Rheology of Perfluorinated Polyether-based MR Fluids with Nanoparticles

Abstract

Motivated by the use of magneto-rheological (MR) technology in prosthetic devices, the goal of this study is to develop a MR fluid composition that is tailored for the requirements of a prosthetic knee actuator. A MR fluid composition is sought with a suitable balance between the field-induced shear stress, the off-state viscosity, and sedimentation stability for the proposed application. Rheological characteristics are investigated for samples with monodisperse micron-sized particles and bidisperse fluids with a mixture of micron- and nanosized particles. Two types of nanosized particles are used. All fluid samples employ a novel perfluorinated polyether oil as carrier liquid which enhances stability. The samples are investigated with respect to both field-induced and off-state characteristics. The results are compared to analytical and empirical models that exist in the literature. The monodisperse fluids are shown to give a favorable trade-off between field-induced strength and off-state viscosity. The addition of a small concentration of nanoparticles is found to moderately increase the field-induced shear-yield stress. However, for a larger concentration of nanoparticles, the yield stress begins to decrease. Nanoparticles exhibit an undesirable effect on the off-state viscosity. The results reveal valuable information for the designers of MR fluids and designers of prosthetic actuators.

Magnetorheology: a review

“…In fact, a dimensionless number has been documented to describe the rheological response under shearing flow. This is the so-called Mason number (Mn) commonly defined as the ratio of the 121 CIP/attapulgite B4000/B10 Sphere/rod CM grade from BASF/Fluorochem Cvek et al 122 CIP/carbon allotropes B2500/B10 Sphere/rod SL grade from BASF/Sigma Aldrich Kwon et al 123 CIP/halloysite B4500/B100 Sphere/unknown CD grade from BASF/Sigma Aldrich Jonsdottir et al 124 CIP/iron B2000/B25 and B2000/B100 Spheres HS grade from BASF/Nanostructured & Amorphous Materials Inc. Ngatu et al 125 Iron/iron Between 6000 and 10 000/230 diameter, 7500 AE 5100 length Sphere/nanowire Alfa Aesar/templated assisted electrodeposition…”

Physical characteristics of magnetorheological suspensions and their applications

“…Additives, together with magnetizable microparticles, form stable structures in the carrier liquid [66]. For example, Wu et al [67] used guar-gum to generate cell-type structures in silicone liquid.…”

An Experimental Investigation of Unimodal and Bimodal Magnetorheological Fluids with an Application in Prosthetic Devices

“…All fluid samples employ a PFPE oil (Hsu et al, 2006;Jonsdottir et al, 2010) as a base fluid. The composition of this base fluid is 95% PFPE UNIFLOR TM 8510 (Hsu et al, 2006) and 5% PFPE Krytox TM 157-FSL (Hsu et al, 2006) as a dispersion agent.…”