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Preface / xiii

Chapter 1 EAP History, Current Status, and Infrastructure / 3
Yoseph Bar-Cohen

1.1 Introduction / 4

1.2 Biological Muscles / 8

1.3 Historical Review and Currently Available Active Polymers / 8

1.4 Polymers with Controllable Properties or Shape / 10

1.5 Electroactive Polymers (EAP) / 22

1.6 The EAP Roadmap - Need for an Established EAP Technology Infrastructure / 39

1.7 Potential / 41

1.8 Acknowledgments / 42

1.9 References / 43

Chapter 2 Natural Muscle as a Biological System / 53
Gerald H. Pollack, Felix A. Blyakhman, Frederick B. Reitz, Olga V. Yakovenko,

and Dwayne L. Dunaway

2.1 Conceptual Background / 53

2.2 Structural Considerations / 56

2.3 Does Contraction Involve a Phase Transition? / 59

2.4 Molecular Basis of the Phase Transition / 62

2.5 Lessons from the Natural Muscle System That May Be Useful for the Design of Polymer Actuators / 68

2.6 References / 70

Chapter 3 Metrics of Natural Muscle Function / 73
Robert J. Full and Kenneth Meijer

3.1 Caution about Copying and Comparisons / 74

3.2 Common Characterizations - Partial Picture / 75

3.3 Work-Loop Method Reveals Diverse Roles of Muscle Function during Rhythmic Activity / 79

3.4 Direct Comparisons of Muscle with Human-Made Actuators / 85

3.5 Future Reciprocal Interdisciplinary Collaborations / 86

3.6 Acknowledgments / 87

3.7 References / 87

Chapter 4 Electric EAP / 95
Qiming Zhang, Cheng Huang, Feng Xia, and Ji Su

4.1 Introduction / 96

4.2 General Terminology of Electromechanical Effects in Electric EAP / 96

4.3 PVDF-Based Ferroelectric Polymers / 103

4.4 Ferroelectric Odd-Numbered Polyamides (Nylons) / 114

4.5 Electrostriction / 119

4.6 Field-Induced Strain Due to Maxwell Stress Effect / 132

4.7 High Dielectric Constant Polymeric Materials as Actuator Materials /133

4.8 Electrets / 137

4.9 Liquid-Crystal Polymers /141

4.10 Acknowledgments / 142

4.11 References / 142

Chapter 5 Electroactive Polymer Gels / 151
Paul Calvert

5.1 Introduction - the Gel State / 151

5.2 Physical Gels / 152

5.3 Chemical Gels / 152

5.4 Thermodynamic Properties of Gels / 154

5.5 Transport Properties of Gels / 155

5.6 Polyelectrolyte Gels / 156

5.7 Mechanical Properties of Gels / 156

5.8 Chemical Actuation of Gels / 157

5.9 Electrically Actuated Gels / 158

5.10 Recent Progress / 162

5.11 Future Directions / 164

5.12 References / 165

Chapter 6 Ionomeric Polymer-Metal Composites / 171
Sia Nemat-Nasser and Chris W. Thomas

6.1 Introduction / 172

6.2 Brief History of IPMC Materials / 173

6.3 Materials and Manufacture / 175

6.4 Properties and Characterization / 178

6.5 Actuation Mechanism / 196

6.6 Development of IPMC Applications / 219

6.7 Discussion: Advantages/Disadvantages / 220

6.8 Acknowledgments / 223

6.9 References / 223

Chapter 7 Conductive Polymers / 231
Jose-Maria Sansinena and Virginia Olazabal

7.1 Brief History of Conductive Polymers / 231

7.2 Applications of Conductive Polymers / 233

7.3 Basic Mechanism of CP Actuators / 236

7.4 Development of CP Actuators / 241

7.5 Advantages and Disadvantages of CP Actuators / 249

7.6 Acknowledgments / 252

7.7 References / 252

Chapter 8 Carbon Nanotube Actuators: Synthesis, Properties, and Performance / 261
Geoffrey M. Spinks, Gordon G. Wallace, Ray H. Baughman, and Liming Dai

