Magnetic bead microrheology

2018 ◽  
Author(s):  
Eric M. Furst ◽  
Todd M. Squires
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Particles ◽  
Colloidal Particles ◽  
Permanent Magnets ◽  
Operating Regime ◽  
Magnetic Bead ◽  
Magnetic Tweezers ◽  
Linear Measurements ◽  
Magnetic Forces ◽  
Magnetic Tweezer

Magnetism is a convenient force for actively pulling colloidal particles in a material. Many materials of interest in a microrheology experiment have a negligible magnetic susceptibility, and so embedded magnetic particles can be subject to relatively strong forces by fields imposed from outside of the sample. These are usually generated by electromagnets, but can also include the use of permanent magnets, or a combination of both. Such “magnetic tweezers” are used as sensitive force probes, capable of generating forces ranging from femtonewtons to nanonewtons. Magnetic forces and magnetic materials are reviewed and magnetic tweezer designs discussed. Linear and non-linear measurements using magnetic tweezers are presented, including studies yield stress and shear thinning. The operating regime of magnetic tweezer microrheology is presented, which enables microrheology experiments to access stiffer materials.

Separation of Particles Composed of a Solid Solution [Mg2SiO4 -Fe2SiO4] in the Sequence of Fe2+ Concentration Using a Pocketsize Magnetic-Circuit

2020 ◽  
Vol 843 ◽  
pp. 105-109
Author(s):  
Chiaki Uyeda ◽  
Keiji Hisayoshi ◽  
Kentaro Terada
Keyword(s):  
Solid Solution ◽  
Magnetic Susceptibility ◽  
Magnetic Particles ◽  
Magnetic Force ◽  
Magnetic Beads ◽  
Magnetic Circuit ◽  
Cross Sectional ◽  
Volume Force ◽  
Magnetic Forces ◽  
Magnetic Ions

Magentic separation generally required strong magnetic forces induced in ferromagnetic or strong paramagnetic particles; in order to realize the separation in diamagnetic or weak paramagnetic particles, it was necessary to attach magnetic beads or magnetic ions to induce the strong magnetic force. A method to separate mixture of weak magnetic particles by its concentration of paramagnetic ferrous ion is newly proposed, which does not require the abovementioned magnetic attachments. The efficiently of the new method is experimentally examined using a pocketsize magnetic circuit (4.5 cm x2.0 cm x 1.0 cm) and a piece of cross sectional paper (5.0 cm x1.0cm). The separation is based on a principle that velocity of a translating particle, induced by a magnetic volume force in an area of monotonically decreasing field, is uniquely determined only by its magnetic susceptibility (per unit mass) of the particle; the velocity is independent to mass of particle. By examining the spectra of the separated particles recovered on the cross sectional paper, a histogram on Fe concentration is easily obtained for the particles without the need of consuming them.

scholarly journals Geochemical and Mineralogical Characteristics of Airborne Particulate Matter in Relation to Human Health Risk

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 866 ◽  
Author(s):  
Marzena Rachwał ◽  
Małgorzata Wawer ◽  
Mariola Jabłońska ◽  
Wioletta Rogula-Kozłowska ◽  
Patrycja Rogula-Kopiec
Keyword(s):  
Magnetic Susceptibility ◽  
Particulate Matter ◽  
Human Health ◽  
Magnetic Particles ◽  
Rank Order ◽  
Human Health Risk ◽  
Airborne Particulate Matter ◽  
Ambient Air ◽  
Average Concentration ◽  
Health Indices

