IPMC Actuators Fundamentals

National Institute of Advanced Industrial Science and Technology (AIST), Japan 

Relatively high response (up to several hundreds of Hertz) 

The possibility and ease to miniaturize and to mould into any shape 

Can be activated in water or in wet condition. Possible to work in dry condition. 

Biomedical Applications of Electroactive Polymer Actuators Edited by Federico Carpi and Elisabeth Smela 2009 John Wiley Sons Ltd. ISBN 978-0-470-77305-5 

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Aoyagi W, Omiya M (2013) Mechanical and electrochemical properties of an IPMC actuator with palladium electrodes in acid and alkaline solutions. Smart Mater Struct 22 055028 (10 pp) Asaka K, Oguro K (2000) Bending of Polyelectrolyte Membrane-platinum composites by electric stimuli. Part II. Response kinetics. I Electroanal Chem 480 186-198 Asaka K, Oguro K (2009a) IPMC actuators fundamentals. In Carpi F, Smela E (eds) Biomedical applications of electroactive polymer actuators. Wiley, Chichester, pp 103-119 Asaka K, Oguro K (2009b) Active microcatheter and biomedical soft devices based on IPMC actuators. In Carpi F, Smela E (eds) Biomedical applications of electroactive polymer actuators. Wiley, Chichester, pp 103-119... 

Chapter 2 is focused on physical principles of IPMCs. It starts with an introduction to the fundamentals of IPMCs, including the fabrication techniques, and then takes a careful look at the effect of electrodes on material behavior and actuation performance. Several novel approaches, including a fluorescence spectroscopic visualization method, are then used to yield unique insight into IPMC actuation behaviors, such as the back-relaxation phenomenon. More sophisticated configurations than a singlelayer bender are also discussed in this chapter. 

In this chapter, the fundamental aspects of the ionic polymer-metal composite (IPMC) actuators have been described. The IPMC actuators have many unique characteristics such as softness, large bending response, low voltage drive, easy forming into any shape, and so on, which are suitable for biomedical applications. In the next chapter, the biomedical applications of IPMC actuators are described. 

As shown in the chapter on the fundamentals of this technology, the bending characteristics of the IPMC actuator depend on the counter cation in the ionic polymCT. Yamakita et al. developed the application of the IPMC hnear actuator to a biped walking robot (Figure 6.21) and optimized the performanee of the aetuator by selecting the coimter cation in the ionic polymer. 

To estimate time dependent deflection, and frequency of IPMC selfoscillation in HCHO solution with different concentrations, a physical finite element (FE) model was developed. Some of the advantages of the FE model over the equivalent beam model that was introduced in Chapter 2 are the physics-based governing equations of the fundamental actuation mechanisms of IPMC. This allows the model to be extended to different geometries both in 2D and in 3D. Furthermore, it is convenient to couple the differential equations describing the electrochemical processes into a finite element bending model of IPMC. 

Note that the impedance model, the actuation model, and the reduced model are all expressed in terms of fundamental physical parameters of IPMC and thus are geometrically scalable. On the other hand, the resulting models are amenable to system analysis and control design. Such physics-based, control-oriented models effectively bridge the gap between PDE-based physical models and low-order black-box models. For blackbox models, the parameters have no physical meanings and have to be re-identified empirically whenever the actuator dimensions are changed. 

The forth direction, analytical modeling for understanding the behaviors of these materials, has been popular approach. Testing and characterization have been conducted for developing the models. Such attempts have been done especially for ionic polymer metal composites (IPMCs)[58, 70, 72, 120]. Nemab Nasser and his co-workers carried out extensive experimental studies on both Nafion- and Flemion-based IPMCs consisting of a thin perfluorinated ionomer in various cation forms, seeking to imderstand the fundamental properties of these composites, to explore the mechanism of their actuation, and finally, to optimize their performance for various potential applications[121]. They also performed a systematic experimental evaluation of the mechanical response of both metal-plated and bare Nafion and Flemion in various cation forms and various water saturation levels. They attempted to identify potential micromechanisms responsible for the observed electromechanical behavior of these materials, model them, and compare the model results with experimental data[122]. A computational micromechanics model has been developed to model the initial fast electromechanical response in these ionomeric materials[123]. A number... 

This chapter reviews the fundamentals of ionic polymer-metal composites (IPMCs), which are used for sensors and actuators. First, the basic structure of IPMCs is described, and a brief review of their development is provided. Then,... 

These basic equations form the so-called Poisson-Nemst-Planck (PNP) model for IPMCs and describe the fundamental physics wifliin the polymer membrane. A number of aufliors have developed electromechanical (actuator) and mechanoe-lectrical (sensor) models based on the PNP model as well as modified PNP models (Nemat-Nasser 2002 Nemat-Nasser and Zamani 2006 Wallmersperger et al. 2007 Zhang and Yang 2007 Porfiri 2008 Chen and Tan 2008 Aureli et al. 2009). This model will be described further in subsequent chapters of this book. 

Rajagopalan M, Jeon JH, Oh IK (2010) Electric-stimuli-responsive bending actuator based on sulfonated polyetherimide. Sens Actuators B 151 198-204 Shahinpoor M (1992) Conceptual design, kinematics and dynamics of swimming robotic stmctures using ionic polymeric gel muscles. Smart Mater Stmct 1 91-94 Shahinpoor M, Kim KJ (2000) The effect of surface-electrode resistance on the performance of ionic polymer-metal composite (IPMC) artificial muscles. Smart Mater Stmct 9 543 551 Shahinpoor M, Kim KJ (2001) Ionic polymer-metal composites - I. Fundamentals. Smart Mater Struct 10 819-833... 

The fundamental theory of IPMC electromechanical transduction (actuation) and mechanoelectrical transduction (sensing) will be presented using the same governing equations. Differences between actuation and sensing phenomena will be highlighted throughout. 

In this chapter, latest physics-based models and control models of IPMC were reviewed. Physics-based models provide thorough understanding of the underlying physics of IPMC transduction phenomena. However, these models are more complex and often limited to numerical solving methods. The fundamental theory of IPMC electromechanical and mechanoelectrical transduction were presented using the same governing equations. Differences between actuation and sensing phenomena were explicitly explained. 

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