Electrorheological Research Articles

Multiobjective optimization of hydrostatic thrust bearing operating with electrorheological lubricant using Taguchi-fuzzy technique

An electrorheological (ER) fluid falls in the category of a smart lubricant. In an ER lubricant, the dielectric microparticles are suspended in an insulating lubricant like silicon oil. The properties of ER fluids change when they encounter an external electric field. In the present study, the ER lubricant is modeled using a continuous Bingham model. The finite element method is utilized to solve the Reynolds equation to compute fluid film pressure and associated performance indices like load-carrying capacity, stiffness, and damping parameters of hydrostatic thrust bearing. In the present study, the influencing variables, that is, recess shapes, compensating elements, and strength of an electric field have been optimized using the fuzzy-based Taguchi optimization technique. The optimal combination of recess shape, compensating element, and electric field is required to enhance the performance of the hydrostatic thrust bearing. The authors attempt to see the interaction of the input variable by the trade-off study graph. A Taguchi fuzzy-based multipurpose optimization was proposed to optimize the performance indices and an optimal combination of compensating elements, recess shape, and electric field has been presented.

Parameter characterization of variable bending stiffness module with electrostatic layer jamming based on giant electrorheological fluid

Soft grippers exhibit good adaptability, but their grasping performance is limited. Variable-stiffness technology has been applied to soft grippers to address this problem. Therefore, a variable bending stiffness module (VBSM) with electrostatic layer jamming based on a giant electrorheological fluid (ELJ-GERF) for soft robots is proposed in this study, which exhibits a faster response time and a wider range of stiffness variation. A VBSM prototype is fabricated, and a theoretical model is established. The stiffness is mainly affected by the electrode quantity, overlapping area of electrode plates, insulator and conductive layers’ thickness, medium thickness and the exciting voltage. Direct current (DC) voltage experiments and alternating current (AC) voltage experiments were conducted on the test samples of filled with air (ELJ-AIR), silicone oil (ELJ-OIL), and ELJ-GERF. The experimental result show that stiffness-regulation of the VBSM can be achieved by adjusting the exciting voltage, and AC voltage being more suitable for regulating the stiffness of the VBSM than DC voltage. For AC voltage, the stiffness of ELJ-GERF increases to 53.5 times when a 4 kV voltage is applied. The stiffness variation range is about 2 to 3 times greater than that of ELJ-AIR or ELJ-OIL. Through the stiffness characterization experiment, the stiffness of the VBSM in this study is influenced by the viscosity of the GERF and the gap between the electrode plates. Through the capacitance test, the VBSM exhibits self-sensing ability. Finally, the VBSM is applied to a soft gripper, the vibration performance and variable stiffness performance in its application are verified.

Effect of textured shapes on slot entry hybrid conical journal bearing with ER lubricant behavior

This article investigates the influence of textured shapes and electrorheological fluid (ERF) behavior on slot entry hybrid conical journal bearing system (HCJBs). The slot entry restrictor is used as a compensating element to supply the lubricant in the clearance space. Spherical, rectangular, and triangular textured shapes over the surface of conical bearings have been employed. Furthermore, the intelligent properties of ERF on the behavior of textured slot entry HCJBs have been analyzed. The finite element method (FEM) and the successive iteration-based Gauss-Seidel method have been used to solve the modified Reynolds equation. The results drawn from this study show different influences on the bearing performance for different textured shapes. Using textured surfaces and ERF improves the minimum fluid film thickness, stability, and bearing stiffness compared to the non-textured bearing.

Effects of promoter and dedoping process on electrorheological response of polyaniline-graft-chitosan copolymer