The main objective of this research was the determination of the geochemical and mineralogical properties of particulate matter: TSP (total suspended particles) and, especially PM1 (particles with aerodynamic diameter not greater than 1 µm) suspended in the air of a selected urban area in southern Poland. Identification of the emission sources of metals and metalloids bound in TSP and PM1 as well as the assessment of potential risk of urban ambient air to human health using hazard indices was an additional aim of this investigation. The daily TSP and PM1 quartz fiber filters collected during heating season were subjected to mass magnetic susceptibility (χ) measurements, SEM (Scanning Electron Microscopy) observations and geochemical analyses. Obtained results revealed that the concentration of TSP and PM1 well correlated with their mass-specific magnetic susceptibility. The good relationship between the PM concentration and χ suggests that magnetic susceptibility measurements can be a good proxy of low-level atmospheric dust pollution. The rank order of potentially toxic elements (PTE) based on average concentration was Ba > Zn > Al > Fe > Pb > Mn > Ti > Cu > Cr > Ni >As > Cd > V > Tl, both for TSP and PM1. PM1/TSP ratios for PTE concentrations and χ were around or slightly above unity, which indicated that PM1 was the main carrier of PTE (with the exception of cadmium, copper and lead) and technogenic magnetic particles. The non-carcinogenic and carcinogenic risks were confirmed by very high values of human health indices.

scholarly journals High-force magnetic tweezers with hysteresis-free force feedback

2019 ◽  
Author(s):  
D. Kah ◽  
C. Dürrbeck ◽  
W. Schneider ◽  
B. Fabry ◽  
R. C. Gerum
Keyword(s):  
Force Feedback ◽  
Magnetic Hysteresis ◽  
Iron Alloy ◽  
Magnetic Tweezers ◽  
Core Material ◽  
Magnetic Field Measurement ◽  
Exponential Relationship ◽  
Plastic Properties ◽  
Magnetic Tweezer ◽  
Elastic And Plastic Deformations

ABSTRACTMagnetic tweezers based on solenoids with iron alloy cores are widely used to apply large forces (~100 nN) onto micron-sized (~5 μm) superparamagnetic particles for mechanical manipulation or microrheological measurements at the cellular and molecular level. The precision of magnetic tweezers, however, is limited by the magnetic hysteresis of the core material, especially for time-varying force protocols. Here, we eliminate magnetic hysteresis by a feedback control of the magnetic induction, which we measure with a Hall sensor mounted to the distal end of the solenoid core. We find that the generated force depends on the induction according to a power-law relationship, and on the bead-tip distance according to a stretched exponential relationship. Together, both relationships allow for an accurate force calibration and precise force feedback with only 3 calibration parameters. We apply our method to measure the force-dependence of the viscoelastic and plastic properties of fibroblasts using a protocol with stepwise increasing and decreasing forces. We find that soft cells show an increasing stiffness but decreasing plasticity at higher forces, indicating a pronounced stress stiffening of the cytoskeleton. By contrast, stiff cells show no stress stiffening but an increasing plasticity at higher forces. These findings indicate profound differences between soft and stiff cells regarding their protection mechanisms against external mechanical stress. In summary, our method increases the precision, simplifies the handling and extends the applicability of magnetic tweezers.SIGNIFICANCEMagnetic tweezers are widely used, versatile tools to investigate the mechanical behavior of cells or to measure the strength of receptor-ligand bonds. A limitation of existing high-force magnetic tweezer setups, however, is caused by the magnetic hysteresis of the tweezer core material. This magnetic hysteresis requires that the tweezer core must be de-magnetized (de-Gaussed) prior to each measurement, and that flexible force protocols with decreasing forces are not possible. We describe how these limitations can be overcome with a force feedback though direct magnetic field measurement. We demonstrate the applicability of our setup by investigating the visco-elastic and plastic deformations of fibroblasts to forces of different amplitudes.

