Self-similarity in electrorheological behavior

Abstract

In this work we study creep flow behavior of suspension of Polyaniline (PANI) particles in silicone oil under application of electric field. Suspension of PANI in silicone oil, a model electrorheological fluid, shows enhancement in elastic modulus and yield stress with increase in the magnitude of electric field. Under creep flow field, application of greater magnitude of electric field reduces strain induced in the material while application of greater magnitude of shear stress at any electric field enhances strain induced in the material. Remarkably, time evolution of strain in PANI suspension at different stresses, electric field strengths and concentrations show superposition after appropriate shifting of the creep curves on time and strain axes.Observed electric field -shear stress -creep time -concentration superposition demonstrates self-similarity in electrorheological behavior. We analyze the experimental data using Bingham and Klingenberg -Zukoski model and observe that the latter predicts the experimental behavior very well. We conclude by discussing remarkable similarities between observed rheological behavior of ER fluids and rheological behavior of aging soft glassy materials.

Polypyrrole-wrapped halloysite nanocomposite and its rheological response under electric fields

“…The isotherm for PPy/HNT showed steep increments in the adsorption capacity at relative pressures (P/P o ) of approximately 0.45 with a clear hysteresis loop, indicating that PPy/HNT also contains mesopores. The ER fluid was prepared by dispersing the PPy/HNT nanocomposite particles in silicone oil, and the microstructural change in this ER fluid was then observed directly by optical microscopy under an applied electric field with a DC high voltage source [35]. The PPy/HNT nanocomposite-based ER fluid exhibited a typical ER chain structure.…”

“…The exponent m can be obtained by fitting the yield stresses over a broad electric field range on a logarithmic scale [35]. Figure 9 shows the dynamic yield stress (s y ) as a function of the electric field strength (E 0 ) for the PPy/ HNT composite-based ER fluid.…”

Flow curve analysis of a Pickering emulsion-polymerized PEDOT:PSS/PS-based electrorheological fluid

“…Electrorheological (ER) fluids, which are smart and tunable colloidal suspensions comprised of an insulating medium and polarizable particles, have attracted considerable attention because of their ability to respond promptly and reversibly to external electric fields [1][2][3][4]. When an external electric field is applied, ER fluids exhibit an instant liquid-solid phase transition as a result of the formation of a chain structure caused by the attractive force among dispersed polarizable particles [5,6].…”

“…On the other hand, one of the most important rheological parameters in ER fluids is the yield stress. In particular, for the application of ER fluids in devices, the correlation between the yield stress and external electric field strength is essential along with its precise determination [2,3,30]. When analyzing the correlation between the yield stress and external electric field strength, power law models with a variable exponent typically described the behavior.…”

Three-dimensional yielding in anisotropic materials: validation of Hill's criterion

“…However, once the applied deformation field exceeds the yield stress, particle-chains start breaking, which leads to structural breakdown. [18][19][20][21] Such electric field-controlled fluidity makes these fluids a potential candidate for many practical applications such as, breaks, clutches, dampers etc. [22][23] Many experimental as well as simulation studies have been performed to understand the yielding phenomenon in ER fluids, however most of such studies were performed in unidirectional flow modes such as, purely rotational, purely squeeze, or purely tensile/elongation flow mode.…”