Cardoso und Paulo P. Freitas. „Manipulation of Magnetic Beads with Thin Film Microelectromagnet Traps“. Micromachines 10, Nr. 9 (13.09.2019): 607. http://dx.doi.org/10.3390/mi10090607.
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Integration of point-of-care assays can be facilitated with the use of actuated magnetic beads (MB) to perform testing in less expensive settings to enable the delivery of cost-effective care. In this paper we present six different designs of planar microelectromagnets traps (MEMT) with four external coils in series and one central coil connected for an opposite direction of manipulation of MB in microfluidic flows. The development of a simulation tool facilitated the rapid and efficient optimization of designs by presenting the influence of system variables on real time concentrations of MB. Real time experiments are in good agreement with the simulations and showed that the design enabled synchronous concentration and dispersion of MB on the same MEMT. The yield of local concentration is seen to be highly dependent on coil design. Additional coil turns between the central and external coils (inter-windings) doubled magnetic concentration and repulsion with no significant electrical resistance increase. The assemblage of a copper microchannel closed loop cooling system to the coils successfully eliminated the thermal drift promoted by joule heating generated by applied current.
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Zhang, Bailin, Juan Manuel Tamez-Vela, Steven Solis, Gilbert Bustamante, Ralph Peterson, Shafiqur Rahman, Andres Morales, Liang Tang und Jing Yong Ye. „Detection of Myoglobin with an Open-Cavity-Based Label-Free Photonic Crystal Biosensor“. Journal of Medical Engineering 2013 (02.06.2013): 1–7. http://dx.doi.org/10.1155/2013/808056.
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The label-free detection of one of the cardiac biomarkers, myoglobin, using a photonic-crystal-based biosensor in a total-internal-reflection configuration (PC-TIR) is presented in this paper. The PC-TIR sensor possesses a unique open optical microcavity that allows for several key advantages in biomolecular assays. In contrast to a conventional closed microcavity, the open configuration allows easy functionalization of the sensing surface for rapid biomolecular binding assays. Moreover, the properties of PC structures make it easy to be designed and engineered for operating at any optical wavelength. Through fine design of the photonic crystal structure, biochemical modification of the sensor surface, and integration with a microfluidic system, we have demonstrated that the detection sensitivity of the sensor for myoglobin has reached the clinically significant concentration range, enabling potential usage of this biosensor for diagnosis of acute myocardial infarction. The real-time response of the sensor to the myoglobin binding may potentially provide point-of-care monitoring of patients and treatment effects.
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Sakurai, Yumiko, Elaissa T. Hardy, Byungwook Ahn, Shannon L. Meeks, W. Hunter Baldwin, Shawn M. Jobe und Wilbur A. Lam. „Engineering a Valve-Regulated Endothelialized Microfluidic Device As an "in Vitro" Bleeding Time for Assessing Global Hemostasis“. Blood 126, Nr. 23 (03.12.2015): 3485. http://dx.doi.org/10.1182/blood.v126.23.3485.3485.
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Abstract Introduction: Hemostasis encompasses an ensemble of regulated and balanced interactions among platelets (and other blood cells), coagulation factors, the endothelium, and the hemodynamic forces of the circulation. Unfortunately, current bleeding assays assess only isolated aspects of this complex process. A single assay that incorporates all of the major components of hemostasis would be of significant value in the research and clinical settings. To that end, we leveraged our laboratory's expertise in microfluidic systems to construct an "in vitro" bleeding time. Specifically, we developed a perfusable "endothelialized" microvasculature model that, via a pressure-controlled microscale valve, sustains a controlled, localized vascular "injury" after which bleeding and hemostatic plug formation ensues. This system incorporates recalcified human whole blood with minimal anticoagulation with corn trypsin inhibitor (CTI), controlled perfusion at physiologic flow conditions, and a confluent monolayer of any endothelial cell type. When used in conjunction with fluorescently tagged antibodies or cellular dyes, the entire hemostatic process can be tracked in real time with single cell resolution. As human blood and cells can be used exclusively, this microfluidic system is ideal for studying healthy as well as patient samples. Here, we describe proof of concept experiments utilizing healthy human blood samples and a high-titer antibody that completely inhibits Factor VIII activity. Materials and Methods: The polydimethysiloxane (PDMS)-based microfluidic bleeding time device is comprised of a fluidic, membrane valve, and channel layer (Figure 1A). The fluidic channel was pre-coated with collagen type 1 and fibronectin. Human umbilical cord vein or aortic endothelial cells were seeded in the main fluidic channel with membrane valve in the closed position (Figure 1B, valve closed), then cultured under flow to reach confluence. The "vascular injury" was introduced by providing negative pressure to pull down membrane valve at the middle of the device, where the endothelium is disrupted and an opening (i.e., the "bleed") is created (Figure 1B, valve opened). Human blood was collected in citrated buffer with CTI. Immediately after the injury, recalcified blood was perfused into the device at a shear rate of 500 s-1 and time-lapse images were taken by a confocal microscope. Wound width, bleeding time, and fluorescent intensity were measured and analyzed. Results and Discussion: Here we demonstrate that our microfluidic system enables us to directly analyze microvascular injury, bleeding, and then hemostasis using human cells and blood. After the wound was introduced, blood flow in fluidic channel divided into main channel (Figure 2, horizontal flow) and into the collagen I-coated wound channel, i.e. "bleeding" (vertical flow). The wound width was varied depending on the valve size and pressure given, and ranged from 73.22 to 231.86 µm (n=55, average 132.67 ± 5.48 µm). The average time to cessation of blood flow into the wound channel (i.e. the "bleeding time") was 546.02 ± 38.26 seconds. Interestingly, individual wound width and bleeding time did not correlate (R2 = 0.087), suggesting that the time course of hemostasis was not affected by wound size. Immediately after the injury, platelet adhesion and aggregation led to the formation of hemostatic plug at the wound area followed by fibrin formation, which were visually confirmed via immunofluorescence (CD41) and fluorescent-tagged fibrinogen (Figure 2). In addition, fluorescently-tagged CD15, CD45, and Annexin V binding enabled us to visualize other cellular and molecular components pertinent in hemostasis. Finally, treating healthy blood with an antibody against A2 domain of Factor VIII (anti-A2 MAb 2-76) effectively induced a severe Hemophilia A phenotype. While platelet plug formation was unchanged, the antibody caused instability of clot and repeated re-bleeding. In fact, none of the MAb 2-76-treated conditions exhibited hemsostasis (n=5, the longest recording period 4865 sec), compared to the vehicle control. Also reduced fibrinogen/fibrin accumulation was observed in MAb 2-76-treated blood (Figure 3). Our ongoing studies will provide spatiotemporal insights into how different cellular and molecular components interact during hemostatic process and with use of patient samples, how they go awry in diseased conditions. Disclosures Jobe: Bayer: Membership on an entity's Board of Directors or advisory committees; Biogen: Membership on an entity's Board of Directors or advisory committees; CSL-Behring: Membership on an entity's Board of Directors or advisory committees.
