Journal articles: 'High pressure microfluidics'

1

Ogden, Sam, Roger Bodén, and Klas Hjort. "A Latchable Valve for High-Pressure Microfluidics." Journal of Microelectromechanical Systems 19, no. 2 (April 2010): 396–401. http://dx.doi.org/10.1109/jmems.2010.2041749.

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Chen, C. F., J. Liu, L. P. Hromada, C. W. Tsao, C. C. Chang, and D. L. DeVoe. "High-pressure needle interface for thermoplastic microfluidics." Lab Chip 9, no. 1 (2009): 50–55. http://dx.doi.org/10.1039/b812812j.

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Bodén, Roger, Klas Hjort, Jan-Åke Schweitz, and Urban Simu. "A metallic micropump for high-pressure microfluidics." Journal of Micromechanics and Microengineering 18, no. 11 (September 26, 2008): 115009. http://dx.doi.org/10.1088/0960-1317/18/11/115009.

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Andersson, Martin, Klas Hjort, and Lena Klintberg. "Fracture strength of glass chips for high-pressure microfluidics." Journal of Micromechanics and Microengineering 26, no. 9 (July 8, 2016): 095009. http://dx.doi.org/10.1088/0960-1317/26/9/095009.

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Serra, M., I. Pereiro, A. Yamada, J. L. Viovy, S. Descroix, and D. Ferraro. "A simple and low-cost chip bonding solution for high pressure, high temperature and biological applications." Lab on a Chip 17, no. 4 (2017): 629–34. http://dx.doi.org/10.1039/c6lc01319h.

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Lee, Kevin S., and Rajeev J. Ram. "Plastic–PDMS bonding for high pressure hydrolytically stable active microfluidics." Lab on a Chip 9, no. 11 (2009): 1618. http://dx.doi.org/10.1039/b820924c.

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Yao, Junyi, Fan Lin, Hyun Kim, and Jaewon Park. "The Effect of Oil Viscosity on Droplet Generation Rate and Droplet Size in a T-Junction Microfluidic Droplet Generator." Micromachines 10, no. 12 (November 23, 2019): 808. http://dx.doi.org/10.3390/mi10120808.

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There have been growing interests in droplet-based microfluidics due to its capability to outperform conventional biological assays by providing various advantages, such as precise handling of liquid/cell samples, fast reaction time, and extremely high-throughput analysis/screening. The droplet-based microfluidics utilizes the interaction between the interfacial tension and the fluidic shear force to break continuous fluids into uniform-sized segments within a microchannel. In this paper, the effect of different viscosities of carrier oil on water-in-oil emulsion, particularly how droplet size and droplet generation rate are affected, has been investigated using a commonly used T-junction microfluidic droplet generator design connected to a pressure-controlled pump. We have tested mineral oils with four different viscosities (5, 7, 10, and 15 cSt) to compare the droplet generation under five different flow pressure conditions (i.e., water flow pressure of 30–150 mbar and oil flow pressure of 40–200 mbar). The results showed that regardless of the flow pressure levels, the droplet size decreased as the oil viscosity increased. Average size of the droplets decreased by approximately 32% when the viscosity of the oil changed from 5 to 15 cSt at the flow pressure of 30 mbar for water and 40 mbar for oil. Interestingly, a similar trend was observed in the droplet generation rate. Droplet generation rate and the oil viscosity showed high linear correlation (R2 = 0.9979) at the water flow pressure 30 mbar and oil flow pressure 40 mbar.

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Gerhardt, Renata F., Andrea J. Peretzki, Sebastian K. Piendl, and Detlev Belder. "Seamless Combination of High-Pressure Chip-HPLC and Droplet Microfluidics on an Integrated Microfluidic Glass Chip." Analytical Chemistry 89, no. 23 (November 15, 2017): 13030–37. http://dx.doi.org/10.1021/acs.analchem.7b04331.

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Huang, Chien-Chih, Martin Z. Bazant, and Todd Thorsen. "Ultrafast high-pressure AC electro-osmotic pumps for portable biomedical microfluidics." Lab Chip 10, no. 1 (2010): 80–85. http://dx.doi.org/10.1039/b915979g.

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Chen, Weiqi, Bruno Pinho, and Ryan L. Hartman. "Flash crystallization kinetics of methane (sI) hydrate in a thermoelectrically-cooled microreactor." Lab on a Chip 17, no. 18 (2017): 3051–60. http://dx.doi.org/10.1039/c7lc00645d.

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Ripken, Renée M., Stefan Schlautmann, Remco G. P. Sanders, Johannes G. E. Gardeniers, and Séverine Le Gac. "Monitoring phase transition of aqueous biomass model substrates by high-pressure and high-temperature microfluidics." ELECTROPHORESIS 40, no. 4 (January 4, 2019): 563–70. http://dx.doi.org/10.1002/elps.201800431.

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Wasay, A., and D. Sameoto. "Gecko gaskets for self-sealing and high-strength reversible bonding of microfluidics." Lab on a Chip 15, no. 13 (2015): 2749–53. http://dx.doi.org/10.1039/c5lc00342c.

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We report a novel reversible bonding method for microfluidic devices using gecko-inspired dry adhesives that result in an instant high-strength bond suitable for pressure driven flows. The concept also provides for viable stick and play interconnections.

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Filatov, Nikita A., Anatoly A. Evstrapov, and Anton S. Bukatin. "Negative Pressure Provides Simple and Stable Droplet Generation in a Flow-Focusing Microfluidic Device." Micromachines 12, no. 6 (June 5, 2021): 662. http://dx.doi.org/10.3390/mi12060662.

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Droplet microfluidics is an extremely useful and powerful tool for industrial, environmental, and biotechnological applications, due to advantages such as the small volume of reagents required, ultrahigh-throughput, precise control, and independent manipulations of each droplet. For the generation of monodisperse water-in-oil droplets, usually T-junction and flow-focusing microfluidic devices connected to syringe pumps or pressure controllers are used. Here, we investigated droplet-generation regimes in a flow-focusing microfluidic device induced by the negative pressure in the outlet reservoir, generated by a low-cost mini diaphragm vacuum pump. During the study, we compared two ways of adjusting the negative pressure using a compact electro-pneumatic regulator and a manual airflow control valve. The results showed that both types of regulators are suitable for the stable generation of monodisperse droplets for at least 4 h, with variations in diameter less than 1 µm. Droplet diameters at high levels of negative pressure were mainly determined by the hydrodynamic resistances of the inlet microchannels, although the absolute pressure value defined the generation frequency; however, the electro-pneumatic regulator is preferable and convenient for the accurate control of the pressure by an external electric signal, providing more stable pressure, and a wide range of droplet diameters and generation frequencies. The method of droplet generation suggested here is a simple, stable, reliable, and portable way of high-throughput production of relatively large volumes of monodisperse emulsions for biomedical applications.

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Andersson, Martin, Johan Ek, Ludvig Hedman, Fredrik Johansson, Viktor Sehlstedt, Jesper Stocklassa, Pär Snögren, et al. "Thin film metal sensors in fusion bonded glass chips for high-pressure microfluidics." Journal of Micromechanics and Microengineering 27, no. 1 (November 16, 2016): 015018. http://dx.doi.org/10.1088/0960-1317/27/1/015018.

