•A novel magnetoactive metamaterials with intriguing symmetry-breaking properties is proposed.•The design strategy utilizes the transformative ability of hard-magnetic active elastomers coupled with ...zero-mode metamaterial characteristics.•The proposed magnetoactive metamaterials enable remotely-tunable elastic cloaking.
We propose a magnetic field-induced asymmetric mechanical metamaterial for tunable transformation-based elastic cloaking. The metamaterial is designed by integrating hard-Magnetic Active Elastomers (hMAEs) and combining zero-stress collapse modes to produce a unique asymmetric behavior controlled by an external magnetic field. The relationship bridging the microstructure and the desired cloaking performance is presented. This magneto-metamaterial design is applied to achieve tunable static elastic cloaking. The theoretical predictions, together with the numerical tests under various static loads, demonstrate encouraging cloaking performance. The study also highlights the impact of magneto-mechanical coupling and offers the first remotely-controllable hMAE-based cloaking solution, with promising potential in various applications including stress shielding and stealth technologies.
•We report the magnetic field-enabled propagation of solitary waves.•We propose to exploit the unique magneto-mechanical coupling of hard-magnetic active elastomers to remotely tune the width, ...amplitude, and velocity of the nonlinear solitary waves propagating within.•This work provide a fundamental understanding of the effects of magneto-mechanical coupling on the unusual nonlinear vector solitary wave phenomenon.
We propose a design of a metamaterial for magnetically tunable propagation of nonlinear vector solitary waves. The metamaterial consists of a periodic array of units of hard-magnetic inclusion embedded in a soft matrix. The units are connected via thin and highly deformable ligaments. Our theoretical and numerical modeling results show that the configuration of the metamaterial undergoes drastic transformations when activated by a magnetic field. These controllable microstructural transformations significantly influence the propagation of vector solitary waves in the proposed metamaterial system. We report the magnetic field-enabled propagation of solitary waves. We show that the proposed soft magnetoactive metamaterial allows us to tune the key characteristics of the enabled nonlinear solitary waves, including their pulse width and amplitude. Our findings also highlight the potential of magneto-mechanical coupling in the development of untethered mechanical metamaterial systems for applications in nondestructive testing, energy harvesting, and smart soft wave devices.
•Onset of magnetoelastic instabilities is studied in magnetoactive laminates with ferromagnetic phases under magneto-mechanical loading•The analysis is performed using the small-amplitude ...perturbations superimposed on finite deformations in presence of magnetic field•Interplay between macroscopic and microscopic instabilities, and tunability of buckling pattern wavelengths by magnetic field is studied•Magnetoactive laminates are observed to develop antisymmetric buckling modes, in addition to classical symmetric mode•An explicit expression is derived for the magnetic field-induced deformation of magneto-active laminates
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We investigate the microscopic and macroscopic instabilities developing in magnetoactive elastomer (MAE) composites undergoing large deformations in the presence of an external magnetic field. In particular, we consider the MAEs with bi-phasic layered microstructure, with phases exhibiting ferromagnetic behavior. We derive an explicit expression for the magnetic field-induced deformation of MAEs with hyperelastic phases. To perform the magnetoelastic instability analysis, we employ the small-amplitude perturbations superimposed on finite deformations in the presence of the magnetic field. We examine the interplay between the macroscopic and microscopic instabilities. We find that the layered MAEs can develop microscopic instability with antisymmetric buckling modes, in addition to the classical symmetric mode. Notably, the antisymmetric microscopic instability mode does not appear in a purely mechanical scenario (when a magnetic field is absent). Furthermore, our analysis reveals that the wavelength of buckling patterns is highly tunable by the applied magnetic field, and by the properties and volume fractions of the phases. Our findings provide the information for designing materials with reconfigurable microstructures. This material ability can be used to actively tune the behavior of materials by a remotely applied magnetic field. The results can be utilized in designing tunable acoustic metamaterials, soft actuators, sensors, and shape morphing devices.
