External Magnetic Force Research Articles

Tertiary amine ionic liquid incorporated Fe3O4 nanoparticles as a versatile catalyst for the Knoevenagel reaction

In order to develop a functional ionic liquid catalyst with good stability and excellent catalytic effect on the organic reactions under alkaline conditions, a magnetic nanocatalyst of tertiary amine ionic liquid incorporated Fe3O4 was prepared and applied in the Knoevenagel reaction, the catalyst exhibits good stability and excellent catalytic performance in the Knoevenagel reaction, short reaction time and excellent yields of Knoevenagel products were obtained. In addition, the catalyst can be separated rapidly under the external magnetic force and reused for 8 times without significant loss of activity. Through the activity comparison of the catalyst and the FTIR, XRD, TG, VSM, SEM, TEM, and BET analysis, the excellent catalytic effect of the catalyst may be attributed to the synergistic effect of the catalytic action of tertiary amine, ionic liquid structure and the small size and strong surface effect of nanoparticles.

Exact boundary controllability for the ideal magneto-hydrodynamic equations

We address the problem of controllability of the MHD system in a rectangular domain with a control prescribed on the side boundary. We identify a necessary and sufficient condition on the data to be null-controllable, i.e., can be driven to the zero state. We also show that the validity of this condition allows the states to be stirred to each other. If the condition is not satisfied, one can move from one state to another with the help of a simple shear external magnetic force.

Magnetic Peristaltic Ciliary Flow Regulates an Embryo Growth in the Human Fallopian Tube

The flow transport behavior in a peristaltic-ciliary fallopian tube in the human system caused by a sinusoidal pressure gradient due to magnetic lines of force has been investigated. A descriptive prototype model is established and presented in cylindrical coordinates for the fallopian tapered tubal linearly viscous fluid influenced by an external magnetic force in the human body. Under the wavelength approximation, the consequential partial differential equations governing this biological phenomenon are solved analytically. The solutions obtained are presented in modified Bessel functions of zeroth order of the first kind. Also, solutions are obtained for the velocity components along the axial and the radial directions, pressure gradient, pressure differences over a wavelength, and the stream function. The impacts of the various physical quantities of interest on the momentum transport, wavy curve patterns depicting the velocity range, and the pressure change are plotted. A comparison study of peristaltic, peristaltic-ciliary, and magnetic peristaltic-ciliary flows is also presented as a special case. Furthermore, the embryo's development in the interior of the narrow fallopian tube intramural fluid coming from the ampulla is discussed.

Uniform iron oxide nanoparticles reduce the required amount of polyethylenimine in the gene delivery to mesenchymal stem cells

Cationic polyethylenimine (PEI) is regarded as the ‘golden standard’ of non-viral gene vectors. However, the superiority of PEI with high positive charge density also induces its major drawback of cytotoxicity, which restricts its application for an effective and safe gene delivery to stem cells. To redress this shortcoming, herein, a magnetic gene complex containing uniform iron oxide nanoparticles (UIONPs), plasmid DNA, and free PEI is prepared through electrostatic interactions for the gene delivery to bone marrow-derived mesenchymal stem cells (BM-MSCs). Results show that UIONPs dramatically promote the gene delivery to BM-MSCs using the assistance of magnetic force. In addition, decreasing the free PEI nitrogen to DNA phosphate (N/P) ratio from 10 to 6 has little adverse impact on the transgene expression levels (over 300 times than that of PEI alone at the N/P ratio of 6) and significantly reduces the cytotoxicity to BM-MSCs. Further investigations confirmed that the decrease of free PEI has little influence on the cellular uptake after applying external magnetic forces, but that the reduced positive charge density decreases the cytotoxicity. The present study demonstrates that magnetic gene delivery not only contributes to the enhanced gene expression but also helps to reduce the required amount of PEI, providing a potential strategy for an efficient and safe gene delivery to stem cells.

