Browsing by Author "Ganguly, Ranjan"

Now showing 1 - 6 of 6
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    The effects of magnetic nanoparticle properties on magnetic fluid hyperthermia
    Kappiyoor, Ravi; Liangruksa, Monrudee; Ganguly, Ranjan; Puri, Ishwar K. (American Institute of Physics, 2010-11-01)
    Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material used for hyperthermia should be one that is readily produced and is nontoxic while providing sufficient heating. We examine six materials that have been considered as candidates for MFH use. Examining the heating produced by nanoparticles of these materials, barium-ferrite and cobalt-ferrite are unable to produce sufficient MFH heating, that from iron-cobalt occurs at a far too rapid rate to be safe, while fcc iron-platinum, magnetite, and maghemite are all capable of producing stable controlled heating. We simulate the heating of ferrofluid-loaded tumors containing nanoparticles of the latter three materials to determine their effects on tumor tissue. These materials are viable MFH candidates since they can produce significant heating at the tumor center yet maintain the surrounding healthy tissue interface at a relatively safe temperature. (c) 2010 American Institute of Physics. [doi:10.1063/1.3500337]
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    Field-Induced Self-Assembled Ferrofluid Aggregation in Pulsatile Flow
    Ganguly, Ranjan; Zellmer, B.; Puri, Ishwar K. (AIP Publishing, 2005-09-01)
    Ferrofluid aggregation and dispersion occurs at several length scales in pulsatile flow applications, e. g., in ferrofluidic pumps, valves, and biomedical applications such as magnetic drug targeting. Because of a yet limited understanding, ferrohydrodynamic investigations involving laboratory-scale studies in idealized geometries are of considerable use. We have injected a ferrofluid into a pulsatile host flow and produced field-induced dissolution (aggregation) using external magnets. A comparison is made with ferrofluid aggregation in a steady flow. Subsequently, the accumulation and dispersion of the ferrofluid aggregates in pulsatile flow are characterized by analyzing their size, mean position, and the flow frequency spectrum. The maximum aggregate size A(max), time to form it t(max), and the aggregate half-life t(half) are found to scale according to the relations A(max) proportional to Re-0.71, t(max) proportional to Re-2.1, and t(half) proportional to Re-2.2. While the experiments are conducted at a macroscopic length scale for useful experimental resolution, the results also enable an understanding of the micro- and mesoscale field-assisted self-assembly of magnetic nanoparticles. (c) 2005 American Institute of Physics.
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    Magnetic Microsphere-Based Mixers for Microdroplets
    Roy, T.; Sinha, Ashok; Chakraborty, Shibaji; Ganguly, Ranjan; Puri, Ishwar K. (AIP Publishing, 2009-02-01)
    While droplet-based microfluidic systems have several advantages over traditional flow-through devices, achieving adequate mixing between reagents inside droplet-based reactors remains challenging. We describe an active mixing approach based on the magnetic stirring of self-assembled chains of magnetic microspheres within the droplet as these stirrers experience a rotating magnetic field. We measure the mixing of a water-soluble dye in the droplet in terms of a dimensional mixing parameter as the field-rpm, fluid viscosity, and microsphere loading are parametrically varied. These show that the mixing rate has a maximum value at a critical Mason number that depends upon the operating conditions.
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    Numerical investigation of flow-through immunoassay in a microchannel
    Sinha, Ashok; Ganguly, Ranjan; Puri, Ishwar K. (American Institute of Physics, 2010-02-01)
    Immunomagnetic separation (IMS) is a method to isolate biomaterials from a host fluid in which specifically selected antibodies attached to magnetic particles bind with their corresponding antigens on the surface of the target biological entities. A magnet separates these entities from the fluid through magnetophoresis. The method has promising applications in microscale biosensors. We develop a comprehensive model to characterize the interaction between target species and magnetic particles in microfluidic channels. The mechanics of the separation of target nonmagnetic N particles by magnetic M particles are investigated using a particle dynamics simulation. We consider both interparticle magnetic interactions and the binding of the functionalizing strands of complementary particles. The temporal growth of a particle aggregate and the relative concentrations of M and N particles are investigated under different operating conditions. A particle aggregate first grows and then exhibits periodic washaway about a quasisteady mean size. The washaway frequency and amplitude depend on the initial fractional concentration of N particles while the aggregate size scales linearly with the dipole strength and inversely with the fluid flow rate.
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    Single Magnetic Particle Dynamics in a Microchannel
    Sinha, Ashok; Ganguly, Ranjan; De, A. K.; Puri, Ishwar K. (AIP Publishing, 2007-11-01)
    Functionalized magnetic particles are used in micrototal analysis systems since they act as magnetically steered mobile substrates in microfluidic channels, and can be collected for bioanalytical processing. Here, we examine the motion of magnetic microbeads in a microfluidic flow under the influence of a nonuniform external magnetic field and characterize their collection in terms of the magnetic field strength, particle size, magnetic susceptibility, host fluid velocity and viscosity, and the characteristic length scale. We show that the collection efficiency of a magnetic collector depends upon two dimensionless numbers that compare the magnetic and particle drag forces. (c) 2007 American Institute of Physics.
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    A Strategy for the Assembly of Three-Dimensional Mesoscopic Structures Using a Ferrofluid
    Ganguly, Ranjan; Gaind, Amit P.; Puri, Ishwar K. (AIP Publishing, 2005-05-01)
    A novel technique for the self-assembly of three-dimensional mesoscopic structures in a forced fluid flow by employing a magnetic field is described. There are advantages of using magnetic fields for this purpose: unlike many other forces, a magnetic force is effective even from a distance, permitting "action at a distance," it is also localized, and competition between the magnetic force and fluid shear enables unique self-assembled ferrofluid structures. Herein, a simulation provides insight into the possibility of using magnetic field to assemble colloidal nanoparticles into aggregates. Subsequently, a demonstration experiment is conducted to characterize the development and decay of such aggregates. The analysis provides a basis for developing effective self-assembly techniques for various engineering applications. (c) 2005 American Institute of Physics.