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Ciftlik, A. T., and M. A. M. Gijs. "A low-temperature parylene-to-silicon dioxide bonding technique for high-pressure microfluidics." Journal of Micromechanics and Microengineering 21, no. 3 (February 8, 2011): 035011. http://dx.doi.org/10.1088/0960-1317/21/3/035011.

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Bergs, Christian, Paul Simon, Yurii Prots, and Andrij Pich. "Ultrasmall functional ZnO2 nanoparticles: synthesis, characterization and oxygen release properties." RSC Advances 6, no. 88 (2016): 84777–86. http://dx.doi.org/10.1039/c6ra16009c.

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Ultrasmall zinc peroxide nanoparticles with diameter between 3.3 ± 0.9 and 14.4 ± 5.2 nm were synthesized via a completely new synthesis method (high-pressure impinging-jet reactor; MRT CR 5, Microfluidics®).

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Chen, Siyuan, Wei Liu, Jiangling Wan, Xin Cheng, Conghui Gu, Hui Zhou, Shan Chen, Xiaojing Zhao, Yuxiang Tang, and Xiangliang Yang. "Preparation of Coenzyme Q10 nanostructured lipid carriers for epidermal targeting with high-pressure microfluidics technique." Drug Development and Industrial Pharmacy 39, no. 1 (November 2, 2012): 20–28. http://dx.doi.org/10.3109/03639045.2011.650648.

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Ciftlik, Ata Tuna, and Martin A. M. Gijs. "Parylene to silicon nitride bonding for post-integration of high pressure microfluidics to CMOS devices." Lab Chip 12, no. 2 (2012): 396–400. http://dx.doi.org/10.1039/c1lc20727j.

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Karakitsiou, Stamatina, Bodil Holst, and Alex Christian Hoffmann. "Pressure-Driven Gas Flow through Nano-Channels at High Knudsen Numbers." Journal of Nano Research 50 (November 2017): 116–27. http://dx.doi.org/10.4028/www.scientific.net/jnanor.50.116.

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Flow through nano-channels is important in several fields, ranging from natural porous media to microfluidics. It is therefore important to study the flow under controlled conditions. While quite a lot of work has been done on the flow of liquids through nano-channels, comparatively little systematic work has been done on gas flow. Here we present a study of the flow of argon through nano-channels. We study samples with 2000 parallel nano-channels, with quadratic cross section. Each side is 100nm. The total length is 20 m. The nano-channels are made by patterning a Si<110> wafer usingelectron beam lithography (EBL) followed by reactive ion etching and with subsequent anodic bonding between silicon and a borosilicate glass as a top plate. The samples were investigated using a home-built apparatus which allows us to measure flow at high Knudsen numbers (from around 10 to 550). We compare our results with a range of theoretical flow models. As innovation this work provides measurements of gas transport from the home-built apparatus. The system records the pressure profile of each sample and the mass flow rate is calculated numerically from the pressure data.

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Natu, Rucha, Suvajyoti Guha, Seyed Ahmad Reza Dibaji, and Luke Herbertson. "Assessment of Flow through Microchannels for Inertia-Based Sorting: Steps toward Microfluidic Medical Devices." Micromachines 11, no. 10 (September 24, 2020): 886. http://dx.doi.org/10.3390/mi11100886.

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The development of new standardized test methods would allow for the consistent evaluation of microfluidic medical devices and enable high-quality products to reach the market faster. A comprehensive flow characterization study was conducted to identify regulatory knowledge gaps using a generic inertia-based spiral channel model for particle sorting and facilitate standards development in the microfluidics community. Testing was performed using 2–20 µm rigid particles to represent blood elements and flow rates of 200–5000 µL/min to assess the effects of flow-related factors on overall system performance. Two channel designs were studied to determine the variability associated with using the same microchannel multiple times (coefficient of variation (CV) of 27% for Design 1 and 18% for Design 2, respectively). The impact of commonly occurring failure modes on device performance was also investigated by simulating progressive and complete channel outlet blockages. The pressure increased by 10–250% of the normal channel pressure depending on the extent of the blockage. Lastly, two common data analysis approaches were compared—imaging and particle counting. Both approaches were similar in terms of their sensitivity and consistency. Continued research is needed to develop standardized test methods for microfluidic systems, which will improve medical device performance testing and drive innovation in the biomedical field.

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Nawrot, Witold, Kamila Drzozga, Sylwia Baluta, Joanna Cabaj, and Karol Malecha. "A Fluorescent Biosensors for Detection Vital Body Fluids’ Agents." Sensors 18, no. 8 (July 24, 2018): 2357. http://dx.doi.org/10.3390/s18082357.

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The clinical applications of sensing tools (i.e., biosensors) for the monitoring of physiologically important analytes are very common. Nowadays, the biosensors are being increasingly used to detect physiologically important analytes in real biological samples (i.e., blood, plasma, urine, and saliva). This review focuses on biosensors that can be applied to continuous, time-resolved measurements with fluorescence. The material presents the fluorescent biosensors for the detection of neurotransmitters, hormones, and other human metabolites as glucose, lactate or uric acid. The construction of microfluidic devices based on fluorescence uses a variety of materials, fluorescent dyes, types of detectors, excitation sources, optical filters, and geometrical systems. Due to their small size, these devices can perform a full analysis. Microfluidics-based technologies have shown promising applications in several of the main laboratory techniques, including blood chemistries, immunoassays, nucleic-acid amplification tests. Of the all technologies that are used to manufacture microfluidic systems, the LTCC technique seems to be an interesting alternative. It allows easy integration of electronic and microfluidic components on a single ceramic substrate. Moreover, the LTCC material is biologically and chemically inert, and is resistant to high temperature and pressure. The combination of all these features makes the LTCC technology particularly useful for implementation of fluorescence-based detection in the ceramic microfluidic systems.

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Hilber, W., and B. Jakoby. "Ethanol Fermentation as the Basis for Autonomous, Long-term and High-pressure Fluid Transport in Microfluidics." Procedia Engineering 120 (2015): 100–105. http://dx.doi.org/10.1016/j.proeng.2015.08.575.

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Schneider, Stefan, Eduardo J. S. Brás, Oliver Schneider, Katharina Schlünder, and Peter Loskill. "Facile Patterning of Thermoplastic Elastomers and Robust Bonding to Glass and Thermoplastics for Microfluidic Cell Culture and Organ-on-Chip." Micromachines 12, no. 5 (May 18, 2021): 575. http://dx.doi.org/10.3390/mi12050575.

