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Magnetorheological Materials and Application Systems

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A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "E：Engineering and Technology".

Deadline for manuscript submissions: 30 April 2025 | Viewed by 14736

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Prof. Dr. Seung-Bok Choi

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Guest Editor

Department of Mechanical Engineering, The State University of New York at Korea (SUNY Korea), 119 Songdo Moonhwa-Ro, Yeonsu-Gu, Incheon 21985, Republic of Korea
Interests: magnetorheological (MR) fluid; electrorheological (ER) fluid; control theory; robot control; vibration control; haptic devices using MR/ER fluids; sensors and actuators using smart materials
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Miao Yu

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Guest Editor

College of Opto-Electronic Engineering , Chongqing University, Chongqing, China, 400044
Interests: magnetorheological materials, devices, and systems; noise and vibration active control; the ultra-precision machining and testing

Special Issue Information

Dear Colleagues,

Despite numerous works on magnetorheological materials (fluids, elastomers, greases, gels, and foams) since the 1990s, few application systems have been commercialized, for example, automotive shock absorbers. One of the potential solutions to develop successful market products utilizing MR materials is resolving the temperature problem that affects the field-dependent properties of such materials and application systems. Recently, studies on this topic have actively sought to mitigate adverse temperature-related effects by proposing recipes such as the addition of nanosized particles and proper additives. However, most of the methods proposed so far have a limitation or trade-off as a result. For example, the thermal conductivity of MR materials can be reduced, but the field-dependent yield stress is decreased.

Based on the topic "Magnetorheological Materials and Application Systems", we aim to collect articles for a Special Issue in the journal Micromachines. We hope to accelerate the technology of MR materials in several research fields, including chemical engineering, chemistry, polymer sciences, chemical physics, mechanical engineering, electrical engineering, and medical engineering.

We look forward to receiving your contributions.

Prof. Dr. Seung-Bok Choi
Prof. Dr. Miao Yu
Guest Editors

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Keywords

magnetorheological materials
temperature effect
thermal conductivity
heat transfer

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Published Papers (10 papers)

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Research

21 pages, 10563 KiB

Open AccessArticle

6DOF Aircraft Landing Gear System with Magnetorheological Damper in Various Taxing and Touchdown Scenarios

by Quoc-Viet Luong, Quang-Ngoc Le, Jai-Hyuk Hwang and Thi-My-Nu Ho

Micromachines 2025, 16(3), 355; https://doi.org/10.3390/mi16030355 - 20 Mar 2025

Viewed by 238

Abstract

This manuscript presents a new approach to describe aircraft landing gear systems equipped with magnetorheological (MR) dampers, integrating a reinforcement learning-based neural network control strategy. The main target of the proposed system is to improve the shock absorber efficiency in the touchdown phase, in addition to reducing the vibration due to rough ground in the taxing phase. The dynamic models of the aircraft landing system in the taxing phase with standard landing ground roughness, one-point touchdown, two-point touchdown, and third-point touchdown are built as the first step. After that, Q-learning-based reinforcement learning is developed. In order to verify the effectiveness of the controller, the co-simulations based on RECURDYN V8R4-MATLAB R2019b of the proposed system and the classical skyhook controller are executed. Based on the simulation results, the proposed controller provides better performance compared to the skyhook controller. The proposed controller provided a maximum improvement of 16% in the touchdown phase and 10% in the taxing phase compared to the skyhook controller. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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18 pages, 4487 KiB

Open AccessArticle

Current–Pressure Dynamics Modeling on an Annular Magnetorheological Valve for an Adaptive Rehabilitation Device for Disabled Individuals

by Fitrian Imaduddin, Zaenal Arifin, Ubaidillah, Essam Rabea Ibrahim Mahmoud and Abdulrahman Aljabri

