Magnetic and structural analysis of magnetorheological foam fabricated by constraining volumes of foaming process

Abstract

Magnetorheological (MR) foam has become a topic of research interest due to its potential breakthrough in smart soft robotic applications, due to its versatility, high flexibility and durability. In fact, it has controllable properties that could be actively changed, reversibly by manipulating external magnetic fields. The process of magnetizing MR foam is highly dependent on the incorporation and distribution of magnetic particles (CIPs) in the porous structure of the foam. In fact, the resultant properties would be affected by the structural arrangement of the material. Therefore, this study provides an insightful analysis on the microstructure of MR foams and its resultant magnetic properties, after undergoing different constrained volumes of foaming process. The magnetizations of fabricated samples were determined via vibrating sample magnetometer (VSM) and the morphological characteristic was carried out by using atomic-force microscopy (AFM). The results demonstrate that the magnetic properties of MR foam increased as constrained volumes were applied during foaming process, from free foaming to 50% constrained volume. This indicates the improvement in the magnetic response of MR foams, and higher magnetic saturation due to more localized CIPs in the structure of MR foams. AFM analysis then further supports these findings by showing distinct structural changes in the porous structure of MR foams as the constrained volume during foaming decreased. Consequently, a more compact structure with improved distribution of CIPs has been acquired, which enhances the connectivity between the CIPs and contributes to a more robust magnetic network when MR foam is exposed to applied magnetic fields. This research provides a foundation for further exploration of MR foams, as the improvements are critical for future applications, particularly in robotic fields, requiring high-performance MR foams.