Electrorheological Research Articles

Rheological analysis of titanium dioxide nano-whisker based electrorheological fluids

Understanding yield stress of electrorheological (ER) fluids becomes important for not only development of advanced ER materials but also their engineering applications. This study reanalyzed dynamic yield stresses of both titanium dioxide nano-whisker- and titanium dioxide nano-particle-based ER suspensions under an input electrical field, based on the universal yield stress function proposed. The experimental data was plotted well to a single line by the scaled universal yield stress function via a deduced critical electrical field value which divides electric field dependent yield stress region with a slope of 1.5 from that with 2.0 of polarization mechanism.

Microfibrillated Cellulose Suspension and Its Electrorheology.

Microfibrillated cellulose (MFC) particles were synthesized by a low-pressure alkaline delignification process, and their shape and chemical structure were investigated by SEM and Fourier transformation infrared spectroscopy, respectively. As a novel electrorheological (ER) material, the MFC particulate sample was suspended in insulating oil to fabricate an ER fluid. Its rheological properties—steady shear stress, shear viscosity, yield stress, and dynamic moduli—under electric field strength were characterized by a rotational rheometer. The MFC-based ER fluid demonstrated typical ER characteristics, in which the shear stresses followed the Cho–Choi–Jhon model well under electric field strength. In addition, the solid-like behavior of the ER fluid was investigated with the Schwarzl equation. The elevated value of both dynamic and elastic yield stresses at applied electric field strengths was well described using a power law model (~E1.5). The reversible and quick response of the ER fluid was also illustrated through the on–off test.

BaTiO3 piezoelectric powder blended electrorheological fluids

In this paper, composite electrorheological (ER) fluids were prepared by blending piezoelectric particles (PEPs) with organic polymer ER particles in silicone oil. The shear stress of the composites was greatly improved by adding surfactant polyethylene glycol (PEG) to disperse the particle aggregation. Composites with 500 nm BaTiO3 showed better ER properties than that of the 50 nm BaTiO3 composite. Nano-sized SiO2 powder was effective in making the composite suspension stable. Optic microscope observation indicated that the particles in the composite ER fluid formed a chain structure under an applied electric field. Compared with the DC electric field, the high-frequency AC electric field made the chain structure of fluids thinner and weakened the strength of the chain. The main reason was considered to be that the response time of the ER particles was of the microsecond order.

Description and visualization of the highly dynamic behavior of the electrorheological effect

When an electrorheological fluid is located between two electrodes and an electrical voltage is applied to them, the particles in the fluid move and form chains along the electric field lines. This phenomenon is called the electrorheological effect. The exact behavior of the particles has not yet been studied completely. Some optical investigations of particle motion or behavior have been performed, but did not take into account the high dynamic range directly after the application of an electric field. This study is intended to help explain how the particles behave when they encounter an electric field and then try to align themselves with it. There is an investigation into how these chains develop in a microchannel within milliseconds. For this purpose, the particle behavior of the electrorheological fluid is investigated with high dynamic imaging using a microscope. A high-speed camera records videos of the first milliseconds at 3000 fps synchronously with the application of an electric field. The results provide a better understanding of the chain formation and particle behavior of the electrorheological effect in the high dynamic range and can be used for the design of electrorheological applications as well as simulations of the particle movement.

Influence of the Polarity of the Electric Field on Electrorheometry

Uniaxial extensional flow is a canonical flow typically used in rheological characterization to provide complementary information to that obtained by imposing simple shear flow. In spite of the importance of having a full rheological characterization of complex fluids, publications on the rheological characterization of mobile liquids under extensional flow have increased significantly only in the last 20 years. In the case of the rheological characterization of electrorheological fluids, the situation is even more dramatic, as the ERFs have been exclusively determined under simple shear flow, where an electrorheological cell is attached to the rotational rheometer generating an electric field perpendicular to the flow direction and that does not allow for inverting the polarity. The very recent work published by Sadek et al., who developed a new electrorheological cell to be used with the commercial Capillary Breakup Extensional Rheometer (CaBER), allows for the very first time performing electrorheometry under extensional flow. By means of the same experimental setup, this study investigates the influence of the polarity of the imposed electric field on the filament thinning process of a Newtonian and an electrorheological fluid. Results show that a polarity against the gravity results in filament thinning processes that live longer or reach a stable configuration at lower intensities of the applied electric field.