8.1 Introduction / 261

8.2 Nanotube Synthesis / 262

8.3 Characterization of Carbon Nanotubes / 266

8.4 Macroscopic Nanotube Assemblies: Mats and Fibers / 269

8.5 Mechanical Properties of Carbon Nanotubes / 270

8.6 Mechanism of Nanotube Actuation / 275

8.7 Experimental Studies of Carbon Nanotube Actuators/ 279

8.8 Conclusions and Future Developments / 288

8.9 References / 288

Chapter 9 Molecular Scale Electroactive Polymers / 299
Michael J. Marsella

9.1 Introduction / 299

9.2 Intrinsic Properties and Macroscale Translation / 301

9.3 Stimulus-Induced Conformational Changes within the Single Molecule / 303

9.4 Final Comments / 311

9.5 References / 311

Chapter 10 Computational Chemistry / 317
Kristopher E. Wise

10.1 Introduction / 317

10.2 Overview of Computational Methods / 318

10.3 Quantum Mechanical Methods / 320

10.4 Classical Force Field Simulations / 328

10.5 Mesoscale Simulations / 332

10.6 References / 333

Chapter 11 Modeling and Analysis of Chemistry and Electromechanics / 335
Thomas Wallmersperger, Bernd Kroplin, and Rainer W. Gulch

11.1 Introduction / 335

11.2 Chemical Stimulation / 337

11.3 Electrical Stimulation / 342

11.4 Conclusion / 360

11.5 References / 360

Chapter 12 Electromechanical Models for Optimal Design and Effective Behavior of Electroactive Polymers / 363
Kaushik Bhattacharya, Jiangyu Li, and Yu Xiao

12.1 Introduction / 363

12.2 Introduction to Finite Elasticity / 364

12.3 Optimal Design of Electrostatic Actuators / 369

12.4 Models of Ionomer Actuators / 374

12.5 Reduced Models / 379

12.6 Conclusion / 382

12.7 Acknowledgment / 383

12.8 References / 383

Chapter 13 Modeling IPMC for Design of Actuation Mechanisms / 385
Satoshi Tadokoro, Masashi Konyo, and Keisuke Oguro

13.1 Models and CAE Tools for Design of IPMC Mechanisms / 386

13.2 A Physicochemical Model Considering Six Phenomena / 388

13.3 Gray-Box Macroscopic Model for Mechanical and Control Design / 396

13.4 Simulation Demonstration by Models / 402

13.5 Applications of the Model / 406

13.6 References / 425

Chapter 14 Processing and Fabrication Techniques / 431
Yoseph Bar-Cohen, Virginia Olazabal, Jose-Maria Sansinena, and Jeffrey Hinkley

14.1 Introduction / 431

14.2 Synthesis and Material Processing / 462

14.3 Fabrication and Shaping Techniques / 434

14.4 Electroding Techniques / 441

14.5 System Integration Methods / 449

14.6 EAP Actuators / 452

14.7 Concluding Remarks / 453

14.8 References / 454

Chapter 15 Methods of Testing and Characterization / 467
Stewart Sherrit, Xiaoqi Bao, and Yoseph Bar-Cohen

15.1 Introduction / 468

15.2 Characterization of EAP with Polarization-Dependent Strains / 468

15.3 Characterization of Ionic EAP with Diffusion-Dependent Strain / 498

15.4 Summary of Test Methods / 516

15.5 Conclusion / 516

15.6 Acknowledgments / 518

15.7 References / 518

Chapter 16 Application of Dielectric Elastomer EAP Actuators / 529
Roy Kornbluh, Ron Pelrine, Qibing Pei, Marcus Rosenthal, Scott Stanford, Neville Bonwit, Richard Heydt, Harsha Prahlad, and Subramanian V. Shastri

16.1 Introduction / 530

16.2 Dielectric Elastomer EAP�Background and Basics / 535

16.3 Actuator Design Issues / 539

16.4 Operational Considerations / 546

16.5 Examples of Dielectric Elastomer EAP Actuators and Applications / 551

16.6 Artificial Muscles and Applications to Biologically Inspired Devices / 552

16.7 General Purpose Linear Actuators / 566

16.8 Planar and Other Actuator Configurations / 567

16.9 Motors / 573

16.10 Generators / 574

16.11 Sensors / 575

16.12 Summary and Future Developments / 576

16.13 Acknowledgments / 577

16.14 References / 577

Chapter 17 Biologically Inspired Robots / 581
Brett Kennedy, Chris Melhuish, and Andrew Adamatzky

