Use Of Magnetic Force Research Articles

The Evolving Use of Magnets in Surgery: Biomedical Considerations and a Review of Their Current Applications.

The novel use of magnetic force to optimize modern surgical techniques originated in the 1970s. Since then, magnets have been utilized as an adjunct or alternative to a wide array of existing surgical procedures, ranging from gastrointestinal to vascular surgery. As the use of magnets in surgery continues to grow, the body of knowledge on magnetic surgical devices from preclinical development to clinical implementation has expanded significantly; however, the current magnetic surgical devices can be organized based on their core function: serving as a guidance system, creating a new connection, recreating a physiologic function, or utilization of an internal-external paired magnet system. The purpose of this article is to discuss the biomedical considerations during magnetic device development and review the current surgical applications of magnetic devices.

Identification of the Position of a Tethered Delivery Catheter to Retrieve an Untethered Magnetic Robot in a Vascular Environment.

In this paper, we propose a method of identifying the position of a tethered delivery catheter in a vascular environment, recombining an untethered magnetic robot (UMR) to the tethered delivery catheter, and safely retrieving them from the vascular environment in an endovascular intervention by utilizing a separable and recombinable magnetic robot (SRMR) and a magnetic navigation system (MNS). From images of a blood vessel and a tethered delivery catheter taken from two different angles, we developed a method of extracting the position of the delivery catheter in the blood vessel by introducing dimensionless cross-sectional coordinates. Then, we propose a retrieval method for the UMR by using the magnetic force considering the delivery catheter's position, suction force, and rotating magnetic field. We used thane MNS and feeding robot to simultaneously apply magnetic force and suction force to the UMR. In this process, we determined a current solution for generating magnetic force by using a linear optimization method. Finally, we conducted in vitro and in vivo experiments to verify the proposed method. In the in vitro experiment, which was in a glass tube environment, by using an RGB camera, we confirmed that the location of the delivery catheter in the glass tube could be recognized within an average error of 0.05 mm in each of the X- and Z-coordinates and that the retrieval success rate was greatly improved in comparison with that in the case without the use of magnetic force. In an in vivo experiment, we successfully retrieved the UMR in the femoral arteries of pigs.

Using Magnetic Field to Measure Detachment Force between a Nonmagnetic Droplet and Fibers

The ability to predict and/or measure the force needed to detach a droplet from a fiber (or an assembly of fibers) is important in designing efficient droplet?air or droplet?fluid separation media for a variety of applications. This paper reports on the use of magnetic force to measure the force of detachment for nonmagnetic droplets for the first time. This is accomplished by adding a small amount of ferrofluid (the secondary fluid) to the original nonmagnetic droplet (the primary fluid) to create a compound droplet with the ferrofluid nesting inside or cloaking the nonmagnetic droplet. Either way, the secondary ferrofluid can be used to induce a body force to the resulting compound droplet and thereby detach it from the fiber(s). The recorded detachment force can be used directly (the case of nesting ferrofluid) or after scaling (the case of cloaking ferrofluid) to obtain the force of detachment for the original nonmagnetic droplet. The novelty of the proposed method lies in the fact that it circumvents the need for using an external object, an airflow, or a centrifugal device for force measurement. The accuracy of our measurements was examined through comparison with validated numerical simulations as well as experimental data in the literature and good agreement was observed.

On the use of high-gradient magnetic force field in capturing airborne particles

Airborne particles in the environment are generally smaller than a couple of microns. Use of magnetic force to collect aerosol particles thus has not been popular as the other means. There are billions of airborne particles emitted by a host of man-made sources with the particle size smaller than 1 µm and possess some magnetic susceptibility. We are thus interested in the use of high-gradient magnetic collection to extract the magnetic fraction in an aerosol population. In this study, we reported that the magnetic force is the dominant force in collection of ferromagnetic particles of mobility equivalent size larger than or equal to 50 nm in a high-gradient permanent-magnetic aerosol collector, while the diffusiophoretic force is responsible for particles smaller than 10 nm. Both forces compete for particles in between these two sizes in the magnetic aerosol collector designed for this study. To enable a wide-range effective collection of aerosol particles across entire size spectrum from a few nanometers to tens of a micron, the ORNL-designed high-gradient magnetic collector would require the use of an engineered matrix. Thus, the matrix design for a specific application becomes application specific. Irrespective of the collection efficiency, the use of permanent magnets to collect magnetic particles is feasible and also highly selective because it tunes into the magnetic susceptibility of the particles as well as the size. Lastly, the use of permanent magnets enables the collector to be operated at a minimal power requirement, which is a critical factor in long-term field operation.