Multi-proxy study of the Cretaceous-Paleogene (K-Pg) boundary in deep-sea turbiditic sediments in the Uzgruň section (Outer Flysch Carpathians, Czech Republic)

2021 ◽  
Author(s):  
Šimon Kdýr ◽  
Tiiu Elbra ◽  
Miroslav Bubík ◽  
Petr Schnabl ◽  
Lilian Švábenická
Keyword(s):  
Magnetic Susceptibility ◽  
Czech Republic ◽  
Detection Limit ◽  
Remanent Magnetization ◽  
Magnetic Particles ◽  
Principal Component ◽  
Natural Remanent Magnetization ◽  
Ongoing Research ◽  
Small Stream ◽  
Magnetic Methods

<p>The composite profile, with 4 studied sections, is located near the Uzgruň village (Czech Republic) next to a small stream. The profile is composed of Late Maastrichtian to Palaeocene flysch sediments and the K-Pg boundary is set in claystones within this turbiditic setting. Ongoing research of local paleoenvironment and stratigraphy is based on paleo- and rock-magnetic methods, micropaleontology and geochemistry to obtain more detailed view of the local situation during the K-Pg extinction event. Based on biostratigraphy, two dinocyst zones (Bubík et al., 2002): Palynodium grallator and Carpatella cornuta (first occurrence in the Danian), two calcareous nannofossil zones in the Upper Maastrichtian, and the agglutinated foraminifer zone Rzehakina fissistomata in the Paleogene were distinguished. Biostratigraphic data support the K-Pg boundary interval. The uppermost Maastrichtian is indicated by nannofossil species Micula prinsii, UC26d<sup>TP</sup> zone. Basal Paleogene non-calcareous strata contain dinocyst Carpatella cornuta and agglutinated foraminifers of Rzehakina fissistomata zone. The presence of low-latitude nannofossil taxa M. prinsii and Ceratolithoides kamptneri show input of warm waters during the uppermost Maastrichtian. Several rock-magnetic methods, such as acquisition of Isothermal remanent magnetization (IRM), acquisition of Anhysteretic remanent magnetization (ARM), Anisotropy of magnetic susceptibility (AMS), Field dependence of magnetic susceptibility (HD) and Frequency dependence of magnetic susceptibility (FD), were applied to estimate behaviour and origin of magnetic particles. Natural remanent magnetization (NRM) values of samples range from 0.09 to 2.48 mA/m. Volume normalized magnetic susceptibility (MS) show values from 130 up to 1197 SI*10-6. There is no increase observed in MS across stratigraphic boundary due to turbiditic evolution of sediment. Due to character of sediments, we applied alternating field (AF) demagnetization and used principal component analysis (PCA; Kirschvink, 1980) for estimation of characteristic remanent component. Most of the K/Pg sections worldwide have well documented Iridium anomaly. In Uzgruň, the preliminary results show that although the values are not as pronounced, the Ir at K-Pg boundary is still higher than in surrounding sediments. For tracing of Deccan traps effect we plan to apply mercury (Hg)/total organic carbon (TOC) stratigraphy. TOC content of 20 pilot samples is low, but not under detection limit of the instrumentation (mean value 0.92 wt%). One sample reached value 4.41 wt% of TOC. Sulphur contents are reaching 1 wt%, but several samples were under detection limit of the instrumentation. Sulphur concentrations suggest more reduction conditions of burial.</p><p>Current research is supported by Czech Science Foundation project no. 19-07516S and is in accordance with research plan no. RVO67985831.</p><p>Bubík, M., Adamová, M., Bąk, M., Franců, J., Gedl, P., Mikuláš, R., Švábenická, L., & Uchman, A. (2002). Výsledky výzkumu hranice křída/terciér v magurském flyši u Uzgruně. Geologické výzkumy na Moravě a ve Slezsku, 9, 18–22</p><p>L. Kirschvink (1980), The least-squares line and plane and the analysis of palaeomagnetic data, Geophysical Journal International, 62(3), 699–718, https://doi.org/10.1111/j.1365-246X.1980.tb02601.x</p>

scholarly journals Continuous-Flow Separation of Magnetic Particles from Biofluids: How Does the Microdevice Geometry Determine the Separation Performance?