In this study, electrorheological (ER) properties of biodegradable and conducting polyaniline-graft-chitosan (PAni-g-CS) copolymer particles were investigated. For this purpose, PAni and PAni-g-CS particles were synthesized by using in situ oxidative radicalic polymerization method. At first, PAni and PAni-g-CS/silicone oil (SO) ER suspensions (15% V/V) were subjected to external electric field and they exhibited low ER activity. When the external electric field strengths ([Formula: see text] were increased, both the suspensions showed electrical breakdown. Therefore, virgin PAni and PAni-g-CS were first subjected to dedoping process by treating with 1.0 M NaOH(aq) and non-ionic surfactant Triton X-100 (T-X) surfactant to enhance the expected ER activity and prevent the electrical breakdown. But we observed that the addition of T-X as promoter had no significant effect on the ER activity. On the other hand, electric filed-induced viscosities of both the suspensions were observed to enhance after the dedoping (DD) process and electrical breakdown prohibited. After the DD process, DD PAni-g-CS/SO ER system exhibited the highest electric field-induced viscosity by reaching 400[Formula: see text]Pa[Formula: see text]⋅[Formula: see text]s at [Formula: see text][Formula: see text]kV/mm. The highest ER efficiency was also obtained for DD PAni-g-CS/SO system at 15% (V/V) as 79. Additionally, typical shear thinning non-Newtonian viscoelastic behavior was observed under externally applied E. The conduction model of DD PAni-g-CS/SO system was determined to well fit the conduction model by showing a slope of [Formula: see text] calculated from the E vb. yield stress graph. In conclusion, conducting and biodegradable-dedoped PAni-g-CS particles would be a good candidate for potential ER applications as dry-based ER materials having high colloidal stability of 76%.

Experimental research on response characteristics of optically controlled micro-damping system based on PLZT ceramic-electrorheological fluid

Electro and magnetic rheological materials show an increasingly important position in potential applications, such as clutch, vibration damping, and micro-valves because of their fast response speed. However, easy to cause electromagnetic interference is always an unresolved problem of electro and magnetic stimulated smart materials. In this paper, combining the advantages of PLZT ceramic and electrorheological fluid (ERF), an optically controlled micro-damping system is designed, with advantages of little electromagnetic interference and non-contact control. The mechanism of the optically controlled micro-damping system is carried out, and the electrorheological fluid pressure difference of optically controlled micro-damping system under different light intensities are obtained via experimental methods. Compared experimental data with theoretical analysis, the results show the feasibility of the optically controlled micro-damping system based on PLZT ceramic-ERF and its application prospect in the field of damping control are proved.

Influence of alternating electric field on electrorheological effect of aqueous dispersions of stevensite

Upon deionization of the aqueous dispersion of stevensite, a type of smectite clay minerals, a low-viscosity colorless transparent dispersion is obtained. The phenomenon known as the electrorheological (ER) effect has been previously reported when a weak electric field of several V/mm is applied to the stevensite aqueous dispersion. In this study, the influence of the waveform and frequency of the electric field was investigated while keeping the electric field intensity constant. It was observed that as the acceleration of the applied electric field intensity increased, the stress response to the electric field improved. Increasing the frequency of the electric field led to a reduction in the induced stress; however, it improved the response rate of stress. It has been indicated that even at higher electric field frequencies, the potential for observing the ER effect exists with higher electric field intensities. Maintaining a low electrolyte concentration may facilitate the development of novel ER fluids capable of instantaneously responding to the application or removal of electric fields.

Probing effect of counterions on electric field stimuli responsive behaviours of smart organoboron-based polyelectrolytes

This is the first study to be introduced to the electrorheology (ER) literature focusing on organoboron-based polyelectrolyte colloidal systems namely: polymeric lithium tartaric acid borate (Poly-LiTB) and polymeric sodium tartaric acid borate (Poly-NaTB). Syntheses of functional polyelectrolytes were monitored via 1H-NMR, ATR-FTIR and SEM-EDX analyses. Electrical conductivity measurements indicated that Poly-LiTB and Poly-NaTB were in semi-conductive region indicating potential smart ER behaviour. A higher polarizability was detected for 20 wt.% Poly-LiTB dispersions in silicone oil (SO) by dielectric measurements. As expected, improved ER performances were obtained for Poly-LiTB/SO colloidal dispersion (τy = 265 Pa, EReff = 87, G′ = 80 kPa at 10 Hz, τc = 98 Pa, recovery% = 68) compared to Poly-NaTB/SO colloidal dispersion (τy = 195 Pa, EReff = 38, G′ = 42 kPa at 10 Hz, τc = 42 Pa, recovery% = 67). To sum up, it was determined that the best ER activity was detected by the organoboron-based polyelectrolyte containing Li+ counterion with smaller ionic radius and higher ionic mobility when their physicochemical properties are taken into account.

Sensors and Sensing Devices Utilizing Electrorheological Fluids and Magnetorheological Materials-A Review.

