Ionic Polymer-metal Composite Beam Research Articles

Dynamic modeling of a fish tail actuated by IPMC actuator based on the absolute nodal coordinate formulation

Ionic polymer metal composite (IPMC) is a smart material with low driving voltage, high energy conversion, light weight and simple structure. It is suitable for driving the tail fin of small bionic fish. Actuators made of this material are quite flexible, and they are laborious to accurately describe the complex deformation of structures. Absolute nodal coordinate formulation (ANCF) has great merits in describing large deformation and large displacement problems. In this paper, the feasibility of ANCF in dynamic modeling of a fish tail actuated by IPMC actuator will be explored for the first time. The tail fin is simplified into two forms: a pure flexible IPMC beam and a hybrid beam that consists of an IPMC beam and a fixed rigid beam. The ANCF one-dimensional two-node beam element is adopted. Considering the influence of deformation curvature, the exact expression of generalized elastic force is obtained. The proposed dynamic model can describe the large deformation problem of the flexible beam. The dynamic responses of the pure IPMC beam tail fin and the hybrid tail fin driven by square wave voltage are calculated. The displacement changes of end nodes are compared, and the swing law under different driving voltage amplitude, frequency, and fluid resistance is analyzed. It is found that the driving efficiency of IPMC can be improved by increasing the driving voltage amplitude, reducing the voltage frequency, and reducing the fluid resistance in a certain range. This research would be beneficial to the study of the large swing motion mechanism of bionic robotic fish.

Humidity-dependence of IPMC sensing dynamics: characterization and modeling from a physical perspective

Ionic polymer−metal composites (IPMCs) exhibit humidity-dependent sensing behavior when operating in air, which weakens the reliability of the IPMC sensors. To better understand the underlying physics of this behavior and capture the humidity-dependence analytically, in this paper the influence of the ambient humidity on IPMC sensors is characterized and modeled from a physical perspective. In particular, we study a cantilevered IPMC beam subjected to base-excitation inside a custom-built humidity chamber with controlled humidity level. The empirical frequency responses of the sensor dynamics under different humidity levels are first obtained. Charging experiments are also conducted under each humidity level, in order to identify the corresponding effective dielectric constant. At each given humidity level, the humidity-dependent physical parameters are identified by curve-fitting the measured frequency responses with the model predictions. These identified parameters indicate a noticeable dependence on the humidity, which is captured with polynomial functions. The polynomial functions are then plugged into the physics-based model to predict the sensing output of the IPMC sensor under other humidity conditions. Additional experimental results are presented to support the effectiveness of the model.

A thermodynamic model for ionic polymer–metal composites and finite volume-finite element solution

The transient electromechanical response of an ionic polymer–metal composite (IPMC) is modeled within a thermodynamic framework using the Euler–Bernoulli beam theory coupled with electrostatically driven diffusion to account for the flow of the ionic fluid phase. A finite volume-finite element model to handle general electromechanical load conditions has been developed based on the new beam theory. The model has been shown to simulate various electromechanical responses of IPMC strips including initial overshoot followed by a back-relaxation, and anode and cathode side equilibrium configurations. Water–polymer interaction has been shown to be sufficient to capture these responses. The model can be used in both actuator and sensor applications of IPMC beams.

Model-Based Estimation of Flow Characteristics Using an Ionic Polymer–Metal Composite Beam

An ionic polymer-metal composite (IPMC) beam is capable of producing an electric signal closely correlated with its mechanical movement, due to the redistribution of mobile ions inside the IPMC material. Motivated by the potential application of this intrinsic sensing characteristic to flow property measurements in automotive engines, this paper investigates the feasibility of detecting the start and end of a pulsating flow and its fluid characteristics using an IPMC-beam-based sensor. A dynamic model is developed for the IPMC beam under the flow. The model consists of multiple rigid elements connected by rotational springs and, under suitable conditions, has a closed-form solution that enables efficient estimation of fluid properties and flow parameters with the least-squares minimization approach. The proposed fluid estimation scheme is validated using experimental results with different fluid media, and it is found that the estimated fluid drag coefficients (highly correlated with fluid viscosity) have good agreement with their actual values. This is very important for automotive applications where the characteristics of the fuel blend (such as gasoline and ethanol) need to be identified in real time.