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3030 ◽  
Author(s):  
Cristina González Fernández ◽  
Jenifer Gómez Pastora ◽  
Arantza Basauri ◽  
Marcos Fallanza ◽  
Eugenio Bringas ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Rational Design ◽  
Magnetic Particles ◽  
Magnetic Beads ◽  
Permanent Magnets ◽  
System Throughput ◽  
Separation Performance ◽  
High Particle ◽  
Section Shape ◽  
Geometrical Features

The use of functionalized magnetic particles for the detection or separation of multiple chemicals and biomolecules from biofluids continues to attract significant attention. After their incubation with the targeted substances, the beads can be magnetically recovered to perform analysis or diagnostic tests. Particle recovery with permanent magnets in continuous-flow microdevices has gathered great attention in the last decade due to the multiple advantages of microfluidics. As such, great efforts have been made to determine the magnetic and fluidic conditions for achieving complete particle capture; however, less attention has been paid to the effect of the channel geometry on the system performance, although it is key for designing systems that simultaneously provide high particle recovery and flow rates. Herein, we address the optimization of Y-Y-shaped microchannels, where magnetic beads are separated from blood and collected into a buffer stream by applying an external magnetic field. The influence of several geometrical features (namely cross section shape, thickness, length, and volume) on both bead recovery and system throughput is studied. For that purpose, we employ an experimentally validated Computational Fluid Dynamics (CFD) numerical model that considers the dominant forces acting on the beads during separation. Our results indicate that rectangular, long devices display the best performance as they deliver high particle recovery and high throughput. Thus, this methodology could be applied to the rational design of lab-on-a-chip devices for any magnetically driven purification, enrichment or isolation.

Study on Improvement of Transmission Torque for a Surface Permanent Magnet Type Magnetic Gear

2012 ◽  
Vol 721 ◽  
pp. 237-242 ◽  
Author(s):  
Masaru Oka ◽  
Takashi Todaka ◽  
Masato Enokizono ◽  
Kousuke Nagaya ◽  
Tomoyuki Fujita
Keyword(s):  
Permanent Magnet ◽  
Flux Density ◽  
Flux Distribution ◽  
Permanent Magnets ◽  
Torque Density ◽  
Magnetic Forces ◽  
Dimensional Finite Element ◽  
Flux Concentration ◽  
Magnetic Gear ◽  
Flux Density Distribution

Magnetic gears are a force transmitter consisting of permanent magnets. The mechanical input can be transmitted to an output shaft without contact by magnetic forces. The magnetic gears are not worn out because there is no friction. As a result, the running costs such as the maintenance fee can be suppressed and the resources can be saved. However, the transmission torques of the conventional magnetic gears, which have so far been developed, are very low. Besides, new structure models designed for high torque density need a lot of permanent magnets and multi-pole constructions. Those structures are complex and the manufacturing is difficult. In this research, we applied a flux concentration type surface permanent magnet arrangement to a surface permanent magnet type magnetic gear in order to improve the transmission torque and to reduce the amount of permanent magnets. The magnetic flux distribution, the gap flux density and the transmission torque of the developed new models are numerically analyzed by using the two-dimensional finite element method. In this paper, a permanent magnet structure optimized to reduce its amount and influence of the flux concentration type surface permanent magnet arrangement on the gap flux density distribution and transmission torque are reported.

General Formulation for Magnetic Forces in Linear Materials and Permanent Magnets

2008 ◽  
Vol 44 (9) ◽  
pp. 2134-2140 ◽  
Author(s):  
R. Sanchez Grandia ◽  
V. Aucejo Galindo ◽  
A. Usieto Galve ◽  
R. Vives Fos
Keyword(s):  
Permanent Magnets ◽  
Magnetic Forces

Microstructure Of Fe-Nd-B Alloys Tailored To Approach Theoretical Coercrvtty Limits

