Yield Hardening of Electrorheological Fluids in Channel Flow

Helal, Ahmed; Qian, Bian; McKinley, Gareth H.; Hosoi, A. E.

doi:10.1103/physrevapplied.5.064011

Cited by 11 publications

(13 citation statements)

References 40 publications

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“…The shear stress of the ER fluids is generally measured from a controlled shear rate (CSR) test mode under various electric field strengths, and increases linearly with increasing shear rate in the absence of an electric field, indicating Newtonian fluid-like characteristics. On the other hand, upon the application of an electric field, ER fluids exhibit Bingham fluid-like properties with a significant yield stress [ 131 , 132 ]. The Bingham model, a well-known rheological equation of state used to explain the shear stress characteristics of suspensions, has also been adopted to ER fluids under an electric field.…”

Section: Electrorheological Characteristicsmentioning

confidence: 99%

Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

Dong¹,

Han²,

Choi³

2018

Polymers

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Functional core-shell-structured particles have attracted considerable attention recently. This paper reviews the synthetic methods and morphologies of various electro-stimuli responsive polyaniline (PANI)-coated core-shell-type microspheres, including PANI-coated Fe 3 O 4 , SiO 2 , Fe 2 O 3 , TiO 2 , poly(methyl methacrylate), poly(glycidyl methacrylate), and polystyrene along with their electrorheological (ER) characteristics when prepared by dispersing these particles in an insulating medium. In addition to the various rheological characteristics and their analysis, such as shear stress and yield stress of their ER fluids, this paper summarizes some of the mechanisms proposed for ER fluids to further understand the responses of ER fluids to an externally applied electric field.

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Section: Electrorheological Characteristicsmentioning

confidence: 99%

Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

Dong¹,

Han²,

Choi³

2018

Polymers

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“…However, playing on the above physico-chemical parameters turns out to be difficult, if not impossible when the chemistry of the material is strongly constrained. Electro-or magnetorheological materials allow for such tuning through the use of electrical and magnetic fields [11][12][13][14]. Yet, applications are obviously restricted to materials with specific compositions [15][16][17].The exquisite sensitivity of colloidal gels to external mechanical perturbations provides an alternative route to interact with their microstructure [18][19][20].…”

mentioning

confidence: 99%

Rheoacoustic Gels: Tuning Mechanical and Flow Properties of Colloidal Gels with Ultrasonic Vibrations

et al. 2020

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Colloidal gels, where nanoscale particles aggregate into an elastic yet fragile network, are at the heart of materials that combine specific optical, electrical and mechanical properties. Tailoring the viscoelastic features of colloidal gels in real-time thanks to an external stimulus currently appears as a major challenge in the design of "smart" soft materials. Here we show that ultrasound allows one to achieve this goal in well-controlled conditions. By using a combination of rheological and structural characterization, we evidence and quantify a strong softening in three widely different colloidal gels submitted to ultrasonic vibrations (with submicron amplitude and frequency 20-500 kHz). This softening is attributed to the fragmentation of the gel network into large clusters that may or may not fully re-aggregate once ultrasound is turned off depending on the acoustic intensity. Ultrasound is further shown to dramatically decrease the gel yield stress and accelerate shear-induced fluidization, thus opening the way to a full control of elastic and flow properties by ultrasonic vibrations.Colloidal gels constitute a class soft materials with a huge spectrum of applications, ranging from paints, oil extraction and construction to pharmaceuticals and food products [1,2]. These gels are typically formed from the aggregation of attractive nanoscale particles that arrange into a space-spanning network which strength provides the system with elastic properties at rest. The particle network is, however, fragile enough that rather weak external forces disrupt the gel structure and induce flow above a critical yield strain or stress [3]. Such unique mechanical and flow properties are key to applications that require an interplay between solid and fluid behaviour, including cement placement, ink-jet printing or flow-cell batteries. In this context, decades of research have investigated the influence of physico-chemical parameters such as temperature, pH and ionic strength on the aggregation of attractive particles into colloidal gels [4][5][6][7][8][9]. While electrostatic repulsion, van der Waals attraction and steric interaction, combined in the well-known DLVO interparticle potential, generically lead to the formation of fractal networks through diffusion-or reaction-limited cluster aggregation, additional chemical effects such as hydration layers or particle bridging generate a wealth of more complex gel microstructures [10]. In the quest of smart, responsive materials, tuning the gel architecture in realtime and reversibly is a key challenge. However, playing on the above physico-chemical parameters turns out to be difficult, if not impossible when the chemistry of the material is strongly constrained. Electro-or magnetorheological materials allow for such tuning through the use of electrical and magnetic fields [11][12][13][14]. Yet, applications are obviously restricted to materials with specific compositions [15][16][17].The exquisite sensitivity of colloidal gels to external mechanical perturbations provides an...

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“…In comparison, response times were even very slow, sometimes too slow. These saturation problems can also be seen in Qian et al (2016), but were not completely solved. The reasons for this had to be investigated first to find out how it can be solved and what the problem is.…”

Section: Saturationmentioning

confidence: 99%

“…With the results of the visualization, it is possible to compare them with the simulations. Yield stress investigation on microchannels with fluids of different particle volume fractions was performed by Helal et al (2016). Chen and Luckham (1993), Ginder and Ceccio (1995), 1 Ma et al (1996), Misono et al (2004) and Espin et al (2007) described the alternating current (AC) response of ER-Fluids and showed a dependence on the electric frequency.…”

Section: Introductionmentioning

confidence: 99%

Alternating current response and visualization of electrorheological fluid

Bauerochs

Huo

Yossifon

et al. 2019

Journal of Intelligent Material Systems and Structures

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The electrorheological effect produced by an ER-Fluid with an applied electric field is not yet fully understood. However, it is significant to understand how the viscosity increases, and thus, the ER-Effect works to optimally design ER-Applications. In this article, the ER-Effect and its response to different voltage forms with varying frequencies within a miniature fluidic device are described and visualized using a microscope. The different pressure drops across the channel are measured. Problems such as long saturation times using microchannels in combination with low flow velocities are described and explained. An electric frequency dependence of the chain formation has been discovered and that the use of alternating current offers superior performance in comparison with direct current. The optimal operating point for achieving the largest possible pressure difference is from 5 to 10 Hz for square wave voltages. In this frequency range, the performance of the electrorheological effect is greater than using direct current. From approximately 10 Hz, the power decreases with increasing electric frequency. Above 20 Hz, direct current is superior to alternating current voltage, so is not recommended for use in this range.

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Yield Hardening of Electrorheological Fluids in Channel Flow

Cited by 11 publications

References 40 publications

Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

Polyaniline Coated Core-Shell Typed Stimuli-Responsive Microspheres and Their Electrorheology

Rheoacoustic Gels: Tuning Mechanical and Flow Properties of Colloidal Gels with Ultrasonic Vibrations

Alternating current response and visualization of electrorheological fluid

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