879 research outputs found
Continuous Magnetophoretic Separation of Blood Cells from Plasma at the Microscale
We present a method for the direct and continuous separation of red and white
blood cells from plasma at the microscale. The method is implemented in a
microfluidic system with magnetic functionality. The fluidic structure within
the microsystem consists of an inlet and a single microfluidic channel with
multiple outlets. The magnetic functionality is provided by an array of
integrated soft-magnetic elements that are embedded transverse and adjacent to
the microchannel. The elements are magnetized using an external field, and once
magnetized they produce a magnetic force on blood cells as they flow through
the microchannel. In whole blood, white blood cells (WBCs) behave as
diamagnetic microparticles, while red blood cells (RBCs) exhibit diamagnetic or
paramagnetic behavior depending on the oxygenation of their hemoglobin. We
study the motion of blood cells through the microchannel using a mathematical
model that takes into account the magnetic, fluidic and gravitational forces on
the cells. We use the model to study blood cell separation, and our analysis
indicates that the microsystem is capable of separating WBC-rich plasma,
deoxygenated RBC-rich plasma and cell-depleted plasma into respective outlets.Comment: Submitted to Journal of Applied Physic
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CFD-based, Lagrangian-Eulerian coupling approach for magnetophoretic particle capture
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.We study magnetophoretic capture of magnetic particles in microfluidic devices and present a parametric characterization for the capture efficiency. We model particle transport and capture using a computational fluid dynamic, CFD-based, Lagrangian-Eulerian approach that takes into account the
dominant particle forces and particle-fluid coupling. We introduced two dimensionless groups that characterize particle capture, one that scales the magnetic and hydrodynamic forces on the particle and
another that scales the distance to the magnetic field source. We use the model to parameterize capture efficiency with respect to the dimensionless numbers for both one-way and two-way particle-fluid coupling.
We demonstrate that for dilute suspensions, the simplified one-way coupling analysis marginally underpredicts the capture efficiency computed using the two-way fully coupled analysis.This study is financially supported from the Research Affairs at the UAE University under contract number. 01-05-7-12/10
Possible Recycling of End-of-Life Dolomite Refractories by the Production of Geopolymer-Based Composites: Experimental Investigation
Production and characterization of geopolymers prepared by mixing metakaolin, end-of-life dolomite refractories, sodium silicate solution, and sodium hydroxide solution have been performed. The as-received refractory was crumbled in order to obtain products having, respectively, 250\ua0\u3bcm, 1 mm, and 2.5\ua0mm maximum particles size. Each batch of powder was added in different proportions to a blank geopolymeric matrix. It has been observed that the addition of waste refractory reduces workability of the reference refractory-free slurry. After hardening, only the set of samples prepared with powders with maximum size of 250\ua0\u3bcm maintain integrity while the others resulted affected by the presence of fractures caused by volumetric instabilities; samples with composition R100 showed the highest compressive strength, whereas higher refractory addition lowers strength. Specific surface area appears independent by materials composition; conversely pore volume slightly increases with the addition of dolomite refractory powder. During the thermodilatometric tests all compositions display a shrinkage of about 0.1% between 170 and 400\ua0\ub0C; however, sintering starts at higher temperature (above 600\ua0\ub0C) and samples melt in the range between 650 and 750\ua0\ub0C as a function of their composition, thus showing that the resulting materials loose refractoriness with respect to both the reference geopolymer and the dolomite refractory. Graphical Abstract: [Figure not available: see fulltext.
Analysis of Particle Transport in a Magnetophoretic Microsystem
An analytical analysis is presented of the transport and capture of magnetic
micro/nano-particles in a magnetophoretic microsystem that consists of an array
of integrated soft-magnetic elements embedded beneath a microfluidic channel.
The elements, which are polarized by a bias field, produce a nonuniform field
distribution that gives rise to a force on magnetic particles within the
microchannel. The equations governing particle motion are derived using
analytical expressions for the dominant magnetic and fluidic forces. The
magnetic force is obtained using an analytical expression for the field
distribution in the microchannel combined with a linear magnetization model for
the magnetic response of particles. The theory takes into account particle size
and material properties, the bias field, the dimensions of the microchannel,
the fluid properties, and the flow velocity. The equations of motion are solved
to study particle transport and capture. The analysis indicates that the
particles exhibit an oscillatory motion as they traverse the microsystem, and
that a high capture efficiency can be obtained in practice
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