Model study of IPMC beam electroactive response based on root deformation

Ionic polymer-metal composite (IPMC) is a type of electroactive polymer (EAP). In this paper, based on Nemat-Nasser model, an improved model is developed to explain the initial nonlinear response of electric actuation on the fixed end deformation. Three IPMC strip samples with different surface resistance are chosen for analysis. Further, from simulation and experiment results, it is found that the root deformation made the tip movement of the IPMC strip with little surface resistance, but this effect was less and less when the surface resistance reduced. The calculation results of this model for the fixed end show a more accurate simulation for the actual deformation of IPMC strips.

New computational model for predicting the mechanical behavior of ionic polymer metal composite (IPMC) actuators

Predicting of electro-mechanical behavior of ionic polymer metal composites (IPMCs) is important in many actuator design applications, but a general model for such predictions has not been successfully developed yet. A simple but versatile modeling method based on the concentrated ion boundary layer model was developed to advance the modeling of the bending behavior of IPMCs of different sizes. IPMC beams with different thicknesses and sizes were fabricated by stacking and hot-pressing method, and their mechanical bending characteristics were measured. Finite element analysis of the beams was performed using a concentrated ion boundary layer model that uses a thermal analogy. The calculated deformation and tip blocking force agreed well with the measured values for specimens of different sizes. This study shows that the proposed modeling method is simple but general enough to simulate the deformation characteristics of IPMC actuators of various sizes.

Modeling and Inverse Compensation of Temperature-Dependent Ionic Polymer–Metal Composite Sensor Dynamics

Ionic polymer-metal composites (IPMCs) have intrinsic sensing capabilities. Like many other sensing materials, however, IPMC sensors demonstrate strong temperature-dependent behaviors. In this paper, we present the first systematic studies on temperature-dependent IPMC sensing dynamics. A cantilevered IPMC beam, soaked in a water bath with controlled temperature, is excited mechanically at its tip. The empirical frequency response of the sensor, with the tip displacement as an input and the short-circuit current as an output, shows a clear dependence on the bath temperature. The sensing dynamics is modeled with a transfer function with temperature-dependent coefficients. By fitting the values of the coefficients at a set of test temperatures, we capture the temperature dependence of the coefficients with polynomial functions, which can be used to predict the sensing dynamics at other temperatures. We also investigate the inversion of the sensing dynamics, for extracting the mechanical signal given the sensor output. A stable but noncausal inversion algorithm is applied to deal with the unstable zeros of the original sensing dynamics. Inversion with finite preview time is further explored to achieve near real-time decoding of the sensor output. Experimental results with both harmonic stimuli and free vibrations have validated the effectiveness of the proposed modeling and inversion schemes for IPMC sensors under different temperatures.

Modeling of Biomimetic Robotic Fish Propelled by An Ionic Polymer–Metal Composite Caudal Fin

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, a physics-based model is proposed for a biomimetic robotic fish propelled by an ionic polymer–metal composite (IPMC) actuator. Inspired by the biological fin structure, a passive plastic fin is further attached to the IPMC beam. The model incorporates both IPMC actuation dynamics and the hydrodynamics, and predicts the steady-state cruising speed of the robot under a given periodic actuation voltage. The interactions between the plastic fin and the IPMC actuator are also captured in the model. Experimental results have shown that the proposed model is able to predict the motion of robotic fish for different tail dimensions. Since most of the model parameters are expressed in terms of fundamental physical properties and geometric dimensions, the model is expected to be instrumental in optimal design of the robotic fish. </para>

Experimental Studies on Using Ionic Polymer-Metal Composite Materials for Automotive Flow Sensing Applications

Accurate measurements of air and fuel flows in automobile engines are critical because they govern the fuel-air mixing processes in the combustion chamber that could directly impact the combustion efficiency and exhaust emissions. In this paper, we present preliminary results on using ionic polymer-metal composite (IPMC) materials as a flow sensing mechanism for automotive applications. Under a mechanical stimulus, an IPMC beam undergoes physical movement, which causes ions to redistribute inside the material and results in an electrical signal closely correlated with the mechanical response of the beam. We have performed a series of flow experiments to evaluate the electrical response of an IPMC beam subjected to a fluid motion in a flow channel. Experimental results reveal distinct response characteristics in different fluid media and under different flow conditions. The vibrating motion of the IPMC element has been further verified with high-speed imaging in an open stagnant air environment. The images have shown strong and clean correlation with the IPMC electrical signal. These results suggest that IPMC holds promise as a compact flow sensing mechanism for automotive systems.

