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Xiaoyi Hu, Thomas Cubaud
Rapid layering of viscous materials in microsystems encompasses a range of hydrodynamic instabilities that facilitate mixing and emulsification processes of fluids having large differences in viscosity. We experimentally study the stability of high-viscosity stratifications made of miscible and immiscible fluid pairs in square microchannels and characterize the propagation dynamics of interfacial waves, including breaking and viscous ligament entrainment from wave crests at moderate Reynolds numbers. For large viscosity contrasts, parallel fluid streams adopt widely different velocities and provide a simple model system to probe the role of inflectional instabilities of stratified microflows in relation with classic inviscid-stability theory...
July 27, 2018: Physical Review Letters
Yong-Gyun Jung, Young-Ran Yun, Suk-Heung Song, Wook Park
Background: Pen-based devices have emerged as useful tools for measuring pH and glucose, and for fabricating microchannels and microarrays. Pen-based devices take advantage of flexible patterning, inexpensive costs, and small volumes, thereby saving time and increasing efficiency. We have developed a gradient nib marker pen device that generated simultaneously different antibiotic concentrations in bacteria antibiotic susceptibility testing (AST). Methods: The device can deposit on the target surface with the antibiotic gradient...
August 13, 2018: Journal of Korean Medical Science
Arinori Inagawa, Mao Fukuyama, Akihide Hibara, Makoto Harada, Tetsuo Okada
This paper proposes a simple and versatile method for the determination of the zeta potential of a channel wall and discusses the values measured for the surface of frozen solvents, which are not only of scientific interest but also of potential use for microfluidic platforms. The zeta potential of the solid surface is an important parameter for discussing its electrokinetic properties, the distribution and reaction of ions in an electric double layer, and the fluidic behavior in the space surrounded by the surface...
August 1, 2018: Journal of Colloid and Interface Science
Hasan Motaghi, Sima Ziyaee, Masoud Ayatollahi Mehrgardi, Abolghasem Abbasi Kajani, Abdol-Khalegh Bordbar
In the present manuscript, a closed bipolar electrode system integrated with electrochemiluminescence (ECL) detection has been introduced for sensitive diagnosis of human breast cancer cells (MCF-7). For sensitive and selective detection, the anodic pole of the bipolar electrode was modified with the AS1411 aptamer, a specific aptamer for the nucleolin, and treated by the secondary aptamer modified gold nanoparticles. The electrochemiluminescence of luminol was followed in the presence of hydrogen peroxide on the anode pole of bipolar electrode (BPE) as an analytical signal...
July 31, 2018: Biosensors & Bioelectronics
Juan M Bolivar, Donya Valikhani, Bernd Nidetzky
Continuous (flow) reactors have drawn a wave of renewed interest in biocatalysis. Many studies find that the flow reactor offers enhanced conversion efficiency. What the reported reaction intensification actually consists in, however, often remains obscure. Here, we examined a canonical microreactor design for heterogeneously catalyzed continuous biotransformations, featuring flow microchannels that contain the enzyme immobilized on their wall surface. We use glycosylations by sucrose phosphorylase to assess the potential for reaction intensification due to microscale effects...
August 9, 2018: Biotechnology Journal
Saurabh Deshpande, Phanindra Tallapragada
Size based separation and identification of particles in microfluidics through purely hydrodynamic means has gained significant interest due to a number of possible biomedical applications. Curved micro-channels, particularly spiral micro-channels with rectangular cross-section and the dynamics of particles in such channels have been extensively researched to achieve size based separation of particles. In this paper we present evidence that sheds new light on the dynamics of particles in such curved channels; that a unique particle slip velocity is associated with the focusing positions in the cross sections, which leads to a balance of forces...
August 7, 2018: Scientific Reports
Ze Zhong Wang, Matthew D Wood, Susan E Mackinnon, Shelly E Sakiyama-Elbert
BACKGROUND: One potential treatment strategy to enhance axon regeneration is transplanting Schwann Cells (SCs) that overexpress glial cell line-derived neurotrophic factor (GDNF). Unfortunately, constitutive GDNF overexpression in vivo can result in failure of regenerating axons to extend beyond the GDNF source, a phenomenon termed the "candy-store" effect. Little is known about the mechanism of this axon entrapment in vivo. NEW METHOD: We present a reproducible in vitro culture platform using a microfluidic device to model axon entrapment and investigate mechanisms by which GDNF causes axon entrapment...
