Ionic Electroactive Polymer Actuators with Aligned Carbon Nanotube/Nafion Nanocomposite Electrodes
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Ionic Electroactive Polymer Actuators with Aligned Carbon Nanotube/Nafion Nanocomposite Electrodes Yang Liu1, Sheng Liu1, Hülya Cebeci2, Roberto Guzman de Villoria2, Jun-Hong Lin3, Brian L. Wardle2 and Q. M. Zhang1,3 1
Department of Electrical Engineering, 2Department of Materials Science and Engineering The Pennsylvania State University, University Park, PA 16802 U.S.A. 3 Department of Aeronautics and Astronautics, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 U.S.A. ABSTRACT Recent advances in fabricating controlled-morphology vertically aligned carbon nanotube (VA-CNTs) with ultrahigh volume fraction create unique opportunities for markedly improving the electromechanical performance of ionic polymer conductor network composite actuators (IPCNCs). Actuator experiments show that the continuous paths through inter-VA-CNT channels and low electrical conduction resistance due to the continuous CNTs in the composite electrodes of the IPCNC lead to fast ion transport and actuation speed (>10% strain/second). One critical issue in developing advanced actuator materials is how to suppress or eliminate unwanted strains generated under electric stimulation, which reduce the actuation efficiency and also the actuation strains. We observe that the VA-CNTs in the composite electrodes yields non-isotropic elastic modulus that suppresses the unwanted strain and markedly enhances the actuation strain (>8% strain under 4 volts). A transmission line model has been developed to understand the electrical properties of the actuator device. INTRODUCTION Ionic electroactive polymers (i-EAPs) are attractive because relatively large electromechanical actuations can be generated under low voltage (~ a few volts). [1,2] Hence, they can be directly integrated with microelectronic controlling circuits, which have operation voltage of several volts, to perform complex actuation functions and low applied voltage also makes them safe to use. These i-EAP actuators hold promises for applications including artificial muscles, robots, micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS), and energy harvesting. On the other hand, one critical issue in applying the i-EAPs for these applications is how to significantly improve the electromechanical performance, including the actuation speed, actuation strain level and efficiency. [1-3] Recent advances in fabricating controlled-morphology aligned carbon nanotube (VACNTs) with ultrahigh volume fraction create unique opportunities for markedly improving the electromechanical performance of i-EAPs.[4-6] Here, we report on developing i-EAPs utilizing continuous aligned CNTs with high packing fraction and will show that by making use of the highly aligned and high volume fraction VA-CNTs, significant improvement in the electromechanical performance [7]. Actuator performance enhancement due to the electrodes includes the strain level and actuation response time, when compared to the ionic polymer metal composites (IPMC) that have tortuous ioni
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