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Busek, Mathias, Mario Schubert, Kaomei Guan, Frank Sonntag, Florian Schmieder, Uwe Marschner und Andreas Richter. „Microphysiological system for heart tissue - going from 2D to 3D culture“. Current Directions in Biomedical Engineering 5, Nr. 1 (01.09.2019): 269–72. http://dx.doi.org/10.1515/cdbme-2019-0068.
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AbstractRecently, we could demonstrate positive effects of microfluidic cultivation conditions on maturation of cardiomyocytes derived from human induced pluripotent stem cells (iPS-CMs) in a 2D model. However, 3D cell culture models are much closer to physiological conditions. Combined with microfluidics, 3D systems should resemble the in-vivo conditions even better than standard 2D cultivation. For 3D models, two main technical challenges arise, the tissue integration and sufficient nutrient supply for the cells. This work focuses on concepts for the tissue integration based on a modular approach and different manufacturing technologies as well as using an oxygenator in the microfluidic device to provide sufficient oxygen supply for the cells.
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Mu, Ruojun, Nitong Bu, Jie Pang, Lin Wang und Yue Zhang. „Recent Trends of Microfluidics in Food Science and Technology: Fabrications and Applications“. Foods 11, Nr. 22 (20.11.2022): 3727. http://dx.doi.org/10.3390/foods11223727.
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The development of novel materials with microstructures is now a trend in food science and technology. These microscale materials may be applied across all steps in food manufacturing, from raw materials to the final food products, as well as in the packaging, transport, and storage processes. Microfluidics is an advanced technology for controlling fluids in a microscale channel (1~100 μm), which integrates engineering, physics, chemistry, nanotechnology, etc. This technology allows unit operations to occur in devices that are closer in size to the expected structural elements. Therefore, microfluidics is considered a promising technology to develop micro/nanostructures for delivery purposes to improve the quality and safety of foods. This review concentrates on the recent developments of microfluidic systems and their novel applications in food science and technology, including microfibers/films via microfluidic spinning technology for food packaging, droplet microfluidics for food micro-/nanoemulsifications and encapsulations, etc.
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Weislogel, Mark M., J. Alex Baker und Ryan M. Jenson. „Quasi-steady capillarity-driven flows in slender containers with interior edges“. Journal of Fluid Mechanics 685 (23.09.2011): 271–305. http://dx.doi.org/10.1017/jfm.2011.314.
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AbstractIn the absence of significant body forces the passive manipulation of fluid interfacial flows is naturally achieved by control of the specific geometry and wetting properties of the system. Numerous ‘microfluidic’ systems on Earth and ‘macrofluidic’ systems aboard spacecraft routinely exploit such methods and the term ‘capillary fluidics’ is used to describe both length-scale limits. In this work a collection of analytic solutions is offered for passive and weakly forced flows where a bulk capillary liquid is slowly drained or supplied by a faster capillary flow along at least one interior edge of the container. The solutions are enabled by an assumed known pressure (or known height) dynamical boundary condition. Following a series of assumptions this boundary condition can be in part determined a priori from the container dimensions and further quantitative experimental evidence, but not proof, is provided in support of its expanded use herein. In general, a small parameter arises in the scaling of the problems permitting a decoupling of the edge flow from the global bulk meniscus flow. The quasi-steady asymptotic system of equations that results may then be easily solved in closed form for a useful variety of geometries including uniform and tapered sections possessing at least one critically wetted interior edge. Draining, filling, bubble displacement and other imbibing flows are studied. Cursory terrestrial and drop tower experiments agree well with the solutions. The solutions are valued for the facility they provide in computing designs for selected capillary fluidics problems by way of passive transport rates and meniscus displacement. Because geometric permutations of any given design are myriad, such analytic tools are capable of efficiently identifying and comparing critical design criteria (i.e. shape and size) and the impact of various wetting conditions resulting from the fluid properties and surface conditions. Sample optimizations are performed to demonstrate the utility of the method.
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Cantwell, Christy, John S. McGrath, Clive A. Smith und Graeme Whyte. „Image-Based Feedback of Multi-Component Microdroplets for Ultra-Monodispersed Library Preparation“. Micromachines 15, Nr. 1 (22.12.2023): 27. http://dx.doi.org/10.3390/mi15010027.
