Magnetically Switchable Adhesion and Friction of Soft Magnetoactive Elastomers

Herein, the effect of an applied moderate (approximate to 240 mT) magnetic field on the work of adhesion (WoA) of mechanically soft (the shear modulus approximate to 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 (approximate to 10 mu m) 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.

Automated summary

This study investigates the effect of a moderate magnetic field on the work of adhesion of mechanically soft magnetoactive elastomer samples. The results show that the magnetic field increases the adhesion on the particle-enriched side, while it has no effect on the particle-depleted side. These findings are relevant for the development of magnetically controllable soft robots.