Modeling of bending behavior of IPMC beams using concentrated ion boundary layer

Ionic polymer metal composites (IPMCs) are an emerging class of electroactive polymers (EAP), which have many potential applications as sensors and actuators. Recently, IPMCs have been intensively studied because of their huge potential in medical, mechanical, electronic, and aerospace engineering. However, before the benefits of these materials can be effectively exploited for practical use, a mathematical model must be established to enhance understanding and predictability of IPMC actuation. The coupled electrical-chemical-mechanical response of an IPMC depends on the structure of the polyelectrolyte membrane, the morphology and conductivity of the metal electrodes, the cation properties, and the level of hydration. With this in mind, the purpose of this study is to establish a finite element model for bending behavior of IPMC beams. With reference to their operation principle, it is assumed that an IPMC beam has three virtual layers. We draw an analogy between thermal strain and real strain in IPMC due to volume change. This is a coupled structure/thermal model, and the finite element method is used to solve this model. The ion concentration distribution in the IPMC boundary layer is mimicked with the temperature distribution, and the electromechanical coupling coefficient is mimicked with the thermal expansion coefficient. Theoretical and experimental results demonstrate that our suggested model is practical and effective enough in predicting the blocking force of IPMC strips for different input voltages and strip thicknesses.

Modeling of Dynamic Characteristics of Ionic Polymer-Metal Composite Beam near Resonant Frequencies

In this paper, the dynamic characteristic of an ionic polymer-metal composite (IPMC) cantilevered beam near resonant frequencies is investigated. A dynamic model is formulated on the basis of beam vibration, charge distribution and charge interactions. Experimental tests are conducted with an IPMC cantilevered beam actuated in frequency domain. Comparison with experimental results shows that the theoretical model is able to predict the dynamic responses of IPMC near resonant frequencies.

Modelling of ionic polymer–metal composites by a multi-field finite element method

Ionic polymer–metal composites (IPMCs), a new type of smart material, offer the attractive features of high sensitivity and light weight for developing novel designs in the fields of dynamic sensors, robotic actuators and artificial muscles. The non-linear water molecule diffusion resistance force exists in the process of sodium ion migration, which may cause a significant effect on the dynamic electro-mechanical properties of this kind of material. In this paper, Tadokoro's model constructed by taking the electrostatic force, the viscous resistance force, the sodium ion diffusion force, and the water molecule diffusion resistance force into account was applied for simulation of electro-mechanical properties of IMPC. By coupling these forces and based on the principle of internal force equilibrium and the laws of motion, a multi-field finite element method (MFFEM) was derived using the dynamic electro-mechanical model, and a numerical solving scheme was proposed. Using the MFFEM, the electro-active behaviours of an IPMC beam have been simulated and discussed. The simulation results show that the water molecule diffusion resistance force has various effects on an IPMC beam, such as the water concentration, charge density of sodium ions and internal equilibrium forces. Furthermore, MFFEM has also been applied to study the migration speed of the hydrated sodium ions, electric-field intensity and bending displacement distribution across the thickness direction of the IPMC beam. Compared with the experimental findings reported by other investigators, it has been demonstrated that the proposed method provided a more realistic and scientific way to predict the electro-mechanical behaviours of IPMC by introduction of the non-linear force component in the model. Hence, the accuracy of prediction may also be improved and more information may be provided for developing new IPMC devices.

A model of ionic polymer–metal composite actuators in underwater operations

Ionic polymer metal composites (IPMCs) are active materials that exhibit a bi-directionalelectromechanical coupling: a voltage produces membrane bending, while by bending anIPMC membrane a voltage output is obtained.IPMCs are of increasing interest in a number of application fields. More specifically, IPMCscan work in wet environments, even in water, and this represents a valuable capability in anumber of applications fields such as underwater robotics, surveillance, and biomedicalapplications.In this work a totally new model of an active IPMC beam, solicited by a voltage signal andimmersed in water, is introduced. The model estimates the moment produced by theapplied voltage. Therefore, the classical Euler–Bernoulli cantilever beam theory and theconcept of hydrodynamic function are used to describe the interaction between the beamand the water. Knowledge of this interaction allows estimation of the IPMC active beammotion in water.