August 3, 2018: Journal of Neuroscience Methods
Boyang Zhang, Benjamin Fook Lun Lai, Ruoxiao Xie, Locke Davenport Huyer, Miles Montgomery, Milica Radisic
Microengineered biomimetic systems for organ-on-a-chip or tissue engineering purposes often fail as a result of an inability to recapitulate the in vivo environment, specifically the presence of a well-defined vascular system. To address this limitation, we developed an alternative method to cultivate three-dimensional (3D) tissues by incorporating a microfabricated scaffold, termed AngioChip, with a built-in perfusable vascular network. Here, we provide a detailed protocol for fabricating the AngioChip scaffold, populating it with endothelial cells and parenchymal tissues, and applying it in organ-on-a-chip drug testing in vitro and surgical vascular anastomosis in vivo...
August 2, 2018: Nature Protocols
Benjamin J Brownlee, Meisam Bahari, John N Harb, Jonathan C Claussen, Brian D Iverson
Free-standing, vertically aligned carbon nanotubes (VACNTs) were patterned into 16 µm diameter microchannel arrays for flow-through electrochemical glucose sensing. Non-enzymatic sensing of glucose was achieved by the chemical reaction of glucose with methyl viologen (MV) at an elevated temperature and pH (0.1 M NaOH), followed by the electrochemical reaction of reduced-MV with the VACNT surface. The MV sensor required no functionalization (including no metal) and was able to produce on average 3.4 electrons per glucose molecule...
August 1, 2018: ACS Applied Materials & Interfaces
I Ferrer, M Vives-Mestres, A Manresa, M L Garcia-Romeu
Ultrasonic molding is a new technology for processing small and micro polymeric components with reasonable cost and energy savings when small and medium batch sizes are required. However, when microcomponents are manufactured, the replicability of different micro features has to be guaranteed. The aim is to investigate the capability of ultrasonic molding technology for processing thin-wall plates of polystyrene with a microchannel, analyzing the filling behavior, the optical transparency, and the dimensional accuracy of the thin plate...
July 30, 2018: Materials
Emmy Luu, Kevin B Ita, Matthew J Morra, Inna E Popova
It is well documented in the scientific literature that high blood pressure can lead to cardiovascular disease. Untreated hypertension has clinical consequences such as coronary artery disease, stroke or kidney failure. Diltiazem hydrochloride (DH), a calcium-channel blocker, and perindopril erbumine (PE), an inhibitor of the angiotensin converting enzyme are used for the management of hypertension. This project will examine the effect of microneedle rollers on the transport of DH and PE across pig ear skin...
July 30, 2018: Current Drug Delivery
Xiao Zhao, Xinfang Li, Peng Zhang, Jianwei Du, Youxiang Wang
5-Aminolevulinic acid (ALA) based photodynamic therapy (PDT) is a modality for the treatment of cancers. However, due to its hydrophilicity and zwitterionic nature, the transdermal delivery of ALA is limited for the PDT of subcutaneous tumor. To address this problem, tip-loaded fast-dissolving microneedles made of sodium hyaluronate (HA) were fabricated by two casting method. 122 μg of ALA was loaded per microneedle patch and mainly distributed in the tips, which could improve the utilization of drug and avoid the waste of drug residue in the base of microneedle patch after use...
July 26, 2018: Journal of Controlled Release: Official Journal of the Controlled Release Society
Xiaohe Ren, Ziyi Yu, Yuchao Wu, Ji Liu, Chris Abell, Oren A Scherman
Catalytic microreactors manufactured using microfluidic devices have received significant research interest in recent years. However, little attention has been paid to immobilising metallic nanoparticles (NPs) onto microchannel walls for high efficiency catalytic reactions. We demonstrate a facile preparation of cucurbit[7]uril-based catalytic microreactors, where metallic NPs are immobilised onto microchannels via supramolecular complexation with methyl viologen@cucurbit[7]uril (CB[7]). These microreactors exhibit a remarkable catalytic activity owing to the substantially high surface area to volume ratio of the microchannels and metallic NPs...