Free and forced vibration of sandwich plates with electrorheological core and functionally graded face layers

The free and forced vibration of a sandwich plate with functionally graded face layers and electrorheological fluid core is presented in this article. Assuming classical thin plate theory for face sheets and first order shear theory for the core layer, the equations of motions are derived using Hamilton’s principle. The simply-supported boundary condition is considered for all edges and the generalized Fourier series are employed to represent the displacements of the sandwich plate. The natural frequencies and loss factors are obtained by solving the complex eigenvalue problem. The results of free and forced responses are compared and validated with the previous articles and effects of electric field, geometric aspect ratio, functionally graded component ratios and core layer thickness on the dynamic behavior of the sandwich plate are studied.

Electrorheological Effects of Synthesized Octa-cyanopropylsilsesquioxane Cage Structure.

This article introduces a new electrorheological (ER) fluid. A molecular cage structure for electrorheological applications has been synthesized, and the ER behavior of the octa-functionalized polyhedral oligomeric silsesquioxane (POSS) variant in silicone oil (PDMS) has been shown. The hydrolyzation route has been used in the synthesis, the microstructure has been displayed using scanning electron microscopy, the yield has been ascertained, and the compound has been characterized. The rheological properties are demonstrated on the ER fluid through steady flow and oscillatory tests to investigate the effects of change in concentration on the functional group attached to the inorganic silicon–oxygen core structure of the POSS compound. The electrorheological efficiency was analyzed, and dielectric characterization was done. The flow curve was described by the Herschel–Bulkley model, and yield stress values were derived from the model. The octa-cyanoPOSS/PDMS electrorheological fluid has been shown to have ER activity.

Comparing the Electrorheological Effect of Polyhedral Silsesquioxane Cage Structures with Different Numbers of Cyanopropyl Functional Groups.

Previous research has shown that polyhedral oligomeric silsesquioxane (POSS) particles in silicone oil show electrorheological (ER) activity. The effect of the number of same functional groups attached to POSS cage structures on the ER activity of these structures is discussed in this article. Two compounds of the octahedral geometry (T8) of cyanopropyl POSS (cPOSS) were used for this investigation. One of the compounds (monofunctionalized cPOSS) was commercially available, and the other (octafunctionalized cPOSS) was synthesized. The effects of the number of cyanopropyl functional groups attached to the inorganic silicon–oxygen core structure of the POSS compounds on the rheological properties are demonstrated through steady flow and oscillatory tests. Particular attention is paid to how the number of cyano functional groups affects the behavior of these suspensions of cPOSS compounds in silicone oil under increasing electric field strength. The research also contributed answers to the effects of changing the concentration of the cPOSS particles in the suspension. The flow curve was described by the Herschel–Bulkley model, and the yield stress values were ascertained from the model. The dielectric characterization was also done to support the ER response results, which showed that the octafunctionalized compound gave a better response. The differences in the ER properties of these compounds have also been discussed with the tests.

Alternating current response and visualization of electrorheological fluid

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.

Effect of surfactant on the dielectric and electrorheological properties of zinc borate/silicone oil dispersions

Zinc borate (ZB) particles dispersed in silicone oil (SO) at concentrations of ϕ = 5vol%-20vol% were subjected to dielectric analysis to elucidate their polarization strength, time, and mechanism. Results revealed that all virgin dispersions lacked polarization. Triton X-100, a non-ionic surfactant, was added to ZB/SO dispersions to enhance the polarizability of ZB particles. The addition of 1vol% Triton X-100 enhanced the polarizability of ZB/SO dispersions, and the 15vol%ZB/SO system provided the highest dielectric difference Δe′ (the difference in e′ values at zero and infinite frequency, Δe′ = e0 - e221D) of 3.64. The electrorheological (ER) activities of the ZB/SO/Triton-X dispersion system were determined through the ER response test, and viscoelastic behaviors were investigated via oscillation tests. A recoverable deformation of 36% under an applied electrical field strength of 1.5 kV/mm was detected through creep and creep recovery tests.

The influence of alternating current and direct current electric fields on the rheological behavior of electrorheological fluids with particles of the different crystalline structure

The rheological behavior of electrorheological fluids with dispersed fillers whose particles have different crystalline structures is investigated in direct and alternating electric fields. The dielectric characteristics of the materials were measured and the influence of the strength, frequency, and shape of the signal of electric field was investigated, and the influence of temperature on the shear stress in electrorheological fluids was estimated in direct current electric field.