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Using devices with microfluidic channels can allow for precise control over liquids flowing through them. Merging flows of immiscible liquids can create emulsions with highly monodispersed microdroplets within a carrier liquid, which are ideal for miniaturised reaction vessels which can be generated with a high throughput of tens of thousands of droplets per second. Control of the size and composition of these droplets is generally performed by controlling the pumping system pushing the liquids into the device; however, this is an indirect manipulation and inadequate if absolute precision is required in the size or composition of the droplets. In this work, we extend the previous development of image-based closed-loop feedback control over microdroplet generation to allow for the control of not only the size of droplets but also the composition by merging two aqueous flows. The feedback allows direct control over the desired parameters of volume and ratio of the two components over a wide range of ratios and outperforms current techniques in terms of monodispersity in volume and composition. This technique is ideal for situations where precise control over droplets is critical, or where a library of droplets of different concentrations but the same volume is required.
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Wuchter, Patrick, Rainer Saffrich, Stefan Giselbrecht, Anthony D. Ho und Eric Gottwald. „Novel 3D-Model for the Hematopoietic Stem Cell Niche Using MSC in a KITChip Based Bioreactor“. Blood 118, Nr. 21 (18.11.2011): 1331. http://dx.doi.org/10.1182/blood.v118.21.1331.1331.
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Abstract Abstract 1331 Human mesenchymal stromal cells (MSC) maintain “stemness” of human hematopoietic stem cells (HSC) by cell-cell contact when used as feeder-layer. We previously demonstrated the presence of specific cadherin-catenin-based junctions between HSC and MSC in a two-dimensional coculture-setting. To develop a more physiological in vitro model for the hematopoietic stem cell niche, we have established a novel 3D-coculture-system based on the so-called 3D-KITChip capable of accommodating up to 1×107 MSC on an area of ∼2cm2. For a precise reproduction of the microenvironment of the niche, the 3D-KITChip is inserted in a microfluidic bioreactor, allowing active nutrient and gas supply. MSC were derived from bone marrow aspirates of healthy voluntary donors and grown to confluence following standard protocols. MSC were then trypsinized and reseeded (3×105 cells) on a unique microchip with defined microwell cavities, developed by the Karlsruhe Institute of Technology (“3D-KITChip”). After 48–72h, 2×105 HSC isolated from umbilical cord blood were added and the chip was inserted in a microfluidic bioreactor. The closed circulation system comprising the bioreactor, a cassette pump, and a medium reservoir was run for up to 7 days. In this closed loop setup, oxygen concentration, medium composition and medium flow could be controlled precisely. After 1–7d of coculture, the bioreactor was re-opened and the two cell populations were analyzed by immunostaining, RT2-PCR, genomics and functional assays such as colony forming assays (CFA). The MSC form a complex 3D mesh in the microcavities of the 3D-KITChip which is very stable for the time of the experiments and could be cultured in this way for up to 6 weeks. It could be demonstrated that HSC are distributed three dimensionally inside this MSC mesh. HSC could be kept alive in this environment for at least 7 days and a defined proportion of CD34+-HSC adhered to the MSC in the microcavities and built up direct cellular connections to the surrounding MSC. A direct comparison of the adhering vs. the non-adhering cell-fraction is currently underway. By means of RT2-PCR, we could demonstrate that the proportion of CD34+/nestin+/p21+/CXCR4+ cells could be maintained throughout the whole culture period of 7 days. Moreover, no CD38 or CD44-expression could be detected, whereas c-kit-expression continuously decreased during the culture period. This novel setup allows the precise adjustment of the key elements in the hematopoietic stem cell niche that govern stem cell homing, engraftment and mobilization. Further experiments aim to elucidate the role of the 3D-environment, oxygen tension, sheer stress, composition of the medium and perfusion conditions on the above mentioned stem cell behavior. The impact of junctional complexes comprising alpha-/beta-catenin, p120 and N-cadherin in this context will be determined. Disclosures: Ho: Genzyme: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.
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Tran, Reginald, David R. Myers, Jordan E. Shields, Byungwook Ahn, Yongzhi Qiu, Caroline Hansen, Yumiko Sakurai et al. „Improving Lentiviral Transduction Efficiency with Microfluidic Systems“. Blood 126, Nr. 23 (03.12.2015): 4415. http://dx.doi.org/10.1182/blood.v126.23.4415.4415.