1999 ◽  
Vol 5 (S2) ◽  
pp. 26-27
Author(s):  
Kannan M. Krishnan ◽  
Er. Girt ◽  
E. C. Nelson ◽  
G. Thomas ◽  
Ferdinand Hofer
Keyword(s):  
Magnetic Particles ◽  
Permanent Magnets ◽  
Spontaneous Magnetization ◽  
Particle Interaction ◽  
Maximum Energy ◽  
Interacting Particles ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Oriented Samples ◽  
The Difference

Performance of permanent magnets for a variety of applications is often determined by the maximum energy product (BH)max. In order to obtain high (BH)max permanent magnetic materials have to have large coercivity. In theory the coercive field of ideally oriented, non-interacting, single domain, magnetic particles, assuming Kl is much bigger than K2, was shown to be He = 2K1/Ms - N Ms, where Kl and K2 are the magnetocrystalline anisotropy constants, Ms is the spontaneous magnetization and N is the demagnetization factor. For randomly oriented non-interacting particles the Stoner-Wohlfarth model predicts that the value of Hc decreases to about half. However, experimentally obtained values of the coercitive fields in permanent magnets are 3 to 10 and 2 times smaller for well oriented and randomly oriented samples, respectively. This discrepancy was attributed to inter-particle interaction and the microstructure of the permanent magnets. In order to understand the difference between the theoretically predicted and experimentally obtained results for He we prepared rapidly quenched, Nd-rich, NdxFe14B (2 < x < 150) ribbons.

Nanometer-Scale Iron Oxide Magnetic Particles: Synthesis and Magnetic Properties

1990 ◽  
Vol 206 ◽  
Author(s):  
John K. Vassiliou ◽  
Vivek Mehrotra ◽  
Michael W. Russell ◽  
Emmanuel P. Giannelis
Keyword(s):  
Magnetic Susceptibility ◽  
Iron Oxide ◽  
Magnetic Particles ◽  
Average Diameter ◽  
Nanometer Scale ◽  
Iron Oxide Particles ◽  
Porous Network ◽  
Synthesis Conditions ◽  
Oxide Particles ◽  
The Magnetic Field

ABSTRACTNanometer-scale iron oxide magnetic particles have been formed in the porous network of a cross-linked polymer matrix by ion exchange and subsequent hydrolysis. The oxide particles are uniform, well-dispersed and spherical with a diameter ranging between 30 and 1200 Å depending on the synthesis conditions. The DC magnetic susceptibility, measured between 4 and 300 K, continuously increases with decreasing temperature and tends to saturate at low temperatures. Composites containing iron oxide particles with an average diameter of 80 Å exhibit superparamagnetism while those on the order of 1000 Å undergo an antiferromagnetic-type transition at 33 K. The magnetic susceptibility is critically dependent upon the particle size and the strength of the magnetic field.

Trapping and Steering a Magnetic Microbead Using 3D Magnetic Tweezers

2010 ◽  
Author(s):  
Zhipeng Zhang ◽  
Chia-Hsiang Menq
Keyword(s):  
Feedback Control ◽  
Feedback Linearization ◽  
Magnetic Force ◽  
Three Dimensional ◽  
Magnetic Bead ◽  
Magnetic Tweezers ◽  
Three Dimensions ◽  
Force Model ◽  
Magnetic Actuation ◽  
Magnetic Microbead

The development of a magnetic micromanipulation system that is capable of trapping and steering a magnetic microbead in three dimensions is presented in this paper. Hexapole magnetic tweezers were designed and implemented to realize three-dimensional (3D) magnetic actuation. Because magnetic actuation is inherently unstable without feedback control, visual measurement based on computer processing of video images was employed to detect the displacement of the microbead, facilitating real-time feedback control. An analytical magnetic force model was developed to characterize the nonlinearity and position dependency of the magnetic force exerted on the magnetic bead by the hexapole magnetic tweezers. Its inverse model was then derived and employed in feedback linearization. A proportionalintegral controller along with feedback linearization was implemented and the motion of the magnetic bead was successfully stabilized. The control results in terms of 100-nanometer stepping and 3D motion steering were experimentally demonstrated.

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