Exploration of an Electroactive Polymer as an Actuator for Microrobotics
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EXPLORATION OF AN ELECTROACTIVE POLYMER AS AN ACTUATOR FOR MICROROBOTICS C. Bielmeier and W. Walter RIT Mechanical Engineering Robotics Laboratory, Rochester Institute of Technology 76 Lomb Memorial Drive, Rochester, New York 14623 ABSTRACT The development of lightweight low power consumption actuators is critical to the development of micro-robotics. Electroactive Polymers (EAP), i.e. Nafion N-117, meet these requirements. In the actuation of an EAP, the current does not remain constant over time. The development of a circuit model of current draw over time to best predict a current dynamic has been explored. While the material mimics a parallel plate capacitor, it has been found that capacitance plays no role in achieving steady state current levels. This development is critical to understanding and developing the material as an actuator. This paper discusses the necessary developments required for the EAP actuator to be utilized in micro-robotic devices. Specifically, the development of a lightweight reliable electrode for EAP material actuation and the current draw over time model and equations were developed. In addition, current research of a grasshopper inspired hopper is discussed. 1. INTRODUCTION An Electroactive Polymer (EAP) is a material whose electric properties such as conductivity, charge, and shape can be controlled by an environmental change such as voltage, light, or stress. The ability to custom make these materials to fit a variety of properties such as stress, voltage, shape, and cost make them a cutting-edge material in many fields including biological, aerospace, and robotics [1]. The Electroactive Polymer materials are often used as actuators. There are several different types used for these EAP Actuators such as Ionic Polymer, Ionic Polymer Metal Composite (IPMC), Ionic Metal Polymer Composite (IMPC), and Ionic Conducting Polymer Film (ICPF). Most often the IPMC type of actuator is used when an electroactive polymer device is required [2]. IMPCs are active actuators that show large deformation in the presence of low applied voltage and exhibit low impedance [2]. IPMCs are commercially made by DuPont under the name of Nafion and then plated with platinum. This material was used in the testing shown in this paper. The material was donated from Virginia Polytechnic Institute and State University. The bending of electroactive polymers occurs from contraction and expansion of the outer most remote fiber (see Figure 1). The bending can be induced by electrical field [2]. The benefit of this material is that the output voltage can be calibrated for a standard size sensor and can be correlated to the applied loads or stresses [3]. Also low voltage and power consumption rate make this ideal for micro-robotics.
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Figure 1- Bending in EAP [2]. In comparison to other EAPs, such as shape memory and electroactive ceramics, ionic polymers are lighter and their potential electrostriction capabilities can be as great as two orders of magnitude higher than Electroactive Ceramics (EAC), and hav
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