Micromachines 2025, 16(2), 144; https://doi.org/10.3390/mi16020144 - 26 Jan 2025

Viewed by 560

Abstract

The dynamic relationship between current and pressure in magnetorheological (MR) valves is essential for the design of adaptive rehabilitation devices aimed at health rehabilitation for disabled individuals, yet it remains under-explored in existing modeling approaches. Accurately capturing this relationship is vital to predict the pressure drop response to current variations, facilitating the development of effective control systems in such rehabilitation applications. This study employs a linear black-box modeling approach to characterize the current–pressure dynamics of an annular MR valve. Experimental data are used to develop a set of transfer function models, with parameters identified through MATLAB’s system identification tools, utilizing invariant variable regression and the Levenberg–Marquardt (LM) iteration. The modeling yielded a 14th-order transfer function, labeled TF14, which closely aligns with experimental data, achieving a root mean square error of 12.64%. These findings contribute valuable insights into the current–pressure dynamics of MR valves and establish a foundational model for adaptive rehabilitation devices designed for individuals with disabilities. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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15 pages, 5046 KiB

Open AccessArticle

Inchworm Robots Utilizing Friction Changes in Magnetorheological Elastomer Footpads Under Magnetic Field Influence

by Yun Xue and Chul-Hee Lee

Micromachines 2025, 16(1), 19; https://doi.org/10.3390/mi16010019 - 26 Dec 2024

Cited by 1 | Viewed by 3720

Abstract

The application of smart materials in robots has attracted considerable research attention. This study developed an inchworm robot that integrates smart materials and a bionic design, using the unique properties of magnetorheological elastomers (MREs) to improve the performance of robots in complex environments, as well as their adaptability and movement efficiency. This research stems from solving the problem of the insufficient adaptability of traditional bionic robots on different surfaces. A robot that combines an MRE foot, an electromagnetic control system, and a bionic motion mechanism was designed and manufactured. The MRE foot was made from silicone rubber mixed with carbonyl iron particles at a specific ratio. Systematic experiments were conducted on three typical surfaces, PMMA, wood, and copper plates, to test the friction characteristics and motion performance of the robot. On all tested surfaces, the friction force of the MRE foot was reduced significantly after applying a magnetic field. For example, on the PMMA surface, the friction force of the front leg dropped from 2.09 N to 1.90 N, and that of the hind leg decreased from 3.34 N to 1.75 N. The robot movement speed increased by 1.79, 1.76, and 1.13 times on PMMA, wooden, and copper plate surfaces, respectively. The MRE-based intelligent foot design improved the environmental adaptability and movement efficiency of the inchworm robot significantly, providing new ideas for the application of intelligent materials in the field of bionic robots and solutions to movement challenges in complex environments. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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11 pages, 3375 KiB

Open AccessArticle

A Pressure Sensor Based on the Interaction between a Hard Magnet Magnetorheological Elastomer and a Hall Effect Structure

by Onejae Sul, Sung Joong Choo, In-Sik Jee, Jeengi Kim and Hyeong-Jun Kim

Micromachines 2024, 15(10), 1221; https://doi.org/10.3390/mi15101221 - 30 Sep 2024

Viewed by 949

Abstract

In this article, we report a novel pressure sensing method based on the Hall effect and a hard magnet magnetorheological elastomer (hmMRE). The elastic property of the MRE under pressure was used to generate spatial variation in the magnetic flux density around the MRE, and the variation was detected by the Hall effect device underneath. As the first development in this kind of pressure sensing mechanism, we conducted research for the following three purposes: (1) to verify the Hall effect on the output signal, (2) to understand the sensor output variations under different modes of operation, and (3) to utilize the mechanism as a pressure sensor. We characterized the sensor with its operation parameters, such as signal polarity switching depending on wiring directions, signal amplitude, and offset shift depending on the input voltage. Based on the analyses, we concluded that the Hall voltage represents the pressure applied on the hmMRE, and the new pressure sensing mechanism was devised successfully. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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14 pages, 15754 KiB

Open AccessArticle

Development of Second Prototype of Twin-Driven Magnetorheological Fluid Actuator for Haptic Device

by Takehito Kikuchi, Asaka Ikeda, Rino Matsushita and Isao Abe

Micromachines 2024, 15(10), 1184; https://doi.org/10.3390/mi15101184 - 25 Sep 2024