We study the magneto-mechanical behavior of periodic laminates made of hard-magnetic active elastomers (HMAEs). We formulate the amended free-energy function for HMAEs, and derive an explicit ...expression for the induced deformation of the HMAE laminate as a function of the applied magnetic field. Next, we employ the “small-on-large” framework and examine the small-amplitude shear waves propagating in the finitely deformed HMAE laminate in a magnetic field.
We find that the remanent magnetization of HMAE phases can result in compressive deformations (in the direction of the applied magnetic field), as opposed to the induced tensile deformation in previously considered soft-magnetic active laminates. Further, we derive the dispersion relations for the transverse elastic waves propagating in the direction perpendicular to the layers. We use the analytical results to illustrate the tunability of the shear wave band gaps with varying remanent magnetizations of the phases; moreover, the shear wave band gaps can be actively controlled by a remotely applied magnetic field.
Efficient transportation of droplets (≈10
1
–10
2
μL) and small solid objects (≈10
1
–10
2
mm
3
) have important applications in many fields, such as microfluidics, lab‐on‐a‐chip devices, drug ...delivery, etc. A novel multifunctional surface consisting of a periodic array of micro‐lamellae from a soft magnetoactive elastomer on a plastic substrate is reported for these purposes. The physical origin of the propulsion is the bending of soft magnetic lamellae in nonuniform magnetic fields, which is also observed in uniform magnetic fields. The magnetoactive surface is fabricated using a facile and rapid method of laser ablation. The propulsion of items is realized using a four‐pole rotating magnet. This results in a cyclic lamellar fringe motion over the microstructured surface and brings an advantage of easy reciprocation of transport by rotation reversal. Two modes of object transportation are identified: “pushing” mode for precise control of droplet and solid positioning and “bouncing” mode for heavier solid objects transportation. A water droplet of 5 μL or a glass sphere with a 2.1 mm diameter can be moved at a maximum speed of 60 mm s
−1
. The multifunctionality of the proposed mechatronic platform is demonstrated on the examples of selective solid–liquid separation and droplet merging.
•Magnetoactive elastomer with filled with iron-nickel particles carried out.•Changing its conductivity under the influence of magnetic field and hydrostatic load.•Magnetoactive elastomer is ...haracterizade the tunneling mechanism of electroconductivity.
As a result of a study carried out on the capability of magnetoactive elastomer filled with particles obtained from carbonyl iron and nickel by the mechanochemical method to conduct direct current, there were obtained volt-ampere characteristics corresponding to different magnetic fields.
In the whole, it has been demonstrated that such a composite material is capable of changing its conductivity under the influence of magnetic field and hydrostatic load by 5–6 orders of magnitude. The material also exhibits certain features of a semi-conductor which gives some grounds to suppose that electron transfer occurring among the particles might be conditioned by a tunneling mechanism. The possibility to carry out the DC measurements was determined by the good magnetic properties and high electric conductivity of the filling substance. Magnetoactive elastomer of this type is a prospective material for designing sensors for mechanical pressure, magnetic field, and strain.
In this study, we report on the experimentally observed phenomenon of ring-like structures formation from chains of magnetic microparticles in magnetoactive elastomers based on magnetic hard powder. ...In order to find an explanation for the specific macroscopic magnetic properties of composites, microstructural observations on the elastic composite based on a thin layer of magnetic hard particles have been carried out. Particles embedded in such magnetic composites can move inside the matrix with some restrictions and form chain-like structures on being subjected to magnetizing and turn over as first the strength of the external magnetic field decreases and then the polarity of the field switches to opposite. The quantitative parameters of these processes depend on a number of factors including coercivity and remanence of particles, polymer matrix elasticity, and external field intensity. In zero-field, the magnetized particles can assemble into ring-like structures, thus tending to bring the free energy of the overall system to a minimum. The study is primarily aimed to shed a light on understanding the specific magnetic properties of magnetic polymers, such as magnetoactive or magnetorheological elastomers with a magnetic hard filler. Furthermore, the phenomenon of ring-like structures formation can be used for controlled remote patterning of particles in magnetic elastic composite thin films, which is attractive for various applications.
