Development of a Magneto-Mechanical Bench and Experimental Characterization of Magneto-Rheological Elastomers

Hard-magnetic soft materials (hMSMs) are smart composites that consist of a mechanically soft polymer matrix impregnated with mechanically hard magnetic filler particles. This dual-phase composition renders them with exceptional magneto-mechanical properties that allow them to undergo large reversible deformations under the influence of external magnetic fields. Over the last decade, hMSMs have found extensive applications in soft robotics, adaptive structures, and biomedical devices. However, despite their widespread utility, they pose considerable challenges in fabrication and magneto-mechanical characterization owing to their multi-phase nature, miniature length scales, and nonlinear material behavior. Although noteworthy attempts have been made to understand their coupled nature, the rudimentary concepts of inter-phase interactions that give rise to their mechanical nonlinearity remain insufficiently understood, and this impedes their further advancements. This holistic review addresses these standalone concepts and bridges the gaps by providing a thorough examination of their myriad fabrication techniques, applications, and experimental, and modeling approaches. Specifically, the review presents a wide spectrum of fabrication techniques, ranging from traditional molding to cutting-edge four-dimensional (4D) printing, and their unbounded prospects in diverse fields of research. The review covers various modeling approaches, including continuum mechanical frameworks encompassing phenomenological and homogenization models, as well as microstructural models. Additionally, it addresses emerging techniques like machine learning-based modeling in the context of hMSMs. Finally, the expansive landscape of these promising material systems is provided for a better understanding and prospective research.

Section: Experimental Approachesmentioning

confidence: 99%

Hard magnetics and soft materials—a synergy

Narayanan,

Pramanik,

Arockiarajan

2024

“…An H-MAE consists of magnetically hard particles and an elastomer matrix [17]. It can be permanently magnetized and is mechanically soft at the same time (Young's Modulus between several kPa and several MPa [18][19][20]). Complex shape changes occur when the H-MAE presents regions with different orientations of the magnetic moments that align with external magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Magnetofriction—a new concept for shape memory composites

Hermann¹,

Muniz²,

Ouisse³

et al. 2023

Self Cite

This paper introduces a new concept for shape memory based on elastic forces and magnetically induced friction forces in composite materials consisting of magnetoactive elastomers (MAEs). Magnetic attraction forces between two MAEs generate a contact pressure at their interface and the friction allows to maintain stable deformed shapes of the so-called Magnetofriction Shape Memory Polymers (MF-SMPs). When the contact is loosened, the friction forces vanish and the elastic forces in each part of the assembly bring the parts back into their initial state where the contact can be established once again. The shape memory effect is studied in three-point bending tests with two stacked MAEs. The global force-displacement relations reveal a hysteretic behavior due to local residual displacements after the test are observed by the help of digital image correlation (DIC). The test structure stores up to 25% of the applied displacement. The local contact state (sliding or sticking) is evaluated in different regions of the MF-SMP which gives an insight into the shape memory mechanism magnetofriction. Two methods for the shape-recovery of the MF-SMP by elastic forces in the MAEs are proposed, a manual separation and an air flow at the interface of the MF-SMP, and a comparison of magnetofriction to other shape memory mechanisms is performed.

“…Few publications investigate the magneto-mechanical response of MEs, with most focusing on the rheological behavior of the material for use in damping systems [17]. A recent publication aimed to characterize the field-dependent Young's modulus of MEs, and developed a testing apparatus for this behavior and future studies [18]. Another publication discussed the effect of pre-strain on the resulting stress-strain relationship and magneto-mechanical properties of MEs using spherical carbonyl iron particles [19].…”

Section: Introductionmentioning

confidence: 99%

Tuning the grasping strength of soft actuators with magnetic elastomer fingertips

Bira¹,

Dhagat²,

Davidson³

2022

In this work, we present an approach that uses multifunctional materials to increase the grip strength of soft grippers, while still maintaining the benefits of gripper compliance. Here, magnetic particles embedded in an elastomeric fingertip, or magnetic elastomers (MEs) are shown to increase grasping strength and influence actuation trajectories in soft robotic actuators when coupled with external magnets. Two PneuNet-style actuators with ME fingertips generated up to 45 N of holding force, compared to only 10 N without a magnet. The actuator demonstrated enhanced grip strength while the ME tip was within approximately 13 mm of the magnet. This paper characterizes numerous ME compositions and demonstrates specific applications where MEs expand upon soft robotic actuation methods. Both the opportunities as well as limitations presented by ME composition are discussed at length.