Surface patterning and auxetic metamaterial response with magnetorheological elastomers

In this work, we propose the use of magnetorheological elastomers (MREs) as designer active materials or even metamaterials by proper combination of geometry, material selection and combined magnetomechanical loadings. Specifically, we study experimentally and numerically the response of an MRE film/substrate assembly subjected to transverse magnetic fields and in-plane pre-compressions. We show that a single material assembly allows for a single and/or double-period wrinkling as well as surface patterning by proper combination of magnetic and mechanical loads. In addition, we show critical magnetic field for wrinkling can be substantially reduced in the presence of compressive prestress of the assembly, thus opening the possibility of controlling haptic interfaces with low magnetic fields. Finally, we propose novel auxetic MREs by use of general numerical framework.