Magnetic conditioning of sulfide minerals to improve recovery of fines in flotation � a plant practice

In flotation practices, as particles become finer, such as smaller than 20 µm, process efficiency declines markedly. Selective agglomeration of fine particles is a technique to enhance the recovery of fine valuable minerals in flotation circuits. Different agglomerating methods have been introduced and tested. One method that has recently received much attention is to make use of magnetic force to aggregate fine particles. A selective aggregation of fine paramagnetic particles, such as sulfide minerals, can be achieved in the high-intensity magnetic field prior to or during flotation. The method is simple, selective and effective for fine particles and has low operational cost, though a minimum magnetic susceptibility for fine grains is required to promote the process. In this paper, the implementation of the ProFlote magnetic conditioning device in Boliden’s Garpenberg old concentrator in Sweden, where a complex massive sulfide ore is treated, is presented and discussed based on Boliden’s Garpenberg plant. The results showed an increase in the flotation recovery of fine valuable minerals. Zinc (Zn) production was increased by between 1,100 and 1,500 t/a, while salable yearly silver (Ag) production was increased by 1,500 kg. The copper (Cu) grade in the final concentrate was increased by 1 percent, while reductions in its Zn and lead (Pb) grades were obtained. Moreover, considerable reduction in Zn deportment to the final tail was observed.

Systemic delivery and activation of the TRAIL gene in lungs, with magnetic nanoparticles of chitosan controlled by an external magnetic field.

Recently, functional therapies targeting a specific organ without affecting normal tissues have been designed. The use of magnetic force to reach this goal is studied in this work. Previously, we demonstrated that nanocarriers based on magnetic nanoparticles could be directed and retained in the lungs, with their gene expression under the control of a promoter activated by a magnetic field. Magnetic nanoparticles containing the TRAIL gene and chitosan were constructed using the ionic gelation method as a nanosystem for magnetofection and were characterized by microscopy, ζ-potential, and retention analysis. Magnetofection in the mouse melanoma cell line B16F10 in vitro induced TRAIL-protein expression and was associated with morphological changes indicative of apoptosis. Systemic administration of the nanosystem in the tail vein of mice with melanoma B16F10 at the lungs produced a very significant increase in apoptosis in tumoral cells that correlated with the number of melanoma tumor foci observed in the lungs. The high levels of apoptosis detected in the lungs were partially related to mouse survival. The data presented demonstrate that the magnetofection nanosystem described here efficiently induces apoptosis and growth inhibition of melanoma B16F10 in the lungs. This new approach for systemic delivery and activation of a gene based in a nanocomplex offers a potential application in magnetic gene delivery for cancer.

Paper-Based Sensor for Electrochemical Detection of Silver Nanoparticle Labels by Galvanic Exchange

Here we report a three-dimensional paper fluidic device configured for electrochemical detection of biomolecules labeled with silver nanoparticles (AgNPs). This new sensor, which we call a NoSlip, represents a major improvement of our previously reported oSlip system. Specifically, detection of AgNPs in the NoSlip is based on galvanic exchange rather than a chemical oxidant (bleach or MnO4– in the oSlip). Galvanic exchange is implemented by depositing a very small amount of gold onto the working electrode. Once the AgNP labels are brought into the proximity of the electrode through the use of magnetic force, a fraction of the Au0 is electrochemically oxidized to Au3+. The Au3+ reacts with the AgNPs to form Ag+ and Au0. The Ag+ is then detected by anodic stripping voltammetry. This new methodology resolves three shortcomings of the oSlip while simultaneously simplifying the basic sensor form factor. First, the NoSlip resolves an oxidant instability issue because of the inherent stability of the Au0 coating...

Electromagnetic Method for Resonance Tuning of a Mechatronic System

Process of vertical vibrations of the weight suspended on a spring at harmonic kinematic excitation is examined. It is shown that the resonance tuning of a system can be done with the use of magnetic force which occurs if the coil turns while moving cross external magnetic field lines.

Design and implementation of a novel two stage mechanical–magnetic variable stiffness actuator (M²-VSA)

This paper presents the design and implementation of a novel joint-based magnetic actuator for robotic manipulators using variable stiffness mechanism. This new actuator prototype, namely M2-VSA, is developed as an improvement over previous actuators in its class. The robotic arm with M2-VSA joint can safely interact with human operators and work in hazardous conditions. The main novelty in this work is the use of magnetic force in accompanying with springs in a novel arrangement to adjust the joints’ stiffness and mitigate the effect of impact. The theoretical framework and advantages of the design are discussed in detail. Experimental studies through various tests show the effectiveness and efficiency of mechanical–magnetic joint as a safe mechanism in environments where human and robotics have interaction.