A novel bending microactuator with integrated flexible electro-rheological microvalves using an alternating pressure source for multi-actuator systems

This paper presents a novel bending microactuator with integrated flexible electro-rheological microvalves (FERVs) using an alternating pressure source for multi-actuator systems. The proposed bending microactuator is a fluidic elastomer actuator that has two fluidic chambers inside and can bend with the chamber pressures controlled by the integrated FERVs, each of which has a flexible structure and changes a flow of electro-rheological fluid (ERF) through its viscosity change due to an applied electric field. The utilization of the FERVs in the actuator reduces the overall size, while the benefits of the alternating pressure source are reduction of the number of pipes in a multi-actuator system and removal of the fluid reservoir tank. The mathematical models were demonstrated and utilized for optimizing and designing the dimensions of the actuator to obtain the maximum bending angle, the fast response, and the highest output force. The designed actuator was successfully fabricated using MEMS technologies and experiments were conducted to investigate the bending angle and the response time of the successfully fabricated actuator. The results showed good agreement between the experimental results and the simulation results, which proved the validity of the proposed models. Comparing with the previously proposed microactuator with an FERV, the proposed actuator had 4.5 times larger bending angle. From the results, the optimized actuator showed the feasibility for use in e.g. micro gripper application.

Tunable Electrorheological Fluid Microfluidic Rectifier: Irreversibility of Viscous Flow Due to Spatial Asymmetry Induced Memory Effects.

Because of the reversibility of viscous flow it is not expected to obtain a fluidic rectifier simply from geometrical asymmetry without any moving mechanical parts. Here, we found a counterexample by using spatial asymmetry combined with an electric field to inject memory effects that render the flow irreversible. This stems from the strong dependency of the electrorheological fluid particle chaining on the flow direction. A funnel-shaped microfluidic rectifier with electrorheological fluid has been shown to be easily and rapidly tuned via the applied electric field to achieve an almost order of magnitude rectification along with pressure oscillations. These findings are of importance for the realization of fluidic diodes, rectifiers, and ratchets.

Comparative study of three robust observers for automotive damper force estimation

This paper aims at comparing three robust observers used to estimate the damping force of electrorheological (ER) dampers in a vehicle suspension system. Firstly, a nonlinear quarter-car model, augmented with a first-order dynamical nonlinear damper model, is developed. The first two methods are designed considering the nonlinearity as an unknown input and minimizing the effect of the unknown input disturbances (including a nonlinearity term, the measurement noise and the unknown road profile) on the estimation errors, by using an H2 and H∞ criterion, respectively. The latter method aims at minimizing only the effects of measurement noises and road profiles on the state variable estimation errors by using a H∞ criterion, while the nonlinearity is bounded through a Lipschitz condition. For implementation issue, two low-cost sensors signals (two accelerometers data from the sprung mass and the unsprung mass) are considered as inputs for the observer designs. Then, the observers are implemented in real-time on the INOVE test bench from GIPSA-lab (1/5-scaled real vehicle) to assess and compare experimentally the performances of the approaches. Both simulations and experimental results demonstrate a better effectiveness of the latter observer in terms of the ability of estimating the damper force in real-time despite the nonlinearity, the measurement noises and the road disturbances.

First MnO2-based electrorheological fluids: high response at low filler concentration

Nanoparticles of MnO2 with different shapes (needle-like α-MnO2 and spherical δ-MnO2) were proposed as promising fillers for electrorheological fluids (ERFs). A thorough study of the dielectric properties of α-MnO2 and δ-MnO2 suspensions in silicone oil enabled estimation of the values of their dielectric permittivity and dielectric relaxation times. The study of MnO2-filled materials with various filler contents, and under various electric field strengths, in shear and uniaxial tensile and compressive stress regimes, revealed that needle-like α-MnO2 nanoparticles, in comparison with spherical δ-MnO2 particles, lead to better mechanical properties of the fluids. The most intriguing property of MnO2-based electrorheological fluids is their high electrorheological response at low filler content: ERF containing only 4.5 vol.% of α-MnO2 in silicone oil demonstrated a 18 kPa tensile strength in a 5 kV electric field.

