Electroactive Polymers Electroactive Polymers Aaron Lubiszewski Jesse Gwynne Engr-45 Ataiiyan December 4, 2003 Introduction Smaller, lighter, cheaper…these are three major concerns one must keep in mind when attempting to make improvements.
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Electroactive Polymers Electroactive Polymers Aaron Lubiszewski Jesse Gwynne Engr-45 Ataiiyan December 4, 2003 Introduction Smaller, lighter, cheaper…these are three major concerns one must keep in mind when attempting to make improvements on existing technology. Electroactive polymers (EAPs) achieve all of these goals. Natural Polymers Wood Silk Cotton Wool Leather Rubber Hydrocarbons Hydrogen and Carbon Covalent Bonding Intermolecular Bonding hydrogen bonding van der wall forces Synthetic Polymers Plastics Rubber Fibers Structures Repeating structures called mers Comes from Greek work “meros” meaning part many mers = polymer Polymers are thousand or mer units long Can have elements other than Carbon and Hyrdogen….Fl, Cl, side groups Polymer Vocabulary All-the-same-mers = homopolymer a-couple-different-mers = copolymers two-ways-to-function-mers = bifunctional (chains) three-ways-to-function-mers = trifunctional (matrix) Fabrication of Polymers Chemical Reactions Catalyst Don’t have to be straight Types of Polymers Linear Branched Crosslinked Network Mechanical Properties Similar to metals Modulus of Elasticity…7 Mpa to 4Gpa Tensile strength…generally less than metals Percent Elongation…up to 1000% Most have yield strengths Stress vs. Strain for Polymers EAPs • A type of polymer that is affected by an applied electric field. • This affect may be in the form of deformation, movement, bending, or actuation . • Scientists and engineers envision using EAPs to replace a wide range of heavy, expensive, and power hungry equipment. • Existing EAPs fall into two main categories • electronic • ionic • Function similar to… • Piezoelectric materials • Shape memory alloys (SMAs) Comparison Strain of EAP with Other Technologies 250 Strain (%) 200 150 100 50 0 EAP-Acrylic EAP-Silicone Electrostrictor Polymer Electrostatic Devices Technology Electromagnetic PiezoelectricCeramic Shape Memory Alloy Ionic Polymers- Creation Polymers...Nafion, Flemion Infused conductive electrodes…Pt, Au Flow of ions create bending and swelling Positive ions attracted to negative electrode and visa versa Water creates medium for ion movement Ionic Polymer Types Ionic Polymer Gel (IPG) ions created from acidic environment Ionomeric Polymer-Metal Composite (IPMC) (+) “counter ions” and negative fixed ions are imbedded in matrix Conductive Polymers (CP) redox reactions exchange ions with electrolyte Carbon Nanotubes (CNT) ions change bond length to create movement Polarization of an Ionic EAP Ionic Polymer- Advantages Low voltages required1- 10 V Large bending displacements greater than 90 degrees Ionic Polymer-Disadvantages Don’t hold strain under DC current Relatively low actuation forces Relatively slow reaction times Hard to produce consistent materials Must be kept moist Ionic Polymer-Performance Moisture Voltage Voltage Frequency Deflection Reaction Rate Force/Lift Deflection Electric EAPs Stimulated by an applied electric field. Types: • Dielectric EAP • A dielectric material is placed between two electrodes. • To allow for movement of the EAP, the electrodes must be flexible. • Electrodes are a thin, conductive film, only a few nanometers thick, is deposited onto the surface of the EAP. • EAP is distorted when a voltage is applied. • Can be deformed by up to 400 percent of their original size. • Ferroelectric EAP • Become polarized when an electric field is applied to them. • Ability to transfer electrical energy to mechanical energy, and visa versa. Applications Grippers EAP fingers hold and release objects depending on sign of charge Hand Gripper Applications Generators When a ferroelectric EAP is deformed, a voltage difference is created across it. EAP generators on the ocean floor. Boot heel generator. Applications NASA is extremely interested in the progression of EAPs. They envision EAPs replacing a wide range of heavy, expensive, and power hungry equipment. The first application NASA has found for EAPs is as a wiper that would use small EAP fingers to clean dust and debris from sensitive equipment and lenses. Other Applications EAP motivated Creatures Snakes, aquatic animals, bugs, and airborne robots Speakers Pumps and Valves Summary of advantages Inexpensive to manufacture Large deformation Ability to hold deformation Rapid response time Light weight Outlook for EAPs The ultimate goal for scientists and engineers is to create EAPs that mimic human muscles. Works Cited Ashley, Steven. “Artificial Muscles.” Scientific American October, 2003. Bar-Cohen, Yoseph Dr. “Electroactive Polymers – EAPs.” http://www.azom.com, April, 2003. Bar-Cohen, Yoseph Dr. “Miniature Electroactive-Polymer Rakes.” http://www.nasatech.com/Briefs/Oct01/NPO20613.html, October, 2001. Callister, William D. Materials Science and Engineering: An Introduction 6th Ed. New York: John Wiley & Sons, Inc. 2003 ElectorActive Polymers- EAP’s. Azom.com. November 2003. <http://www.azom.com/details.asp?ArticleID=885#_Ionic_EAPs> The International Society for Optical Engineering. “Low-Mass Muscle Actuatiors Act almost like the real thing.” http://www.spieweb.com, September 1998. Staff. “Battery in a Boot.” http://www.techtv.com, March 13, 2002.