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Abstract Background: Recent clinical trials have demonstrated the efficacy and safety of gene therapy utilizing HIV-derived lentiviral vectors (LVs) for blood disorders. However, the LV requirements and clinical ex vivo cell transduction protocols used in these studies exposes the limitations of the technology and beckons the need for improved LV manufacturing and clinical transduction efficiency. Many methods have been devised to enhance efficiency, although none have circumvented the exorbitant amounts of virus required to achieve therapeutic HSC transduction. Furthermore, prolonged ex vivo cell culture is necessary to achieve sufficient transduction despite exposure to toxic byproducts of LV production. To that end, we developed a novel, scalable microfluidic for clinical LV transduction that leverages mass transfer principles to significantly reduce the amount of LV required to achieve therapeutic levels of gene transfer and transduction time by more efficiently exposing cells to virus. Results: Jurkats were transduced with a GFP-encoding clinical LV in microfluidics with surface areas (SAs) comparable to the bottom surface of 96 and 6-well plates. Microfluidic transductions were compared to well plate transductions with matched SA, cell numbers, viral particles, and incubation times. After LV incubation, cells were removed from the microfluidics and well plates, spun down, re-suspended with fresh media, and cultured for at least 72 hours at 37°C and 5% CO2. Cells were assessed for GFP expression with flow cytometry. Preliminary mouse studies utilized Sca+ cells isolated from CD45.1 donor mice via positive selection. The cells were transduced in the scaled up microfluidic with a bioengineered coagulation factor VIII (fVIII) transgene encoding LV and transplanted into host hemophilia A mice after myeloablative conditioning. Two weeks post-transplantation, blood samples were taken from the recipient animals and assayed for donor cell engraftment by flow cytometry and plasma fVIII activity by chromogenic assay. The high SA:volume ratio of the microfluidic enhances transduction by physically bringing cells and virus into closer proximity and enabling high concentrations of virus to be used without increasing the amount of virus set by the minimum volume requirements of LV transduction platforms (Fig. 1A). The polystyrene bottom of the microfluidic allows for Retronectin coating that immobilizes non-adherent cells on the bottom surface. LV can then be perfused at low concentrations to maintain a constant supply of fresh virus to the cells, increase convective mixing, and to minimize cell exposure to the toxic byproducts of LV production (Fig. 1B). These microfluidics have been scaled up to accommodate 106 cells, with potential to scale up to 107-108 cells (Fig. 1C). Cells transduced in the microfluidics showed 2-6 fold increases in GFP expression over well plates utilizing the same amount of cells, virus, and incubation times (Fig. 2A). The kinetics of LV transduction in the microfluidics also are faster, as seen by the steeper transduction curve. Five hours of incubation in the microfluidic yielded comparable transduction to 24 hours in the 6-well plate (Fig. 2B). Improvements in transduction also were observed by perfusing virus despite using lower virus concentrations (Fig. 2C). Finally, hemophilia A mice transplanted with donor CD45.1 Sca+ cells transduced in the microfluidic have engrafted (Fig. 3A) and produce fVIII (Fig. 3B) after two weeks with similar profiles to control cells transduced in a 6-well plate despite using half the amount of virus and shorter incubation times. Conclusions and ongoing efforts: We describe a novel microfluidic that significantly reduces the amount of virus and ex vivo processing time required for therapeutic levels of transduction in clinical gene therapy. This device is versatile in its compatibility with current transduction strategies such as Retronectin and polybrene in addition to offering new approaches to boosting gene transfer efficiency. Furthermore, we have shown that the device has clinical potential by successfully scaling up cell numbers and transplanting mice with microfluidic transduced cells, of which there is an ongoing effort to monitor fVIII production and determine virus copy number. Future work will involve optimization with transduction-enhancing compounds, further scaling, and continued in vivo experiments. Disclosures Spencer: Expression Therapeutics: Equity Ownership. Doering:Bayer Healthcare: Consultancy, Honoraria, Research Funding; Expression Therapeutics: Equity Ownership.
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Raub, Aini Ayunni Mohd, Ida Hamidah, Asep Bayu Dani Nandiyanto, Jaenudin Ridwan, Mohd Ambri Mohamed, Muhamad Ramdzan Buyong und Jumril Yunas. „ZnO NRs/rGO Photocatalyst in a Polymer-Based Microfluidic Platform“. Polymers 15, Nr. 7 (31.03.2023): 1749. http://dx.doi.org/10.3390/polym15071749.
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This paper reports the development of ZnO NRs/rGO-based photocatalysts integrated into a tree-branched polymer-based microfluidic reactor for efficient photodegradation of water contaminants. The reactor system includes a photocatalytic reactor, tree-branched microfluidic channels, and ZnO nanorods (NRs) coated with reduced graphene oxide (rGO) on a glass substrate within an area of 0.6 × 0.6 cm2. The ZnO NRs/rGO acts as a photocatalyst layer grown hydrothermally and then spray-coated with rGO. The microfluidic system is made of PDMS and fabricated using soft lithography (micro molding using SU-8 master mold patterned on a silicon wafer). The device geometry is designed using AutoCAD software and the flow properties of the microfluidics are simulated using COMSOL Multiphysics. The microfluidic platform’s photocatalytic process aims to bring the nanostructured photocatalyst into very close proximity to the water flow channel, reducing the interaction time and providing effective purification performance. Our functionality test showed that a degradation efficiency of 23.12 %, within the effective residence time of less than 3 s was obtained.
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Rehmani, Muhammad Asif Ali, Swapna A. Jaywant und Khalid Mahmood Arif. „Study of Microchannels Fabricated Using Desktop Fused Deposition Modeling Systems“. Micromachines 12, Nr. 1 (25.12.2020): 14. http://dx.doi.org/10.3390/mi12010014.
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Microfluidic devices are used to transfer small quantities of liquid through micro-scale channels. Conventionally, these devices are fabricated using techniques such as soft-lithography, paper microfluidics, micromachining, injection moulding, etc. The advancement in modern additive manufacturing methods is making three dimensional printing (3DP) a promising platform for the fabrication of microfluidic devices. Particularly, the availability of low-cost desktop 3D printers can produce inexpensive microfluidic devices in fast turnaround times. In this paper, we explore fused deposition modelling (FDM) to print non-transparent and closed internal micro features of in-plane microchannels (i.e., linear, curved and spiral channel profiles) and varying cross-section microchannels in the build direction (i.e., helical microchannel). The study provides a comparison of the minimum possible diameter size, the maximum possible fluid flow-rate without leakage, and absorption through the straight, curved, spiral and helical microchannels along with the printing accuracy of the FDM process for two low-cost desktop printers. Moreover, we highlight the geometry dependent printing issues of microchannels, pressure developed in the microchannels for complex geometry and establish that the profiles in which flowrate generates 4000 Pa are susceptible to leakages when no pre or post processing in the FDM printed parts is employed.
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Stella, Giovanna, Lorena Saitta, Alfredo Edoardo Ongaro, Gianluca Cicala, Maïwenn Kersaudy-Kerhoas und Maide Bucolo. „Advanced Technologies in the Fabrication of a Micro-Optical Light Splitter“. Micro 3, Nr. 1 (10.03.2023): 338–52. http://dx.doi.org/10.3390/micro3010023.
