Dielectric Elastomer Actuators Fundamentals

Biomedical Applications of Electroactive Polymer Actuators Edited by Federico Carpi and Hisabeth Smela 

This chapter introduces dielectric elastomer teehnology so that its application to medical devices, discussed in subsequent chapters, can be better understood. 

Dielectric elastomer transducers are based on the electromechanical response of an elastomeric dielectric film with comphant electrodes on each surface. These transducers may be actuators, generators, or sensors. In aU cases, the basic stmcture is the same. 

The polymers are largely incompressible. Therefore, the electrodes must be compliant to allow the film to strain in area as well as in thickness. 

The observed response of the film is caused primarily by the interaction between the electrostatic charges on the electrodes [4,5]. Simply put, the opposite charges on the two electrodes attract each other, while the like charges on the electrodes repel each other. Based on this simple electrostatic model, it is possible to derive the effective pressure produced by the electrodes on the film as a function of the applied voltage [6]. This pressure, p, is  

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Carpi F, DeRossi D, Kombluh R, Pelrine R, Somer-Larsen P (2008) Dielectric elastomers as electromechanical transducers, fundamentals, materials, devices, models and applications of an emerging electroactive polymer technology. Elsevier Press, Amsterdam Chapter 7 Benslimane M, Kiil H-E, Tryson MJ (2010) Electromechanical properties of novel large strain PolyPower film and laminate components for DEAP actuator and sensor applications. Proc SPIE 7642 764231... 

The multi-stacked actuator is designed to be directly driven by the Maxwell stress without any strain as mentioned above. Its fundamental principle of operation is shown in Fig. 7.1. When a voltage is applied between the two electrode layers, Maxwell stress is produced and thus, the dielectric elastomer is compressed along the axial direction. The compression of each layer results in the lateral expansion of the actuator because of the incompressibility of the polymer. Consequently, the deformation of the multi-stacked actuator is the summation of the deformations of individual layers and, thus, the total deformation is expressed as follows. 

Many fundamental studies have been carried out to fully understand the nature of the positive effect of prestraining on the actuation performance of dielectric elastomers. The observed improvements have been mainly attributed to the enhancement of the actuator s stability. The main electromechanical instability in the dielectric elastomers is called the pull-in... 

This book intends to provide a comprehensive and updated insight into both the fundamentals of each class of EAP, and examples of the most significant applications of EAP actuators in the biomedical field, either already demonstrated or currently under development. Eor this purpose, the book comprises five sections devoted to the most technologically mature EAPs, namely polymer gels, ionic polymer-metal composites, conjugated polymers, piezoelectric/electrostrictive polymers and dielectric elastomers. Each section is... 

PeMne, R., Kornbluh, R., Eckerle, J., et al. (2000) Dielectric Elastomers Generator Mode Fundamentals and Applications, in Smart Structures and Materials 2001 Electroactive Polymer Actuators and Devices, Proceedings of SPIE (ed. Bar-Cohen, Y.), 4329, 148 56. 

Pelrine R, Kombluh R, Eckerle J, et al (2001) Dielectric elastomers generator mode fundamentals and apphcations. In Proceedings of SPIE 4329, smart stmctures and materials 2001 electroactive polymer actuators and devices, Newport Beach, pp 148-156. doi 10.1117/ 12.432640... 

Smart Mater Struct 19 055025. doi 10.1088/0964-1726/l 9/5/055025 Pelrine R, Kombluh RD, Pei Q, Joseph J (2000) High-speed electrically actuated elastomers with strain greater than 100%. Science 287(5454) 836-839. doi 10.1126/science.287.5454.836 Pelrine R, Kombluh RD, Eckerle J, Jeuck P, Oh S, Pei Q, Stanford S (2001) Dielectric elastomers generator mode fundamentals and applications. In Proceedings of SPIE 4329, smart structures and materials 2001 electroactive polymer actuators and devices, vol 148. doi 10.1117/ 12.432640... 

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