Piezoelectric-magnetic behavior of ferroelectrets coated with magnetic layer

Electrically charged porous electret films, reported as ferroelectrets or piezoelectrets, have drawn the attention of researchers due to their high piezoelectric activity, low density, and flexibility. This paper introduces a ferroelectret design for the development of piezoelectric-magnetic responses. Samples are prepared with an additional magnetic layer placed above open tubular channels made from fused electret films, and the piezoelectric direct effect of electrically charged samples is monitored. The results of the measurements show approximately 900 pC N−1 piezoelectric coefficients d33. The piezoelectric-magnetic effect is an electrical response from a mechanical deformation caused by an external magnetic force. The magnetic field pulls the magnetic layer, mechanically deforming the electrically charged tubular structure, which creates a charge compensation to be measured as a charge density variation. A setup especially assembled for measuring the piezoelectric-magnetic response is described together with piezoelectric-magnetic values ranging from 94 up to 275 pC T−1.

Magnetization Improved Fine Particle Biochar Adsorption of Lead

ABSTRACT Biochar can be an alternative sorbent to the high cost activated carbon for wastewater treatment. Its adsorption capacity for heavy metals can be increased by magnetizing it with iron. In this study, we compared the physiochemical properties and sorption capacity of an iron-coated fine empty fruit bunch biochar (IC-EFBB) for Pb with a commercially available activated carbon (AC) and the uncoated fine empty fruit bunch biochar (EFBB). The results revealed that the AC had greater micropores surface area (671.14 m2 g−1), compared to the IC-EFBB (25.79 m2 g−1) and EFBB (2.57 m2 g−1). On the other hand, the IC-EFBB had the highest pH, and content of functional groups (OH and CO) while the EFBB had the highest total oxygen containing functional groups, CEC, and the lowest PZC. The sorption data of Pb by EFBB, IC-EFBB and AC were better fitted to the Langmuir adsorption as indicated by the R2 (1.00, 1.00 and 0.98, respectively) and RMSE values (0.009, 0.017 and 0.428, respectively). The IC-EFBB (142.86 mg g−1) had the highest adsorption capacity for Pb followed by EFBB (103.09 mg g−1) and the lowest was AC (50.51 mg g−1). The results indicated that surface area was not an important indicator for Pb sorption by the adsorbents but the amount of oxygen-containing functional groups, pH and CEC were the dominant factors. The IC-EFBB was readily separated from the aqueous solution using an external magnetic force. Therefore, it can be concluded that the IC-EFBB can be a very good alternative sorbent to remove heavy metals from wastewater.

Facile synthesis of superparamagnetic thiamine/Fe3O4 with enhanced adsorptivity toward divalent copper ions

The development of environmentally friendly adsorbents has been extensively carried out to overcome the detrimental effects of heavy metal accumulation, which has persistently become a global ecological problem. In pursuit of generating eco-friendly adsorbents, a green method for synthesizing thiamine functionalized-Fe3O4 (FT) was developed in this study. A one-step chemical oxidation and functionalization technique was used to prepare FT using the ammonia-containing solvent. A molar ratio of ammonia:Fe:thiamine of 15:1:1 was shown to produce FT15 with high yield, adsorptivity, and purity. XRD, XPS, FTIR, SEM, and SQUID characterization of FT15 revealed the formation of superparamagnetic thiamine functionalized Fe3O4 in their particles. This superparamagneticity facilitates the easy recovery of FT15 particles from the waste-containing solution by using an external magnetic force. The batch adsorption of Cu(II) onto FT15 showed the best fit with the Sips adsorption isotherm model with a maximum adsorption capacity of 426.076 mg g−1, which is 5.69-fold higher capacity than the control unmodified Fe3O4 (F15). After five adsorption-desorption cycles, the FT15 can maintain up to 1.95-fold higher capacity than the freshly synthesized F15. Observation on the physicochemical properties of the post-adsorption materials showed the contribution of an amine group, pyrimidine ring, and the thiazolium group of thiamine in boosting its adsorption capacity. This study provides important findings to advance the adsorptivity of magnetic adsorbents with promising recoverability from aqueous solution by employing naturally available and environmentally friendly compounds such as thiamine.

