Direct observation of abrupt shape transition in ferrogels induced by nonuniform magnetic field

Zrı́nyi, Miklós; Barsi, L.; Szabó, Dénes; Kilian, H. G.

doi:10.1063/1.473589

Cited by 117 publications

(104 citation statements)

References 7 publications

(6 reference statements)

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“…Anisotropic, field-induced structure in a colloidal suspension can be locked in to place using chemical gelation, yielding an anisotropic magnetic gel or "ferrogel". [5][6][7] The properties of ferrogels can also be inferred from knowledge of the field-dependent PDF; in earlier work, this has been achieved by computer simulations, 8,9 but already a more general theory of ferrogel a) Author to whom correspondence should be addressed. Electronic mail:…”

Section: Introductionmentioning

confidence: 99%

Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields

Elfimova

Иванов

Camp

2012

The Journal of Chemical Physics

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Articles you may be interested inMagnetic field role on the structure and optical response of photonic crystals based on ferrofluids containing Co0.25Zn0.75Fe2O4 nanoparticles J. Appl. Phys. 115, 193502 (2014) Anisotropic pair correlations in ferrofluids exposed to magnetic fields are studied using a combination of statistical-mechanical theory and computer simulations. A simple dipolar hard-sphere model of the magnetic colloidal particles is studied in detail. A virial-expansion theory is constructed for the pair distribution function (PDF) which depends not only on the length of the pair separation vector, but also on its orientation with respect to the field. A detailed comparison is made between the theoretical predictions and accurate simulation data, and it is found that the theory works well for realistic values of the dipolar coupling constant (λ = 1), volume fraction (ϕ ≤ 0.1), and magnetic field strength. The structure factor is computed for wavevectors either parallel or perpendicular to the field. The comparison between theory and simulation is generally very good with realistic ferrofluid parameters. For both the PDF and the structure factor, there are some deviations between theory and simulation at uncommonly high dipolar coupling constants, and with very strong magnetic fields. In particular, the theory is less successful at predicting the behavior of the structure factors at very low wavevectors, and perpendicular Gaussian density fluctuations arising from strongly correlated pairs of magnetic particles. Overall, though, the theory provides reliable predictions for the nature and degree of pair correlations in ferrofluids in magnetic fields, and hence should be of use in the design of functional magnetic materials.

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Section: Introductionmentioning

confidence: 99%

Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields

Elfimova

Иванов

Camp

2012

The Journal of Chemical Physics

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“…The coupling between the soft elastic medium and the magnetic NPs allows the manipulation of the volume and shape of the ferrogels through the application of external magnetic fields. The effects of the magnetic fields on strain (Faidley et al 2010), shape (Raikher and Stolbov 2005;Zrínyi et al 1997), water retention François et al 2007), stiffness (Mitsumata et al 1999), and the effect of the polymeric matrix on the structural and magnetic properties (Longo et al 2012) have been reported. Because of these properties, ferrogels have many potential applications in the fields of pharmaceutics and medicine as biomembranes, biosensors, artificial muscles, and matrices for drug delivery, among others (Furukawa et al 2003;Gonzalez et al 2012;Liu et al 2006;Mao et al 2005;Miyata et al 2002;Pich et al 2004;Qiu and Park 2001;Sivudu and Rhee 2009).…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical crosslinking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical crosslinking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

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“…Depending on a hydrogel's structure and chemical composition, its dimensions can change in response to alterations in environmental temperature, [11][12][13] pH, [14][15][16][17][18][19] ionic strength, 20 21 electric field, 22 23 magnetic field, 24 light, 25 26 or concentration of specific analytes. [27][28][29][30] When mechanically constrained, responsive hydrogels exert swelling forces on the constraining structures.…”

Section: Introductionmentioning

confidence: 99%

Integration of Hydrogels with Hard and Soft Microstructures

Lei¹,

Ziaie²,

Nuxoll³

et al. 2007

j nanosci nanotechnol

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Hydrogels, i.e., water-swollen polymer networks, have been studied and utilized for decades. These materials can either passively support mass transport, or can actively respond in their swelling properties, enabling modulation of mass and fluid transport, and chemomechanical actuation. Response rates increase with decreasing hydrogel dimension. In this paper, we present three examples where incorporation of hydrogels into solid microstructures permits acceleration of their response, and also provides novel functional capabilities. In the first example, a hydrogel is immobilized inside microfabricated pores within a thin silicon membrane. This hydrogel does not have a swelling response under the conditions investigated, but under proper conditions it can be utilized as a part of an electrolytic diode. In the second example, hydrogels are polymerized under microcantilever beams, and their swelling response to pH or glucose concentration causes variable deflection of the beam, observable under a microscope. In the third example, swelling and shrinking of a hydrogel embedded in a microfabricated valve structure leads to chemical gating of fluid motion through that valve. In all cases, the small size of the system enhances its response rate.

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Direct observation of abrupt shape transition in ferrogels induced by nonuniform magnetic field

Cited by 117 publications

References 7 publications

Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields

Theory and simulation of anisotropic pair correlations in ferrofluids in magnetic fields

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Integration of Hydrogels with Hard and Soft Microstructures

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