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The emergence and spread of microfluidics over the last decades relied almost exclusively on the elastomer polydimethylsiloxane (PDMS). The main reason for the success of PDMS in the field of microfluidic research is its suitability for rapid prototyping and simple bonding methods. PDMS allows for precise microstructuring by replica molding and bonding to different substrates through various established strategies. However, large-scale production and commercialization efforts are hindered by the low scalability of PDMS-based chip fabrication and high material costs. Furthermore, fundamental limitations of PDMS, such as small molecule absorption and high water evaporation, have resulted in a shift toward PDMS-free systems. Thermoplastic elastomers (TPE) are a promising alternative, combining properties from both thermoplastic materials and elastomers. Here, we present a rapid and scalable fabrication method for microfluidic systems based on a polycarbonate (PC) and TPE hybrid material. Microstructured PC/TPE-hybrid modules are generated by hot embossing precise features into the TPE while simultaneously fusing the flexible TPE to a rigid thermoplastic layer through thermal fusion bonding. Compared to TPE alone, the resulting, more rigid composite material improves device handling while maintaining the key advantages of TPE. In a fast and simple process, the PC/TPE-hybrid can be bonded to several types of thermoplastics as well as glass substrates. The resulting bond strength withstands at least 7.5 bar of applied pressure, even after seven days of exposure to a high-temperature and humid environment, which makes the PC/TPE-hybrid suitable for most microfluidic applications. Furthermore, we demonstrate that the PC/TPE-hybrid features low absorption of small molecules while being biocompatible, making it a suitable material for microfluidic biotechnological applications.

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Rupp, Jochen, Manuela Schmidt, Bettina Günther, Michael Stumber, Sven Zinober, Roland Müller-Fiedler, Bashir Alabsi, et al. "The Way to High Volume Fabrication of Lab-on-a-Chip Devices—A Technological Approach for Polymer Based Microfluidic Systems with Integrated Active Valves and Pumps." Journal of Microelectronics and Electronic Packaging 6, no. 4 (October 1, 2009): 198–204. http://dx.doi.org/10.4071/1551-4897-6.4.198.

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We present a technology platform suitable for the mass production of laboratory-on-a-chip devices made of polymers with integrated active and passive components. The presented microfluidic platform with integrated valves and pumps for active flow management is realized with three layers consisting of two polymer parts separated by a thin elastic TPE (thermoplastic elastomer) membrane welded together in one step. The elastic TPE membrane acts as an integrated deflectable membrane layer between the two outer polymer layers, each made of a weldable thermoplastic polymer (polycarbonate). Valving is realized by applying pressure in a displacement chamber above a hydraulic channel causing the membrane to deform and to seal the channel. A pump is fabricated using a displacement chamber with a valve on the inlet and outlet. The presented components, namely valve and pump, show excellent behavior regarding response time, sealing quality, and pump rate needing only a low actuation pressure. The three-layer-stack is joined in a single process step by using laser welding, creating devices with high mechanical stability. This production technology fulfills the requirements of a high volume fabrication at high quality and has the potential to manufacture cost-efficient and reliable laboratory-on-a-chip systems. The used materials show a high chemical resistance against a broad range of commonly used liquids and good optical characteristics for the use in μTAS. This consistent technological approach represents a flexible platform for microfluidics with active components to be used in complex applications.

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Wang, Fei, and Xiaoming Tao. "Carbon/Silicone Nanocomposite-Enabled Soft Pressure Sensors with a Liquid-Filled Cell Structure Design for Low Pressure Measurement." Sensors 21, no. 14 (July 10, 2021): 4732. http://dx.doi.org/10.3390/s21144732.

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In the fields of humanoid robots, soft robotics, and wearable electronics, the development of artificial skins entails pressure sensors that are low in modulus, high in sensitivity, and minimal in hysteresis. However, few sensors in the literature can meet all the three requirements, especially in the low pressure range (<10 kPa). This article presents a design for such pressure sensors. The bioinspired liquid-filled cell-type structural design endows the sensor with appropriate softness (Young’s modulus < 230 kPa) and high sensitivity (highest at 0.7 kPa−1) to compression forces below 0.65 N (6.8 kPa). The low-end detection limit is ~0.0012 N (13 Pa), only triple the mass of a bee. Minimal resistance hysteresis of the pressure sensor is 7.7%. The low hysteresis is attributed to the study on the carbon/silicone nanocomposite, which reveals the effect of heat treatment on its mechanical and electromechanical hysteresis. Pressure measurement range and sensitivity of the sensor can be tuned by changing the structure and strain gauge parameters. This concept of sensor design, when combined with microfluidics technology, is expected to enable soft, stretchable, and highly precise touch-sensitive artificial skins.

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Woodall, Julia Lins Arrighi, Meredith Ellen Fay, Jordan Ciciliano, Reza Abbaspour, Muhannad S. Bakir, and Wilbur A. Lam. "Real-Time Visualization of Shear-Dependent Erythrocyte Deformation into Schistocytes Using Single Micron Microfluidics." Blood 132, Supplement 1 (November 29, 2018): 1030. http://dx.doi.org/10.1182/blood-2018-99-120113.

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Abstract Background: The vasculature consists of a dynamic mechanical microenvironment whereby blood cells experience a wide variety of shear stresses and pressures (Wootton et al., Annu. Rev. Biomed. Eng., 1999).This is enhanced in the context of prothrombotic conditions, especially in the microvasculature, during which the introduction of a pathologic fibrin matrix can affect both the fluidic microenvironment and create physical obstacles in the blood stream. These forces act as erythocytic biophysical cues and have been found to affect ATP release and the deformation into abnormal cell morphologies (Gov et al., Biophysical Journal, 2005). These deformations affect both cell form and function in turbulent conditions such as heart valves, thrombotic microangiopathies, and prothrombotic disorders like disseminated intravascular coagulation (Levi et al., N Engl J Med, 1999). The presence of mechanically damaged erythrocytes like schistocytes in blood smears are used to detect these disorders, however, the underlying biophysical mechanisms of how they are formed remains largely unknown (Zini, et al., Int. J. Lab. Hematol., 2012). To that end, we developed microfluidic devices with single-micron sizescales and "canal-like" features of varying lengths to recreate the mechanical microenvironment in biophysical constrictions that occur in microvascular thrombotic disorders associated with schistocyte formation. With these specialized microfluidics, we previously observed the fragmentation of erythrocytes in real-time and found that the extent of erythrocyte damage was dependent on the length of the constricting canal, which affects the pressure differential and transit time (Ciciliano et al., Lab on a Chip, 2017). Here, we hypothesize that increasing shear rate in these microchannel canals will increase the formation of altered erythrocytes including schistocytes. Methods: Our microfluidic devices are fabricated via electron beam lithography and consist of microcanals with a 2 µm width, a 3 µm height, and lengths varying from 5 µm to 45 µm, simulating the physical dimension of in vivo microvascular constrictions (Figure 1A). A PBS solution containing 20% erythrocytes by volume was perfused through the microfluidic devices at shear rates of 30,000 to 120,000 dyne/cm2 at the microcanals. Erythrocyte deformation was observed in real-time using high speed video microscopy. To our knowledge, there are no other systems allowing for visual analysis of erythrocyte fragmentation through single micron microfluidic constrictions. Further, this microfluidic platform decouples biochemical cues from the biophysical cues being studied that lead to deformation of erythrocytes in real-time. Results: We show that increasing shear rate at lower microcanal lengths of 5 µm, 10 µm and 15 µm resulted in little or no erythrocyte fragmentation. However, increasing shear rates at microcanal lengths of 20 µm resulted in reversible burr cell formation at low shear rates, and then increased fragmentation to potential schistocyte and ghost cell formation at the highest shear rates (Figure 1B). The percentage of non-reversible erythrocyte deformation continued to rise with increased shear rate at microcanal lengths greater than 25 µm (Figure 1C). Conclusion: Our results suggest that shear rate and constriction time work synergistically to affect plastic erythrocyte deformation into a variety of abnormal morphologies typical in thrombotic microangiopathic disorders. These results align with literature findings in larger experimental systems, where increased hemolysis has been observed through increasing shear stress (Leverett et al., Biophys J., 1972) and increasing pressure when coupled with high shear rates (Yasuda et al., ASAIO Journal, 2001). We plan to further characterize the formation of schistocytes by examining the interactions between the biophysical parameter space and the biochemical parameter space in microfluidic systems. By studying how variables such as shear, compression, fibrin density, and platelet concentration affect erythrocyte fragmentation, we will find the optimal conditions for schistocyte formation. These findings will lead to an improved understanding of microangiopathic pathological processes and aid in developing diagnostic assays in the future. Disclosures No relevant conflicts of interest to declare.

