Humidity and heat transport during electrical heating of an ionic hydrogel

Abstract

With an ever-increasing range of applications found for aqueous electrically conducting gels, it is necessary to not only understand their electrical properties, but also how they dissipate heat and change the surrounding humidity. Here, an experimental setup for simultaneously investigating the electrical properties, the surface temperature and the relative humidity in the vicinity of ionically conducting gelatine is reported. It is found that the sample surface temperature increases quadratically with conducting current until the gel approaches breakdown at sufficiently high temperatures. Simultaneous measurements of the relative humidity indicate that this parameter increases linearly with sample surface temperature in the temperature range investigated. At currents of about 20 mA, the temperature and relative humidity increase approximately 10 °C and 10 %, respectively. Fluctuations in electrical parameters for even larger currents resulted in significant variations in the observed temperature increase and humidity change. The present work provides better insight into mechanisms behind and how electrically conducting biocompatible hydrogels can be used to increase temperature and enhance evaporation.