Ionic polymer metal composites (IPMCs) are electroactive materials made of ionic polymer thin membranes with platinum metallization on their surfaces. They are interesting materials due to not only their electromechanical applications as transducers but also to their electrochemical features and the relationship between the ionic/solvent current and the potential field. Their electrochemical properties thus suggest the possibility for exploiting them as compact fractional-order elements (FOEs) with a view of defining fabrication processes and production strategies that assure the desired performances. In this paper, the experimental electrical characterization of a brand new IPMC setup in a fixed sandwich configuration is proposed. Two IPMC devices with different platinum absorption times (5？h and 20？h) are characterized through experimental data: first, a preliminary linearity study is performed for a fixed input voltage amplitude in order to determine the frequency region where IPMC can be approximated as linear; then, a frequency analysis is carried out in order to identify a coherent fractional-order dynamics in the bode diagrams. Such analyses take the first steps towards a simplified model of IPMC as a compact electronic FOE for which the fractional exponent value depends on fabrication parameters as the absorption time. 1. Introduction Ionic polymer-metal composites (IPMCs) as electroactive polymers (EAPs) have the very interesting capabilities of transforming electrical energy into mechanical energy, and vice versa [1, 2], making them privileged candidates for the realization of actuators or sensors with features as low required voltage, high compliance, lightness, softness, and so forth, thus, creating great interest in possible applications in very different fields such as robotics, aerospace, and biomedics [3–5]. They are composite materials made of ionic polymers in presence of solvent with layers of noble metals on their surfaces. Their structure and composition make their full exploitation currently limited because of the incomplete knowledge of their working principles and therefore a not clearly defined design procedure. Due to their electromechanical properties, they have been traditionally characterized as transducers, both as sensors and actuators, and three different strategies have been used to describe the relationship between the electrical and the mechanical behaviors [6]. The first one, referred to as black box and behavioral model, provides a purely empirical model of IPMCs obtained through a series of curve fits based on
References
[1]
M. Shahinpoor and K. J. Kim, “Ionic polymer-metal composites: I. Fundamentals,” Smart Materials and Structures, vol. 10, no. 4, pp. 819–833, 2001.
[2]
M. Shahinpoor, Y. Bar-Cohen, J. O. Simpson, and J. Smith, “Ionic polymer-metal composites (IPMCs) as biomimetic sensors, actuators and artificial muscles—a review,” Smart Materials and Structures, vol. 7, no. 6, pp. R15–R30, 1998.
[3]
M. Shahinpoor and K. J. Kim, “Ionic polymer-metal composites: IV. Industrial and medical applications,” Smart Materials and Structures, vol. 14, no. 1, pp. 197–214, 2005.
[4]
W.-S. Chu, K. T. Lee, S.-H. Song, et al., “Review of biomimetic underwater robots using smart actuators,” International Journal of Precision Engineering and Manufacturing, vol. 13, no. 7, pp. 1281–1292, 2012.
[5]
D. Pugal, K. Jung, A. Aabloo, and K. J. Kim, “Ionic polymer-metal composite mechanoelectrical transduction: review and perspectives,” Polymer International, vol. 59, no. 3, pp. 279–289, 2010.
[6]
K. M. Newbury and D. J. Leo, “Linear electromechanical model of ionic polymer transducers—part I: model development,” Journal of Intelligent Material Systems and Structures, vol. 14, no. 6, pp. 333–342, 2003.
[7]
R. Kanno, A. Kurata, S. Tadokoro, T. Takamori, and K. Oguro, “Characteristics and modeling of ICPF actuator,” in Proceedings of the Japan-USA Symposium on Flexible Automation, pp. 219–225, 1994.
[8]
C. Bonomo, L. Fortuna, P. Giannone, S. Graziani, and S. Strazzeri, “A nonlinear model for ionic polymer metal composites as actuators,” Smart Materials and Structures, vol. 16, no. 1, pp. 1–12, 2007.
[9]
P. Brunetto, L. Fortuna, S. Graziani, and S. Strazzeri, “A model of ionic polymer-metal composite actuators in underwater operations,” Smart Materials and Structures, vol. 17, no. 2, Article ID 025029, 12 pages, 2008.