This paper comprehensively reviews sensors and sensing devices developed or/and proposed so far utilizing two smart materials: electrorheological fluids (ERFs) and magnetorheological materials (MRMs) whose rheological characteristics such as stiffness and damping can be controlled by external stimuli; an electrical voltage for ERFs and a magnetic field for MRMs, respectively. In this review article, the MRMs are classified into magnetorheological fluids (MRF), magnetorheological elastomers (MRE) and magnetorheological plastomers (MRP). To easily understand the history of sensing research using these two smart materials, the order of this review article is organized in a chronological manner of ERF sensors, MRF sensors, MRE sensors and MRP sensors. Among many sensors fabricated from each smart material, one or two sensors or sensing devices are adopted to discuss the sensing configuration, working principle and specifications such as accuracy and sensitivity. Some sensors adopted in this article include force sensors, tactile devices, strain sensors, wearable bending sensors, magnetometers, display devices and flux measurement sensors. After briefly describing what has been reviewed in a conclusion, several challenging future works, which should be undertaken for the practical applications of sensors or/and sensing devices, are discussed in terms of response time and new technologies integrating with artificial intelligence neural networks in which several parameters affecting the sensor signals can be precisely and optimally tuned. It is sure that this review article is very helpful to potential readers who are interested in creative sensors using not only the proposed smart materials but also different types of smart materials such as shape memory alloys and active polymers.

Magnetic Characterization of MR Fluid by Means of Neural Networks

Magnetorheological and electrorheological fluids manifest a change in rheological behavior when subjected to a magnetic or electric field, respectively, such that they require electrical and magnetic characterization. In this paper, a simple and accurate mathematical model based on a small number of parameters provides the relative magnetic permeability of magnetorheological fluids as a function of the applied magnetic field. Furthermore, for the testing and magnetic characterization of magnetorheological fluids, a new metering equipment setup is implemented. Starting with the achieved experimental data, the mathematical relation μr=f(B) is represented by means of a radial basis function neural network, with neurons having a Gaussian activation function; by means of post-training pruning procedures, the trained neural network is applied using the proposed data. Therefore, the obtained mathematical relation μr=f(B) is in good agreement with the experimental data, with an approximate error of 8%.

Investigation of a 2-DOF GER fluid damper in cut mode

Dampers incorporating smart materials have attracted significant interest for their application in vibration and shock isolation. Traditionally, these dampers work through shear, flow, and squeeze modes, each unique in its strengths and limitations. However, this study introduces a working mode, termed cut mode, which integrates the strengths of these existing modes. Structurally resembling the flow mode, operationally akin to the shear mode, and behaving similarly to the squeeze mode, the cut mode promises a novel approach to damping. Consequently, extensive research has been conducted at the particle level to develop a mathematical model for the cut mode, grounded in chain formation and breaking mechanisms. Thereafter, a verification prototype damper was designed to demonstrate this concept’s practicality, with the Giant Electrorheological (GER) fluid—a rheological fluid with exceptional yield strength—being employed. This damper features a multilayer cylindrical structure tailored for the cut mode, providing 2-degree of freedom (DOF) damping capabilities. This dual-DOF design is ideal for robotic arm joint applications, as it can offer damping for both axial translation and circumferential rotation simultaneously. In addition, four orifice boards were designed, fabricated, and tested to optimize and enhance the effectiveness of the cut mode further. The results are impressive, the proposed cut mode damper exhibits superior performance characteristics, indicating its great potential for engineering applications.

A new ER valve composed of multilayer mesh electrodes

In many cases, ER valves are required to be used at lower operating voltages. For example, to develop a two-dimensional Braille matrix display, it is necessary to lay out many ER valves and control each Braille dot independently. If the commonly used parallel plate electrodes are applied, a low voltage can only be used when the electrode gap is very small, which will make the ER valve flow resistance very large, thus making it difficult to achieve effective control. A new type of ER valve composed of multilayer mesh electrodes was designed, which are arranged vertically in the direction of ER fluid flow. The flow rate of the ER valve is determined by the opening ratio of the mesh electrodes. This type of mesh electrode results in a more complex electric field distribution, which has a different action pattern on ER fluid yield stress compared to parallel electrodes. The non-uniform electric field generated by mesh electrodes under different operating voltages was simulated using COMSOL software, and the pressure drops of ER valves with various sizes of mesh electrodes under different voltages were experimentally investigated. The results indicate that the longitudinal electric field component plays a dominant role, and the stress of the ER fluid exhibits a periodic and gradient distribution. This valve exhibits good ER performance when the applied voltage is much lower than that of parallel electrodes. At the same time, the flow rate of the ER valve can be increased by enlarging the opening ratio of the mesh electrodes. Even if the applied voltage is 180 V, the pressure drop of the ER valve is large enough and the operation stability is good. This new type of ER valve makes the device small in size, easy to control intelligently and low cost. Multilayer mesh electrodes also have universal application value in ER technology.