Numerical insights into magnetic particle enrichment and separation in an integrated droplet microfluidic system

Particle concentration and manipulation inside droplets hold great potential in expanding lab-in-a-droplet applications ranging from biological to chemical assays. Herein, we present a numerical model that provides sufficient insights into magnetic particle enrichment in an integrated microfluidic system considering the most possible interactions and forces. The proposed system comprises three distinct interconnected modules: droplet generator, spacer, and splitter with a permanent magnet placed under the splitting zone. Two approaches are developed to predict the particle trajectories inside the droplet, namely, magnetohydrophoretic streamline (static) and multi-particle tracing (dynamic). It is found that although the presence of an external magnetic force may help to improve the separation/enrichment of the magnetic particles in such microfluidic systems, however, the location of the magnet must be carefully determined to avoid the inverse effect of the magnetic field on the separation/enrichment efficiency. Moreover, the full particle enrichment is obtained at a maximum magnetic force to drag force ratio of >0.8% and a magnetophoretic velocity to the mean fluid velocity ratio of >6% for both 2.83 µm and 4.4 µm magnetic beads. The presented accurate numerical model, together with its unique features of low computational cost and broad applicability, such as separating particles with different properties, can further broaden utility in droplet microfluidics.

Simulation of magnetic nanoparticles crossing through a simplified blood-brain barrier model for Glioblastoma multiforme treatment

Background and ObjectivesGlioblastoma multiforme is considered as one of the most aggressive types of cancer, while various treatment techniques have been proposed. Magnetic nanoparticles (MNPs) loaded with drug and magnetically controlled and targeted to tissues affected by disease, is considered as a possible treatment. However, MNPs are difficult to penetrate the central nervous system and approach the unhealthy tissue, because of the blood-brain barrier (BBB). This study investigates numerically the delivery of magnetic nanoparticles through the barrier driven by normal pressure drop and external gradient magnetic fields, employing a simplified geometrical model, computational fluid dynamics and discrete element method. The goal of the study is to provide information regarding the permeability of the BBB under various conditions like the imposed forces and the shape of the domain, as a preliminary predictive tool. MethodsTo achieve that, the three-dimensional Navier-Stokes equations are solved in the margin of a blood vessel along with a discrete model for the MNPs with various acting forces. The numerical results are compared with experimental measurements showing that the model can predict acceptably the flow behavior. ResultsThe effect of nanoparticles’ size, external magnetic field and blood flow in the vessel, on the brain-barrier's permeability are investigated. Three different cases of available area among the endothelial cells per the MNPs’ size ratio are also examined, showing that the MNPs’ size and available area is not the dominant parameter affecting the permeability of the BBB. The results indicate that the applied magnetic field enhances the drug delivery into the central nervous system (CNS). When larger MNPs (∼100 nm) are exposed to an external magnetic field, the permeability can be improved up to 30%, while it is shown that smaller MNPs (∼10 nm) cannot be driven by the applied magnetic field and in this case the permeability remains relatively unchanged. Finally, the blood flow increase leads to a permeability improvement up to 15%. ConclusionsThe applied magnetic field improves up to 45% the permeability of the BBB for MNPs of 100 nm. The geometric characteristics of the endothelial cells, the nanoparticles’ size and the blood flow are not so decisive parameters for the drug delivery into the CNS, compared to the external magnetic force.

O025 Smart polymer implants as an emerging technology for treating airway collapse in obstructive sleep apnea: proof of concept

Abstract Study objectives To assess the use of a novel magnetic polymer implant in reversing airway collapse and identify potential anatomical targets for airway implant surgery in an in vivo porcine model. Methods Target sites of airway collapse were genioglossus muscle, hyoid bone, and middle constrictor muscle. Magnetic polymer implants were sutured to these sites, and external magnetic forces, through magnets with pull forces rated at 102 kg and 294 kg, were applied at the skin. The resultant airway movement was assessed via nasendoscopy. Pharyngeal plexus branches to the middle constrictor muscle were stimulated at 0.5 mA, 1.0 mA, and 2.0 mA and airway movement assessed via nasendoscopy. Results At the genioglossus muscles, large magnetic forces were required to produce airway movement. At the hyoid bone, anterior movement of the airway was noted when using a 294 kg rated magnet. At the middle constrictor muscle, an anterolateral (or rotatory) pattern of airway movement was noted when using the same magnet. Stimulation of pharyngeal plexus branches to the middle constrictor revealed contraction and increasing rigidity of the lateral walls of the airway as stimulation amplitude increased. The resultant effect was prevention of collapse as opposed to typical airway dilation, a previously unidentified pattern of airway movement. Conclusions Surgically implanted smart polymers are an emerging technology showing promise in the treatment of airway collapse in obstructive sleep apnea. Future research should investigate their biomechanical role as an adjunct to treatment of airway collapse through nerve stimulation.

