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†

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

Preparation, microstructure, and microstructure-properties relationship of thermoplastic vulcanizates (TPVs): A review

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

Novel smart thermoplastic magnetorheological elastomer composites containing micron-sized magnetic carbonyl iron (CI) particles were prepared with a poly(styrene-ethylene-butylene-styrene) (SEBS) triblock copolymer utilized as the thermoplastic matrix rubber, and the structures and properties of the CI-SEBS composites were examined. The CI particles were uniformly dispersed in the composites prepared in the absence of the magnetic field at high temperatures T (>T\(_{\rm g}^{\rm S})\), and this isotropic composite exhibited a larger storage modulus G′ compared to the SEBS matrix at room temperature ( T\(_{\rm g}^{\rm S})\) contained a chain structure of CI particles. This chain structure became longer and better aligned on an increase of ψ up to a saturation of the particle magnetization and on an increase of the time interval of applying the field (that allowed the particles to move and equilibrate their aligned structure). The modulus G′ of this “pre-structured” composite measured for both cases of ψ = 0 and ψ > 0 in the direction perpendicular to the chain structure at room temperature was enhanced compared to G′ of the isotropic composites. This difference of the filler effect (for ψ = 0) and the magnetorheological effect (for ψ > 0) between the pre-structured and isotropic composites was enhanced when the chain structure of the CI particles in the pre-structured composites became longer and better aligned. A mechanism(s) of this enhancement was discussed in relation to the morphologies (particle distribution) in the composites with the aid of a filler model and a molecular expression of the stress due to magnetically interacting particles.

Mechanical and structural investigation of isotropic and anisotropic thermoplastic magnetorheological elastomer composites based on poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS)

The invention relates to a thermoplastic magnetorheological elastomer composite material and a preparation method thereof, belonging to the technical field of materials. The composite material comprises the following components in percentage by weight: 40-85% of carbonyl iron, 0.4-2.0% of coupling agent, 8-30% of thermoplastic elastomer and 6-40% of plasticizing agent. The preparation method of the composite material comprises the following steps of: step 1, taking all the components in the percentage by weight; step 2, stirring the carbonyl iron and the coupling agent in a high-speed mixer to obtain a mixture; step 3, stirring the mixture, the thermoplastic elastomer and the plasticizing agent in a low-speed mixer to obtain a premix; step 4, taking the premix, mixing and milling the premix by a double screw extruder at 180-240 DEG C, extruding and granulating; and then, molding the granules at 180-240 DEG C under the action of a magnetic field, cooling, forming and demolding to obtain the thermoplastic magnetorheological elastomer composite material. The method of the invention has simple processes, and the thermoplastic magnetorheological elastomer composite material prepared bythe method of the invention has excellent mechanical properties, stability and magnetic response efficiency, can be formed by multiple processes and can realize industrialization and commercialization easily.

Qi Yin

Papers

Mechanical and structural investigation of isotropic and anisotropic thermoplastic magnetorheological elastomer composites based on poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS)

Thermoplastic magnetorheological elastomer composite material and preparation method thereof