Interfacial polarization and electrorheological effect of homo-poly(ionic liquid) and poly(ionic liquid)-hexyl methacrylate copolymer microsphere particles

Homo-poly(ionic liquid) (HomoPIL) microsphere particles of poly[2-(methacryloyloxy)ethyltrimethylammonium][bis(trifluoromethanesulfonyl)imide] (P[MTMA][TFSI]) and poly[2-(methacryloyloxy)ethyltrimethylammonium][hexafluorophosphate] (P[MTMA][PF6]), as well as their corresponding copolymer microsphere particles obtained through copolymerization with hexyl methacrylate (HMA), were synthesized as electrorheological (ER) materials. The morphology and structure of these synthesized particles were characterized using scanning electron microscopy (SEM), 1H nuclear magnetic resonance spectroscopy (1H NMR), Fourier-transform infrared spectroscopy (FT-IR), and small-angle X-ray scattering spectra (SAXS). Electrorheological measurements were conducted for these polyelectrolyte-based suspensions at room temperature, revealing that the HMA composition has a different effect on the ER effect of the two poly(ionic liquid)s. Differential scanning calorimetry (DSC) and temperature-modulated dielectric analysis (TMDA) were employed to investigate the effect of HMA composition on the glass transition temperature and interfacial polarization of these polyelectrolytes, suggesting that the incorporation of HMA affect the ER effect of PILs via changing the density of charge carriers and the counterion mobility. This study presents a potential approach for enhancing the electrorheological properties of poly(ionic liquid)s.

Development of Novel Hydraulic 3D Printed Actuator Using Electrorheological Fluid for Robotic Endoscopy

Endoscopy has made a significant and noteworthy contribution to the field of medical science and technology. Nevertheless, its potential remains constrained due to the limited availability of rigid or flexible endoscopes. This paper introduces a novel hydraulic actuator based on electrorheological fluid (ERF) as a pivotal advancement in bridging the existing gap within the realm of endoscopy. Following a comprehensive introduction that briefly outlines the electrorheological effect, the subsequent section is dedicated to the elucidation of the actuator’s development process. Challenges arise, particularly in terms of miniaturization and the realization of a hydraulically sealed system with integrated valve electrodes. An internal electrorheological valve system consisting of four valves that are controlled using a pulse-width modulated high voltage was suitable for position control of the antagonistic hydraulic actuators. High-precision stereolithography (SLA) printing has proven practical for manufacturing actuator components. For functional testing, a test bench was set up in which the actuator follows a setpoint through a PI control loop. The control deviation ranged from 0.6 to 1 degree, with a response time between 6 and 8 s. The experiments have demonstrated that through the use of ERF and integrated valve electrodes, a miniaturized functional actuator can be constructed.

Mimicking Emotional Chinese Calligraphy Using a Variable Stiffness Flexible Gripper

AbstractFlexible grippers require appropriate stiffness to ensure stability and efficiency in unpredictable environments. While combining materials with variable stiffness and elastomers holds significant promise in this regard, concurrently achieving actuation and stiffness modulation typically results in heightened structural complexity and responsiveness issues. In this study, a giant electrorheological dielectric elastomer (GERDE) with high dielectric and high electrorheological (ER) properties is obtained by introducing giant electrorheological particles into silicone elastomers, further substantiating the ability to functionally couple actuation and stiffness‐tuning, as well as application of a flexible gripper in mimicking emotive calligraphy. Specifically, GERDE exhibits better actuating (area strain rate of 33%) and ER performance (storage modulus increment of 1.5 MP) than existing conventional dielectric elastomer (DE) actuators (such as PDMS and VHB4910) under a low electric field. Compared to reported flexible grippers, bionic flexible grippers based on GERDE actuator have enhanced actuation, stiffness adjustment capability (i.e., stiffness is increased by 2.4 times), fast response (≈180 ms), and coupling effect, and can write Chinese calligraphy of different emotions by the same trajectory. This work provides ideas and methods for achieving the integration of actuator‐variable stiffness and emotional transmission in robots.