17.1 Introduction / 583

17.2 Biologically Inspired Mechanisms and Robots / 584

17.3 Aspects of Robotic Design / 584

17.4 Active Polymer Actuators in a Traditional Robotic System / 594

17.5 Using Rapid Prototyping Methods for Integrated Design / 596

17.6 Evolutionary Design Algorithms (Genetic Algorithm Design) / 598

17.7 EAP Actuators in Highly Integrated Microrobot Design / 602

17.8 Solving the Power Problem - Toward Energetic Autonomy / 614

17.9 The Future of Active Polymer Actuators and Robots / 616

17.10 References / 617

Chapter 18 Applications of EAP to the Entertainment Industry / 621
David Hanson

18.1 Introduction / 622

18.2 Entertainment and Its Shifting Significance / 626

18.3 Technical Background to Entertainment Application of EAP / 627

18.4 The Craft of Aesthetic Biomimesis in Entertainment / 637

18.5 A Recipe for Using EAP in Entertainment / 647

18.6 Facial Expression Robot - Practical Test Bed for EAP / 647

18.7 Conclusion / 655

18.8 Acknowledgment / 655

18.9 References / 655

Chapter 19 Haptic Interfaces Using Electrorheological Fluids / 659
Constantinos Mavroidis, Yoseph Bar-Cohen, and Mourad Bouzit

19.1 Introduction / 659

19.2 Electrorheological Fluids / 661

19.3 Haptic Interfaces and Electrorheological Fluids / 666

19.4 MEMICA Haptic Glove / 668

19.5 ECS Element Model Derivation / 673

19.6 Parametric Analysis of the Design of ECS Elements / 677

19.7 Experimental ECS System and Results / 679

19.8 Conclusions / 682

19.9 Acknowledgments / 682

19.10 References / 683

Chapter 20 Shape Control of Precision Gossamer Apertures / 687
Christopher H. M. Jenkins

20.1 Introduction / 687

20.2 Shape Control of PGAs / 691

20.3 Shape Control Methodologies Involving Electroactive Polymers / 697

20.4 Conclusions / 702

20.5 Nomenclature / 703

20.6 Acknowledgments / 703

20.7 References / 704

Chapter 21 EAP Applications, Potential, and Challenges / 709
Yoseph Bar-Cohen

21.1 Introduction / 710

21.2 Lesson Learned Using IPMC and Dielectric EAP / 711

21.3 Summary of Existing EAP Materials / 717

21.4 Scalability Issues and Needs / 718

21.5 Expected and Evolving Applications / 719

21.6 EAP Characterization / 746

21.7 Platforms for Demonstration of EAP / 748

21.8 Future Expectations / 749

21.9 Acknowledgments / 751

21.10 References / 752

Index / 757

Preface

This book reviews the state of the art of the field of electroactive polymers (EAPs), which are also known as artificial muscles for their functional similarity to natural muscles. This book covers EAP from all its key aspects, i.e., its full infrastructure, including the available materials, analytical models, processing techniques, and characterization methods. This book is intended to serve as reference tool, a technology users' guide, and a tutorial resource, and to create a vision for the field's future direction. In preparing this second edition, efforts were made to update the chapters with topics that have sustained major advances since the first edition was prepared three years ago. Following the reported progress and milestones that were reached in this field has been quite heartwarming. These advances are bringing the field significantly closer to the point where engineers consider EAPs to be actuators of choice. In December 2002, the Japanese company Eamex produced a robot fish that swims in a water tank without batteries or a motor. For power, the robot fish uses an inductive coil that is energized from the top and bottom of the tank. Making a floating robot fish may not be an exciting event, but this is the first commercial product to use an EAP actuator.

EAPs are plastic materials that change shape and size when given some voltage or current. They always had enormous potential, but only now is this potential starting to materialize. Advances reported in this second edition include an improved understanding of these materials' behavior, better analytical modeling, as well as more effective characterization, processing, and fabrication techniques. The advances were not only marked with the first commercial product; there has also been the announcement by the SRI International scientists who are confident they have reached the point that they can now meet the challenge posed by this book's editor of building a robot arm with artificial muscles that could win an arm wrestling match against a human. This match may occur in the coming years, and the success of a robot against a human opponent will lead to a new era in both making realistic biomimetic robots and implementing engineering designs that are currently considered science fiction.

