Years of research in the field of electro- and magneto-rheological fluids, also called smart fluids, have led to development of outstanding applications in various fields: from medicine and biomedical devices to optics, defense industry and mechanical engineering. In order to fit these special applications, new types of smart materials, with improved properties have been designed. While rheological testing provides information on the macroscopic behavior of the fluids under the influence of electric and magnetic fields, the need for microscopic knowledge is omnipresent.

The development of new measuring techniques aimed at characterizing the microscopic structure is made possible through the knowhow accumulated over the years from close cooperation with R&D departments and universities.

Particle alignment, structure forming and breakage are strongly influenced by the type of material and the composition, shape, size and concentration of particles as well as the physical properties of the carrier liquid. In addition to these parameters, the relationship between the applied electric or magnetic fields and the external mechanical load strongly influences the structural changes of the smart fluids.

We study this interplay of macroscopic sample behavior and microscopic structure in two ways. First, the structure is visualized by combining established magneto- and electro- rheological devices with optical visualization methods. Second, the response of the smart fluid structure to mechanical oscillation at large strains is measured. The theoretical framework, experimental data and analysis results for large amplitude oscillatory shear (LAOS) on a commercial magnetorheological fluid will be presented.