Vibration control of giant electrorheological damper combining nonlinear fractional-order controller and extended state observer

As a typical smart material, giant electrorheological fluid (GERF) has a greater yield stress than electrorheological fluid for vibration isolation. However, as rheological material, the modeling precision is severely degraded by its innate rate-dependent hysteretic nonlinearity and uncertainty. In this paper, a novel control method is proposed, which requires little information about the damper based on GERF. The proposed method combines nonlinear fractional-order control (FC) and extended state observer (ESO) by constructing damper as a second-order disturbance-based structure to handle hysteretic nonlinearities, dynamic uncertainties and unknown disturbances. In contrast to the prevalent model-free control (MFC) that neglects hysteresis nonlinearity, the proposed control algorithm considers it as a general disturbance and eliminates it. In addition, compared with linear FC with complex fractional-order ESO, where the order needs to be known in advance, nonlinear FC has improved robustness for uncertain fractional-order systems only via pure ESO. Simulations and experimental results demonstrate that the nonlinear controller outperforms the linear counterpart and the proposed method exhibits superior control performance compared to the existing MFC, with an improvement of 26.9%.

Superior nanocomposites of phosphonium-based poly(ionic liquid) with halloysite and graphene oxide: Electrorheological investigations

Phosphonium-based poly(ionic liquid) (PPIL) as well as its nanocomposites with halloysite (HNT) and graphene oxide (GO) were synthesized in this study. PPIL structure was engineered to be poly[(4-vinylbenzyl) trimethyl phosphonium trifluoromethane sulfonate] for high electrorheological (ER) performance. To improve ER properties of PPIL, HNT clay with strong mechanical, thermal, and insulating properties and GO with strong dielectric properties were introduced into the PPIL structure by covalent bonding. The synergistic electroactive effect of HNT and GO in the hybrid nanocomposites were investigated by comparing PPIL, HNT/PPIL and HNT/GO/PPIL structures. Structural, thermal, and morphological characterizations approved the successful synthesis of samples. Dielectric and ER flow tests of dispersions of the engineered structures in insulating silicone oil (SO) indicated that PPIL (Δε′ = 1.80 and τy = 250 Pa, EReff = 35, G′ = 33 kPa at 2.0 kV mm-1) and HNT/PPIL (Δε′ = 1.55 and τy = 260 Pa, EReff = 51, G′ = 100 kPa at 2.0 kV mm-1) have similar electroactive properties whereas the highest polarizability and ER response are achieved with HNT/GO/PPIL hybrid nanocomposite (Δε′ = 2.50 and τy = 410 Pa, EReff = 67, G′ = 790 kPa at 2.0 kV mm-1). The findings indicated that electrical stability and electric field induced polarizability of PPIL have been improved by the presence of HNT and GO, respectively. When compared with the previously reported ER studies for ammonium-based poly(ionic liquid)s, PPIL and its nanocomposites of HNT/PPIL and HNT/GO/PPIL exhibited better ER properties, as projected. The application of electric field resulted in the switchable viscoelastic character for PPIL/SO, HNT/PPIL/SO and HNT/GO/PPIL/SO dispersions. Similar to the ER flow properties, the best electroactive viscoelastic properties were obtained for the dispersion of triple HNT/GO/PPIL hybrid nanocomposite. Overall, new ER dispersions of phosphonium-based poly(ionic liquid) and its superior nanocomposites were introduced to the literature.

