Abstract
In order to function as soft actuators, depending on their field of use, magnetorheological elastomers (MREs) must fulfill certain criteria. To name just a few, these can include rapid response to external magnetic fields, mechanical durability, mechanical strength, and/or large deformation. Of particular interest are MREs which produce macroscopic deformation for small external magnetic field variations. This work demonstrates how this can be achieved by just a small change in magnetic field orientation. To achieve this, (super)paramagnetic nickel particles of size ≈ 160 μm were embedded in a non-magnetic polydimethylsiloxan (PDMS) (661–1301 Pa) and their displacement in a stepwise rotated magnetic field (170 mT) recorded using a video microscope. Changes in particle aggregation resulting from very small variations in magnetic field orientation led to the observation of a new strongly magneto-active effect. This configuration is characterized by an interparticle distance in relation to the angle difference between magnetic field and particle axis. This causes a strong matrix deformation which in turn demonstrates hysteresis on relaxation. It is shown that the occurrence strongly depends on the particle size, particle distance, and stiffness of the matrix. Choosing the correct parameter combination, the state can be suppressed and the particle-matrix system demonstrates no displacement or hysteresis. In addition, evidences of non-negligible higher order magnetization effects are experimentally ascertained which is qualitatively in agreement with similar, already theoretically described, particle systems. Even at larger particle geometries, the new strongly magneto-active configuration is preserved and could create macroscopic deformation changes.
Highlights
Magnetorheological elastomers (MREs) are hybrid materials, comprising an elastic non-magnetizable matrix, such as polydimethylsiloxane (PDMS), interspersed with magneticDresden, Germany fillers like iron oxide particles
When applying a magnetic field, MREs undergo a reversible variation of their visco-elastic characteristics and/or undergo a reversible shape change that can be used for actuation
An efficient usage of MREs for applications would be strongly facilitated by a fundamental understanding of the macroscopic and internal mechanisms under applied magnetic fields: Their physical response to external magnetic fields depends on the influence of experimental parameters such as concentration and distribution of filler particles, matrix stiffness, magnetic field strength, etc
Summary
Magnetorheological elastomers (MREs) are hybrid materials, comprising an elastic non-magnetizable matrix, such as polydimethylsiloxane (PDMS), interspersed with magnetic. The specified examples for twoand three-particle systems in [59, 60] are of particular importance in providing a solid theoretical basis for the systems described in this work These experiments reveal specific dependencies of the results on the sample characteristics such as the number of magnetic particles, elastic modulus of the surrounding gel matrix, and the typical particle distance. Leaving the elastic modulus (≈ (1221±100) Pa) and magnetic field strength (≈ 170 mT) unchanged but varying the initial distance, the influence of the particle positioning on the new strongly magneto-active configuration can be obtained. For initial distances smaller than ≈ 220 μm, the two-particle system approaches the state of remaining in contact for any orientation of the applied external magnetic field at this flux density They rotate according to the field until a pairwise reorientation takes place. The particles at the edges show only an overall distance change of ≈ 1%
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
