THE 19 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS Introduction The stability and low melting point make ionic liquids favorable electrolytes to be used in a wide range of electrochemical systems. The application field includes lithium ion batteries, electric double- layer capacitors (EDLCs), and ionic electromechanically active polymer (iEAP) actuators. The iEAP is a laminate structure that consists of electronically conductive high surface area electrodes bonded to the opposite sides of an ion- permeable polymeric separator [1]. When electric potential is applied between the electrodes, the laminate changes its size or shape, depicted as bending of the laminate in unobstructed cantilevered beam configuration in Figure 1. The structure of iEAPs is rather similar to the EDLCs and their energy storage properties are sometimes comparable [2]. Fig. 1. The iEAP actuator at its maximum bending deflection at 2.8 V input voltage with opposite polarities. In the considered iEAP laminate, titanium carbide- derived carbon is used as electrode material, while Nafion is used as a separator and electrode binder. Carbide-derived carbon and Nafion are both strongly hydrophilic. The whole structure contains ionic liquid as an electrolyte. Ionic liquid is used due to its high stability and negligible vapor pressure, which makes possible to use the actuator devices in air. In addition to the melting point, viscosity, and conductivity; hydrophilicity data of ionic liquids is of great importance [3]. Ionic liquids are often classified to be either hydrophilic or hydrophobic; although, it has been claimed that all ionic liquids sorb considerable amount of water from the environment [4]. The water content has a considerable impact on the physiochemical properties. In some fields of application, the infusion of water into the structure must be avoided. However, there is a great demand in the industry for flexible, transparent and highly integrable electronics, which are expected to function under the atmospheric conditions. The research on the physiochemical properties of ionic liquid-water mixtures has attracted an increasing attention in the recent years. Theories for sorption mechanisms have been proposed and water uptake kinetics has been investigated in numerous studies [3, 4], but to date only small attention has been turned on the impact of sorbed water on the performance of real electrochemical devices such as EDLCs or iEAP actuators. In the current study, electrochemical impedance method is applied for investigation of the properties of an iEAP actuator working at different ambient conditions. Material preparation A Nafion membrane is impregnated with 1-ethyl-3- methylimidazolium trifluoromethanesulfonate ionic liquid. Electrodes are formed on both sides of the membrane by spray-painting them with an electrode dispersion, which consists of titanium carbide- derived carbon powder and Nafion solution. A gold THE PERFORMANCE OF THE IONIC LIQUID-CONTAINING ELECTROACTIVE POLYMER ACTUATORS UNDER AMBIENT AIR CONDITIONS I. Must*, I. Põldsalu, F. Kaasik, U. Johanson, A. Punning, A. Aabloo Intelligent Materials and Systems Laboratory, Institute of Technology, Univ. of Tartu, Estonia * Corresponding author (indrekm@ut.ee) Keywords: IEAP, carbide-derived carbon, ionic liquid, impedance, environmental conditions ICCM19 8282