[10]
C. Bonomo, L. Fortuna, P. Giannone, S. Graziani, and S. Strazzeri, “A model for ionic polymer metal composites as sensors,” Smart Materials and Structures, vol. 15, no. 3, pp. 749–758, 2006.
[11]
D. Pugal, H. Kasem？gi, K. J. Kim, M. Kruusmaa, and A. Aabloo, “Finite element simulations of the bending of the IPMC sheet,” in Electroactive Polymer Actuators and Devices (EAPAD '07), Proceedings of SPIE, San Diego, Calif, USA, March 2007.
[12]
R. Caponetto, V. De Luca, S. Graziani, F. Sapuppo, and E. Umana, “A multi-physics model of an IPMC actuator in the electrical, chemical, mechanical and thermal domains,” in Proceedings of the International Conference on Synthesis, Modeling, Analysis and Simulation Methods and Applications to Circuit Design (SMACD '12), Seville, Spain, September 2012.
[13]
R. Caponetto, G. Dongola, L. Fortuna, S. Graziani, and S. Strazzeri, “A fractional model for IPMC actuators,” in Proceedings of IEEE International Instrumentation and Measurement Technology Conference, pp. 2103–2107, Victoria, Canada, May 2008.
[14]
L. Chang, H. Chen, and Z. Zhu, “A structure model for Ionic polymer-metal composite (IPMC),” in Electroactive Polymer Actuators and Devices (EAPAD '12), vol. 8340 of Proceedings of SPIE, April 2012.
[15]
S. C. D. Roy, “On the realization of a constant-argument immittance or fractional operator,” IEEE Transactions on Circuit Theory, vol. 14, no. 3, pp. 264–274, 1967.
[16]
G. W. Bohannan, “Analog realization of a fractional control element—revisited,” 2002.
[17]
H. Sheng, H. G. Sun, C. Coopmans, Y. Q. Chen, and G. W. Bohannan, “A physical experimental study of variable-order fractional integrator and differentiator,” European Physical Journal: Special Topics, vol. 193, no. 1, pp. 93–104, 2011.
[18]
T. C. Haba, G. Ablart, T. Camps, and F. Olivie, “Influence of the electrical parameters on the input impedance of a fractal structure realised on silicon,” Chaos, Solitons & Fractals, vol. 24, no. 2, pp. 479–490, 2005.
[19]
G. W. Bohannan, “Analog fractional order controller in temperature and motor control applications,” Journal of Vibration and Control, vol. 14, no. 9-10, pp. 1487–1498, 2008.
[20]
I. S. Jesus and J. A. Tenreiro MacHado, “Development of fractional order capacitors based on electrolyte processes,” Nonlinear Dynamics, vol. 56, no. 1-2, pp. 45–55, 2009.
[21]
K. Biswas, S. Sen, and P. K. Dutta, “Realization of a constant phase element and its performance study in a differentiator circuit,” IEEE Transactions on Circuits and Systems II, vol. 53, no. 9, pp. 802–806, 2006.
[22]
K. Biswas, Studies on design, development and performance analysis of capacitive type sensors [Ph.D. dissertation], Dep. Elect. Eng., IIT Kharagpur, Kharagpur, India, 2006.
[23]
M. S. Krishna, S. Das, K. Biswas, and B. Goswami, “Characterization of a fractional order element realized by dipping a capacitive type probe in polarizable medium,” in Proceedings of the Lisbon Symposium on Fractional Signals and Systems, Lisbon, Portugal, November 2009.
[24]
“Aldrich Technical Information Bulletin AL-163,” Nafion Resins.
[25]
K. B. Oldham and J. Spanier, The Fractional Calculus: Theory and Applications of Differentiation and Integration to Arbitrary Order, Dover Books on Mathematics, 2006.
[26]
I. Podlubny, Fractional Differential Equations, vol. 198 of Mathematics in Science and Engineering, Academic Press, San Diego, Calif, USA, 1999.
[27]
R. Caponetto, G. Dongola, L. Fortuna, and I. Petras, “Fractional order systems: modelling and control applications,” in Nonlinear Science, Series A, vol. 72, World Scientific, Singapore, 2010.
[28]
Z. Jiao, Y. Chen, and I. Podlubny, Distributed-Order Dynamic Systems, Springer, New York, NY, USA, 2012.