We investigate the behavior of magnetoactive elastomers (MAEs) with periodic and random distributions of circular and elliptical fibers. For the MAEs with periodic microstructures, we develop finite ...element models and determine the local fields as well as the effective properties of MAEs with rectangular and quasi-hexagonal unit cells. For the MAEs with random microstructures, we derive a closed-form expression for the effective response making use of a recently developed theory (Ponte Castañeda and Galipeau, 2011). In particular, we determine the responses to pure shear loading in the presence of a magnetic field, both of which are aligned with the geometric axes of the fibers, and examine the roles of the deformation, concentration, particle shape, and distribution on the magnetostriction, actuation stress, and the magnetically induced stiffness of the composite. We show that the coupling effects are of second order in the concentration. This is consistent with the fact that these effects are primarily the result of the interaction between inclusions. We also demonstrate explicitly that the magnetomechanical coupling of these MAEs, when subjected to aligned loading conditions, depends not only on the magnetic susceptibility, but also, crucially, on its derivative with respect to the deformation. As a consequence, we find that the magnetoelastic effects may be quite different, even for composites with similar effective susceptibilities.
•Direction dependent tensile modulus implies transverse isotropy in the MAE.•Magneto-rheological effect as a function of the initial shape of the MAE.•An effective material model of the MAE based on ...a dipole approximation.
Magnetoactive elastomers (MAEs) are field-controllable materials with magnetically switchable properties. The presence of an external magnetic field results in the change in the macroscopic shape of the MAE. The magnetic field also introduces a mechanical anisotropy with an axis of symmetry along the magnetic field. We aim to derive an effective material model which considers the initial shape of the MAE from the free energy of an isotropic MAE in the dipole approximation. Primarily, we consider uniaxial deformations parallel and perpendicular to the applied field direction. The stress–strain behaviour of the MAE yields direction-dependent tensile modulus. It indicates that the MAE behaves as a transversely isotropic material in the presence of an external magnetic field. Finally, we compare our predictions with the conventional transversely isotropic material model and find a good agreement. This comparison allows us to extract the dimensionless scaling parameter of a transversely isotropic MAE which characterizes the influence of the magnitude of a magnetic field as well as the initial shape of an MAE sample.
•Magneto-active elastomers (MAEs) are characterized as actuators for bistable kinetic shadings.•Two different polymer matrices are tested for MAEs—polyvinyl alcohol (PVA) and polydimethylsiloxane ...(PDMS) —to determine their suitability for the intended application.•Increasing the clamped height can drastically reduce the magnetic field required for actuation.
Kinetic building envelopes can significantly improve energy efficiency by adapting to changing outdoor conditions. A challenge for the widespread implementation of kinetic envelopes is related to the complexity and cost of conventional mechanical actuation. Current trends in kinetic building design have proposed embedding smart materials for actuation within kinetic shades and simplifying the shape-morphing mechanisms. This paper reports on a study that aims to characterize magneto-active elastomers (MAEs) as actuators for bistable kinetic shadings. In particular, this study seeks to determine adequate bistable and MAE configurations and their potential to deform a bistable kinetic shading setup. The studies characterize the force and displacement of two types of MAEs materials fabricated by embedding magnetic fillers into different soft polymeric matrices- polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) hydrogel. In addition, we compared the actuation capabilities of both MAE-PDMS and MAE-PVA and studied the effect of changing the boundary condition of bistable laminates. The results suggest that MAE materials can actuate bistable composites remotely. The boundary condition study found that clamping 25% of the laminates' height reduced the magnetic field required for actuation by 29% and thus might be a suitable design strategy. This study adds magnetic actuation to the growing body of work on kinetic envelopes and smart materials, contributing to a deeper understanding of the required application conditions of MAEs.
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