Electrostatic Layer Jamming Variable Stiffness Enhanced by Giant Electrorheological Fluid

The traditional electrostatic layer jamming (ELJ) utilizes air as the dielectric, which leads to the ELJ system that can withstand less voltage. A novel electrostatic layer jamming based on giant electrorheological fluid (ELJ-GERF) for soft robotics is proposed in this paper. The principle of ELJ-GERF is to use electrostatic attraction to squeeze the flexible planar electrodes to generate friction and then engage jamming, where GERF acts as the dielectric. Three specimens for variable tensile stiffness applications, namely ELJ-GERF, ELJ-AIR, and ELJ-OIL, are fabricated by adding giant electrorheological fluid, air, and silicone oil. Tensile experiments are conducted to investigate the stiffness adjustment characteristics of these specimens. Advantages of ELJ-GERF are indicated by the experimental results. ELJ-GERF has a more than 4 times faster response time than well-known pneumatic layer jamming. Compared to ELJ, the stiffness variation range of ELJ-GERF is enhanced by more than 1.7 times under DC voltage and more than 1.9 times under AC voltage. And the decay rate of the output force of the ELJ-GERF is reduced by a factor of nearly 3 at DC voltage. Moreover, the ELJ-GERF system has better stability at AC voltage and can withstand about 6.7 times higher breakdown voltages. We found that the GERF particles have an important effect on the variable stiffness performance of ELJ-GERF and that the application of AC voltage can further improve the stiffness of the specimen. The stiffness of ELJ-GREF increased nearly four times at 5000V applied. The same enhancement exists for the ELJ-AIR and ELJ-OIL.

A highly homogeneous electrorheological fluid with potential applications in optics

A new type of electrorheological fluid (ERF) with high ER efficiency, low zero-field viscosity and high uniformity was synthesized by a hydrolysis method, based on modified titanium and succinic acid. The electro-responsive performance of ERF under electric field 0–3 kV mm−1 were studied in detail. In addition to traditional research methods to explore the morphology of the ER particles, we also utilized optical diffraction imaging to study the uniformity of the chain-like structure formed by the ER particles. Due to the relatively uniform size, the particles aggregate into a periodic spatial modulation structure parallel to the electric field direction and similar to a grating on the macroscopic scale, which can further manufacture liquid controllable gratings. The observed diffraction spots, up to six levels, indicate the ERFs have potential applications in the field of optics.

Lubrication subjected to effects of electric and magnetic fields: recent research progress and a generalized MEMT-field Reynolds equation

Electric and magnetic fields have been used in various ways to enhance the performance of lubrication systems. The presence of these fields can significantly change the properties of lubricants. The rapid adoption of electric vehicles (EVs) has presented new lubrication-related challenges due to the presence of electric current. There is an urgent need for an in-depth study of lubrication systems subjected to such fields. This paper highlights recent research works on several key areas of lubrication involving electric or magnetic fields, which are:1) electric double layer in lubrication, 2) electrorheological fluids, 3) magnetorheological fluids, 4) ferrofluids, and 5) typical fluids used in the current EVs and typical surface failures of bearing components in EVs. Commonly used lubricants in each area are reviewed; lubrication mechanisms and related mathematical models are summarized; methods for and results from numerical analyses and experimental explorations are discussed; and common features of lubrications in different fields are explored. Based on the current research progress in these fields and the classic generalized Reynolds equation, a generalized mechanical-electro-magnetic-thermal-field (MEMT-field) Reynolds equation is proposed to describe the aforementioned lubrication scenarios and the effects of coupled mechanical, electric, magnetic, and thermal fields, which can be solved with a numerical iteration method.

Synthesis and electrorheological behaviour of silica-coated porous metal-organic frameworks

In this paper, Ti-based metal-organic frameworks (MOF-Ti) with internal holes were prepared by a solvothermal method. The Stöber hydrolysis method was used to coat silicon dioxide (SiO2) on the surface of MOF-Ti with ethyl silicate as the silicon source, and the conductivity of the composite particles was controlled by the amount of TEOS added. Furthermore, core-shell MOF-Ti@SiO2 composite nanoparticles were successfully synthesized. Some analyses were performed to determine the morphology, crystal structure, elemental state, and N2 adsorption/desorption properties of MOF-Ti@SiO2 composite particles, and the results show that the synthesis of core/shell structure composite particles was successful. The electrorheological fluid (ERF) with a concentration of 10 wt% made from composite particles demonstrated good electrorheological (ER) performance and anti-settlement capacity. It has been found that the amount of TEOS has a significant impact on the ER performance of ERFs. Furthermore, it is also found in dielectric performance analysis that MOF-Ti with internal holes exhibited a distinctive dual relaxation peak in the ERFs and showed stronger interfacial polarization after SiO2 coating, which is useful for enhanced ER behaviour.