Nonlinear Deformation of a Ferrofluid Droplet in a Uniform Magnetic Field

Zhu, Guiping; Nguyen, Nam‐Trung; Ramanujan, R.V.; Huang, Xiaoyang

doi:10.1021/la203931q

Cited by 116 publications

(91 citation statements)

References 36 publications

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“…contact angle) of fluids on specialized surfaces 22 and to directly change the shape and behavior of ferrofluid droplets. 23,24,25 The behavior of ferrofluid droplets placed on a surface tension gradient in the presence of a uniform magnetic field however needs more study. In this research, we study the behavior of ferrofluid droplets placed on surfaces that either contain a surface tension gradient or are uniformly hydrophilic or hydrophobic in the presence of various uniform magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

et al. 2016

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This work demonstrates the controlled motion and stopping of individual ferrofluid droplets due to a surface tension gradient and a uniform magnetic field. The surface tension gradients are created by patterning hydrophilic aluminum regions, shaped as wedges, on a hydrophobic copper surface. This pattern facilitates the spontaneous motion of water-based ferrofluid droplets down the length of the wedge toward the more hydrophilic aluminum end due to a net capillarity force created by the underlying surface wettability gradient. We observed that applying a magnetic field parallel to the surface tension gradient direction has little or no effect on the droplet's motion, while a moderate perpendicular magnetic field can stop the motion altogether effectively "pinning" the droplet. In the absence of the surface tension gradient, droplets elongate in the presence of a parallel field but do not travel. This control of the motion of individual droplets might lend itself to some biomedical and lab-on-a-chip applications. The directional dependence of the magnetoviscosity observed in this work is believed to be the consequence of the formation of nanoparticle chains in the fluid due to the existence of a minority of relatively larger magnetic particles.

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Section: Introductionmentioning

confidence: 99%

Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

et al. 2016

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“…43 Thus, when E 0 = 0 and H 0 ≠ 0 the Rosensweig instability represents a balance where the magnetic energy of the system is reduced when the fluid forms elongated structures aligned with a vertical magnetic field. This behavior is exemplified by the well documented distortion of discrete magnetic fluid droplets subjected to a field H. 3,4,31,32 When E and H are aligned both the magnetic and electric potential energies favor fluid configurations that are elongated in the common field direction so that N is reduced in magnitude. 35,36 As N decreases so too does the system energy associated with the electric and magnetic fields.…”

Section: A Potential Energy Analysis Of Emitter Formationmentioning

confidence: 97%

“…23 Analytic models of magnetic pools, droplets, and jets have been studied since the first realization of ferrofluids in the 1960s. 3,4,[24][25][26][27][28][29][30][31][32] Electrohydronamically stressed conducting and polar liquids have received even more attention due to their wide technical utility in the field of electrospray. 10,[33][34][35] There has been some limited work on combined electric/magnetic fluids, mostly studies of equilibrium droplet shapes under combined field stress for instance by Tyatushkin, 36 Dikansky,37,38 and Zakinyan.…”

Section: Introductionmentioning

confidence: 99%

Wavelength measurements of Rosensweig instabilities in a ferrofluid in a non-uniform magnetic field

Meyer¹,

King²

2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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A suitably strong electric field, applied at the free surface of a conducting or even dielectric fluid, will exert electrostatic traction on the fluid surface that can stretch the meniscus into a pointed conical shape. 1 Electrospray results when the field is strong enough to cause the tip of this 'Taylor cone' to exhaust a jet of charged droplets or ions. 2 By exact analogy with electrostatically stressed dielectric fluids, magnetic fields can distort magnetizable fluids into identical pointed geometries, 3,4 however magnetostatic jetting is never observed. 5 It is believed, yet not completely understood, that electrostatic jetting is a result of finite charge conductivity, a phenomenon which has no parallel in the magnetic fluid. Recently Meyer and King have shown that it is possible to induce hybrid electromagnetostatic jets by exciting surface instabilities in a novel electrically conductive superparamagnetic liquid. 6,7 When this fluid is subjected to simultaneous magnetic and electric fields a self-assembling array of discrete and stable cone-shaped emitters forms spontaneously in the fluid surface. While electrohydrodynamic flows, ferrohydrodynamic flows, and magnetohydrodynamic flows have long been studied separately, the ionic liquid ferrofluid described by Meyer and King is the first liquid to simultaneously respond strongly to electrostatic, magnetostatic, and Lorentz stresses, requiring a unification of EHD/FHD/MHD fluid physics. The purpose of this paper is to begin an analytic description of the fluid mechanics encountered when electromagnetically stimulating a highly conductive ferrofluid to produce spray. A potential energy analysis is used to describe the formation of the emitting cone. A linear stability analysis is performed on the resulting jet, showing that magnetic effects can radically shift the stability bounds of an electrospray.

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“…[284] They also studied the shape deformation of a water-based FF on a superhydrophobic surface under a uniform field, which showed an increase in droplet width and decrease in droplet height with increase in magnetic flux density. [285] The deformation of the FF droplets was calculated using the magnetic bond number B m , which is defined as the ratio of magnetic force to interfacial tension force. Sneyd and Moffatt proposed a theory based on a potential energy minimization and perturbation method for finding the equilibrium shape of a sessile FF droplet under the influence of a magnetic field.…”

Section: Ferrofluid Thin Films and Dropletsmentioning

confidence: 99%

Ferrofluids: Synthetic Strategies, Stabilization, Physicochemical Features, Characterization, and Applications

Joseph

Mathew

2014

ChemPlusChem

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Ferrofluids (FFs) or magnetic nanofluids are incredible smart materials consisting of ultrafine magnetic nanoparticles suspended in a liquid carrier medium, which exhibit both fluidity and magnetic controllability. Studies involving the dynamics and physicochemical properties of these magnetic nanofluids are an interdisciplinary area of research attracting researchers from different fields of science and technology. Herein, a comprehensive Review on the different aspects of FF research is presented. First, the synthesis and stabilization of various types of FFs are discussed followed by their physicochemical features such as polydispersity, magnetic behavior, dipolar interactions, formation of chainlike aggregates, and long‐range ordering. The Review also details the rheological and thermal properties, dynamic instabilities, phase behavior, and particle assemblies in FFs to form complex multipolar geometries, photonic nanostructures, labyrinth structures, thin films, and droplets. Many important characterization techniques for probing FF properties are also briefly discussed, and the numerous innovative applications and future prospects of FFs are outlined.

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Nonlinear Deformation of a Ferrofluid Droplet in a Uniform Magnetic Field

Cited by 116 publications

References 36 publications

Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning

Wavelength measurements of Rosensweig instabilities in a ferrofluid in a non-uniform magnetic field

Ferrofluids: Synthetic Strategies, Stabilization, Physicochemical Features, Characterization, and Applications

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