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In microfluidics, it is important to confine and transport light as close as possible to the sample by guiding it into a small volume of the microfluidic channel, acquiring the emitted/transmitted radiation. A challenge in this context is the miniaturization of the optical components and their integration into the microfluidic device. Among all of the optical components, a particular role is played by the beam splitter, an important optical device capable of splitting light into several paths. In this paper, a micro-splitter is designed and realized by exploiting low-cost technologies. The micro-splitter consists of a micro-mirror in-between two micro-waveguides. This component was fabricated in different materials: poly-dimethyl-siloxane (PDMS), poly(methyl methacrylate) (PMMA), and VeroClear RGD810. A 3D printing master–slave fabrication protocol was used with PDMS, a direct 3D printing approach with VeroClear, and a laser cutting procedure with PMMA. The experimental results obtained show the high potential of the proposed fabrication protocols, based on low-cost technologies, for the realization of micro-optical components, which could also be easily integrated with microfluidics systems.
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Wang, Weiqiang, und Thomas B. Jones. „Moving droplets between closed and open microfluidic systems“. Lab on a Chip 15, Nr. 10 (2015): 2201–12. http://dx.doi.org/10.1039/c5lc00014a.
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Nguyen, Duong Thanh, Van Thi Thanh Tran, Huy Trung Nguyen, Hong Thi Cao, Thai Quoc Vu und Dung Quang Trinh. „Preparation of microfluidics device from PMMA for liposome synthesis“. Vietnam Journal of Science and Technology 61, Nr. 1 (28.02.2023): 84–90. http://dx.doi.org/10.15625/2525-2518/16577.
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Microfluidics has emerged in recent years as a technology that has advantages and is well suited for studying chemistry, biology, and physics at the microscale. A common material which has been widely use to fabricate the microfluidic system is thermoplastic materials. The method of fabricating microfluidic devices has been growing because of advantages such as high-quality feature replication, inexpensiveness, and ease of use. However, the major barrier to the utilization of thermoplastics is the lack of bonding methods for different plastic layers to close the microchannels. Therefore, this study focused on fabricating a microfluidic device on poly(methyl methacrylate) (PMMA) plates by laser engraving. The bonding technique for plastic layers has relied on the application of small amounts of ethanol with conditions of low temperatures (100 ⁰C), and relatively low pressures (5 tons) for 2 minutes. With this technique, the microfluidic device is created to operate stably, without leakage or cracking even under high pressure. The microfluidic device was applied to synthesize liposomes with a 5:1 ratio of syringe pump velocity between water and lipid solution. The size of liposomes after synthesis is 109.64 ± 4.62 nm (mean ± sd) and the PDI is in accordance with standard conditions (PDI < 0.200).
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Pinck, Stéphane, Lucila Martínez Ostormujof, Sébastien Teychené und Benjamin Erable. „Microfluidic Microbial Bioelectrochemical Systems: An Integrated Investigation Platform for a More Fundamental Understanding of Electroactive Bacterial Biofilms“. Microorganisms 8, Nr. 11 (23.11.2020): 1841. http://dx.doi.org/10.3390/microorganisms8111841.
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It is the ambition of many researchers to finally be able to close in on the fundamental, coupled phenomena that occur during the formation and expression of electrocatalytic activity in electroactive biofilms. It is because of this desire to understand that bioelectrochemical systems (BESs) have been miniaturized into microBES by taking advantage of the worldwide development of microfluidics. Microfluidics tools applied to bioelectrochemistry permit even more fundamental studies of interactions and coupled phenomena occurring at the microscale, thanks, in particular, to the concomitant combination of electroanalysis, spectroscopic analytical techniques and real-time microscopy that is now possible. The analytical microsystem is therefore much better suited to the monitoring, not only of electroactive biofilm formation but also of the expression and disentangling of extracellular electron transfer (EET) catalytic mechanisms. This article reviews the details of the configurations of microfluidic BESs designed for selected objectives and their microfabrication techniques. Because the aim is to manipulate microvolumes and due to the high modularity of the experimental systems, the interfacial conditions between electrodes and electrolytes are perfectly controlled in terms of physicochemistry (pH, nutrients, chemical effectors, etc.) and hydrodynamics (shear, material transport, etc.). Most of the theoretical advances have been obtained thanks to work carried out using models of electroactive bacteria monocultures, mainly to simplify biological investigation systems. However, a huge virgin field of investigation still remains to be explored by taking advantage of the capacities of microfluidic BESs regarding the complexity and interactions of mixed electroactive biofilms.
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Behmardi, Yasna, Laurissa Ouaguia, Laura Jean Healey, MinJung Kim, Cole Jones, Hani Rahmo, Alison Skelley et al. „Deterministic Cell Separation Recovers >2-Fold T Cells, and More Naïve T Cells, for Autologous Cell Therapy As Compared to Centrifugally Prepared Cells“. Blood 138, Supplement 1 (05.11.2021): 2847. http://dx.doi.org/10.1182/blood-2021-153528.
