AC Impedance Analysis of Electrorheological Fluids - Activated Biomedical Devices

Abstract

Electrorheological fluids (ERFs) have been described as highly engineered variable-impedance fluids that possess rheological and electrical properties that demonstrate dramatic nonlinear change with an applied electric field. ERF is a two-phase composite colloidal suspension of electrically polarizable particles dispersed in insulating media. This article describes an application of low-voltage electrochemical impedance spectroscopy (EIS) to comparative characterization of four different ERFs and a prediction of their performance in ER-activated medical prosthetic devices. The ERF impedance response is interpreted in the context of a classical Debye relaxation model. EIS data analysis allows the determination of the electrical characteristics of polarizable particles and base fluid, an investigation of the preferred conduction mechanisms in the fluid, an evaluation of the potential for chemical agglomeration, and modification of the electrical properties of the ERF to achieve better fluid performance. The ERF performance improves significantly for highly concentrated suspensions of well-dispersed, small, closely packed particles. The recent introduction of nanoparticles-based ERF has created an opportunity for further development of fluids with transformationally superior performance.