Papers by Keyword: Magnetic Particles

Abstract: In this paper, we report the effects of fractional relaxation time on the parameters of blood flow together with magnetic particles through straight circular cylindrical arterial segment. A mathematical model of blood flow subject to pulsatile pressure gradient in the axial direction with external magnetic field applied normal to the direction of flow is presented. Combining the momentum equation together with the Maxwell model parameter appropriately, leads to the governing fractional partial differential equation which permits to obtain the velocity profile of blood along with magnetic particles. By adopting the non-dimensionalized form of the new version of the governing fractional partial differential equation allowed us to obtain the dimensionless relaxation time parameter λ₁ which controls blood flow conditions. Solving the fractional partial differential equations using Laplace and finite Hankel transforms we found that the influence of the order of Caputo's fractional time-derivative and fractional relaxation time on the blood flow parameters with magnetic particles are enormous. The graphical results plotted of different influential parameters are presented and discussed in details. The velocities of blood flow and that of magnetic particles are reduced under the influence of the external magnetic field and the relaxation time parameter. The magnetic particles are assumed to be uniformly distributed within the blood, since they are flowing in the same axial direction designated by along a circular cylindrical coordinates of radius. This is a very good indication that blood velocity can be controlled by the application of external magnetic field as well as the relaxation time parameter during treatment to avoid tissues damage. The present study has important applications in magnetic field control of biotechnological processes, bio magnetic device technology, biomedical engineering and pathology. Keywords: Arterial segment, Blood flow, Relaxation time, Magnetic field, Magnetic particles

Abstract: In this study, liquid natural rubber (LNR) toughened polylactic acid (PLA) incorporated with magnetite (Fe₃O₄) nanocomposites were fabricated via melt-compounding in an internal mixer and followed by hot/cold pressing. The effects of ultrasonic treatment time (1-3 hours) and Fe₃O₄ (0.5-4.0 wt%) nanoparticles loading on tensile, morphology and thermal stability were investigated. Based on tensile testing results, the ultrasonication time of 1 hour was served as the most suitable treatment period to achieve the optimum distribution of Fe₃O₄ within PLA/LNR matrix. Among the investigated nanoparticles loading, 1 wt% Fe₃O₄ nanocomposite presented the highest tensile strength of 23.7 MPa, Young’s modulus of 1293.5 MPa and strain at break of 2.8%. SEM micrographs showed that the over-treated nanocomposites with 2-3 hours and over-high nanoparticles loading had resulted in the formation of clusters in the matrix. With increasing Fe₃O₄ loading, the decomposition of PLA/LNR nanocomposites was initiated earlier.

Abstract: In recent decades the application of magnetic iron oxide micro-and nanoparticles has been established in various technological fields, such as magnetic separation of biomolecules and ions, biosensors, biofuel production and others [1-4]. Working with iron oxide particles is becoming main stream subject thanks to the facility that this kind of materials can be functionalized with a variety of chemical groups which confer them specific selective or catalytic properties [5]. Furthermore, iron oxide nanoparticles present magnetic properties, and in particular super-paramagnetism, which allows to remotely control them making their manipulation easy and cost-effective [6]. In addition, a new method of synthesis has been recently proposed, which can guarantee a cost-effective production of magnetic particles that may further reduce the running cost of separation methods based on magnetism [7]. Nevertheless, biotechnological applications of iron oxide particles are still confined to research level (lab scale devices) or for low throughput clinical applications [8,9]. Indeed, most systems based on the use of magnetic elements are design to work with microfluid dynamic or are able to process samples in bath-based fashion, therefore discontinuously. The need of robust and high-productive methods is demanded especially in bioscience where, independently from the reaction or process involving magnetic particles, once such composite materials are mixed or added to a given solution, inevitably at the end of workflow they must be separated/harvested from the reaction vessel. Therefore, it is vital for a good productivity and processivity of reactions involving magnetic particles to ensure that large volumes of solution can be treated, and magnetic particles withdrew in the most fast and accurate way. The purpose of this paper is to compare an open and a closed type magnetic trapping system regarding their efficiency using two different types of magnetic sources.

Abstract: To resolve the problem of weak magnetic field strength of magnetic materials in wastewater treatment, the methods of preparation of magnetic particles was explored. The main influencing factors of magnetic field strength were investigated using single factor experiment. Results suggested that optimal preparation conditions were as follows: 2% silane coupling agent, 12% PVA/ SA, magnetizing time 1 h, and 5% nano Fe₃O₄ powder. Magnetic particles were prepared based on the optimal conditions and the magnetic field strength was 0.85mT.

