Pattern generation and motion control of a vortex-like paramagnetic nanoparticle swarm

2018 ◽  
Vol 37 (8) ◽  
pp. 912-930 ◽  
Author(s):  
Jiangfan Yu ◽  
Lidong Yang ◽  
Li Zhang
Keyword(s):  
Magnetic Field ◽  
Targeted Delivery ◽  
Pitch Angle ◽  
Dynamic Equilibrium ◽  
Equilibrium Structure ◽  
Pattern Generation ◽  
Analytical Models ◽  
Generation Process ◽  
Rotating Magnetic Fields ◽  
Small Pitch

Controlling a swarm of microrobots with external fields is one of the major challenges for untethered microrobots. In this work, we present a new method to generate a vortex-like paramagnetic nanoparticle swarm (VPNS) from dispersed nanoparticles with a diameter of 500 nm, using rotating magnetic fields. The VPNS exhibits a dynamic-equilibrium structure, in which the nanoparticles perform synchronized motions. The mechanisms of the pattern-generation process are analyzed, simulated, and validated by experiments. By tuning the rotating frequency of the input magnetic field, the pattern of a VPNS changes accordingly. Analytical models for estimating the areal change of the pattern are proposed, and they have good agreement with the experimental data. Moreover, reversible merging and splitting of vortex-like swarms are demonstrated and investigated. Serving as a mobile robotic end-effector, a VPNS is capable of making locomotion by tuning the pitch angle of the actuating rotating field. With a small pitch angle, e.g. 2°, the whole swarm moves as an entity, and the shape of the pattern remains intact. In addition, the trapping forces of VPNSs are verified, showing the critical input parameters of the magnetic field that affect the morphology of the swarm. Finally, we demonstrate that VPNSs pass through curved and branched channels with high positioning precision, and the access rates for targeted delivery are over 90%, which are significantly higher than those in the cases of particle swarms moving with tumbling motions.

scholarly journals A Velocity Profile of a Ferrofluid in the Presence of Rotating Magnetic Fields. Pseudo-Analytical and Numerical Solutions

2020 ◽  
pp. 1-6
Author(s):  
Rodrigo Correa ◽  
Cristian Jimenez ◽  
Hermann Vargas
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Linear Model ◽  
Numerical Solutions ◽  
Velocity Profiles ◽  
Analytical Models ◽  
Parallel Plates ◽  
Rotating Magnetic Fields ◽  
Analytical Strategy ◽  
The Magnetic Field

From the beginning of ferro-hydrodynamics, several authors have proposed analytical models to describe the movement of ferrofluids in the presence of rotating external magnetic fields. To this effect they have made valid simplifications in certain and very restricted physical situations. In this work we analyze the effects of these approaches against numerical solutions that do not make use of them. A sample of ferrofluid immersed in containers with three types of geometries was considered: one of flat and parallel plates, one cylindrical and another coaxial cylindrical. Velocity ​​profiles were obtained by these two strategies. The analytical solution leads to a linear model with several simplifications, while the second, numerical in nature, generates a non-linear model, but without approximations. The simulation results showed that the simplifications made in the analytical strategy generate profiles that are valid only for magnetic field intensities lower than the respective ferrofluid saturation values. Additionally, and given the level of development of analytical modeling, it was found that the numerical solution is currently the most appropriate to evaluate the ferro-hydrodynamic model, since it does not have restrictions related to the intensity of the magnetic field. In the same way, it allows to evidence the phenomenon of saturation in the velocity profiles by increasing the intensity of the magnetic field, a situation observed experimentally, and unpredictable by means of these currently available pseudo-analytical solutions.

scholarly journals Magnetic Nanodiscs—A New Promising Tool for Microsurgery of Malignant Neoplasms

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1459
Author(s):  
Tatiana N. Zamay ◽  
Vladimir S. Prokopenko ◽  
Sergey S. Zamay ◽  
Kirill A. Lukyanenko ◽  
Olga S. Kolovskaya ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Remote Control ◽  
Tumor Cells ◽  
Biological Effects ◽  
Malignant Neoplasms ◽  
Rotating Magnetic Fields ◽  
Magnetic Structures ◽  
Promising Tool

