Evoking the snap-through instability in hard-magnetic soft materials: Rapid actuation and giant deformation

Abstract

In this paper, we break into an appropriate strategy for achieving a rapid actuation and giant deformation in hard magnetoactive elastomers (MAEs). We devise a flat arch with a properly distributed residual magnetic flux field and realize the large deformation by harnessing the snap-through instability. With an ingenious design of the residual magnetic flux field within the arch that has a large slenderness ratio, the applied magnetic field for inducing the onset of instability can be relatively small. Even if the size of the flat arch is up to millimeter level, the applied magnetic field is as small as hundreds of oersted. We also develop a theoretical model for revealing the mechanism of the magnetic-driven instability in hard magnetoactive elastomers. The stress, induced by the coupling between the external magnetic field and the residual magnetic flux field, is transformed into a surface load. We formulate the total energy of the magneto-mechanical system and carry out the first and second variations to study the equilibrium states and their stability. To verify our theoretical predictions, we fabricate the corresponding MAE specimen and observe the tantalizing magneto-mechanical behaviors in the lab. Our theoretical predictions agree with the experimental observations in the case of flat arches of MAEs. This paper is desirable to open new ways of designing multifunctional MAE devices with rapid actuation and giant deformation.