For many years the field of EAP has received relatively little attention because the number of available materials and their actuation capability were limited. The change in this view occurred in the early 1990s, as a result of the development of new EAP materials that exhibit a large displacement in response to electrical stimulation. This characteristic is a valuable attribute, which enabled myriad potential applications, and it has evolved to offer operational similarity to biological muscles. The similarity includes resilient, damage tolerant, and large actuation strains (stretching, contracting, or bending). Therefore, it is natural to consider EAP materials for applications that require actuators to drive biologically inspired mechanisms of manipulation, and mobility. However, before these materials can be applied as actuators of practical devices their actuation force and robustness will need to be increased significantly from the levels that are currently exhibited by the available materials. On the positive side, there has already been a series of reported successes in demonstrating miniature manipulation devices, including a catheter steering element, robotic arm, gripper, loudspeaker, active diaphragm, dust-wiper, and many others. The editor is hoping that the information documented in this book will continue to stimulate the development of niche applications for EAP and the emergence of related commercial devices. Such applications are anticipated to promote EAP materials to become actuators of choice in spite of the technology challenges and limitations they present.

Chapter 1 of this book provides an overview and background to the various EAP materials and their potential. Since biological muscles are used as a model for the development of EAP actuators, Chapter 2 describes the mechanism of muscles operation and their behavior as actuators. Chapter 3 covers the leading EAP materials and the principles that are responsible for their electroactivity. Chapter 4 covers such fundamental topics as computational chemistry and nonlinear electromechanical analysis to predict their behavior, as well as a design guide for the application of an example EAP material. Modeling the behavior of EAP materials requires the use of complex analytical tools, which is one of the major challenges to the design and control of related mechanisms and devices.

The efforts currently underway to model their nonlinear electromechanical behavior and develop novel experimental techniques to measure and characterize EAP material properties are discussed in Chapter 6. Such efforts are leading to a better understanding of the origin of the electroactivity of various EAP materials, which, in turn, can help improve and possibly optimize their performance.

Chapter 5 examines the processing methods of fabricating, shaping, electroding, and integrating techniques for the production of fibers, films, and other shapes of EAP actuators. Generally, EAP actuators are highly agile, lightweight, low power, mass producible, inexpensive, and possess an inherent capability to host embedded sensors and microelectromechanical systems (MEMS). Their many unique characteristics can make them a valuable alternative to current actuators such as electroactive ceramics and shape memory alloys. The making of miniature insectlike robots that can crawl, swim and/or fly may become a reality as this technology evolves as discussed in Chapters 7 and 8. Processing techniques, such as ink-jet printing, may potentially be employed to make complete devices that are driven by EAP actuators. A device may be fully produced in 3D detail, thereby allowing rapid prototyping and subsequent mass production possibilities. Thus, polymer-based EAP-actuated devices may be fully produced by an ink-jet printing process enabling the rapid implementation of science-fiction ideas (e.g., insectlike robots that become remotely operational as soon as they emerge from the production line) into engineering models and commercial products. Potential beneficiaries of EAP capabilities include commercial, medical, space, and military that can impact our life greatly.

In order to exploit the greatest benefit that EAP materials can offer, researchers worldwide are now exploring the various aspects of this field. The effort is multidisciplinary and cooperation among scientists, engineers, and other experts (e.g., medical doctors) are underway. Experts in chemistry, materials science, electro-mechanics, robotics, computer science, electronics, and others are working together to develop improved EAP materials, processing techniques, and applications. Methods of effective control are addressing the unique and challenging aspects of EAP actuators. EAP materials have a significant potential to improving our lives. If EAP materials can be developed to the level that they can compete with natural muscles, drive prosthetics, serve as artificial muscle implants into a human body, and become actuators of various commercial products, the developers of EAP would make tremendously positive impact in many aspects of human life.

