Magnetorheological (MR) materials are classified as smart materials due to their responsiveness to external magnetic stimuli. Intensive research on MR materials has led to broad applications in several potential fields. A solid carrier matrix state called MR elastomer with its exceptional magnetic responsive feature is obtained by merging magnetizable particles within an elastomeric polymer. This integration results in outstanding characteristics on the rheological performances. Special prominence is given to the understanding of the base materials and fabrication as well as the functional behavior through various characterization methods. Broad applications of MREs are also explored to provide a profound market picture and to motivate researchers to develop novel technology. The functional behavior of MREs is briefly explained. The art of the materials provides the current position and mapping of the matrix and filler particles. Types of matrix and particles are mentioned together with the level of the research interest on MREs. Description of the fabrication is provided in simple diagrams as summarized from previous works to enhance the MREs performance. The possible tests to reveal the characteristics of the MREs are delivered with the global experimental setup. The review also explains the applications of MREs as well as discussion on the MREs future promising applications.

Recent Progress on Magnetorheological Solids: Materials, Fabrication, Testing, and Applications†

The solid-state processes for cooling and heat pump technologies are based on the well-known caloric effects (magneto-, electro-, elasto- and baro-caloric). With an interest arisen in 1976, year of the development of the first room-temperature magnetic refrigerator, up to a few years ago, magnetocaloric was among the most investigated caloric cooling techniques and it was considered among the main solid-state alternatives to vapor-compression cooling and heat-pumping. During such period, a remarkable number of prototypes of magnetic refrigerators or heat pumps was built. Recently, the attention toward all the four caloric effects has recently grown; therefore, an increase in projects on solid-state prototype developing (not only on magnetocaloric) was observed. The intention of this paper is to offer a state-of-the-art of all the solid-state prototypes for cooling and heat pumps processes, devoted to room temperature operations, developed before the year 2019.

A review of the state of the art of solid-state caloric cooling processes at room-temperature before 2019.

Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field. The MREs are particulate composites, where micro-sized magnetic particles are dispersed inside a non-magnetic polymeric matrix. These elastomers are known for changing their mechanical and rheological properties in the presence of a magnetic field. This change in properties is widely known as the magnetorheological (MR) effect. The MR effect depends on a number of factors such as type of matrix materials, type, concentration and distribution of magnetic particles, use of additives, working modes, and magnetic field strength. The investigation of MREs’ mechanical properties in both off-field and on-field (i.e. absence and presence of a magnetic field) is crucial to deploy them in real engineering applications. The common magneto-mechanical characterization experiments of MREs include static and dynamic compression, tensile, and shear tests in both off-field and on-field. This review article aims to provide a comprehensive overview of the magneto-mechanical characterizations of MREs along with brief coverage of the MRE materials and their fabrication methods.

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A review on magneto-mechanical characterizations of magnetorheological elastomers

In conventional classification, soft robots feature mechanical compliance as the main distinguishing factor from traditional robots made of rigid materials. Recent advances in functional soft materials have facilitated the emergence of a new class of soft robots capable of tether-free actuation in response to external stimuli such as heat, light, solvent, or electric or magnetic field. Among the various types of stimuli-responsive materials, magnetic soft materials have shown remarkable progress in their design and fabrication, leading to the development of magnetic soft robots with unique advantages and potential for many important applications. However, the field of magnetic soft robots is still in its infancy and requires further advancements in terms of design principles, fabrication methods, control mechanisms, and sensing modalities. Successful future development of magnetic soft robots would require a comprehensive understanding of the fundamental principle of magnetic actuation, as well as the physical properties and behavior of magnetic soft materials. In this review, we discuss recent progress in the design and fabrication, modeling and simulation, and actuation and control of magnetic soft materials and robots. We then give a set of design guidelines for optimal actuation performance of magnetic soft materials. Lastly, we summarize potential biomedical applications of magnetic soft robots and provide our perspectives on next-generation magnetic soft robots.

