Size Analysis of PDMS−Magnetite Nanoparticle Complexes: Experiment and Theory

Mefford, O. Thompson; Carroll, Matthew R J; Vadala, Michael L.; Goff, Jonathan; Mejia-Ariza, Raquel; Saunders, Martin; Woodward, Robert C.; Pierre, Timothy G. St.; Davis, Richey M.; Riffle, Judy S.

doi:10.1021/cm702730p

Cited by 48 publications

(31 citation statements)

References 41 publications

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“…One type of MR materials are the composites formed by dispersing magnetic filler particles into an elastomer polymeric matrix, referred as magnetorheological elastomers (MRE) [1][2][3]. A simple procedure to obtain MRE materials is curing the filler-elastomer composite in the presence of a uniform magnetic field (H curing ) which induces agglomerations of the filler particles into chain-like structures aligned in the direction of the field [4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Superparamagnetic anisotropic elastomer connectors exhibiting reversible magneto-piezoresistivity

Mietta

Jorge

Pérez

et al. 2013

Sensors and Actuators A: Physical

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An anisotropic magnetorheological composite formed by dispersions of silver-covered magnetite microparticles (Fe3O4@Ag) in polydimethylsiloxane (PDMS) displaying electrical conduction only in one preferred direction is presented. A set-up for applying and detecting electrical conduction through the composite is described and applied to characterize the behavior of the system in on-off commutation cycles. The composite is obtained by loading the polymer with relatively low concentration of fillers (5% w/w of the total weight) and curing it in the presence of a uniform magnetic field. The fillers appear in the final composite as an array of needles, i.e. pseudo-chains of particles aligned in the direction of the magnetic field. Using Fe3O4 nanoparticles (13 nm) it is possible to obtain cured composites in a superparamagnetic state, that is, without magnetic hysteresis at room temperature. Hysteresis is not found in the elastic properties either; in particular, Mullins effects (change of physical properties after the first strain-stress cycle) were not observed. No measurable transversal electrical conduction was detected (transversal resistivity larger than 62 Mohms•cm). Thus, significant electrical conductivity is present only between contact points that are exactly facing each other at both sides of the composites in the direction parallel to the needles. The I-V curves in that direction have ohmic behavior and exhibit both piezoresistance and magnetoresistance, that is, the electrical conductivity in the direction parallel to the pseudochains increases when a pressure (i.e. compressive stress) is applied at constant magnetic field and/or when a magnetic field is applied at constant pressure. The materials do not exhibit magnetoelectric or piezoresistive hysteresis. These characteristics illustrate the high potentiality of these systems in elastic connectors where electrical conduction can be varied by external mechanical or magnetic forces. List of changes following suggestions of the reviewerWe improved the language following all the suggestions of the reviewer, listed here: Table 1 Figure 7 shows the absence of significant transversal conductivity for an elastomeric connector of 2 mm thickness. Measurements were performed using the set-up shown in Figure 1.This result was observed also for samples of 1 and 3 mm thickness, which is consistent with the no variation of the resistivities (  and   ) with the sample thickness". Page 14: another sentence was rephrased: "On the other hand, no measurable current was detected between contacts that do not coincide vertically". 1) A glossary of terms is included asPage 15: "…the desired anisotropic properties, which, in this case, are stabilized by the curing of the PDMS resin".Page 15: "The fillers and the matrix appear contactless after curing."Page 15: another sentence was rephrased: "The absence of hysteresis in the elastic, piezoresistive and magnetoresistive properties can be associated to the lack of relevant adhesion between the inorganic fillers ...

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Section: Introductionmentioning

confidence: 99%

Superparamagnetic anisotropic elastomer connectors exhibiting reversible magneto-piezoresistivity

Mietta

Jorge

Pérez

et al. 2013

Sensors and Actuators A: Physical

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“…In particular, we focus on the behaviour of a hydrophobic ferrofluid drop which is being synthesized for the potential treatment of retinal detachment (Mefford et al , 2008a. The ferrofluid consists of magnetite nanoparticles coated with biocompatible polydimethylsiloxane (PDMS) oligomers, with the advantages of a narrow size distribution, and colloidal stability.…”

Section: Introductionmentioning

confidence: 99%

Deformation of a hydrophobic ferrofluid droplet suspended in a viscous medium under uniform magnetic fields

et al. 2010

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The effect of applied magnetic fields on the deformation of a biocompatible hydrophobic ferrofluid drop suspended in a viscous medium is investigated numerically and compared with experimental data. A numerical formulation for the time-dependent simulation of magnetohydrodynamics of two immiscible non-conducting fluids is used with a volume-of-fluid scheme for fully deformable interfaces. Analytical formulae for ellipsoidal drops and near-spheroidal drops are reviewed and developed for code validation. At low magnetic fields, both the experimental and numerical results follow the asymptotic small deformation theory. The value of interfacial tension is deduced from an optimal fit of a numerically simulated shape with the experimentally obtained drop shape, and appears to be a constant for low applied magnetic fields. At high magnetic fields, on the other hand, experimental measurements deviate from numerical results if a constant interfacial tension is implemented. The difference can be represented as a dependence of apparent interfacial tension on the magnetic field. This idea is investigated computationally by varying the interfacial tension as a function of the applied magnetic field and by comparing the drop shapes with experimental data until a perfect match is found. This estimation method provides a consistent correlation for the variation in interfacial tension at high magnetic fields. A conclusion section provides a discussion of physical effects which may influence the microstructure and contribute to the reported observations.

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“…They can be embedded in polymers such as PDMS to form functional elastomers, which combine the properties of the matrix and the nanoparticles [1,2]. Incorporating well-dispersed nanoparticles into a polymeric matrix is, however, not an easy task [3][4][5][6]. When nanoparticles are mixed with polymer melts or polymer solutions, depletion of the free chains in close vicinity of one another [7] can occur.…”

Section: Introductionmentioning

confidence: 99%

Polydimethylsiloxane (PDMS) Coating onto Magnetic Nanoparticles Induced by Attractive Electrostatic Interaction

2012

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Abstract:In this article, we present an efficient synthesis pathway of polydimethylsiloxane (PDMS) coated magnetic nanoparticles from hydrophilic polyacrylate coated ferrofluids (NPPAA). A block copolymer based on polydimethylsiloxane is selected for its propensity to interact with the carboxylate functions on the NPPAA. The interaction is due to negative charges on NPPAA and positive ones on the amphiphilic copolymer. The synthesis is achieved by interfacial interaction, simplifying the purification of the PDMS-coated nanoparticles (NPPDMS) from subproducts such as ions and water. NPPDMS are well dispersed in hydrophobic solvents (toluene, diethyl ether) and can then be embedded into a curable PDMS polymer.

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Size Analysis of PDMS−Magnetite Nanoparticle Complexes: Experiment and Theory

Cited by 48 publications

References 41 publications

Superparamagnetic anisotropic elastomer connectors exhibiting reversible magneto-piezoresistivity

Superparamagnetic anisotropic elastomer connectors exhibiting reversible magneto-piezoresistivity

Deformation of a hydrophobic ferrofluid droplet suspended in a viscous medium under uniform magnetic fields

Polydimethylsiloxane (PDMS) Coating onto Magnetic Nanoparticles Induced by Attractive Electrostatic Interaction

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