Time domain study of Brownian and Néel relaxation in ferrofluids

Kötitz, R.; Fannin, P.C.; Trahms, Lutz

doi:10.1016/0304-8853(95)00333-9

Cited by 126 publications

(87 citation statements)

References 8 publications

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“…In the absence of the magnetic beads, the data are scattered around zero, and in the presence of the bead suspension, the data are proportional to I 2 0 in accordance with Eq. (13). This shows that the data correction procedure works as intended and that the measurements are stable over time.…”

Section: Resultsmentioning

confidence: 66%

“…11,12 However, Brownian relaxation can also be measured in the time domain. [13][14][15] The advantage of time domain measurements is that they can be performed much faster and a single measurement may take less than a second, whereas frequency domain measurements require a sequence of measurements at different frequencies typically resulting in measurement times on the order of minutes or longer. Thus, time domain measurements result in a much shorter analysis time and therefore also enable time-resolved studies.…”

Section: Introductionmentioning

confidence: 99%

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On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain

Østerberg

Rizzi

Hansen

2013

Journal of Applied Physics

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We present and demonstrate a new method for on-chip Brownian relaxation measurements on magnetic nanobeads in the time domain using magnetoresistive sensors. The beads are being magnetized by the sensor self-field arising from the bias current passed through the sensors and thus no external magnetic fields are needed. First, the method is demonstrated on Brownian relaxation measurements of beads with nominal sizes of 40, 80, 130, and 250 nm. The results are found to compare well to those obtained by an already established measurement technique in the frequency domain. Next, we demonstrate the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s, which is about six times faster than in the frequency domain. This substantial reduction of the measurement time allows for continuous monitoring of the bead dynamics vs. time and opens for time-resolved studies, e.g., of binding kinetics. V C 2013 AIP Publishing LLC. [http://dx

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Section: Resultsmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain

Østerberg

Rizzi

Hansen

2013

Journal of Applied Physics

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“…The relaxation depends on temperature, the viscosity of fluids, and the hydrodynamic size of magnetic particles. [11][12][13] Hydrodynamic size is equivalent to the total size of particle, dispersant, adsorbate, and electric double layer. When ion concentration increases, the thickness of the electric double layer decreases, repulsion force between particles becomes weak, and particles aggregate, 14,15) which increases the hydrodynamic size.…”

Section: Introductionmentioning

confidence: 99%

Influence of behaviors of magnetic particles in ferrofluids under alternating magnetic fields on harmonic responses

Oda¹,

Trisnanto²,

Kitamoto³

2018

Jpn. J. Appl. Phys.

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We describe the relationship between the excitation frequency dependence of harmonic signal intensity under alternating magnetic fields and the hydrodynamic size of magnetic particles in ferrofluids. The hydrodynamic size estimated from magnetic susceptibility increases with the increase in ion and particle concentrations in the ferrofluids. The excitation frequency dependence of the fifth-harmonic signal intensity exhibits a minimum point at a certain frequency. The frequency of the minimum point shifts to the lower-frequency range, and after reaching the minimum, it increases with the increase in ion and particle concentrations, reflecting the increase in hydrodynamic size owing to the aggregation of magnetic particles.These behaviors may be useful for applications in ion sensing by a magnetic technique.

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“…These particles are described by two characteristics: magnetization curve and frequency-dependent relaxation effects. The magnetization curve is nonlinear, non-hysteretic and it saturates at high fields [8]. To exploit this nonlinearity, we use the frequency mixing method in order to detect the presence of particles in a microfluidic channel.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Detection Structure for LOC Immunoassays, Multiphysics Simulations and Experimental Results

Rabehi¹,

Garlan²,

Shanehsazzadeh

et al. 2017

Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017

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Abstract:The aim of this work is to develop a completely integrated Lab-On-Chip (LOC) for easy, rapid and cost-effective immunoassays. The pathogen sensing system is composed of a microfluidic channel surrounded by planar microcoils which are responsible for the emission and the detection of magnetic fields. The system allows the detection and quantification of superparamagnetic beads used for immunoassays in a "sandwich" antigen-antibody configuration. Multiphysics simulations have been achieved and preliminary experimental results have allowed to validate the structure.

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Time domain study of Brownian and Néel relaxation in ferrofluids

Cited by 126 publications

References 8 publications

On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain

On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain

Influence of behaviors of magnetic particles in ferrofluids under alternating magnetic fields on harmonic responses

Magnetic Detection Structure for LOC Immunoassays, Multiphysics Simulations and Experimental Results

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