Magnetic Soft Materials and Robots.

https://iopscience.iop.org/article/10.1088/1361-665X/aa549c/pdf

Modeling of magneto-mechanical response of magnetorheological elastomers (MRE) and MRE-based systems: a review

In this paper the magnetomechanical properties of magnetorheological (MR) elastomers with isotropic and anisotropic structure are examined A method for manufacturing magnetorheological elastomers (MRE) with thermoplastic elastomer matrix and 60  µm iron particles is presented The influence of various chemical compositions on the material parameters is investigated The properties of isotropic and anisotropic MR elastomers are examined in a wide range of mechanical and magnetic stimulations Test samples are subjected to cyclic shearing with a constant frequency of 1 Hz The change in magnetomechanical properties is expressed by the relative change of hysteresis loop area δW and stress amplitude δτ

https://iopscience.iop.org/article/10.1088/0964-1726/20/8/085006/pdf

Magnetomechanical properties of anisotropic and isotropic magnetorheological composites with thermoplastic elastomer matrices

A laboratory test stand for magnetocaloric effect investigations has been developed. The test stand is compact and easily reconfigurable. Gadolinium in the form of particles is used as a refrigerant. The material is magnetized/demagnetized due to the reciprocating motion of a magnetic bed. A Halbach array of permanent magnets is employed as a magnetic field source. It generates a magnetic field of about 1 T. In order to decrease the distance along which the magnetic bed has to move, a magnetic shield was used which limits the range of external magnetic field influence. The effectiveness of the shielding and the decrease in magnetic field intensity were shown in the form of magnetic field distribution maps. The paper presents first experimental results which are measured as the temperature difference between the two outermost reservoirs. The achieved results are promising – the temperature span between the heat exchangers amounts to about 2 °C.

A test stand to study the possibility of using magnetocaloric materials for refrigerators

This article describes the dynamic mechanical analysis of the behaviour of magnetorheological composites consisting of a magnetically active filler (carbonyl iron powder) and a soft thermoplastic elastomer matrix (styrene-ethylene-butylene-styrene). The carbonyl iron particle surface was coated by a sol–gel silica layer to improve the adhesion between hydrophilic magnetic particles and the hydrophobic polymer. Isotropic magnetorheological composites containing 81.25 wt% unmodified and silica-coated carbonyl iron powder were manufactured. The surface morphology of the carbonyl iron particles was observed using transmission electron microscopy, while its magnetic properties were analysed with a vibrating sample magnetometer. The magnetomechanical properties of the prepared magnetorheological composites were determined through shearing tests performed in various magnetic fields. The magnetorheological composites containing modified carbonyl iron powder have lower magnetorheological effect in comparison to th...

Dynamic mechanical analysis of magnetorheological composites containing silica-coated carbonyl iron powder

In this paper, the influence of encapsulating carbonyl iron particles with various silica coatings on the properties of magnetorheological elastomers (MREs) was investigated. A soft styrene–ethylene–butylene–styrene thermoplastic elastomer was used as the composite's polymer matrix. Spherical carbonyl iron powder (CIP) acted as the ferromagnetic filler. In order to improve the metal–polymer interaction, carbonyl iron particles were coated with two types of single and six types of double silica layers. The first layer was created through a TMOS or TEOS hydrolysis whereas the second one was composed of organosilanes. The mechanical properties of MREs containing 38.5 vol% of CIP were analysed under dynamic loading conditions. To investigate the magnetorheological effect in these composites, a 430 mT magnetic field, generated by an array of permanent magnets, was applied during testing. The results revealed that the magnetomechanical response of the MREs differs substantially, depending on the kind of particle coating.

https://iopscience.iop.org/article/10.1088/0964-1726/25/10/105030/pdf

Influence of carbonyl iron particle coating with silica on the properties of magnetorheological elastomers

This paper describes investigations of magnetorheological elastomers subjected to cyclic loading. The procedure comprised over 1 million of loading cycles per specimen. Mechanical properties of the manufactured composites have a tendency to stabilize in time. This leads to the conclusion that these MRE have a high application potential in the areas which are connected with energy dissipation, such as damping of vibrations.

Michał Królewicz

Papers

Magnetomechanical properties of anisotropic and isotropic magnetorheological composites with thermoplastic elastomer matrices

A test stand to study the possibility of using magnetocaloric materials for refrigerators

Dynamic mechanical analysis of magnetorheological composites containing silica-coated carbonyl iron powder

Influence of carbonyl iron particle coating with silica on the properties of magnetorheological elastomers

Investigations of Magnetorheological Elastomers Subjected to Cyclic Loading