Intraluminal magnetisation of bowel by ferromagnetic particles for retraction and manipulation by magnetic probes

Feasibility studies are needed to demonstrate that safe and effective manipulation of bowel during Minimal Access Surgery (MAS) can be obtained by use of magnetic force. This paper characterises two classes of magnetic particles: stainless steel microparticles (SS-μPs) and iron oxide nanoparticles (IO-nPs) in terms of their magnetisation, chemical composition, crystallinity, morphology and size distribution. Both magnetic particles were dispersed in a high viscosity biological liquid for intraluminal injection of bowel. Ex vivo porcine bowel segments were then retracted by permanent magnetic probes of 5.0 and 10mm diameter. Strong retraction forces reaching 6N maximum were obtained by magnetic fluid based on dispersion of SS-μPs. In contrast, the IO-nP-based magnetic liquid generated less attraction force, due to both lower magnetic and solution properties of the IO-nPs. The comparison of the two particles allowed the identification of the rules to engineer the next generation of particles. The results with SS-μPs provide proof on concept that intraluminal injection of magnetic fluid can generate sufficient force for efficient bowel retraction. Thereafter we shall carry out in vivo animal studies for efficacy and safety of both types of ferrofluids.

Collection of airborne particles by a high-gradient permanent magnetic method

We report on the use of magnetic force in collection of airborne particles by a high-gradient permanent magnetic separation (HGPMS) device. Three aerosol particles of different magnetic susceptibility (NaCl, CuO, and Fe3O4) were generated in the electrical mobility size range of 10–200nm and were used to study HGPMS collection. One HGPMS matrix element, made of stainless steel wool, was used in the device configuration. Three flow rates were selected to simulate the environmental wind speeds of interest to the study. Magnetic force was found to exhibit an insignificant effect on the separation of NaCl particles, even in the HGPMS configuration. Diffusion was a major mechanism in the removal of the diamagnetic particles; however, diffusion is insignificant under the influence of a high-gradient magnetic field for paramagnetic or ferromagnetic particles. The HGPMS showed high-performance collection (>99%) of paramagnetic CuO and ferromagnetic Fe3O4 particles for particle sizes greater than or equal to 60nm. As the wind speed increases, the influence of the magnetic force weakens, and the capability to remove particles from the gas stream diminishes. The results suggest that the HGPMS principle could be explored for development of an advanced miniaturized passive aerosol collector.

Magnetically driven plasmid DNA delivery with biodegradable polymeric nanoparticles

Targeting gene therapy remains a challenge. The use of magnetic force to achieve this was investigated in the present study. It was hypothesized that nanoparticles with both controllable particle size and magnetic properties would enable magnetically driven gene delivery. We investigated this hypothesis by creating a family of novel biodegradable polymeric superparamagnetic nanoparticle (MNP) formulations. Polylactide MNP were formulated using a modified emulsification-solvent evaporation methodology with both the incorporation of oleate-coated iron oxide and a polyethylenimine (PEI) oleate ion-pair surface modification for DNA binding. MNP size could be controlled by varying the proportion of the tetrahydrofuran cosolvent. Magnetically driven MNP-mediated gene transfer was studied using a green fluorescent protein reporter plasmid in cultured arterial smooth muscle cells and endothelial cells. MNP-DNA internalization and trafficking were examined by confocal microscopy. Cell growth inhibition after MNP-mediated adiponectin plasmid transfection was studied as an example of a therapeutic end point. MNP-DNA complexes protected DNA from degradation and efficiently transfected quiescent cells under both low and high serum conditions after a 15 min exposure to a magnetic field (500 G). There was negligible transfection with MNP in the absence of a magnetic field. Larger sized MNP (375 nm diameter) exhibited higher transfection rates compared with 185 nm- and 240 nm-sized MNP. Internalized larger sized MNP escaped lysosomal localization and released DNA in the perinuclear zone. Adiponectin plasmid DNA delivery using MNP resulted in a dose-dependent growth inhibition of cultured arterial smooth muscle cells. It is concluded that magnetically driven plasmid DNA delivery can be achieved using biodegradable MNP containing oleate-coated magnetite and surface modified with PEI oleate ion-pair complexes that enable DNA binding.