Yoseph Bar-Cohen
February 2, 2004

ACKNOWLEDGMENTS

The research at Jet Propulsion Laboratory (JPL), California Institute of Technology, was carried out under a contract with National Aeronautics and Space Administration (NASA) and Defense Advanced Research Projects Agency (DARPA). The editor would like to thank everyone who contributed to his efforts, both as part of his team advancing the technology as well as those who helped with the preparation of this book. The editor would like to thank the team members of his task LoMMAs that was funded by the Telerobotic and the Cross- Enterprise Programs of the NASA Code S. The team members included Dr. Sean Leary, Mark Schulman, Dr. Tianji Xu, and Andre H Yavrouian, JPL, Dr. Joycelyn Harrison, Dr. Joseph Smith, and Ji Su, NASA LaRC; Prof. Richard Claus, VT; Prof. Constantinos Mavroidis and Charles Pfeiffer, Rutgers University. Also, the editor would like to thank Dr. Timothy Knowles, ESLI, for his assistance with the development of the EAP dust-wiper mechanism using IPMC. Thanks to Marlene Turner, Harry Mashhoudy, Brian Lucky, and Cinkiat Abidin, former graduate students of the Integrated Manufacturing Engineering (IME) Program at UCLA, for helping to construct the EAP gripper and robotic arm. A special thanks to Dr. Keisuke Oguro, Osaka National Research Institute, Japan, for providing his most recent IPMC materials; and to Prof. Satoshi Tadokoro, Kobe University, Japan, for his analytical modeling effort. Prof. Mohsen Shahinpoor is acknowledged for providing IPMC samples as part of the early phase of the LoMMAs task. The editor would like also to thank his NDEAA team members Dr. Virginia Olaz�bal, Dr. Jos�-Mar�a Sansi�ena, Dr. Shyh-Shiuh Lih, and Dr. Stewart Sherrit for their help. In addition, he would like to thank Prof. P. Calvert, University of Arizona, for the information about biological muscles. Thanks to Dr. Steve Wax, DARPA's EAP program Manager, and Dr. Carlos Sanday, NRL, for their helpful comments related to the development of EAP characterization methods. A specific acknowledgement is made for the courteous contribution of graphics for the various chapters of this book; and these individuals and organizations are specified next to the related graphics or tables.

The editor would like to acknowledge and express his appreciation to the following individuals, who took the time to review various book chapters of the first edition and particularly those who where not coauthors of this book. Their contribution is highly appreciated and it helped to make this book of significantly greater value to the readers:

Aluru Narayan, University of Illinois/Urbana-Champaign
Paul Calvert, University of Arizona
Sia Nemat-Nasser, Dr. Chris Thomas and Mr. Jeff McGee, University of California, San Diego
Christopher Jenkins, and Dr. Aleksandra Vinogradov, South Dakota School of Mines and Technology
Kenneth Johnson, Brett Kennedy, Shyh-Shiuh Lih, Virginia Olazabal, Jos�-Mar�a Sansi�ena, and Stewart Sherrit, Jet Propulsion Laboratory
Giovanni Pioggia and Danilo de Rossi, University of Pisa, Italy
Elizabeth Smela, University of Maryland
Gerald Pollack, Washington University
Hugh Brown, Paul Keller, Geoff Spinks, and Gordon Wallace, University of Wollongong, Australia
Jeffrey Hinkley, Ji Su, and Kristopher Wise, NASA LaRC
Jiangyu Li, Caltech
Michael Marsella, University of California, Riverside
Miklos Zrinyi, Budapest University of Technology and Economics, Hungary
Mourad Bouzit and Dinos Mavroidis, Rutgers University
Peter Sommer-Larsen, Risoe Research Center, Denmark
Mary Frecker and Qiming Zhang, Pennsylvania State University
Robert Full, University of California, Berkeley
Roy Kornbluh and Ron Pelrine, SRI International
Satoshi Tadokoro, Kobe University, Japan

Also, the editor would like to acknowledge and express his appreciation to the following individuals who took the time to review the 12 chapters that were revised in this second edition and particularly those who where not coauthors of this book. Their contribution is highly appreciated and it helped making this book of significantly greater value to the readers:

Ahmed Al-Jumaily, Wellesley Campus, Auckland, New Zealand
Narayan Aluru, University of Illinois/Urbana-Champaign
Andy Adamatzky, University of the West of England, Bristol, England
Mary Frecker, Penn State University
Kaneto Keiichi, Kyushu Institute of Technology, Japan
David Hanson, University of Texas at Dallas and Human Emulation Robotics, LLC
Roy Kornbluh, SRI International, CA
Don Leo, Virginia Polytechnic Institute and State University
John Madden, University of British Columbia, Canada
Chris Melhuish, University of the West of England, UK
Walied Moussa, University of Alberta, Canada
Jos�-Mar�a Sansi�ena, Los Alamos National Laboratory (LANL)
Stewart Sherrit, Jet Propulsion Laboratory, CA
Peter Sommer-Larsen, Risoe Research Center, Denmark
Geoffery Spinks, University of Wollongong, Australia
Ji Su, NASA Langley Research Center (LaRC), VA
Minuro Taya, University of Washington
Aleksandra Vinogradov, Montana State University
Eui-Hyeok Yang, Jet Propulsion Laboratory, CA