Magnetically Switchable Adhesion and Friction of Soft Magnetoactive Elastomers

Abstract

Herein, the effect of an applied moderate (≈240 mT) magnetic field on the work of adhesion (WoA) of mechanically soft (the shear modulus ≈10 kPa) magnetoactive elastomer (MAE) samples with two different mass fractions (70 and 80 wt%) of carbonyl iron powder (CIP) is concerned. The unfilled elastomer sample is used for comparison. Due to some sedimentation of filling particles, the concentration of inclusions in thin (≈10 μm) subsurface layers is different. It is shown that the WoA increases (up to 1.8‐fold) on the particle‐enriched side (PES) in the magnetic field and its value is higher for higher filler concentration. On the particle‐depleted side (PDS), WoA does not depend on particle concentration and on the magnetic field. Adhesion and friction are coupled in MAEs. No statistically significant difference in the friction coefficient, determined from the extended Amontons´ law, depending on sample side, CIP concentration, or presence of magnetic field is found. However, the PDS in the magnetic field demonstrates significantly higher critical shear stress compared to that for the PES or PDS in the absence of magnetic field. Correlations between different surface properties are discussed. Obtained results are useful for the development of magnetically controllable soft robots.

Magnetically Tunable Adhesion of Magnetoactive Elastomers’ Surface Covered with Two-Level Newt-Inspired Microstructures

“…Nevertheless, the adhesion of 2L-MAE at 15 vol.% and 20 vol.% increased to 91 mN and 115 mN, respectively, by 152% and 144%. This phenomenon of magnetic field-enhanced adhesion was also found in reference [ 33 ]. We believe that this phenomenon also causes by the magneto-induced modulus E m , which could be expressed as [ 31 ]: where is the average strain of the MAE.…”

Dynamically tunable lamellar surface structures from magnetoactive elastomers driven by a uniform magnetic field

“…MAE surface can be (micro)structured into various topographies leading to intriguing new functionalities 12 . One of the common choices is lamellar topography that enables dynamic modifica-tion of optical 29,30 , wetting 13,31 and friction [32][33][34] properties. The cantilever-type MAE structures have been shown to controllably deflect both in non-uniform and uniform magnetic fields.…”

Extremely Long Chains of Magnetic Particles via Large Plastic Beads Observed in Bimodal Magnetic Elastomers

“…Magnetic elastomers are one of the stimulus-responsive soft materials, i.e., materials whose physical properties change in response to magnetic fields, e.g., macroscopic expansion and contraction under gradient magnetic fields, magnetostriction, rotational motion under rotational magnetic fields, magnetorheological greases, multiferroic cantilevers, adhesion and friction properties due to magnetic switching, tunable vibration–absorption, and variable surface microstructure. , Magnetic elastomers consisting of polymer matrix and magnetic particles generally undergo a large magnetic response and are expected to be practical actuators. When a magnetic field is applied to a magnetic elastomer, the elasticity increases due to the formation of a chain-like structure of the magnetic particles (restructuring), known as the magnetorheological (MR) effect.…”