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Abstract CAR-T autologous cell therapies are delivering impressive results in the clinic. However, there are still significant manufacturing challenges impeding the rapid adoption of these advanced therapies. On the first day of cell processing, most manufacturing approaches require ~5 steps (~4 hours) to obtain a white blood cell (WBC) preparation sufficiently depleted of red blood cells (RBCs) for T-cell selection and activation steps; and involves large cell losses and a great deal of inconsistency. Here we present a single-step procedure that yields >2 fold more cells that centrifugal processing with comparable or better quality in <1 hour. We previously reported a small-scale microfluidic approach using deterministic cell separation (DCS) to effectively isolate and separate WBCs with high recoveries, no loss of WBC subtypes, no cell damage, and greater numbers of central memory T cells than traditional Ficoll-based processing. Extending this work, we now present the results of our fully scaled-up processing of 23 normal donor leukopaks and 4 disease samples using a full-scale DCS prototype. All samples were processed in <45 minutes, with only an additional 10 minutes hands-on time. On average, inclusive of aggregate removal by prefiltering, DCS achieved 88% WBC recovery, 94% RBC removal, and 98% platelet ( PLT) removal from the undiluted leukopak samples (n=23). Furthermore, DCS resulted in a RBC/WBC ratio of 0.1 compared with a ratio of 1.4 for Ficoll. Similarly, the PLT/WBC ratios were 0.89 versus 7.17 for DCS and Ficoll, respectively (n=20). In addition, DCS preparations contained 2-fold more CD3+ T cells (n=17), and, importantly, the CD4+ cells were less differentiated (more cells in naïve and central memory stages) than those recovered by Ficoll. Similarly, DCS processed blood from cancer patients had a ratio of RBC/WBC = 7.0 versus 20.1 for Ficoll, and a PLT/WBC ratio = 0.7 versus 15.6 for Ficoll (n=4). These results demonstrate the capabilities of DCS in processing not only samples from normal donors but also blood from cancer patients with similar efficiencies. Further, with DCS we achieved wash efficiencies of more than 3 log, without the typically associated cell loss, as demonstrated by the removal of viral particles, soluble proteins and cytokines and growth factors present in plasma. Therefore, cells from leukopaks processed by DCS can be washed and collected directly into cell culture media, or other solutions, to ready them for downstream applications without pelleting and repeated washes, greatly simplifying workflows. We integrated our DCS technology into a full scale parallelized, disposable, closed fluid path solution and automated platform prototype, the Curate ® Cell Processing System, capable of processing undiluted leukopacks at rates in excess of 300mL/hour. Designed to process blood products in bags using a single-use cassette containing microfluidic components, the Curate ® delivers a debulked WBC product to a bag. With a hands-on time of only 10 minutes, the Curate ® reduces the time to activation- and expansion-ready cells from leukopaks by 6-fold as compared with centrifugation and elutriation methods (Bowles, et al. Cytotherapy 2018;20(5):S109). The system can process a full leukopak (200-300 mL containing up to 1.2x10 10 WBC) within 40 minutes with a maximal cell throughput of 1.8x10 10 WBC per hour. Additionally, the same Curate ® device can be used to achieve up to 200x10 6 cell/mL in as little as 40 mL of media and without requiring pelleting. In summary, we believe our technology enables a significant breakthrough in the production of CAR-T cells by efficiently recovering more and cleaner total and naÏve T cells, for CAR-T cell production. Furthermore, the closed-system Curate ® will simplify cell processing workflows by reducing the number of cell washing steps, as well as the hands-on time and resources. Supported in part by NIH Grant No 5R42CA228616-03 Disclosures Behmardi: GPB Scientific, Inc: Current Employment. Ouaguia: GPB Scientific, Inc: Current Employment. Healey: GPB Scientific, Inc: Current Employment. Jones: GPB Scientific, Inc: Current Employment. Rahmo: GPB Scientific, Inc: Current Employment. Skelley: GPB Scientific, Inc: Current Employment. Gandhi: GPB Scientific, Inc: Current Employment. Campos-Gonzalez: GPB Scientific, Inc: Current Employment, Current holder of stock options in a privately-held company. Civin: GPB Scientific, Inc: Current holder of individual stocks in a privately-held company. Ward: GPB Scientific, Inc: Current Employment.
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Soenksen, L. R., T. Kassis, M. Noh, L. G. Griffith und D. L. Trumper. „Closed-loop feedback control for microfluidic systems through automated capacitive fluid height sensing“. Lab on a Chip 18, Nr. 6 (2018): 902–14. http://dx.doi.org/10.1039/c7lc01223c.
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Nasibullayev, I. Sh, und O. V. Darintsev. „Two-dimensional dynamic model of the interaction of a fluid and a piezoelectric bending actuator in a plane channel“. Multiphase Systems 14, Nr. 4 (2019): 220–32. http://dx.doi.org/10.21662/mfs2019.4.029.
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The paper proposes a two-dimensional computer model of the fluid flow in a plane channel under the action of an applied pressure drop with a flat ceramic piezoelectric actuator immersed in it, bending in the transverse direction in proportion to the applied electric voltage. A mathematical model of the coupled liquid-piezodrive system in variational form for numerical simulation by the finite element method is proposed. Since the assignment of the Dirichlet boundary conditions for displacement in this problem, is difficult, an equivalent piezo actuator deformation scheme using the Neumann boundary conditions is constructed. The deformations and equivalent stresses of von Mises on a piezo actuator are calculated. The influence of the geometry of the channel and the hydrodynamic resistance formed by the piezo actuator on the dynamics of the fluid flow is analyzed. An algorithm is proposed for adaptive dynamic remeshing of the channel computational mesh under deformations exceeding the size of finite elements. With a symmetric control signal supplied to the piezoelectric actuator, the asymmetry of the geometry leads to a violation of the symmetry of the fluid flow within the period, both in terms of fluid flow rate and in time. In the absence of a pressure drop at low frequencies of the oscillations of the piezoelectric element (of the order of the inverse relaxation time of the velocity), the period-average liquid flow rate is nonzero and increases with increasing frequency. In the presence of an external pressure drop along the layer, the average liquid flow rate is proportional to the pressure drop; at low frequencies, it is inversely proportional to the frequency; with increasing frequency, it reaches saturation. Based on the results of numerical modeling, various variants of new microfluidic technical devices generating a fluid flow using a piezoelectric bending actuator are proposed: a micropump creating a closed-circuit flow; fluid flow regulator and fluid volume dispenser.