Characterization of the harvesting capabilities of an ionic polymer metal compositedevice

Harvesting systems capable of transforming dusty environmental energy into electricalenergy have aroused considerable interest in the last two decades. Several researchworks have focused on the transformation of mechanical environmental vibrationsinto electrical energy. Most of the research activity refers to classic piezoelectricceramic materials, but more recently piezoelectric polymer materials have beenconsidered. In this paper, a novel point of view regarding harvesting systems isproposed: using ionic polymer metal composites (IPMCs) as generating materials.The goal of this paper is the development of a model able to predict the energy harvestingcapabilities of an IPMC material working in air. The model is developed by using the vibrationtransmission theory of an Euler–Bernoulli cantilever IPMC beam. The IPMC is consideredto work in its linear elastic region with a viscous damping contribution ranging from 0.1 to100 Hz. An identification process based on experimental measurements performed on aNafion® 117 membrane is used to estimate the material parameters. The model validation shows agood agreement between simulated and experimental results.The model is used to predict the optimal working region and the optimal geometricalparameters for the maximum power generation capacity of a specific membrane. The modeltakes into account two restrictions. The first is due to the beam theory, whichimposes a maximum ratio of 0.5 between the cantilever width and length. Thesecond restriction is to force the cantilever to oscillate with a specific strain; inthis paper a 0.3% strain is considered. By considering these two assumptionsas constraints on the model, it is seen that IPMC materials could be used aslow-power generators in a low-frequency region. The optimal dimensions for theNafion® 117 membraneare length = 12 cmand width = 6.2 cm, and the electric power generation is 3 nW at a vibrating frequency of7.09 rad s−1. IPMC materials can sustain big yield strains, so by increasing the strain allowed on thematerial the power will increase dramatically, the expected values being up to a fewmicrowatts.

Modeling of Electrochemical-Mechanical Deformations of Ionic Polymer Metal Composite

The bending deformation of the ionic polymer metal composite (IPMC) upon low electric field is dominated by internal water redistribution. The one-dimensional finite element formulation is conducted for the basic field equations governing electrochemical response of the IPMC. The three-dimensional finite element analysis for the mechanical response of the IPMC beam is also conducted. Some numerical studies are carried out to show the validity of the present formulation.

Modeling of an ionic polymer–metal composite beam on human tissue

In this paper, a dynamic model of a simply supported ionic polymer–metal composite(IPMC) beam resting on human tissue is developed. First, the bending moment in theIPMC beam due to the alternative electric potential is derived from Nemat-Nasser’s hybridactuation model. This explicit bending moment expression provides an easy way toestimate the bending capacity of the IPMC. Subsequently, the bending momentexpression is incorporated in the analytical solution of beam transverse vibration todescribe the response of the IPMC beam to an electric potential. The pressuregenerated by the IPMC beam on human tissue is then estimated by numericalintegration. Comparisons show that the results obtained are comparable with theexperimental data in the literature. Finally, to achieve the maximum deflection and totalpressure, the optimal electrode length and location are discussed. To increase theflexibility and variety of beam deformation, multiple electrodes are considered. Thedeflection curve and generative pressure for multiple electrodes are also derived. Thedeveloped model is useful not only for biomedical devices that employ IPMC materialsbut also for any other applications that utilize the vibration of IPMC materials.

Experimental estimate of viscoelastic properties for ionic polymer-metal composites

We propose an experimental method for estimating the general time-dependent elastic moduli of ionic polymer-metal composites (IPMCs). The materials exhibit fast and large bending motion even when a small voltage about 1 V is applied, and are expected to be used for polymer actuators. Experimental measurements for an IPMC beam of silver plated Nafion are given to demonstrate the usefulness of the proposed method. For the IPMC beam we also present a viscoelastic model, which describes the experimental results successfully.