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.
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
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.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.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.Scientists and engineers envision using EAPs to replace a wide range of heavy, expensive, and power hungry equipment. Existing EAPs fall into two main categoriesExisting EAPs fall into two main categories electronicelectronic ionicionic Function similar to…Function similar to… Piezoelectric materialsPiezoelectric materials Shape memory alloys (SMAs)Shape memory alloys (SMAs)
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
Electric EAPs Stimulated by an applied electric field. Types: Dielectric EAPDielectric EAP A dielectric material is placed between two electrodes.A dielectric material is placed between two electrodes. To allow for movement of the EAP, the electrodes must be flexible.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.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.EAP is distorted when a voltage is applied. Can be deformed by up to 400 percent of their original size.Can be deformed by up to 400 percent of their original size. Ferroelectric EAPFerroelectric EAP Become polarized when an electric field is applied to them.Become polarized when an electric field is applied to them. Ability to transfer electrical energy to mechanical energy, and visa versa.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 Hand Gripper 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, Bar-Cohen, Yoseph Dr. “Electroactive Polymers – EAPs.” April, Bar-Cohen, Yoseph Dr. “Miniature Electroactive-Polymer Rakes.” October, Callister, William D. Materials Science and Engineering: An Introduction 6th Ed. New York: John Wiley & Sons, Inc ElectorActive Polymers- EAP’s. Azom.com. November The International Society for Optical Engineering. “Low-Mass Muscle Actuatiors Act almost like the real thing.” September Staff. “Battery in a Boot.” March 13, 2002.