Pt and ZnFe2O4 Nanoparticles Immobilized on Carbon for the Detection of Glutathione

The catalytic activity of nanozymes has attracted much attention in biochemical analyses and the antibiosis and environmental fields. However, easy aggregation and difficulty in recycling greatly result in a decrease of their catalytic activity and further restrict their practical application. Herein, we immobilized Pt and ZnFe2O4 nanoparticles on poplar-wood-derived carbon (ZnFe2O4/C), which exhibited excellent peroxidase-like activity and high affinity toward H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB). Moreover, it could be easily separated by an external magnetic force from the reaction system. A sensitive and selective colorimetric sensor for glutathione (GSH) was established based on Pt/ZnFe2O4/C nanoperoxidase. The linear range for GSH was from 1 to 30 μM, and the limit of detection for GSH was calculated as 0.38 μM. The colorimetric method was applied to determine GSH in real samples for injection.

MEMS-Based Cantilever Sensor for Simultaneous Measurement of Mass and Magnetic Moment of Magnetic Particles

This study presents a measurement approach suitable for the simultaneous determination of both the mass mp and magnetic moment µp of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an external magnetic field-induced force gradient F′(z). Magnetic induction B(z) and its second spatial derivative δ2B/δz2 is realized, beforehand, through the finite element method magnetics (FEMM) simulation with a pair of neodymium permanent magnets configured in a face-to-face arrangement. Typically, the magnets are mounted in a magnet holder assembly designed and fabricated in-house. The resulting F′ lowers the calibrated intrinsic stiffness k0 of the cantilever to k0-F′, which can, thus, be obtained from a measured resonance frequency shift of the cantilever. The magnetic moment µp per deposited particle is determined by dividing F′ by δ2B/δz2 and the number of the attached monodisperse particles given by the mass-induced frequency shift of the cantilever. For the plain iron oxide particles (250 nm) and the magnetic polystyrene particles (2 µm), we yield µp of 0.8 to 1.5 fA m2 and 11 to 19 fA m2 compared to 2 fA m2 and 33 fA m2 nominal values, respectively.

Simulation research on low frequency sound absorption of monostable metamaterials

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model. The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite element simulation results are in good agreement.

Evaluation of smartphone-integrated magnetometers in detection of safe electromagnetic devices for use near programmable shunt valves: a proof-of-concept study.

External magnetic forces can have an impact on programmable valve mechanisms and potentially alter the opening pressure. As wearable technology has begun to permeate mainstream living, there is a clear need to provide information regarding safety of these devices for use near a programmable valve (PV). The aim of this study was to evaluate the magnetic fields of reference devices using smartphone-integrated magnetometers and compare the results with published shunt tolerances. Five smartphones from different manufacturers were used to evaluate the magnetic properties of various commonly used (n = 6) and newer-generation (n = 10) devices using measurements generated from the internal smartphone magnetometers. PV tolerance testing using calibrated magnets of varying field strengths was also performed by smartphone magnetometers. All tested smartphone-integrated magnetometers had a factory sensor saturation point at around 5000 µT or 50 Gauss (G). This is well below the threshold at which a magnet can potentially deprogram a shunt, based on manufacturer reports as well as the authors' experimental data with a threshold of more than 300 G. While many of the devices did saturate the smartphone sensors at the source, the magnetic flux density of the objects decreases significantly at 2 inches. The existence of an upper limit on the magnetometers of all the smartphones used, although well below the published deprogramming threshold for modern programmable valves, does not allow us to give precise recommendations on those devices that saturate the sensor. Based on the authors' experimental data using smartphone-integrated magnetometers, they concluded that devices that measure < 40 G can be used safely close to a PV.