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Tripathi, J. P., U. P. Singh, and B. K. Singh. "Homotopy Analysis of Circular Plates Squeeze Film Bearings Lubricated with Couple Stress Fluids: Piezo-Viscous Model." Science & Technology Journal 8, no. 2 (July 1, 2020): 95–102. http://dx.doi.org/10.22232/stj.2020.08.02.14.

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The piezo-viscous effect is crucial in fluid flows under high-pressure applications such as fluid film lubrication, microfluidics, and geophysics. We have investigated the combined influences of piezo-viscous dependence and non-Newtonian couple stresses on the performance of circular plate squeeze film bearings using Stokes Micro-Continuum theory of couple stress fluids together with the exponential variation of viscosity with pressure. A closed-form solution for film pressure has been obtained using the homotopy analysis method. The numerical results for pressure and load capacity with different values of the viscosity-pressure parameter have been calculated and compared with iso-viscous couple stress and Newtonian lubricants. An enhanced pressure and load capacity are observed in the analysis. The response time for the bearing (plate approach time) has also been calculated and a significant increase is observed.

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Farré-Lladós, Josep, Jasmina Casals-Terré, Jordi Voltas, and Lars G. Westerberg. "The use of rapid prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and μPIV." Rapid Prototyping Journal 22, no. 1 (January 18, 2016): 67–76. http://dx.doi.org/10.1108/rpj-02-2014-0019.

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Purpose – This paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (μPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 μm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes. Design/methodology/approach – The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for μPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using μPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study. Findings – This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 μm) and according to the experimental results, channels smaller than 250-μm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior. Practical implications – The present methodology is developed due to the need to validate micro-channels using μPIV to lubricate critical components (bearings and gears) in wind turbines. Originality/value – This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-μm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using μPIV.

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Luther, Sebastian K., and Andreas Braeuer. "High-pressure microfluidics for the investigation into multi-phase systems using the supercritical fluid extraction of emulsions (SFEE)." Journal of Supercritical Fluids 65 (May 2012): 78–86. http://dx.doi.org/10.1016/j.supflu.2012.02.029.

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Mutlu, Baris R., Jon F. Edd, and Mehmet Toner. "Oscillatory inertial focusing in infinite microchannels." Proceedings of the National Academy of Sciences 115, no. 30 (July 10, 2018): 7682–87. http://dx.doi.org/10.1073/pnas.1721420115.

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Inertial microfluidics (i.e., migration and focusing of particles in finite Reynolds number microchannel flows) is a passive, precise, and high-throughput method for microparticle manipulation and sorting. Therefore, it has been utilized in numerous biomedical applications including phenotypic cell screening, blood fractionation, and rare-cell isolation. Nonetheless, the applications of this technology have been limited to larger bioparticles such as blood cells, circulating tumor cells, and stem cells, because smaller particles require drastically longer channels for inertial focusing, which increases the pressure requirement and the footprint of the device to the extent that the system becomes unfeasible. Inertial manipulation of smaller bioparticles such as fungi, bacteria, viruses, and other pathogens or blood components such as platelets and exosomes is of significant interest. Here, we show that using oscillatory microfluidics, inertial focusing in practically “infinite channels” can be achieved, allowing for focusing of micron-scale (i.e. hundreds of nanometers) particles. This method enables manipulation of particles at extremely low particle Reynolds number (Rep < 0.005) flows that are otherwise unattainable by steady-flow inertial microfluidics (which has been limited to Rep > ∼10−1). Using this technique, we demonstrated that synthetic particles as small as 500 nm and a submicron bacterium, Staphylococcus aureus, can be inertially focused. Furthermore, we characterized the physics of inertial microfluidics in this newly enabled particle size and Rep range using a Peclet-like dimensionless number (α). We experimentally observed that α >> 1 is required to overcome diffusion and be able to inertially manipulate particles.

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Han, Wenbo, and Xueye Chen. "Numerical Simulation of the Droplet Formation in a T-Junction Microchannel by a Level-Set Method." Australian Journal of Chemistry 71, no. 12 (2018): 957. http://dx.doi.org/10.1071/ch18320.

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To satisfy the increasingly high demands in many applications of microfluidics, the size of the droplet needs accurate control. In this paper, a level-set method provides a useful method for studying the physical mechanism and potential mechanism of two-phase flow. A detailed three-dimensional numerical simulation of microfluidics was carried out to systematically study the generation of micro-droplets and the effective diameter of droplets with different control parameters such as the flow rate ratio, the continuous phase viscosity, the interfacial tension, and the contact angle. The effect of altering the pressure at the x coordinate of the main channel during the droplet formation was analysed. As the simulation results show, the above control parameters have a great influence on the formation of droplets and the size of the droplet. The effective droplet diameter increases when the flow rate ratio and the interfacial tension increase. It decreases when the continuous phase viscosity and the contact angle increase.

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Preiss, Felix Johannes, Teresa Dagenbach, Markus Fischer, and Heike Petra Karbstein. "Development of a Pressure Stable Inline Droplet Generator with Live Droplet Size Measurement." ChemEngineering 4, no. 4 (November 10, 2020): 60. http://dx.doi.org/10.3390/chemengineering4040060.

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For the research on droplet deformation and breakup in scaled high-pressure homogenizing units, a pressure stable inline droplet generator was developed. It consists of an optically accessible flow channel with a combination of stainless steel and glass capillaries and a 3D printed orifice. The droplet size is determined online by live image analysis. The influence of the orifice diameter, the mass flow of the continuous phase and the mass flow of the disperse phase on the droplet diameter were investigated. Furthermore, the droplet detachment mechanisms were identified. Droplet diameters with a small diameter fluctuation between 175 µm and 500 µm could be realized, which allows a precise adjustment of the capillary (Ca) and Weber (We) Number in the subsequent scaled high pressure homogenizer disruption unit. The determined influence of geometry and process parameters on the resulting droplet size and droplet detachment mechanism agreed well with the literature on microfluidics. Furthermore, droplet trajectories in an exemplary scaled high-pressure homogenizer disruption unit are presented which show that the droplets can be reinjected on a trajectory close to the center axis or close to the wall, which should result in different stresses on the droplets.