Cited by 1 | Viewed by 915

Abstract

Magnetorheological fluids (MRFs) are functional fluids that exhibit rapid and reproducible rheological responses to external magnetic fields. An MRF has been utilized to develop a haptic device with precise haptic feedback for teleoperative surgical systems. To achieve this, we developed several types of compact MRF clutches for haptics (H-MRCs) and integrated them into a twin-driven MRF actuator (TD-MRA). The first TD-MRA prototype was successfully used to generate fine haptic feedback for operators. However, undesirable torque ripples were observed due to shaft misalignment and the low rigidity of the structure. Additionally, the detailed torque control performance was not evaluated from both static and dynamic current inputs. The objective of this study is to develop a second prototype to reduce torque ripple by improving the structure and evaluating its static and dynamic torque performance. Torque performance was measured using both constant and stepwise current inputs. The coefficient of variance of the torque was successfully reduced by half due to the structural redesign. Although the time constants of the H-MRC were less than 10 ms, those of the TD-MRA were less than 20 ms under all conditions. To address the slower downward output response, we implemented an improved input method, which successfully halved the response time. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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16 pages, 7370 KiB

Open AccessArticle

Replication of Radial Pulses Using Magneto-Rheological Fluids

by Miranda Eaton, Jeong-Hoi Koo, Tae-Heon Yang and Young-Min Kim

Micromachines 2024, 15(8), 1010; https://doi.org/10.3390/mi15081010 - 6 Aug 2024

Viewed by 1136

Abstract

The radial pulse is a critical health marker with expanding applications in wearable technology. To improve these applications, developing a pulse generator that consistently produces realistic pulses is crucial for validation and training. The goal of this study was to design and test a cost-effective pulse simulator that can accurately replicate a wide range of age-dependent radial pulses with simplicity and precision. To this end, this study incorporated a magneto-rheological (MR) fluid device into a cam-based pulse simulator. The MR device, as a key component, enables pulse shaping without the need for additional cams, substantially reducing the cost and complexity of control compared with existing pulse simulators. To evaluate the performance of the MR pulse simulator, the root-mean-square (RMS) error criterion (less than 5%) was used to compare the experimentally obtained pulse waveform with the in vivo pulse waveform for specific age groups. After demonstrating that the MR simulator could produce three representative in vivo pulses, a parametric study was conducted to show the feasibility of the slope-based pulse-shaping method for the MR pulse simulator to continuously generate a range of age-related pulses. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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11 pages, 7680 KiB

Open AccessArticle

Characterization of Magnetorheological Impact Foams in Compression

by Young Choi and Norman M. Wereley

Micromachines 2024, 15(6), 782; https://doi.org/10.3390/mi15060782 - 14 Jun 2024

Viewed by 891

Abstract

This study focuses on the development and compressive characteristics of magnetorheological elastomeric foam (MREF) as an adaptive cushioning material designed to protect payloads from a broader spectrum of impact loads. The MREF exhibits softness and flexibility under light compressive loads and low strains, yet it becomes rigid in response to higher impact loads and elevated strains. The synthesis of MREF involved suspending micron-sized carbonyl Fe particles in an uncured silicone elastomeric foam. A catalyzed addition crosslinking reaction, facilitated by platinum compounds, was employed to create the rapidly setting silicone foam at room temperature, simplifying the synthesis process. Isotropic MREF samples with varying Fe particle volume fractions (0%, 2.5%, 5%, 7.5%, and 10%) were prepared to assess the effect of particle concentrations. Quasi-static and dynamic compressive stress tests on the MREF samples placed between two multipole flexible strip magnets were conducted using an Instron servo-hydraulic test machine. The tests provided measurements of magnetic field-sensitive compressive properties, including compression stress, energy absorption capability, complex modulus, and equivalent viscous damping. Furthermore, the experimental investigation also explored the influence of magnet placement directions (0

°

and 90

°

) on the compressive properties of the MREFs. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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15 pages, 13175 KiB

