Dielectric Analysis of Response Time in Electrorheological Fluids Developed for Medical Devices

Three electrorheological fluids (ERFs) of recently synthesized Polyaniline.HCl and Cellulose fluids as well as a commercial product from Fludicon® (Germany), were evaluated with a two-electrode probe unit and by Dielectric Analysis (DEA). The study was a part of an ongoing medical device development project. The dielectric response times were calculated using the critical peak frequency in a corresponding Debye plot of Tan Delta (loss factor/permittivity) vs. log frequency. The DEA revealed the response times (tau, τ) in ms. The Fludicon® ERF was DEA durable (repeat cycles produced same results) and the τ was temperature dependent: 16 ms at 25°C and 0.16 ms at 80°C. The Cellulose ERF was somewhat DEA durable and the τ was 5.5 ms at 25°C and 0.21 ms at 80°C. The response times were logarithmic with the temperature (°C) with a correlation coefficient of >0.98 for the Cellulose and Fludicon® ERFs. The Polyaniline ERF had a τ of 53 ms at 25°C in the 1st DEA run and there was no indication of a τ for the remaining DEA tests.