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Cromwell, Evan F., Michelle Leung, Matthew Hammer, Anthony Thai, Rashmi Rajendra, and Oksana Sirenko. "Disease Modeling with 3D Cell-Based Assays Using a Novel Flowchip System and High-Content Imaging." SLAS TECHNOLOGY: Translating Life Sciences Innovation 26, no. 3 (March 30, 2021): 237–48. http://dx.doi.org/10.1177/24726303211000688.

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There is an increasing interest in using three-dimensional (3D) cell structures for modeling tumors, organs, and tissue to accelerate translational research. We describe here a novel automated organoid assay system (the Pu·MA System) combined with microfluidic-based flowchips that can facilitate 3D cell-based assays. The flowchip is composed of sample wells, which contain organoids, connected to additional multiple wells that can hold various assay reagents. Organoids are positioned in a protected chamber in sample wells, and fluids are exchanged from side reservoirs using pressure-driven flow. Media exchange, sample staining, wash steps, and other processes can be performed without disruption to or loss of 3D sample. The bottom of the sample chamber is thin, optically clear plastic compatible with high-content imaging (HCI). The whole system can be kept in an incubator, allowing long-term cellular assays to be performed. We present two examples of use of the system for biological research. In the first example, cytotoxicity effects of anticancer drugs were evaluated on HeLa and HepG2 spheroids using HCI and vascular endothelial growth factor expression. In the second application, the flowchip system was used for the functional evaluation of Ca2+ oscillations in neurospheroids. Neurospheres were incubated with neuroactive compounds, and neuronal activity was assessed using Ca2+-sensitive dyes and fast kinetic fluorescence imaging. This novel assay system using microfluidics enables automation of 3D cell-based cultures that mimic in vivo conditions, performs multidosing protocols and multiple media exchanges, provides gentle handling of spheroids and organoids, and allows a wide range of assay detection modalities.

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Sepulveda, Julian, Agnes Montillet, Dominique Della Valle, Thanina Amiar, Hubert Ranchon, Catherine Loisel, and Alain Riaublanc. "Experimental determination and modeling of flow curves of xanthan gum solutions over a large range of shear rates." Applied Rheology 31, no. 1 (January 1, 2021): 24–38. http://dx.doi.org/10.1515/arh-2020-0116.

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Abstract The viscosities of solutions formulated with xanthan gum and xanthan gum with whey protein isolates are experimentally characterized and modeled over a wide range of shear rates [10−3 to 105 s−1]. As shown by numerous studies [1, 2], the generation of vortices in the cone-plate geometry is making viscosity measurements beyond a certain shear rate unreliable. In the present work, an innovative technique, based on microfluidics and developed by the company Formulaction, has been employed to extend to high shear rates, the viscosity flow curve obtained with a rotational rheometer. The main highlights of this study are firstly, to propose a scaling law for the inertial transition in the cone-plate geometry for different diameters and angles through the determination of the maximum shear rate at which one can expect a true viscosity value. Secondly, the high shear rate measurements allow the determination of the second Newtonian plateau for these solutions thanks to the Williams-Carreau model. An attempt for the second plateau modeling is proposed following the concept of an intrinsic viscosity in the high shear equilibrium. In the same way, other fitted parameters from the Williams-Carreau law are modeled as a function of the polymer concentration. This procedure allows to provide a predictive model for the rheological behavior of xanthan gum-based solutions used in high shear processes like high pressure homogenization, emulsification, foaming, microfluidics, etc in food, pharmaceutical or cosmetics applications.

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Wan, Jing, Chong Cheng Liang, Feng Yan, Ke Gu, Shuai Zhang, Zhi Guo Xie, and Mu Sen Lin. "Electromagnetic Drive of Room-Temperature Ionic Liquids and Application." Applied Mechanics and Materials 189 (July 2012): 374–78. http://dx.doi.org/10.4028/www.scientific.net/amm.189.374.

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Room-temperature ionic liquids are new emerging green material. They have good chemical and thermal stability, negligible vapor pressure, nonflammability, high ionic conductivity, transparence, and a wide electrochemical window. So the ionic liquid material strongly tempts many researchers. But ionic liquids are usually applied in chemistry and rarely applied in physics. In fact ionic liquids are good photoelectric medium material owing to its well ionic conductivity, transparence. However, in applications, the drive of ionic liquids is the key technic and is also a bottle-neck. Here a kind of electromagnetic drive way is presented, There are not any mechanical moving elements and the drive is bidirectional. Theory and experiments indicate the drive pressure and flow rate are distinct undering a few voltages and 0.5T magnetic flux density. So this drive way can be used as a low power liquid pump. Latency applications in Microfluidics, Optoelectronics and industry are given.

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Sathyanarayanan, Gowtham, Markus Haapala, and Tiina Sikanen. "Interfacing Digital Microfluidics with Ambient Mass Spectrometry Using SU-8 as Dielectric Layer." Micromachines 9, no. 12 (December 8, 2018): 649. http://dx.doi.org/10.3390/mi9120649.

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This work describes the interfacing of electrowetting-on-dielectric based digital microfluidic (DMF) sample preparation devices with ambient mass spectrometry (MS) via desorption atmospheric pressure photoionization (DAPPI). The DMF droplet manipulation technique was adopted to facilitate drug distribution and metabolism assays in droplet scale, while ambient mass spectrometry (MS) was exploited for the analysis of dried samples directly on the surface of the DMF device. Although ambient MS is well-established for bio- and forensic analyses directly on surfaces, its interfacing with DMF is scarce and requires careful optimization of the surface-sensitive processes, such as sample precipitation and the subsequent desorption/ionization. These technical challenges were addressed and resolved in this study by making use of the high mechanical, thermal, and chemical stability of SU-8. In our assay design, SU-8 served as the dielectric layer for DMF as well as the substrate material for DAPPI-MS. The feasibility of SU-8 based DMF devices for DAPPI-MS was demonstrated in the analysis of selected pharmaceuticals following on-chip liquid-liquid extraction or an enzymatic dealkylation reaction. The lower limits of detection were in the range of 1–10 pmol per droplet (0.25–1.0 µg/mL) for all pharmaceuticals tested.

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Oberti, Stefano, Dirk Möller, Sascha Gutmann, Adrian Neild, and Jürg Dual. "Novel sample preparation technique for protein crystal X-ray crystallographic analysis combining microfluidics and acoustic manipulation." Journal of Applied Crystallography 42, no. 4 (June 13, 2009): 636–41. http://dx.doi.org/10.1107/s0021889809019177.

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In order to perform X-ray crystallographic analysis, protein crystals are removed from their growing solution by means of a nylon loop, which is then mounted on a goniometer. As this process is repeated for a large number of crystals, there is a need for automation, especially with regard to the placement on the nylon loop. A novel technique involving the use of acoustic radiation forces and a micro-machined fluidic device is introduced here. After insertion into the micro-machined channel, the crystals are positioned in a row along its centre-line by excitation of a high-frequency standing pressure field, and then moved towards an orifice by applying a flow along the channel, which also ensures spatial separation. Once located in a defined orifice, the single crystals can be removed using a nylon loop. X-ray crystallographic analysis showed that application of ultrasound does not influence the diffraction properties of the crystals.

