Magnetorheology of exotic magnetic mesostructures generated under triaxial unsteady magnetic fields

Traditionally, the rheological properties of magnetorheological (MR) fluids are investigated under uniaxial steady (DC) fields. These basic fields promote the aggregation of magnetically attractive particles into chain-like structures aligned in the field driven direction. In this manuscript we show how triaxial unsteady fields can generate a variety of exotic mesostructures and influence the rheological response of the MR fluids. We bridge understanding the rheological response to each unique particle structure through videomicroscopy, x-ray microtomography and rheometry tests. Small-amplitude oscillatory shear and steady shear tests lay out an unmistakable argument for MR enhancement with both elevated storage modulus and yield stress responses following a sequence of steady uniaxial and unsteady fields. We demonstrate that structures assembled through time-averaged particle interactions or typical dipole-dipole magnetostatic interactions, especially when columnar structures are strengthened through lateral chain coalescence, can boost rheological response.

Automated summary

This study investigates the effects of triaxial unsteady fields on magnetorheological (MR) fluids, revealing that such fields can generate various exotic mesostructures and influence the rheological response of the fluids. By bridging the understanding of rheological response to unique particle structures through experimental tests and observation, the study demonstrates the impact of steady and unsteady fields on the performance of MR fluids.