Electroactive Polymers 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.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

Ionic Polymer-Performance MoistureDeflection VoltageReaction Rate VoltageForce/Lift FrequencyDeflection

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.