Controlled production of soft magnetic hydrogel beads by biosynthesis of bacterial cellulose

It describes a simple process to create soft spherical ferrogels by the biosynthesis of bacterial cellulose (BC). Gluconacetobacter xylinus forms the enclosed structure of the ferrogel, which is a hydrogel containing magnetic nanoparticles (MNPs). The core ferrogel is prepared by incorporating MNPs with cellulose nanofibers (CNFs) in culture medium and a BC shell is produced by the bacteria that moves to the medium surface. Spherical BC ferrogels (SBCFs) are fabricated by dropping the core ferrogel with bacteria on a glass surface coated with poly(tetrafluoroethylene) microbeads followed by culture for seven days. The size of the SBCFs is controlled by the external magnetic force, CNF, and MNP concentrations. The CNF immobilizes MNPs and supports the spherical structure by filling the SBCF structure. Because a highly dense BC layer is formed at the surface of the medium droplets, a unique core–shell structure of SBCF is formed.

A novel recyclable absorption material with boronate affinity

• A novel material for boron removal by reversible combination is proposed. • This material shows excellent adsorption capacity and regeneration performance. • This novel material can be separated from aqueous simply by an external magnet. During the boronic acid production process, boronic acid emission causes considerable loss of resources and water pollution. At present, adsorption is the preferred technology to treat boron pollution. Although conventional adsorbents are simple and effective, their regeneration and recovery are challenging, which hinder their wide-scale application. Considerable research efforts have been devoted to resolving the two issues mentioned above. Herein, a novel boron-adsorbing magnetic material with a cis -diol structure possessing boronate affinity was prepared. 3-Hydroxytyramine hydrochloride auto-polymerization (PDA), magnetic graphene oxide (GO) synthesis, polyethylenimine (PEI) self-assembly, and a 3,4-dihydroxyphenylpropionic acid (DHHA) covalent bonding procedure were conducted to synthesize a Fe 3 O 4 /PDA/GO/PEI/DHHA nanocomposite. This nanocomposite exhibited excellent adsorption performance and was easily recycled using an external magnetic force. The boronic acid was separated and recovered by simply adjusting the pH of the solution. The nanocomposite’s adsorption capacity reached 91.46 mg g - 1 at 30 °C with 4-formylphenylboronic acid (FPBA) as a model compound. Besides, the adsorption capacity of the nanocomposite was maintained at >89% of its original value even after five cycles. It was confirmed that the adsorption was primarily a thermochemical reaction controlled by entropy change. Thus, this novel adsorbent can be used for boron removal because it exhibits significant boronate affinity and high regeneration ability and is easy to recycle.

268 Smart polymer implants as an emerging technology for treating airway collapse in OSA: a proof of concept study

Abstract Introduction Implantable 3D printed ‘smart’ polymers are an emerging technology with potential applications in treating collapse in adult obstructive sleep apnea through mechanical airway manipulation. There is a paucity of devices that are commercially available or in research and development stage. Limited studies have investigated the use of implantable smart polymers in reversing the collapsibility of the pharyngeal airway by creating counter forces during sleep. This paper describes an application of implantable magnetic polymer technology in an in-vivo porcine model. Study Objectives: To assess the use of a novel magnetic polymer implant in reversing airway collapse and identifying potential anatomical targets for airway implant surgery in an in-vivo porcine model. Methods Target sites of airway collapse were genioglossus muscle, hyoid bone and middle constrictor. Magnetic polymer implants were sutured to these sites and external magnetic forces, through magnets with pull forces rated at 102kg and 294kg, were applied at the skin. The resultant airway movement was assessed via nasendoscopy. Pharyngeal plexus branches to the middle constrictor muscle were stimulated at 0.5mA, 1.0mA and 2.0mA and airway movement assessed via nasendoscopy. Results At the genioglossus muscles large magnetic forces were required to produce airway movement. At the hyoid bone, anterior movement of the airway was noted when using a 294kg rated magnet. At the middle constrictor muscle, an anterolateral (or rotatory) pattern of airway movement was noted when using the same magnet. Stimulation of pharyngeal plexus branches to the middle constrictor revealed contraction and increasing rigidity of the lateral walls of the airway as stimulation amplitude increased. The resultant effect was prevention of collapse, a previously unidentified pattern of airway movement. Conclusion Surgically implanted smart polymers are an emerging technology showing promise in the treatment of airway collapse in obstructive sleep apnea. Future research should investigate their biomechanical role as an adjunct to treatment of airway collapse through nerve stimulation. Support (if any) Garnett-Passe and Rodney Williams Memorial Foundation, Conjoint Grant, 2016-18.