Magnetomechanical therapy is one of the most perspective directions in tumor microsurgery. According to the analysis of recent publications, it can be concluded that a nanoscalpel could become an instrument sufficient for cancer microsurgery. It should possess the following properties: (1) nano- or microsized; (2) affinity and specificity to the targets on tumor cells; (3) remote control. This nano- or microscalpel should include at least two components: (1) a physical nanostructure (particle, disc, plates) with the ability to transform the magnetic moment to mechanical torque; (2) a ligand—a molecule (antibody, aptamer, etc.) allowing the scalpel precisely target tumor cells. Literature analysis revealed that the most suitable nanoscalpel structures are anisotropic, magnetic micro- or nanodiscs with high-saturation magnetization and the absence of remanence, facilitating scalpel remote control via the magnetic field. Additionally, anisotropy enhances the transmigration of the discs to the tumor. To date, four types of magnetic microdiscs have been used for tumor destruction: synthetic antiferromagnetic P-SAF (perpendicular) and SAF (in-plane), vortex Py, and three-layer non-magnetic–ferromagnet–non-magnetic systems with flat quasi-dipole magnetic structures. In the current review, we discuss the biological effects of magnetic discs, the mechanisms of action, and the toxicity in alternating or rotating magnetic fields in vitro and in vivo. Based on the experimental data presented in the literature, we conclude that the targeted and remotely controlled magnetic field nanoscalpel is an effective and safe instrument for cancer therapy or theranostics.

Magnetic field pitch-angle measurments in the PBX-M tokamak using the motional Stark effect

1989 ◽  
Vol 63 (19) ◽  
pp. 2060-2063 ◽  
Author(s):  
F. M. Levinton ◽  
R. J. Fonck ◽  
G. M. Gammel ◽  
R. Kaita ◽  
H. W. Kugel ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Stark Effect ◽  
Motional Stark Effect

ORIENTATION DYNAMICS OF MAGNETORHEOLOGICAL FLUIDS SUBJECT TO ROTATING EXTERNAL FIELDS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 758-766 ◽  
Author(s):  
SONIA MELLE ◽  
MIGUEL A. RUBIO ◽  
GERALD G. FULLER
Keyword(s):  
Magnetic Field ◽  
Light Scattering ◽  
Simple Model ◽  
Critical Frequency ◽  
Optical Methods ◽  
Phase Lag ◽  
Rotating Magnetic Fields ◽  
Mr Fluids ◽  
Small Angle Light Scattering ◽  
The Magnetic Field

The formation and orientation of field-induced structures in magnetorheological (MR) fluids subject to rotating magnetic fields have been studied using two optical methods: scattering dichroism and small angle light scattering (SALS). The SALS patterns show how these chain-like aggregates follow the magnetic field with the same frequency but with a retarded phase angle for all the frequencies measured. Using scattering dichroism two different behaviors for both, dichroism and phase lag, are found below or above a critical frequency. Experimental results have been reproduced by a simple model considering the torques balance on the chain-like aggregates.

scholarly journals The hardening of metals by rotating magnetic fields

1931 ◽  
Vol 130 (814) ◽  
pp. 514-523 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Work Hardening ◽  
Rotating Magnetic Fields ◽  
Hardening Process ◽  
Hard Steel ◽  
Steel Balls ◽  
Hardened Condition

In a previous paper by the author experiments were described in which the hardness of various metals was increased by rotating them in a magnetic field. It had been observed that metals in a work-hardened condition, and in particular hard steel which had been super-hardened by the “Cloudburst” process of bombardment with steel balls, exhibit a propensity to become still harder by a process of ageing, the spontaneous increase of hardness commencing with the termination of the work-hardening process, and contiuning during a period of several hours or days.

