Skin electrode impedance of textile electrodes for bioimpedance spectroscopy

Abstract

Bioimpedance Spectroscopy (BIS) has several applications in the medical field, such as fluid and body composition monitoring. In order to perform monitoring at home, a wearable solution would be an important improvement. In general, a BIS measurement is carried out with at least four conductive electrodes attached directly to the body. However, the latest systems on the market are highly limited with respect to mobile purposes, especially concerning the electrodes which are usually not suitable for a long term use and may cause allergic reactions. A possible solution to this problem is the use of textile electrodes, which combined with the integration of cables and other electrical components into a textile will enable the implementation of a wearable and comfortable application. Due to the lack of a hydrogel, textile electrodes feature different characteristics concerning the skin contact, constituting an important element for bioimpedance measurements. In this article, the skin electrode impedance has been measured using textile bioimpedance electrodes under different temperatures and using different textile structures. Equivalent circuits from the literature have been compared with the measured values in order to suggest a representative model for the skin electrode impedance. The results show the suitability of using the constant phase element rather than just ideal resistive or capacitive elements for its modelling. The influence of other factors like sweating and temperature will also be discussed. © Springer-Verlag 2007.