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Peshin, Snehan, Derosh George, Roya Shiri, Lawrence Kulinsky und Marc Madou. „Capillary Flow-Driven and Magnetically Actuated Multi-Use Wax Valves for Controlled Sealing and Releasing of Fluids on Centrifugal Microfluidic Platforms“. Micromachines 13, Nr. 2 (16.02.2022): 303. http://dx.doi.org/10.3390/mi13020303.
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Compact disc (CD)-based centrifugal microfluidics is an increasingly popular choice for academic and commercial applications as it enables a portable platform for biological and chemical assays. By rationally designing microfluidic conduits and programming the disc’s rotational speeds and accelerations, one can reliably control propulsion, metering, and valving operations. Valves that either stop fluid flow or allow it to proceed are critical components of a CD platform. Among the valves on a CD, wax valves that liquify at elevated temperatures to open channels and that solidify at room temperature to close them have been previously implemented on CD platforms. However, typical wax valves on the CD fluidic platforms can be actuated only once (to open or to close) and require complex fabrication steps. Here, we present two new multiple-use wax valve designs, driven by capillary or magnetic forces. One wax valve design utilizes a combination of capillary-driven flow of molten wax and centrifugal force to toggle between open and closed configurations. The phase change of the wax is enabled by heat application (e.g., a 500-mW laser). The second wax valve design employs a magnet to move a molten ferroparticle-laden wax in and out of a channel to enable reversible operation. A multi-phase numerical simulation study of the capillary-driven wax valve was carried out and compared with experimental results. The capillary wax valve parameters including response time, angle made by the sidewall of the wax reservoir with the direction of a valve channel, wax solidification time, minimum spin rate of the CD for opening a valve, and the time for melting a wax plug are measured and analyzed theoretically. Additionally, the motion of the molten wax in a valve channel is compared to its theoretical capillary advance with respect to time and are found to be within 18.75% of the error margin.
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Neto, Estrela, Cecília J. Alves, Daniela M. Sousa, Inês S. Alencastre, Ana H. Lourenço, Luís Leitão, Hyun R. Ryu et al. „Sensory neurons and osteoblasts: close partners in a microfluidic platform“. Integr. Biol. 6, Nr. 6 (2014): 586–95. http://dx.doi.org/10.1039/c4ib00035h.
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Harink, Björn, Séverine Le Gac, David Barata, Clemens van Blitterswijk und Pamela Habibovic. „Microtiter plate-sized standalone chip holder for microenvironmental physiological control in gas-impermeable microfluidic devices“. Lab Chip 14, Nr. 11 (2014): 1816–20. http://dx.doi.org/10.1039/c4lc00190g.
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Tonooka, Taishi. „Microfluidic Device with an Integrated Freeze-Dried Cell-Free Protein Synthesis System for Small-Volume Biosensing“. Micromachines 12, Nr. 1 (29.12.2020): 27. http://dx.doi.org/10.3390/mi12010027.
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Microfluidic devices enable the precise operation of liquid samples in small volumes. This motivates why microfluidic devices have been applied to point-of-care (PoC) liquid biopsy. Among PoC liquid biopsy studies, some report diagnostic reagents being freeze-dried in such microfluidic devices. This type of PoC microfluidic device has distinct advantages, such as simplicity of the procedures, compared with other PoC devices using liquid-type diagnostic reagents. Despite the attractive characteristic, only diagnostic reagents based on the cloned enzyme donor immunoassay (CEDIA) have been freeze-dried in the microfluidic device. However, development of the PoC device based on the CEDIA method is time-consuming and labor-intensive. Here, we employed a molecule-responsive protein synthesis system as the diagnostic reagent to be freeze-dried in the microfluidic device. Such molecule-responsive protein synthesis has been well investigated in the field of molecular biology. Therefore, using the accumulated information, PoC devices can be efficiently developed. Thus, we developed a microfluidic device with an integrated freeze-dried molecule-responsive protein synthesis system. Using the developed device, we detected two types of bio-functional molecules (i.e., bacterial quorum sensing molecules and mercury ions) by injecting 1 µL of sample solution containing these molecules. We showed that the developed device is applicable for small-volume biosensing.
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Kucukal, Erdem, Anton Ilich, Nigel S. Key, Jane A. Little und Umut A. Gurkan. „Adhesion of Sickle RBCs to Heme-Activated Endothelial Cells Correlates with Patient Clinical Phenotypes“. Blood 130, Suppl_1 (07.12.2017): 959. http://dx.doi.org/10.1182/blood.v130.suppl_1.959.959.