scholarly journals Excitation And Ionization By Auroral Protons

1966 ◽  
Vol 19 (3) ◽  
pp. 309 ◽  
Keyword(s):  
Magnetic Field ◽  
Energy Range ◽  
Pitch Angle ◽  
Proton Energy ◽  
Ionization Rate ◽  
Energy Spectra ◽  
Proton Fluxes ◽  
Atmospheric Ionization ◽  
The Magnetic Field

Height distributions are presented for the atmospheric ionization rate and Balmer radiation resulting from precipitation of auroral protons. These results have been computed assuming proton fluxes with several different energy spectra and pitch-angle distributions about the magnetic field, the total proton energy range being restricted to 1-1000 keY.

scholarly journals Pitch angle scattering of an energetic magnetized particle by a circularly polarized electromagnetic wave

2021 ◽  
Author(s):  
Paul M. Bellan
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Pitch Angle ◽  
Energetic Electron ◽  
Circularly Polarized ◽  
Angle Scattering ◽  
Background Magnetic Field ◽  
Pseudo Potential

<p>The interaction between a circularly polarized electromagnetic wave and an energetic gyrating particle is described [1] using a relativistic pseudo-potential that is a function of the frequency mismatch,  a measure of the extent to which ω-k<sub>z</sub>v<sub>z</sub>=Ω/γ is not true. The description of this wave-particle interaction involves a sequence of relativistic transformations that ultimately demonstrate that the pseudo potential energy of a pseudo particle adds to a pseudo kinetic energy giving a total pseudo energy that is a constant of the motion. The pseudo kinetic energy is proportional to the square of the particle acceleration (compare to normal kinetic energy which is the square of a velocity) and the pseudo potential energy is a function of the mismatch and so effectively a function of the particle velocity parallel to the background magnetic field (compare to normal potential energy which is a function of position). Analysis of the pseudo-potential provides a means for interpreting particle motion in the wave in a manner analogous to the analysis of a normal particle bouncing in a conventional potential well.  The wave-particle  interaction is electromagnetic and so differs from and is more complicated than the well-known Landau damping of electrostatic waves.  The pseudo-potential profile depends on the initial mismatch, the normalized wave amplitude, and the initial angle between the wave magnetic field and the particle perpendicular velocity. For zero initial mismatch, the pseudo-potential consists of only one valley, but for finite mismatch, there can be two valleys separated by a hill. A large pitch angle scattering of the energetic electron can occur in the two-valley situation but fast scattering can also occur in a single valley. Examples relevant to magnetospheric whistler waves are discussed. Extension to the situation of a distribution of relativistic particles is presented in a companion talk [2].</p><p>[1] P. M. Bellan, Phys. Plasmas 20, Art. No. 042117 (2013)</p><p>[2] Y. D. Yoon and P. M. Bellan, JGR 125, Art. No. e2020JA027796 (2020)</p>

Magnetisation of partially ionised dusty disks

2001 ◽  
Vol 66 (3) ◽  
pp. 213-222 ◽  
Author(s):  
GUIDO T. BIRK ◽  
A. KOPP ◽  
H. LESCH
Keyword(s):  
Magnetic Field ◽  
Circumstellar Disks ◽  
The Self ◽  
Charged Dust ◽  
Generation Process ◽  
Magnetic Field Generation ◽  
Field Generation ◽  
Neutral Gas ◽  
Fluid Velocities ◽  
Dust Component

The self-magnetisation of circumstellar disks is considered within an appropriate multifluid description. These disks are composed of ionised and neutral gas as well as of a charged dust component. The most important equation in this context is the general Ohm’s law that includes a magnetic field generation term due to relative dust–neutral fluid velocities. We show that circumstellar disks can carry their own significant magnetic fields. As long as the stellar gravitation sustains the accretion flow, the self-magnetisation of the disk does not saturate until the field strength reaches its local equipartition value. The magnetic field generation process is illustrated by idealised multifluid simulations that are not restricted to a kinematic description, but model the process in a self-consistent way.

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