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Anderluzzi, Giulia, Gustavo Lou, Yang Su, and Yvonne Perrie. "Scalable Manufacturing Processes for Solid Lipid Nanoparticles." Pharmaceutical Nanotechnology 7, no. 6 (December 10, 2019): 444–59. http://dx.doi.org/10.2174/2211738507666190925112942.

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Background: Solid lipid nanoparticles offer a range of advantages as delivery systems but they are limited by effective manufacturing processes. Objective: In this study, we outline a high-throughput and scalable manufacturing process for solid lipid nanoparticles. Method: The solid lipid nanoparticles were formulated from a combination of tristearin and 1,2-Distearoyl-phosphatidylethanolamine-methyl-polyethyleneglycol conjugate-2000 and manufactured using the M-110P Microfluidizer processor (Microfluidics Inc, Westwood, Massachusetts, US). Results: The manufacturing process was optimized in terms of the number of process cycles (1 to 5) and operating pressure (20,000 to 30,000 psi). The solid lipid nanoparticles were purified using tangential flow filtration and they were characterized in terms of their size, PDI, Z-potential and protein loading. At-line particle size monitoring was also incorporated within the process. Our results demonstrate that solid lipid nanoparticles can be effectively manufactured using this process at pressures of 20,000 psi with as little as 2 process passes, with purification and removal of non-entrapped protein achieved after 12 diafiltration cycles. Furthermore, the size could be effectively monitored at-line to allow rapid process control monitoring and product validation. Conclusion: Using this method, protein-loaded solid lipid nanoparticles containing a low (1%) and high (16%) Pegylation were manufactured, purified and monitored for particle size using an at-line system demonstrating a scalable process for the manufacture of these nanoparticles.

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Kuhn, Donald E., Sashwati Roy, Jared Radtke, Sudip Gupta, and Chandan K. Sen. "Laser microdissection and pressure-catapulting technique to study gene expression in the reoxygenated myocardium." American Journal of Physiology-Heart and Circulatory Physiology 290, no. 6 (June 2006): H2625—H2632. http://dx.doi.org/10.1152/ajpheart.01346.2005.

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For focal events such as myocardial infarction, it is important to dissect infarction-induced biological responses as a function of space with respect to the infarct core. Laser microdissection pressure catapulting (LMPC) represents a recent variant of laser capture microdissection that enables robot-assisted rapid capture of catapulted tissue without direct user contact. This work represents the maiden effort to apply laser capture microdissection to study spatially resolved biological responses in myocardial infarction. Infarcted areas of the surviving ischemic-reperfused murine heart were identified using a standardized hematoxylin QS staining procedure. Standard staining techniques fail to preserve tissue RNA. Exposure of the tissue to an aqueous medium (typically used during standard immunohistochemical staining), with or without RNase inhibitors, resulted in a rapid degradation of genes, with ∼80% loss in the 1st h. Tissue elements (1 × 104–4 × 106 μm2) captured from infarcted and noninfarcted sites with micrometer-level surgical precision were collected in a chaotropic RNA lysis solution. Isolated RNA was analyzed for quality by microfluidics technology and reverse transcribed to generate high-quality cDNA. Real-time PCR analysis of the cDNA showed marked (200- and 400-fold, respectively) induction of collagen Ia and IIIa at the infarcted site compared with the noninfarcted site. This work reports a sophisticated yet rapid approach to measurement of relative gene expressions from tissue elements captured from spatially resolved microscopic regions in the heart with micrometer-level precision.

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Chin, Jit Kai. "STUDY OF LIQUID-LIQUID SLUG BREAK UP MECHANISM IN A MICROCHANNEL T-JUNCTION AT VARIOUS MODIFIED WEBER NUMBER." IIUM Engineering Journal 12, no. 2 (October 18, 2011): 111–22. http://dx.doi.org/10.31436/iiumej.v12i2.70.

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The formation of immiscible liquid droplets, or slugs, in microchannels features the advantages of volume control and mixing enhancement over single-phase microflows. Although the applications of droplet-based microfluidics have been widely demonstrated, the fundamental physics governing droplet break-up remains an area of active research. This study defines an effective Weber (Weeff) number that characterizes the interplay of interfacial tension, shear stress and channel pressure drop in driving slug formation in T-junction microchannel for a relative range of low, intermediate and high flow rates. The immiscible fluid system in this study consists of Tetradecane slug formation in Acetonitrile. The progressive deformation of slug interfaces during break-up events is observed. Experimental results indicate that, at a relatively low Weeff, clean slug break-up occurs at the intersection of the side and main channels. At intermediate Weeff, the connecting neck of the dispersed phase is stretched to a short and thin trail of laminar flow prior to breaking up a short distance downstream of the T-junction. At a relatively high Weeff, the connecting neck develops into a longer and thicker trail of laminar flow that breaks up further downstream of the main channel.

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Zhang, Xinjie, and Ayobami Elisha Oseyemi. "Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery." Micromachines 10, no. 12 (November 21, 2019): 798. http://dx.doi.org/10.3390/mi10120798.

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The microvalve for accurate flow control under low fluidic pressure is vital in cost-effective and miniaturized microfluidic devices. This paper proposes a novel microfluidic passive valve comprising of a liquid chamber, an elastic membrane, and an ellipsoidal control chamber, which actualizes a high flow rate control under an ultra-low threshold pressure. A prototype of the microvalve was fabricated by 3D printing and UV laser-cutting technologies and was tested under static and time-dependent pressure conditions. The prototype microvalve showed a nearly constant flow rate of 4.03 mL/min, with a variation of ~4.22% under the inlet liquid pressures varied from 6 kPa to 12 kPa. In addition, the microvalve could stabilize the flow rate of liquid under the time-varying sinusoidal pressures or the square wave pressures. To validate the functionality of the microvalve, the prototype microvalve was applied in a gas-driven flow system which employed an air blower or human mouth blowing as the low-cost gas source. The microvalve was demonstrated to successfully regulate the steady flow delivery in the system under the low driving pressures produced by the above gas sources. We believe that this new microfluidic passive valve will be suitable for controlling fluid flow in portable microfluidic devices or systems of wider applications.

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Gong, Jiahao, Qifu Wang, Bingxin Liu, Huimin Zhang, and Lin Gui. "A Novel On-Chip Liquid-Metal-Enabled Microvalve." Micromachines 12, no. 9 (August 30, 2021): 1051. http://dx.doi.org/10.3390/mi12091051.

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A room temperature liquid metal-based microvalve has been proposed in this work. The microvalve has the advantages of easy fabrication, high flexibility, and a low leak rate. By designing a posts array in the channel, the liquid metal can be controlled to form a deformable valve boss and block the flow path. Besides, through adjustment of the pressure applied to the liquid metal, the microvalve can perform reliable switching commands. To eliminate the problem that liquid metal is easily oxidized, which causes the microvalve to have poor repeatability, a method of electrochemical cathodic protection has been proposed, which significantly increases the number of open/close switch cycles up to 145. In addition, this microvalve overcomes the shortcomings of the traditional microvalve that requires an alignment process to assemble all the parts. When the valve is closed, no leak rate is detected at ≤320 mbar, and the leak rate is ≤0.043 μL/min at 330 mbar, which indicates it has good tightness. As an application, we also fabricate a chip that can control bubble flow based on this microvalve. Therefore, this microvalve has great prospects in the field of microfluidics.