Open AccessArticle

Design and Control of Upper Limb Rehabilitation Training Robot Based on a Magnetorheological Joint Damper

by Jintao Zhu, Hongsheng Hu, Wei Zhao, Jiabin Yang and Qing Ouyang

Micromachines 2024, 15(3), 301; https://doi.org/10.3390/mi15030301 - 22 Feb 2024

Cited by 2 | Viewed by 1893

Abstract

In recent years, rehabilitation robots have been developed and used in rehabilitation training for patients with hemiplegia. In this paper, a rehabilitation training robot with variable damping is designed to train patients with hemiplegia to recover upper limb function. Firstly, a magnetorheological joint damper (MR joint damper) is designed for the rehabilitation training robot, and its structural design and dynamic model are tested theoretically and experimentally. Secondly, the rehabilitation robot is simplified into a spring-damping system, and the rehabilitation training controller for human movement is designed. The rehabilitation robot dynamically adjusts the excitation current according to the feedback speed and human–machine interaction torque, so that the rehabilitation robot always outputs a stable torque. The magnetorheological joint damper acts as a clutch to transmit torque safely and stably to the robot joint. Finally, the upper limb rehabilitation device is tested. The expected torque is set to 20 N, and the average value of the output expected torque during operation is 20.02 N, and the standard deviation is 0.635 N. The output torque has good stability. A fast (0.5 s) response can be achieved in response to a sudden motor speed change, and the average expected output torque is 20.38 N and the standard deviation is 0.645 N, which can still maintain the stability of the output torque. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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15 pages, 8672 KiB

Open AccessArticle

Effect of Additives on Tribological Performance of Magnetorheological Fluids

by Songran Zhuang, Yongbing Cao, Wanli Song, Peng Zhang and Seung-Bok Choi

Micromachines 2024, 15(2), 270; https://doi.org/10.3390/mi15020270 - 14 Feb 2024

Cited by 1 | Viewed by 1561

Abstract

In this study, nano-diamond (ND) and MoS₂ powder are used as additives in a carbonyl iron-based magnetorheological fluid (MRF) to improve its tribological performance. MRFs are prepared by dispersing 35 wt.% of CI particles in silicone oil and adding different proportions (0, 1, 3, or 5 wt.%) of ND and MoS₂ additives. Seven kinds of MRFs are made and tested using reciprocating friction and wear tester under different normal loads, and then the friction characteristics are evaluated by analyzing the experimental results. The morphological properties of MRFs and contacting surfaces before and after the tests are also observed using a scanning electron microscope and analyzed via energy-dispersive X-ray spectroscopy. The results show that the appropriate weight percentage of MoS₂ additives may decrease the friction coefficient and wear zone. It is also demonstrated from detailed analyses of worn surfaces that the wear mechanism is influenced not only by additives, but also by the applied normal load and magnetic field strength. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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19 pages, 16452 KiB

Open AccessArticle

Experimental Study on the Skyhook Control of a Magnetorheological Torsional Vibration Damper

by Zhicheng Wang, Hongsheng Hu, Jiabin Yang, Jiajia Zheng, Wei Zhao and Qing Ouyang

Micromachines 2024, 15(2), 236; https://doi.org/10.3390/mi15020236 - 2 Feb 2024

Cited by 1 | Viewed by 1700

Abstract

This study proposes a dual-coil magnetorheological torsional vibration damper (MRTVD) and verifies the effectiveness of semi-active damping control to suppress the shaft system’s torsional vibration via experimental research. Firstly, the mechanical model of the designed MRTVD and its coupling mechanical model with the rotating shaft system are established. Secondly, the torsional response of the shaft system is obtained via resonance experiments, and the influence of the current on the torsional characteristics of the magnetorheological torsional damper is analyzed. Finally, the MRTVD is controlled using the skyhook control approach. The experimental results demonstrate that when the main shaft passes through the critical speed range at various accelerations, the amplitude of the shaft’s torsional vibration decreases by more than 15%, and the amplitude of the shaft’s torsional angular acceleration decreases by more than 22%. These conclusions validate the inhibitory effect of MRTVD on the main shaft’s torsional vibrations under skyhook control. Full article

(This article belongs to the Special Issue Magnetorheological Materials and Application Systems)

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