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Abstract Severe hemolysis and associated high levels of hemolytic biomarkers, including LDH and heme, are among major constituents of the pathophysiology of sickle cell disease (SCD). Elevated extracellular heme due to hemolysis overwhelms endogenous detoxification mechanisms and leads to oxidative stress, triggering systemic endothelium activation, vascular dysfunction, and end organ damage. To understand the role of red blood cells (RBC) in this process, we assessed sickle RBC adhesion to heme-activated endothelial cells utilizing an endothelialized microfluidic platform in a clinically diverse patient population. Human umbilical vein endothelial cells (HUVECs) were seeded into fibronectin (FN) functionalized microfluidic channels and incubated for 4 hours in a 37°C and 5% CO2 environment. Next, the confluent monolayers were loaded and incubated for 45 minutes with fresh culture medium or at one of two concentrations of heme solutions: (1) 20 μM that corresponds to physiological heme levels in SCD patients, and (2) 40 μM. SCD blood samples, collected from 8 patients (7 HbSS and 1 HbS/β0 thal; 3 males and 5 females), were centrifuged to remove the plasma and washed with PBS thrice prior to flow experiments. RBCs were re-suspended in culture medium at a hematocrit of 25%. A total volume of 15 µl RBC suspension was perfused into the microchannels followed by rinsing with fresh culture medium at 1 dyne/cm2, which corresponds to the typical shear stress value observed in post-capillary venules. The fully closed and hermetically sealed microfluidic system design ensured the stability of gas composition in the culture medium during the experiments. Endothelialized microchannels supported sickle RBC adhesion to non-treated, 20 µM heme-activated, and 40 µM heme-activated HUVECs (Fig. 1A, B, C). Adhesion results suggested that activation of HUVECs by heme mediated RBC adhesion in a concentration-dependent manner, with a significant difference observed at 40 µM (Fig. 1D, paired t-test, p<0.05). Notably, a heterogeneous heme-mediated adhesion profile was seen among patients. Sickle RBC adhesion to 20 μM heme-activated HUVECs was significantly increased in patients with higher LDH levels (Fig. 1E, p=0.024, ANOVA), higher absolute reticulocyte counts (Fig. 1F, p=0.002, ANOVA), and lower total hemoglobin (Fig. 1G, p=0.016, ANOVA), which are indicative of elevated hemolysis. All patients in the high adhesion group (>200 adherent RBCs) had elevations in serum LDH levels and in absolute reticulocyte counts. Moreover, patients with a recent transfusion had higher RBC adhesion to 40 µM heme-activated HUVECs compared to patients with no transfusion in the last 3 months (Fig. 1H, p<0.05, ANOVA). Here, we report a direct link between heme-driven endothelial activation and RBC adhesion in a patient-specific manner. In patients with a more severe clinical phenotype, as reflected in LDH, total hemoglobin, and absolute reticulocyte or recent blood transfusions, we found greater RBC adhesion to heme-activated HUVECs. These findings suggest that RBCs from those patients most likely to experience hemolysis in vivo may also be those RBCs most likely to adhere to heme-activated endothelium. Acknowledgments: This work was supported by grants #2013126 and #2015191 from the Doris Duke Charitable Foundation, National Heart Lung and Blood Institute R01HL133574, and National Science Foundation CAREER Award 1552782. Figure 1: Sickle RBC adhesion to heme-activated HUVECs and clinical associations. Sickle RBCs adherent to immobilized HUVECs in (A) non-activated, (B) 20 µM heme-activated, and (C) 40 µM heme-activated microchannels. The microscope images illustrate a small portion of the full microchannel surface. (D) RBC adhesion to HUVECs increased depending on the heme concentration, with a significant difference at the 40 µM level (paired t test, p<0.05). Patients with higher LDH (E) as well as absolute reticulocyte counts (F), and lower total hemoglobin (G) showed significantly greater RBC adhesion to 20 µM heme-activated HUVECs (ANOVA). (H) Furthermore, patients with a recent transfusion history displayed elevated RBC adhesion to 40 µM heme-activated HUVECs compared to non-transfused patients (ANOVA). The dashed rectangles indicate the normal clinical values for healthy individuals, while all patients had total hemoglobin levels lower than normal. Scale bars represent 30 µm. Figure 1 Figure 1. Disclosures Little: Hemex Health: Equity Ownership. Gurkan: Hemex Health: Employment, Equity Ownership.
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Zizzari, Alessandra, und Valentina Arima. „Glass Microdroplet Generator for Lipid-Based Double Emulsion Production“. Micromachines 15, Nr. 4 (05.04.2024): 500. http://dx.doi.org/10.3390/mi15040500.
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Microfluidics offers a highly controlled and reproducible route to synthesize lipid vesicles. In recent years, several microfluidic approaches have been introduced for this purpose, but double emulsions, such as Water-in-Oil-in-Water (W/O/W) droplets, are preferable to produce giant vesicles that are able to maximize material encapsulation. Flow focusing (FF) is a technique used to generate double emulsion droplets with high monodispersity, a controllable size, and good robustness. Many researchers use polydimethylsiloxane as a substrate material to fabricate microdroplet generators, but it has some limitations due to its hydrophobicity, incompatibility with organic solvents, and the molecular adsorption on the microchannel walls. Thus, specific surface modification and functionalization steps, which are uncomfortable to perform in closed microchannels, are required to overcome these shortcomings. Here, we propose glass as a material to produce a chip with a six-inlet junction geometry. The peculiar geometry and the glass physicochemical properties allow for W/O/W droplet formation without introducing microchannel wall functionalization and using a variety of reagents and organic solvents. The robust glass chip can be easily cleaned and used repeatedly, bringing advantages in terms of cost and reproducibility in emulsion preparation.
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Kimura, Hiroshi, Masaki Nishikawa, Takatoki Yamamoto, Yasuyuki Sakai und Teruo Fujii. „Microfluidic Perfusion Culture of Human Hepatocytes“. Journal of Robotics and Mechatronics 19, Nr. 5 (20.10.2007): 550–56. http://dx.doi.org/10.20965/jrm.2007.p0550.
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Analysis using human cells has been widely used in place of animal experiments. To obtain culture environments closer to those with in vivo, perfusion culture using microfluidic devices is being studied instead of stationary culture such as in a culture dish. With conventional perfusion culture with microfluidic devices, pumping system is externally provided, causing a large dead volume of culture medium. As a result, applied drugs as well as metabolites and signal transmitters from cells are diluted. We minimized this dead volume by embedding micropumps within the device to realize a high concentration of metabolites and signal transmitters from cells by perfusion with small amounts of culture medium and its effects on the cells. Using Hep-G2, established from a human hepatoma, we successfully formed Hep-G2 spheroids which are not observed in conventional culture. Evaluating activity from the DNA amount and albumin produced, we found that Hep-G2 spheroids formed in our device showed higher activity than conventional 2-dimensional culture. We demonstrated that the functionally highly integrated on-chip perfusion cell culture microdevice provided cells with a culture environment close to that in vivo and promoted morphological change and expression of high activity in cells.