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Yáñez, Diana, Rui D. M. Travasso, and Eugenia Corvera Poiré. "Resonances in the response of fluidic networks inherent to the cooperation between elasticity and bifurcations." Royal Society Open Science 6, no. 9 (September 25, 2019): 190661. http://dx.doi.org/10.1098/rsos.190661.

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A global response function (GRF) of an elastic network is introduced as a generalization of the response function (RF) of a rigid network, relating the average flow along the network with the pressure difference at its extremes. The GRF can be used to explore the frequency behaviour of a fluid confined in a tree-like symmetric elastic network in which vessels bifurcate into identical vessels. We study such dynamic response for elastic vessel networks containing viscous fluids. We find that the bifurcation structure, inherent to tree-like networks, qualitatively changes the dynamic response of a single elastic vessel, and gives resonances at certain frequencies. This implies that the average flow throughout the network could be enhanced if the pulsatile forcing at the network’s inlet were imposed at the resonant frequencies. The resonant behaviour comes from the cooperation between the bifurcation structure and the elasticity of the network, since the GRF has no resonances either for a single elastic vessel or for a rigid network. We have found that resonances shift to high frequencies as the system becomes more rigid. We have studied two different symmetric tree-like network morphologies and found that, while many features are independent of network morphology, particular details of the response are morphology dependent. Our results could have applications to some biophysical networks, for which the morphology could be approximated to a tree-like symmetric structure and a constant pressure at the outlet. The GRF for these networks is a characteristic of the system fluid-network, being independent of the dynamic flow (or pressure) at the network’s inlet. It might therefore represent a good quantity to differentiate healthy vasculatures from those with a medical condition. Our results could also be experimentally relevant in the design of networks engraved in microdevices, since the limit of the rigid case is almost impossible to attain with the materials used in microfluidics and the condition of constant pressure at the outlet is often given by the atmospheric pressure.

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Aadland, Reidun C., Salem Akarri, Ellinor B. Heggset, Kristin Syverud, and Ole Torsæter. "A Core Flood and Microfluidics Investigation of Nanocellulose as a Chemical Additive to Water Flooding for EOR." Nanomaterials 10, no. 7 (July 1, 2020): 1296. http://dx.doi.org/10.3390/nano10071296.

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Cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (T-CNFs) were tested as enhanced oil recovery (EOR) agents through core floods and microfluidic experiments. Both particles were mixed with low salinity water (LSW). The core floods were grouped into three parts based on the research objectives. In Part 1, secondary core flood using CNCs was compared to regular water flooding at fixed conditions, by reusing the same core plug to maintain the same pore structure. CNCs produced 5.8% of original oil in place (OOIP) more oil than LSW. For Part 2, the effect of injection scheme, temperature, and rock wettability was investigated using CNCs. The same trend was observed for the secondary floods, with CNCs performing better than their parallel experiment using LSW. Furthermore, the particles seemed to perform better under mixed-wet conditions. Additional oil (2.9–15.7% of OOIP) was produced when CNCs were injected as a tertiary EOR agent, with more incremental oil produced at high temperature. In the final part, the effect of particle type was studied. T-CNFs produced significantly more oil compared to CNCs. However, the injection of T-CNF particles resulted in a steep increase in pressure, which never stabilized. Furthermore, a filter cake was observed at the core face after the experiment was completed. Microfluidic experiments showed that both T-CNF and CNC nanofluids led to a better sweep efficiency compared to low salinity water flooding. T-CNF particles showed the ability to enhance the oil recovery by breaking up events and reducing the trapping efficiency of the porous medium. A higher flow rate resulted in lower oil recovery factors and higher remaining oil connectivity. Contact angle and interfacial tension measurements were conducted to understand the oil recovery mechanisms. CNCs altered the interfacial tension the most, while T-CNFs had the largest effect on the contact angle. However, the changes were not significant enough for them to be considered primary EOR mechanisms.

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Dieujuste, Darryl, Jia Liu, E. Du, and Ofelia A. Alvarez. "Development of a Low-Cost Electrical Impedance-Based Microflow Cytometer." Blood 134, Supplement_1 (November 13, 2019): 4665. http://dx.doi.org/10.1182/blood-2019-129068.

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Sickle Cell Disease (SCD) is a genetic condition caused by a mutated hemoglobin molecule (HbS) found in red blood cells (RBCs). HbS polymerizes in low oxygen environments and contribute to painful vaso-occlusion in patients. Laboratory diagnosis of SCD is typically made by detection of the presence of sickle cells by peripheral blood smear, and presence of HbS by electrophoresis and high-performance liquid chromatography. Recently, flow cytometry technique in companion with sickling assays has demonstrated the capability in quantitative measurements of sickle cells at single-cell level, using software algorithm for cell-imaging analysis (Van Beers et. al. American Journal of Hematology 2014), and electrical impedance (Liu et. al. Sensors and Actuators B: Chemical 2018). Here, we show a portable, cost-efficient electrical impedance-based sensor and its capability to be used in conjunction with microfluidics-based sickling assay for microflow cytometry of sickle cells. The impedance microflow cytometer is based on a commercially available integrated circuit (IC), the AD5933. Using a microcontroller and additional circuitry on a custom designed printed circuit board, we are able to produce sinusoidal signals of up to 100kHz in frequency and sample up to 200 data points per second, at a cost under $60 in materials to create. The impedance measurement range is optimized to work in companion with microfluidic chips in general. In order to measure sickle cells, the impedance microflow cytometer is used in companion with our unique Polydimethylsiloxane (PDMS) microfluidic cell sickling assay (Du et. al. PNAS 2014). Cells are suspended in phosphate buffered saline (PBS) medium and move in the microchannel using a pressure driven flow. Impedance measurement is achieved using two Ti/Au electrodes embedded in the microchannel as cells flow past the electrodes. Data is captured and made available for post processing using a customized MATLAB script. RBCs from healthy donors and SCD patients were used to demonstrate the capability of the developed system. The results showed that our system can separate between normal RBCs and sickle cells, as well as between sickled and unsickled cells. The performance in detection of sickle cells is comparable to a commercial impedance analyzer. This proof-of-concept design aims to minimize the physical space needed for cytometry as well as bring affordable and reliable cytometry results within its given limitations. Figure Disclosures Alvarez: Forma Therapeutics: Consultancy; Novartis: Consultancy.

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Wang, Weiqiang, and Rui Zhang. "Interplay of Active Stress and Driven Flow in Self-Assembled, Tumbling Active Nematics." Crystals 11, no. 9 (September 4, 2021): 1071. http://dx.doi.org/10.3390/cryst11091071.

