The Effect of Ionic Liquid Uptake and Self-assembled Conductive Network Composite Layers on Nafion TM based Ionic Polyme
- PDF / 3,327,075 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 80 Downloads / 161 Views
The Effect of Ionic Liquid Uptake and Self-assembled Conductive Network Composite Layers on NafionTM based Ionic Polymer Metal Composite Electromechanical Bending Actuators Dong Wang1, Reza Montazami2 and James R. Heflin1 1 Department of Physics, Virginia Tech, Blacksburg, VA 24061, U.S.A. 2 Department of Mechanical Engineering, Iowa State University, Ames, IA 50011, U.S.A. ABSTRACT Ionic liquid (IL) is used as the working electrolyte in ionic polymer metal composite (IPMC) electromechanical bending actuators because of its high stability and conductivity, which are crucial for the consistency and speed of the actuation. Because the bending actuation is caused by the migration and accumulation of the cations and anions of the IL, it is clear that both the overall number of ions and the effectiveness of ion transport and accumulation play important roles in the actuation behavior. In this paper, the effect of enhancing the ion accumulation by the self-assembled conductive network composite (CNC) layers is investigated by comparing the bending behavior of actuators with and without CNC layers. In addition, IPMC actuators with various IL uptakes are also tested in order to study the dependence of the bending performance on the amount of the ions available. It is found that, with the CNC layers, the maximum bending curvature of the actuator increases with increased IL, which shows the crucial role played by the IL. However, under the same conditions, the performance improvement of actuators without CNC layers saturates when the IL uptake reaches around 10% wt. This demonstrates the role of the CNC layers to provide a porous electrode with increased capacitance that thus accommodates accumulation of more ions near the electrodes, which in turn boosts the overall bending curvature of the actuator. INTRODUCTION Due to their light weight, low operating voltage and good biological compatibility, IPMC bending actuators with ionic liquid as working electrolyte have potential applications in microelectro-mechanical systems (MEMS), micro robotic devices and artificial muscle. They typically consist of an ion conductive polymer membrane and two electrodes attached to each side of the membrane. The electrolyte incorporated in the actuator provides mobile ions that can migrate through the ion conductive membranes when an external voltage is applied on the electrodes. The bending is generated due to swelling induced by the ion distribution change from a random mixture state to the charge separated state. Having been extensively studied as an ion exchange membrane in fuel cell applications, NafionTM is an excellent candidate as the ion conductive membrane in IPMC actuators because of its high ion conductivity and thermal stability. It contains hydrophobic Teflon-like backbone and hydrophilic sulfonate ionic side groups. When hydrated, the spontaneous phase separation between these two components in Nafion opens channels for ions to migrate[1].Conventionally, the ions for generating the actuation can be provided by common electrolyte
Data Loading...