935. Magnetofection and Ultrasound To Increase “Naked” DNA Delivery to the Myocardium

We, and other have previously shown that using optimised formulations adenovirus (Ad) is several logs more efficient in myocardial gene transfer than “naked” plasmid DNA (pDNA). Here, we evaluated “magnetofection”, the use of magnetic force acting on vectors complexed to magnetic particles and ultrasound to increase non-viral gene transfer to the murine myocardium. C57BL6/J mice were intubated and a thoracotomy performed to expose the heart. The ability of the magnetic force to pass through tissue was tested ex vivo on a dissected lamb's heart. Iron filings sprinkled on the endocardial site moved and clustered together when the magnet was placed on the epicardial side of the left myocardial wall (n=3). A variety of magnetic particles have been described, here we used TransMAGPEI (Chemicell, Germany), a polyethyleneimine (PEI)–coated iron oxide particle. For the myocardial injection the total volume could not exceed 10 μl. The magnetic particle:DNA complexes were carefully optimised by altering the TransMAGPEI to pDNA w/w and v/v ratios to avoid precipitation. The complexes used for in vivo injections were made in the following way: 0.8 μl TransMAGPEI (60 μg/μl) was diluted with 41.7 μl water and mixed with 5 μl pDNA (5 μg/μl) carrying a luciferase reporter gene (pLux). 2.5 μl 0.9% NaCl (18%) was added after 15 minutes. 10 μl of this formulation containing 5 μg pLux were injected into the left ventricular wall. The hearts were exposed to the magnet (AlNiCo Rod magnet plus NeoDelta magnet, IBS) for 5 min straight after injection and for a further 10 min after re-sutering of the chest. The left ventricular wall was harvested 48 hrs after gene transfer and lux expression was measured. Although magnet exposed hearts expressed more lux than the non-magnet exposed heart, this difference was not significant (magnet: 268±124 RLU/mg protein, no magnet: 94.0±41.8 RLU/mg protein, n=8-10/group). It has previously been shown that ultrasound (US) enhances non-viral gene transfer in skeletal muscle probably through acoustic cavitation of the cell membrane. Here, US was applied for 5 minutes before and after myocardial injection of 10 μg pLux in 10 μl total volume containg 1:1 v/v Opitson microbubbles. For this purpose the chest cavity was filled with gel (Henleys Medical, Welwyn Garden City, UK) and a 0.5 cm2 probe massaged over the heart area. The Medi-Link system machine (Electro-Medical Supplies Ltd, Wantage, UK) was set to deliver 1MHz, 2 W/cm2 at 100% duty cycle continous wave. 48 hrs after gene transfer the left vetricular wall was harvested and lux expression measured. In a parallel experiment we demonstrated that ultrasound imaging (14 MHz) using a gel filled chest cavity is feasible and therefore concluded that ultrasound waves were reaching the heart. However, the US conditions described above did not increase lux expression in the mouse heart (US: 71.8±38.4 RLU/mg protein, no US:138±69.2 RLU/mg protein, n=10/group). In conclusion, although physical energy may be useful in improving non-viral gene transfer to the myocardium further optimisation of these techniques will be required.

均一磁気力場発生用ＮｂＴｉ超伝導マグネットの開発

Although protein crystals of high integrity in a microgravity environment have been reported, the actual implementation of these experiments are very limited. The use of magnetic force is among the most promising methods of simulating the virtual microgravity environment on earth. We have been carrying out the development of superconducting magnets for generating uniform magnetic force fields since 1997. It was not clear at the beginning of this study what configuration of superconducting coils could generate high and uniform magnetic force fields most effectively. We used a nonlinear programming method to reach an optimized design. We constructed a superconducting magnet for generating uniform magnetic force fields, whose coil parameters were based on the optimization result. The superconducting magnet was wound with NbTi conductors and designed to generate 240T2/m of the magnetic force field and 9T of the central magnetic field. This magnetic force field can cancel 17% of the gravity force for pure water. The variation of the magnetic force field is less than 1.0% in the axial component and less than 2.0% in the radial component. The uniformity of the axial component was experimentally confirmed. The magnet has now been in operation for protein crystal growth experiments.

Utilization of magnetic force in space experiments

We report in space experiments about the use of magnetic force, which is generally shown by the product of density (ϱ), weight magnetic susceptibility (χ), magnetic field strength ( H ) and its gradient ( dH / dy ). The magnetic force caused by strong permanent magnets was proved to induce buoyancy and convection in μ G as follows: (1) Transport of bubbles in fluid: In most fluids which are diamagnetic, the magnetic buoyancy force could transport bubbles toward a stronger magnetic field. Collision and fusion of two bubbles was also observed. (2) Magnetic Support of Chemical Reaction (2H 2 O 2 → O 2 +2H 2 O on Pt Catalyst): In μ G, the decomposition reaction continued smoothly when O 2 bubbles were removed from the surface of catalyst by magnetic buoyancy force. In the absence of the field, the reaction was observed to stop. (3) Magnetic Support of Combustion in Diffusion Flames: Magnetic convective air flow could support combustion in μ G.