Smart polymers actuating mechanisms

IPMCs are smart materials that exhibit electromechanical (actuator) and mechanoelectrical (sensor) applications. Table 9.1 shows performance properties of state-of-the art IPMCs [5]. They bend quickly under a low voltage, as first reported by Oguro and his co-workers [6]. Later, Abe et al. introduced the important role of existent counter ions and their influence during the bending [7]. Asaka and Oguro introduced a theory of the actuation mechanisms [8] Shahinpoor and Kim demonstrated that the ionic polymer actuator performance depends on the type of cation [9] and further developed a two-step fabrication method [10] in accordance with their findings. In addition, other groups tried to incorporate various metals as electrode materials to articulate physical properties or electrical responses [11-14]. 

Actuators are able to transform environmental stimuli into mechanical responses (Argentiere et al, 2012). As the presence of certain molecules triggers a conformational or chemical change in smart polymers, these materials can be used as actuators or as combined sensors-actuators (Deligkaris et al, 2010). To date, the most exploited response to obtain the autonomous functionality required for actuators has been the volume shifts of pH- and temperature-sensitive hydrogels (Argentiere et a/., 2012). 

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... 

Oh IK, Jung JH, Jeon JH et al (2010) Electro-chemo-mechanical characteristics of fidlerene-reinforced ionic polymer-metal composite transducers. Smart Mater Stmct 19(7) 075009 Palmre V, Brandell D, Maeorg U et al (2009) Nanoporous carbon-based electrodes for high strain ionomeric bending actuators. Smart Mater Stmct 18(9) 095028 Palmre V, Lust E, Janes A et al (2011) Electroactive polymer actuators with carbon aerogel electrodes. J Mater 21 2577-2583... 

Anton M, Aabloo A, Punning A, Kruusmaa M (2008) A mechanical model of a non-uniform ionomeric polymer metal eomposite actuator. Smart Mater Struct 17(2) 25001-25004 Asaka K, Oguro K (2009) Active microcatheter and biomedical soft devices based on IPMC actuators. In Carpi F, Smela E (eds) Biomedical applications of electroactive polymer actuators. 

Vunder V, Punning A, Aabloo A (2012) Mechanical interpretation of back-relaxation of ionic electroactive polymer actuators. Smart Mater Struct 21(11) 115023 Zhang M, Atkinson KR, Baughman RH (2004) Multifimctional carbon nanotube yarns by downsizing an ancient technology. Science 306(5700) 1358-1361... 

Naruse Y et al (2009) Electrostatic micro power generator fiom low frequency vibration such as human motion. J Micromech Microeng 19(9) 094002 Neugschwandtner GS et al (2000) Large and broadband piezoelectricity in smart polymer-foam space-charge electrets. Appl Phys Lett 77(23) 3827-3829 Paajanen M et al (1998) Electro-mechanical film EMFi-a new multipurpose electret material. Sensors Actuators A 84(l-2) 95-102... 

Smart and adaptive or intelligent materials adjust their mechanical properties upon the receipt of an external stimulus. In engineering language, they act as integrated sensors, processors, and actuators. For example, some polymers can be considered to be smart since they change their shapes with a change of temperature [3] this property has been exploited in the development of all-... 

Del Bufalo, G., Placidi, L. and Porfiri, M. (2008). A mixture theory framework for modeling the mechanical actuation of ionic polymer metal composites. Smart Materials and Structures 17, pp. 045010 1-14. 

Stimuli-responsive polymers consist of a class of smart materials that exhibit a physical response to changes in external conditions. Such stimuli include changes in pH, ionic strength, solvent polarity, and temperature, as well as mechanical force or electric fields. On the basis of their ability to switch conformations, stimuli-responsive polymers are being applied as sensors, actuators, and transducers (e.g., mechano-electrical or mechano-optical). Nanoporous membranes can be functionalized with stimuli-responsive polymers to modify their permeability, that is, to reversibly open and close the pores upon a given stimulus. ... 

A piezoelectric sensor is a device that can convert mechanical stress into an electrical charge, and vice versa. An electric polarization occurs in a fixed direction when the piezoelectric crystal is deformed. The polarization causes an electrical potential difference over the crystal. Natural piezoelectric materials are quartz and tourmaline, and synthetic polymers such as polyvinyUdene fluoride (PVDF) exhibit piezoelectricity several times greater than quartz. Because the effect is reversible, which means that the electrical stimuli can lead to mechanical deformations, the piezoelectric effect is also useful to create some actuators in smart clothing. 

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