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排序方式: 共有282条查询结果,搜索用时 15 毫秒
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C.J. Campbell S.K. Smoukov K.J.M. Bishop E. Baker B.A. Grzybowski 《Advanced materials (Deerfield Beach, Fla.)》2006,18(15)
The inside cover shows a hexagonal array of convex microlenses etched directly into glass using a reaction‐diffusion process initiated from a hydrogel stamp. The technique, reported by Grzybowski and co‐workers on p. 2004, allows for direct printing of complex microarchitectures into a variety of materials with sub‐micrometer resolution. The images were generated by longtime exposure of slowly rotating patterns. Cover design by Christopher J. Campbell. 相似文献
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Investigation of viscosity effect on droplet formation in T-shaped microchannels by numerical and analytical methods 总被引:1,自引:1,他引:0
Both numerical and analytical models have been developed to explore the viscosity effect of the continuous phase on drop formation
at a T-shaped junction in immiscible liquids. The effects of the generalized power law coefficient, the power law exponent
and the yield stress on the mechanism of drop breakup, final drop size and frequency of drop formation are studied by using
the numerical three-dimensional volume of fluid model. Droplets coalescence in Bingham fluids is observed in the beginning
transient period. The effect of yield stress on drop extension is also discussed. Predictions of drop size by using an analytical
force balance show satisfactory agreement with simulation results for Newtonian and power law fluids with different viscosity
ratios. The approximation error associated with the analytical model for Bingham fluids is also acceptable. This analytical
model can greatly shorten the prediction time as compared with the numerical model, which is helpful for on-line control. 相似文献
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In this paper, we report a microfluidic chip containing a cross-junction channel for the manipulation of UV-photopolymerized
microparticles. Hydrodynamic-focusing is used to form a series of using 365 nm UV light to solidify the hydrogel droplets.
We were able to control the size of the hydrogel droplets from 75 to 300 μm in diameter by altering the sample and by changing
the flow rate ratio of the mineral oil in the center inlet channel to that of the side inlet channels. We found that the size
of the emulsions increases with an increase in average velocity of the dispersed phase flow (polymer solution flow). The size
of the emulsions decreases with an average velocity increase of the continuous phase flow (mineral oil flow). Experimental
data show that the emulsions are very uniform. The developed microfluidic chip has the advantages of ease of fabrication,
low cost, and high throughput. The emulsions generated are very uniform and have good regularity. 相似文献
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Lung-Ming Fu Jing-Hui Wang Wen-Bo Luo Che-Hsin Lin 《Microfluidics and nanofluidics》2009,6(4):499-507
This paper presents a detection scheme for analyzing the temperature distribution nearby the channel wall in a microfluidic
chip utilizing a temperature-dependent fluorescence dye. An advanced optical microscope system—total internal reflection fluorescence
microscope (TIRFM) is used for measuring the temperature distribution on the channel wall at the point of electroosmotic flow
in an electrokinetically driven microfluidic chip. In order to meet the short working distance of the objective type TIRFM
scheme, microscope cover glass slits are used to fabricate the microfluidic chips. The short fluorescence excitation depth
from a TIRFM system makes the intensity information obtained using TIRFM is not sensitive to the channel depth variation which
ususally biases the measured results while using a conventional Epi-fluorescence microscope (EPI-FM). Therefore, a TIRFM can
precisely describe the temperature profile of the distance within 100 nm of the channel wall where consists of the Stern layer
and the diffusion layer for an electrokinetic microfluidic system. Results indicate the proposed TIRFM provides higher measurement
sensitivity over the EPI-FM. Significant temperature gradient along the channel depth is experimentally observed. In addition,
the measured wall temperature distributions can be the boundary conditions for numerical investigation into the joule heating
effect. The proposed method gives a precise temperature profile of microfluidic channels and shows the substantial impact
on developing a numerical simulation model for precisely predicting the joule heating effect in microfluidic chips. 相似文献
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Particle migration is a relevant transport mechanism whenever suspensions flow in channels with gap size comparable to particle dimensions (e.g. microfluidic devices). Several theoretical as well as experimental studies have been performed on this topic, showing that the occurring of this phenomenon and the migration direction are related to particle size, flow rate, and the nature of the suspending liquid.In this work we perform a systematic analysis on the migration of a single particle in a sheared viscoelastic fluid through 2D finite element simulations in a Couette planar geometry. To focus on the effects of viscoelasticity alone, inertia is neglected. The suspending medium is modeled as a Giesekus fluid.An ALE particle mover is combined with a DEVSS/SUPG formulation with a log-representation of the conformation tensor giving stable and convergent results up to high flow rates. To optimize the computational effort and reduce the remeshing and projection steps, needed as soon as the mesh becomes too distorted, a ‘backprojection’ of the flow fields is performed, through which the particle in fact moves along the cross-streamline direction only, and the mesh distortion is hence drastically reduced.Our results, in agreement with recent experimental data, show a migration towards the closest walls, regardless of the fluid and geometrical parameters. The phenomenon is enhanced by the fluid elasticity, the shear thinning and strong confinements. The migration velocity trends show the existence of a master curve governing the particle dynamics in the whole channel. Three different regimes experienced by the particle are recognized, related to the particle-wall distance. The existence of a unique migration behavior and its qualitative aspects do not change by varying the fluid parameters or the particle size. 相似文献
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Mihaela Carp Raluca Müller Loredana Draghiciu Rodica Voicu Mihai DanilaAuthor vitae 《Sensors and actuators. A, Physical》2011,171(1):26-33
Ferrous chloride has a variety of applications such as a reducing flocculation agent in waste-water treatment, especially for wastes containing chromate, in the laboratory synthesis of iron complexes and it is employed as a reducing agent in many organic syntheses. The device used for experiment was fabricated on the silicon wafer as support for two electrodes in a SU8 polymer microchannel with an inlet, for the injection of aqueous solution of ferrous chloride, and two outlets, for the two by-products of separated solutions. The various parameters of the device were measured by White Light Interferometer (WLI) and Scanning Electron Microscopy (SEM). The magnetic field created by applying different types of potential between two electrodes determined ferrous chloride to separate in ferrous oxide and chlorine (in gaseous form). If a protein is added in this solution we have the possibility to immobilize the protein on the iron particles and on the channel area. The electrical results were collected using a semiconductor system analyzer Keithley and were examined subsequently. The Fe complexes deposited on the electrodes were characterized by XRD analyses. 相似文献
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In this paper we apply the direct non-equilibrium molecular dynamics technique to oscillatory flows of fluids in microscopic channels. Initially, we show that the microscopic simulations resemble the macroscopic predictions based on the Navier–Stokes equation very well for large channel width, high density and low temperature. Further simulations for high temperature and low density show that the non-slip boundary condition traditionally used in the macroscopic equation is greatly compromised when the fluid–wall interactions are the same as the fluid–fluid interactions. Simulations of a system with very narrow channel width confirm earlier findings of Poiseuille flow, namely, that the velocity profiles are modulated. We find that these modulations cannot be explained by the local area density model.
相似文献
Jesper S. HansenEmail: |
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