Characterization and Variational Modeling of Ionic Polymer Transducers

Abstract

Ionomeric polymers are a promising class of intelligent material which exhibit electromechanical coupling similar to that of piezoelectric bimorphs. Ionomeric polymers are much more compliant than piezoelectric ceramics or polymers and have been shown to produce actuation strain on the order of 2% at operating voltages between 1V and 3V (Akle et al., 2004, Proceedings IMECE). Their high compliance is advantageous in low force sensing configurations because ionic polymers have a very little impact on the dynamics of the measured system. Here we present a variational approach to the dynamic modeling of structures which incorporate ionic polymer materials. To demonstrate the method a cantilever beam model is developed using this variational approach. The modeling approach requires a priori knowledge of three empirically determined material properties: elastic modulus, dielectric permittivity, and effective strain coefficient. Previous work by Newbury and Leo has demonstrated that these three parameters are strongly frequency dependent in the range between less than 1Hz to frequencies greater than 1kHz. Combining the frequency-dependent material parameters with the variational method produces a second-order matrix representation of the structure. The frequency dependence of the material parameters is incorporated using a complex-property approach similar to the techniques for modeling viscoelastic materials. A transducer is manufactured and the method of material characterization is applied to determine the mtaerial properties. Additional experiments are performed on this transducer and both the material and structural model are validated. Finally, the model is shown to predict sensing response very well in comparison to experimental results, which supports the use of an energy-based variational approach for modeling ionomeric polymer transducers.

An Energy Harvesting Comparison of Piezoelectric and Ionically Conductive Polymers

“…The magnitude of the ionic polymer model is tuned through the ratio of the coupling coefficient to the frequency-dependent permittivity, d/ T . For modeling purposes the permittivity was specified as 2 Â 10 À4 F/m at 75 Hz based upon published experimental results (Buechler and Leo, 2007). With this value for T , the IPT coupling coefficient d is estimated to be 4.4 Â 10 À13 (C/m 2 )/(N/m 2 ) to properly predict the magnitude of the experimental IPT response.…”

Variational modeling of ionic polymer plate structures

“…These methods were previously demonstrated using this material by the authors and were shown to be very effective. 7 The material properties are summarized in Figure 2.…”

“…This model was extensively validated as a means of predicting both mechanical response to an electrical input and electrical response to a mechanical input. 7 In the sections that follow, we will develop a model of a square plate which can be modeled in two dimensions, briefly discuss the characterization of the materials, and then present an extensive model validation study.…”

Experimental and theoretical investigation of ionic polymer transducers in shear sensing

“…In general, most IPT sensing experiments to date have imposed dynamic stimulation to study several parameters that are known to affect the sensor output in bending (i.e. counter-ion type, hydration level, diluent type, temperature and electrode material) over a range of the frequency bands (Newbury and Leo, 2003; Bennett and Leo, 2004; Bonomo et al, 2006; Buechler and Leo, 2007; Bonomo et al, 2008; Bahramzadeh and Shahinpoor, 2011) while some have looked at imposing impulse functions, ramps and periodic waves (Bonomo et al, 2006; Bahramzadeh and Shahinpoor, 2011). In contrast, relatively few reports focused on step displacement excitation in IPT parameters determination and sensing characterization.…”