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Lyotropic chromonic liquid crystals (LCLCs) are a special type of hierarchical material in which self-assembled molecular aggregates are responsible for the formation of liquid crystal phases. Thanks to its unusual material properties and bio compatibility, it has found wide applications including the formation of active nematic liquid crystals. Recent experiments have uncovered tumbling character of certain LCLCs. However, how tumbling behavior modifies structure and flow in driven and active nematics is poorly understood. Here, we rely on continuum simulation to study the interplay of extensile active stress and externally driven flow in a flow-tumbling nematic with a low twist modulus to mimic nematic LCLCs. We find that a spontaneous transverse flow can be developed in a flow-tumbling active nematic confined to a hybrid alignment cell when it is in log-rolling mode at sufficiently high activities. The orientation of the total spontaneous flow is tunable by tuning the active stress. We further show that activity can suppress pressure-driven flow of a flow-tumbling nematic in a planar-anchoring cell but can also promote a transition of the director field under a pressure gradient in a homeotropic-anchoring cell. Remarkably, we demonstrate that the frequency of unsteady director dynamics in a tumbling nematic under Couette flow is invariant against active stress when below a threshold activity but exhibits a discontinuous increase when above the threshold at which a complex, periodic spatiotemporal director pattern emerges. Taken together, our simulations reveal qualitative differences between flow-tumbling and flow-aligning active nematics and suggest potential applications of tumbling nematics in microfluidics.

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Cardoso, André, Raquel Pinto, Elisabete Fernandes, and Steffen Kroehnert. "Implementation of Wafer Level Packaging KOZ using SU-8 as Dielectric for the Merging of WL Fan Out to Microfluidic and Biomedical Applications." International Symposium on Microelectronics 2017, no. 1 (October 1, 2017): 000569–75. http://dx.doi.org/10.4071/isom-2017-tha34_118.

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Abstract Due to its versatility for high density, heterogeneous integration, Wafer Level Fan Out (WLFO) packaging has recently seen a tremendous growth in a broad array of applications, from telecommunications and automotive, to optical and environmental sensing, while addressing the challenges of the next big wave of the Internet of Things (IoT). In this context, WLFO is continuously being challenged to include new families of MEMS/NEMS/MOEMS sensors, low thermal budget devices and biochips with microfluidics for biomedical applications. Recent developments in WLFO technology by NANIUM [1] demonstrated the implementation of a keep-out-zone (KOZ) mechanism intended to 1st) protect sensitive sensor areas during the backend processing of WLFO wafers and 2nd) create open zones on the Re-Distribution Layers (RDL). This way, the KOZ mechanism provides a physical, direct path from the embedded device to the environment. This is a necessary feature for environment sensing (e.g., pressure) or to create optical paths free of dielectric and protected from the harsh chemistry steps of the WLFO process. This paper describes new developments on KOZ, implemented with SU-8 photoresist as a WLFO dielectric, whose application is a novelty in the WLFO platform. The use of SU-8 and the KOZ with it, addresses some gaps of the current WLFO technology towards the integration of chips with bio-sensitive areas and sensors with low thermal budget. Due to its well-known bio-compatibility and inert behavior, SU-8 can be used as a neutral dielectric to be in direct contact to target fluids (e.g., sera, blood). Also, due to its low curing temperature, SU-8 allows a very low temperature WLFO process and thus the embedding of temperature-limited devices that have been outside the WLFO realm, for example, magneto-resistive or magnetic-spin sensor chips, which degrades its performance above 160°C. More interestingly, SU-8 exhibits a particular non-conformal behavior, which creates very smooth surfaces even over the mildly rough mold compound area of a fan-out package. Adding to this, SU-8 is readily available in the market in a wide range of thicknesses, spanning from 0.5 μm to >100 μm, and further allowing multiple spin coatings to build thick layers. Thus, SU-8 can provide smooth and deep enough channels for microfluidic flow over the chip sensing areas and, at the same time, provide the necessary layer thickness discrimination for the KOZ mechanism. Combining these features, the SU-8 layers in WLFO can play the triple role of 1) RDL dielectric insulation, 2) KOZ mechanism and 3) embedded microfluidic channels as part of the RDL. In summary, besides the unprecedented use of SU-8 in WLFO packaging, KOZ implementation on SU-8 provides a true, attainable bridge between WLFO and integrated microfluidic applications, for biosensing and biomedical applications in general. Outlooking the potentialities of such a merge, a Fan-Out package can embed several chips interconnected by RDL lines, as it currently allows, and also connected by microfluidic channel for multi-point, multi-function biosensing, constituting a true Lab-on-Package, cost-effective solution. Instead of building all sensing areas and microfluidic channels over a large silicon (Si) chip, this solution builds the feed-in, feed-out areas of the microfluidic channel over the inexpensive fan-out area, minimizing the sensing chip area, with the consequent front-end cost reduction.

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Patel, Kamlesh D., Kenneth A. Peterson, and Kyle W. Hukari. "Low Temperature Cofired Ceramic Microfluidic Microsystems for High Temperature and High Pressure Applications." Journal of Microelectronics and Electronic Packaging 3, no. 3 (July 1, 2006): 152–58. http://dx.doi.org/10.4071/1551-4897-3.3.152.

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As an alternative material to glass, silicon, and plastics, Low Temperature Cofired Ceramic (LTCC) substrate technology is becoming increasingly important for enabling microfluidic microsystems and devices for integrated chemical and biological analysis. LTCC's simple fabrication method and unique ability to withstand high temperatures and high pressures make it well-suited for applications not possible with traditional materials. As part of Sandia's initiative to develop an automated sample preparation system for the μChemlab™ bioagent detector, an integrated microfluidic lyser using LTCC technology has been fabricated, which enables the use of aqueous buffers at high temperatures without boiling by using a pressurized system. Thermal lysing of bacterial spores in a flow-through microfluidic device at temperatures as high as 220°C and pressures up to 10.3 MPa (1,500 psi) represents a new method for solubilizing spore proteins for identification and analysis, eliminating the reliance on harsh chemical reducing agents for lysing. This paper will present results on the development of a microfluidic LTCC-based lyser by taking advantage of the inherent properties of LTCC substrates. Specifically, the performance and implementation of a prototype LTCC lyser for solubilizing bacterial spore proteins will be reported.

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Wang, Bao Jun, Fei Xie, Wei Wang, Wen Gang Wu, and Zhi Hong Li. "Bubble-Induced Relaxation in High-Pressure Microfluidic Systems." Key Engineering Materials 562-565 (July 2013): 581–84. http://dx.doi.org/10.4028/www.scientific.net/kem.562-565.581.

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This work reported an analysis of a noticeable relaxation phenomenon caused by undesirable air bubbles in high-pressure microfluidic systems. A model with compression of air bubble considered was established to address the experimental observed pressure relaxation. The results indicated that the dominative factors were flow rate, flow resistance and initial diameter of the trapped air bubble. Meanwhile, the calculated relaxation times in different cases provided a design guideline for high-pressure microfluidic chip to avoid the long-term pressure relaxation.

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Cheng, Xiang, Matthew D. Ooms, and David Sinton. "Biomass-to-biocrude on a chip via hydrothermal liquefaction of algae." Lab on a Chip 16, no. 2 (2016): 256–60. http://dx.doi.org/10.1039/c5lc01369k.

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Hydrothermal liquefaction uses high temperatures and pressures to break organic compounds into smaller fractions, and is considered the most promising method to convert wet microalgae feedstock to biofuel. Here, we present a microfluidic screening platform to precisely control observe, and analyze this process at high temperature and pressure.

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Journal articles on the topic 'High pressure microfluidics'

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