July 27, 2018: Nanoscale
Matthew R DeWitt, M Nichole Rylander
This chapter describes the motivation and protocol for creating a perfused 3D microfluidic in vitro platform representative of the tumor microenvironment to study nanoparticle transport. The cylindrical vascularized tumor platform described consists of a central endothelialized microchannel surrounded by a collagen hydrogel matrix containing cancer cells. This system can be employed to investigate key nanoparticle transport events in the tumor such as extravasation, diffusion within the extracellular matrix, and nanoparticle uptake...
2018: Methods in Molecular Biology
Wei Zheng, Richeng Lin, Zhaojun Zhang, Feng Huang
Over the past twenty years, the astro- and solar-physicists have been working hard to develop a new-generation semiconductor-based vacuum ultraviolet (VUV, 100-200 nm) photodetector with small size and low-power consumption, in order to replace the traditional microchannel detection system which is ponderous and has high energy consumption and finally to reduce the power load and launch costs of explorer satellites. However, this expectation has hardly been achieved due to the relatively low photoresponsivity and external-quantum-efficiency (EQE) of the reported VUV photoconductive detectors based on traditional wide-bandgap materials and structures...
July 25, 2018: ACS Applied Materials & Interfaces
Yeong Jun Yu, Young Hye Kim, Kyuhwan Na, Seo Yun Min, Ok Kyung Hwang, Da Kyeong Park, Doo Yeon Kim, Se Hoon Choi, Roger D Kamm, Seok Chung, Jeong Ah Kim
The microfluidic 3D cell culture system has been an attractive model because it mimics the tissue and disease model, thereby expanding our ability to control the local cellular microenvironment. However, these systems still have limited value as quantitative assay tools due to the difficulties associated with the manipulation and maintenance of microfluidic cells, and their lack of compatibility with the high-throughput screening (HTS) analysis system. In this study, we suggest a microchannel-free, 3D cell culture system that has a hydrogel-incorporating unit integrated with a multi-well plate (24- to 96-well plate), which can provide better reproducibility in biological experiments...
July 25, 2018: Lab on a Chip
Omer Atasi, Benoit Haut, Annaig Pedrono, Benoit Scheid, Dominique Legendre
In this study, we investigate, using direct numerical simulation, the motion of a small bubble in a horizontal microchannel filled with a liquid containing surfactants. In particular, we study the combined effect of surfactants and bubble deformability on the bubble shape, the bubble-liquid relative velocity, the velocity field in the liquid, the liquid velocity on the gas-liquid interface and the surfactant distribution on the interface. The Level-Set method is used to capture the gas-liquid interface. The surfactant transport equation on the gas-liquid interface is solved in an Eulerian framework and is coupled to an equation describing the transport of surfactants inside the liquid phase...
July 24, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Wang Xi, Surabhi Sonam, Chwee Teck Lim, Benoit Ladoux
Epithelial cells demonstrate different collective migratory modes when encountering two (2D) and three dimensional (3D) microenvironment. While planar micropatterns and constraint have been shown to strongly impact collective cell migration (CCM), how out-of-plane curvature and 3D confinement will affect epithelial organization and dynamics remains largely unknown. This is likely due to lack of proper 3D microscaffolds for studying CCM. In this chapter, we briefly review the latest achievement in microengineering approaches to control 3D microenvironment of epithelial development...
2018: Methods in Cell Biology
Xinran Lu, Anwesha Chaudhury, John M Higgins, David K Wood
Although homozygous sickle cell disease is often clinically severe, the corresponding heterozygous state, sickle cell trait, is almost completely benign despite the fact that there is only a modest difference in sickle hemoglobin levels between the two conditions. In both conditions, hypoxia can lead polymerization of sickle hemoglobin, changes in red cell mechanical properties, and impaired blood flow. Here, we test the hypothesis that differences in the oxygen-dependent rheological properties in the two conditions might help explain the difference in clinical phenotypes...
July 23, 2018: American Journal of Hematology
Davar Ali, Sadri Sen
In this work, we investigated surface roughness effects on bone scaffold permeability and fluid flow-induced wall shear stress (WSS) using computational fluid dynamics (CFD) analysis. Scaffolds are made of interconnected microchannels, whose fluid flow can be examined from the perspective of fluid flow dynamics. Given that the roughness of microchannel surfaces serves a non-negligible function in the fluid dynamics within the channels, it is believed that the wall roughness of scaffolds can play an important role in their permeability and WSS...
July 20, 2018: Annals of Biomedical Engineering
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