Abstract: Composite lightweight materials based on a polymeric matrix with embedded magnetic micro-particles have been developed. The application of a magnetic field (MF) during the foaming of samples induced the alignment of magnetic particles along the MF lines, forming reinforcing chain-like structures. The presence of aligned micro-particles imparted an anisotropic mechanical behavior along the particle alignment direction, thus strongly improving mechanical stiffness and strength compared to randomly filled systems. The application of a MF on pre-strained samples during the magneto-mechanical characterization resulted in a direct relationship between the measured variation of the elastic modulus of the foam and the time dependent intensity of the applied MF (also for a magnetic field strength as low as 200 kA/m). In particular, all reinforced samples pre-strained in the linear elastic region of the stress-strain curve exhibited a magneto-strictive response (negative variation of the measured stress). On the contrary, a positive variation of the measured stress (strengthening effect) was detected in samples with aligned particles at pre-strains above the yield point. This behavior has been related to the tendency of chain-like aggregates in buckled cell edges to re-align along the MF lines.

Abstract: There is presented an effect of the changes of the concentration of magnetic particles included in the ferrooil on the dynamic viscosity in the presence of external magnetic field in this paper. The study was conducted in the context of temperature’s changes. In that way, the influence of external physical conditions of ferrooil’s employment was also taken into account. Ferrooil’s dynamic viscosity changes significantly alter the tribological properties and thus its usefulness as a lubricant of the sliding journal bearings. Due to the fact that the ferrooil demonstrates strong magnetic polarity in the presence of an external magnetic field, it is possible to control the viscosity by means of an external magnetic field just by changing the intensity as well as by changing of the concentration of magnetic particles.The paper presents, in the form of graphs, the changes of ferrooil’s dynamic viscosity as a function of temperature and concentration of magnetic particles. The results of research were also subjected to analysis.

Abstract: Flexible magnetic nanoparticles decorated with dialdehyde starch (DAS) were developed and used as a novel enzyme support for the covalent conjugation of papain. The analyses of Fourier transform infrared (FTIR) spectroscopy confirmed the preparation of magnetic particles with flexible long molecular chains on their surfaces and conjugation of papain with the Fe3O4-DAS nanoparticles. Considering that the immobilized papain was found to exhibit better tolerance to the variations of temperature and medium pH, an advantage of easy to magnetic separation and lack of negative effect on biological activity, the kind of flexible magnetic bioconjugate support should be a good immobilized enzyme carrier, and has potential application in textile, leather, food industries.

Abstract: Themagnetic particles in magneto-rheological fluid should have high coercivity,low proportion, and higher stability in a large temperature range. Based onthese, the article summarizes the characteristics, the development process andvarious physical and chemical preparation methods of magnetic particles, andpoints out the existing problems, and looks forward to the development trend ofpreparation methods, structure and property mechanism of magnetic particles.

Abstract: In this paper we research the process of magnetization of iron-containing coatings obtained on aluminum and titanium plasma electrolytic oxidation. It is shown that the formation of a remnant magnetic moment mainly determined by the magnetostatic interaction particles (phases). This interaction leads to a decrease of the blocking volume of particles (phases). Thus, a large number of superparamagnetic particles (phases) obtain stable magnetic moments and are involved in creating of the remnant magnetization of the sample.

Abstract: This paper presents the design and testing of an integrated micro-chip for the controlled trapping and detection of magnetic particles (MPs). A unique magnetic micro-actuator consisting of square-shaped conductors is used to manipulate the MPs towards a giant magnetoresistance (GMR) sensing element which rapidly detects the majority of MPs trapped around the square-shaped conductors. The ability to precisely transport a small number of MPs in a controlled manner over long distances by magnetic forces enables the rapid concentration of a majority of MPs to the sensing zone for detection. This is especially important in low concentration samples. The conductors are designed in such a manner so as to increase the capture efficiency as well as the precision and speed of transportation. By switching current to different conductors, MPs can be manipulated and immobilized on the innermost conductor where the GMR sensor is located. This technique rapidly guides the MPs towards the sensing zone. Secondly, for optimum measurement capability with high spatial resolution the GMR sensor is fabricated directly underneath and all along the innermost conductor to detect the stray fields originating from the MPs. Finally, a microfluidic channel is fabricated on top of this micro-chip. Experiments inside the microchannel were carried out and the MPs were successfully trapped at the sensing area.