Ferromagnetic nanoparticles synthesis and functionalization for laccase enzyme immobilization

Ferromagnetic nanomaterials can easily be separated from the reaction media by using external magnetic force. Nanoparticles are excellent supporting materials that provide large surface area with high mass transfer rate. Ferromagnetic nanoparticle considered as an ideal immobilization supporting materials of biocatalysts for easy and fast recovery. In this study, ferromagnetic iron oxide nanoparticles were synthesized and functionalized as immobilization support materials. Amino functionalization of nanoparticles was performed to improve thermal stability and enzymatic activity. XRD planes at 2θ confirmed the successful synthesis of ferromagnetic nanoparticles. FTIR spectrum used to identify amino functionalization of nanoparticles, and size and surface morphology were studied through transmission electron microscopy (TEM).

Effect of external magnetic field and friction force on the dynamic properties of a system of charged particles

The paper describes the algorithm of the method of molecular (Langevin) dynamics, the modeled system and the main parameters characterizing the system. The presented mathematical model is built for a magnetically active dusty plasma taking into account the influence of the friction force due to the presence of the environment (buffer plasma). To solve the equation of motion of dust particles, a modified numerical Verlet scheme obtained by the authors of the work was used. The mathematical model is built for a two-dimensional system, the particles of which interact using the Yukawa potential. A detailed analysis of the autocorrelation functions of velocities and their Fourier transforms of dust particles for different values ​​of the parameters of the magnetic field, coupling and friction is carried out. It was found that an increase in friction causes a decrease in the dominant peak at a fixed value of the magnetic field parameter. This peak corresponds to the combined effect of the magnetic field and strong correlations in the system; the complete disappearance of the peak corresponding to cyclotron oscillations was found when the friction force is not taking into account. It is shown that, with low friction, an increase in the magnetic field leads to a monotonic increase in the amplitude of the dominant peak and with a large value of friction, in contrast to its decrease, which is explained by us that the decay of ultrasonic waves in the medium increases with increasing frequency, however, a more detailed description of this effect may be a topic for further research. Key words: molecular dynamic method, Verlet algorithm velocity autocorrelation functions, external magnetic field, friction force

Magnetic Nanoparticle-Based Drug Delivery Approaches for Preventing and Treating Biofilms in Cystic Fibrosis

Biofilm-associated infections pose a huge burden on healthcare systems worldwide, with recurrent lung infections occurring due to the persistence of biofilm bacteria populations. In cystic fibrosis (CF), thick viscous mucus acts not only as a physical barrier, but also serves as a nidus for infection. Increased antibiotic resistance in the recent years indicates that current therapeutic strategies aimed at biofilm-associated infections are “failing”, emphasizing the need to develop new and improved drug delivery systems with higher efficacy and efficiency. Magnetic nanoparticles (MNPs) have unique and favourable properties encompassing biocompatibility, biodegradability, magnetic and heat-mediated characteristics, making them suitable drug carriers. Additionally, an external magnetic force can be applied to enhance drug delivery to target sites, acting as “nano-knives”, cutting through the bacterial biofilm layer and characteristically thick mucus in CF. In this review, we explore the multidisciplinary approach of using current and novel MNPs as vehicles of drug delivery. Although many of these offer exciting prospects for future biofilm therapeutics, there are also major challenges of this emerging field that need to be addressed.