High electrorheological effect in Bi1.8Fe1.2SbO7 suspensions

We report on the first experimental evidence of the electrorheological effect in suspensions of superfine pyrochlore-type Bi1.8Fe1.2SbO7 powders. Tensile-compressive and shear stress studies of the electrorheological fluids, with various filler contents, revealed an exceptionally high electrorheological effect in the materials – the tensile yield strength at 5kV/mm reached about 20kPa. The frequency dependencies of dielectric permittivity, dielectric loss tangent, and the conductivity of the suspensions with various filler contents allowed estimation of the dielectric permittivity values for superfine Bi1.8Fe1.2SbO7 particles at zero and infinite frequencies. The study reveals new oxide materials as promising fillers for electrorheological fluids.

Interfacial Polarization and Electroresponsive Electrorheological Effect of Anionic and Cationic Poly(ionic liquids)

Owing to weak ion pair electrostatic interaction and intrinsically hydrophobic nature, poly(ionic liquids) (PILs) have potentiality as anhydrous polyelectrolyte-based electrorheological (ER) smart ...

Experimental investigations on electrorheological properties of lubricating oils containing ionic liquid. Part. 1. Investigations with modified Brookfield DV-III Ultra Viscosimeter

The results of experimental investigations on electrorheological (ER) properties of lubricating oils which contain ionic liquids, are presented in this article. The investigations were carried out on the special stand which was projected for this aim. On this stand there was used the modified Brookfield viscosimeter. Electrorheological properties of two mixtures were tested, i.e., silicone damping liquid GP-1 which is polimethylsiloksane mixture containing 2% (v/v) of ionic liquid CJ 001, i.e., tetrafluoroboran 1-methyl-3-octyloxymethylimidazolium as well as base polialfaolefine oil PAO-6 which contains 2% (v/v) of ionic liquid CJ 008, i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide. Selection of components of both mixtures was based on the results of investigations of miscible and on evaluation of basic phys-chem properties. The investigations showed that the made mixtures have generated the ER effect, but it was short-lived effect, suggesting the changes of inner structure of these mixtures. Therefore, we have planned the next investigations, among others dielectric spectroscopy and microscope observations in situ of these mixtures in external electric fields. The aim of those investigations will be to record the fading ER effect and to understand this mechanism. Keywords: electrorheological effect, homogenous mixtures, lubricants, ionic liquids

Facile fabrication of core-shell typed silica/poly(diphenylamine) composite microparticles and their electro-response

Novel semi-conductively encapsulated microspheres were fabricated by coating poly(diphenylamine) (PDPA) onto spherical silica particles via chemical oxidative polymerization. Their nanoscale-encapsulated spherical structure and PDPA shell thickness of approximately 30 nm were observed by both SEM and TEM. Fourier transform infrared spectroscopy confirmed the successful surface-modification of silica particles with PDPA, which was probably obtained through π−π* stacking interactions between the aromatic groups of PDPA and n-[3-(trimethoxysilyl) propyl]aniline as a grafting agent attached to the silica surface. Thermogravimetric analysis revealed the reasonable thermal stability of the fabricated particles. The electrorheological (ER) suspension (10 vol%) with the silica/PDPA composite microspheres was fabricated without a typically used de-doping process. Their dynamic and elastic yield stresses increased with applied electric field strength, following the power-law model (~E1.5). Their shear stress and their solid-like behavior were explained using the Herschel-Bulkley model and Schwarzl equation, respectively. The immediate and reversible response of the ER fluids was observed using on-off tests.

Application of smart electro-rheological dampers in semi-active control of electro-rheological sandwich plates with nanocomposite facesheets rested on orthotropic visco-Pasternak foundation

In this research, semi-active control of sandwich plates with electro-rheological (ER) core and carbon nanotubes-reinforced composite facesheets using smart ER dampers is studied. Sandwich plate is subjected to the external electric field and rested on orthotropic visco-Pasternak foundation. The material properties of ER core and nanocomposite facesheets are obtained by Yalcintas model and Eshelby–Mori–Tanaka approach, respectively. The governing equations of motion are solved by a combination between finite element and Newmark methods for clamped and simply supported boundary condition. The effects of various parameters such as applied voltage, controlled electric field and initial gap of the electrodes on the vibration suppression time are discussed. The results show that the settling time of system introduced in this work is much less than previous researches in this field which is a very important advantage.