Active sensing methods of ionic polymer metal composite (IPMC) : Comparative study in frequency domain

Ionic polymer-metal composites (IPMCs) are soft transducers that bend in response to low-voltage input, and generate voltage in response to deformations. Their potential applications include compliant locomotion systems, small-scale robotics, energy harvesting and biomedical instrumentation. The materials are inherently compliant, simple to shape, simple to miniaturize and simple to integrate into a system. Compared to actuation, IPMC sensing has not been intensively studied. The existing reports focus on the sensing phenomenon, but provide insufficient characterization for implementation purposes. This work aims to address this gap by studying and comparing the frequency responses and noise dynamics of different IPMC active sensing signals, i.e. voltage, charge and current. These characteristics are experimentally identified by mechanically exciting IPMC samples, and simultaneously measuring the respective signals and material deformations. The results provide a systematic comparison between different implementations of active sensing with IPMCs, and give insights into their strengths and limitations

Integrated static and dynamic modeling of an ionic polymer–metal composite actuator

Ionic polymer–metal composites have been widely used as actuators for robotic systems. In this article, we investigate and verify the characteristics of ionic polymer–metal composite actuators experimentally and theoretically. Two analytical models are utilized to analyze the performance of ionic polymer–metal composites: a linear irreversible electrodynamical model and a dynamic model. We find that the first model accurately predicts the static characteristics of the ionic polymer–metal composite according to the Onsager equations, while the second model is able to reveal the back relaxation characteristics of the ionic polymer–metal composite. We combine the static and dynamic models of the ionic polymer–metal composite and derive the transfer function for the ionic polymer–metal composite’s mechanical response to an electrical signal. A driving signal with a smooth slope and a low frequency is beneficial for the power efficiency

Effects of varied planar dimensions of IPMC on simulated actuation using COMSOL

This study focuses on mechatronic systems and their use of bending smart materials, specifically the ionic polymer metal composite (IPMC), for compliant actuation. The advantages of IPMC actuators, such as low power consumption and high flexibility, are highlighted. The actuation mechanism of IPMCs involving ion migration, water transport, and mechanical stress imbalance is discussed. The influence of geometric parameters, specifically length and width, on IPMC performance is investigated through simulations. Results show a positive correlation between IPMC lengths exceeding 30 mm and displacement, with longer lengths leading to higher displacements. The relationship between width and maximum displacement is attributed to factors like increased active area, larger polymer volume, and potential effects on mechanical properties. Further electromechanical analysis is needed for a comprehensive understanding of these mechanisms

IPMC materjali hp-FEM mudel

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Ioonjuhtivaid polümeer-metall komposiitmaterjale (edaspidi lühendatud IPMC ehk ionic polymer-metal composite) on uuritud juba vähemalt kaks aastakümmet nende huvipakkuvate omaduste tõttu. Võimalikeks kasutusaladeks on vaiksed aktuaatorid või sensorid. IPMC eelised teiste elektroaktiivsete polümeeride ees on töötamine madalal pingel (1...5V), suur paindeulatus, ja toimimine veekeskkonnas. Kuigi põhiliselt on uuritud materjalide omadusi aktuaatoritena, on hiljuti materjalide sensor-omadused rohkem tähelepanu saanud. Et materjali toimimisest aru saada ning seda kirjeldada erinevate rakenduste tarbeks, on vajalik füüsikal baseeruvat mudelit. Sellest lähtuvalt on välja töötatud Poisson-Nernst-Planck-Navier võrranditel baseeruva IPMC mudel. See baseerub füüsikalistel printsiipidest, ehk et saab kasutada võimalikult palju mõõdetavaid suurusi ääretingimustena (nagu materjali paindumine, rakendatud pinge jne). Lisaks on oluline, et meetod millel mudel baseerub, oleks efektiivne ning võimaldaks arvutusi väikese või vähemalt teadaoleva maksimaalse arvutusveaga. Käesoleva töö keskendub peamiselt just arvutusmeetodil ja annab ülevaate uudsest hp-FEM (finite element method) ehk hp lõplike elementide meetodist ja sellel baseeruvast IPMC mudelist. Kõigepealt on täielikult tuletatud võrrandid ja nende integraalne esitus Newtoni meetodi jaoks. Seejärel antakse lühike ülevaade hp-FEM meetodist adaptiivse väljapõhise võrguga ning kogu süsteemi Jakobiaani tuletus hp-FEM tarkvara Hermes jaoks. On näidatud kuidas automaatne adaptiivne hp-FEM võimaldab probleemi suuruse hoida väiksena (süsteemi vabadusastmeid ja kasutatud mälu silmas pidades). Kõige pealt on lahendatud Poisson-Nernst-Plancki võrrandisüsteem ja on käsitletud erinevaid adaptiivusalgoritme. Üks huvitav tulemus on, et adaptiivsed algoritmid võimaldavad lahendada probleemi tingimustel, kus Debye pikkus jääb nanomeetri suurusjärku – seda süsteemis mille mõõtmed on millimeetri skaalas. Nendest tulemustest lähtuvalt esitatakse lahendus terve Poisson-Nernst-Planck-Navier võrrandite süsteemile IPMC paindumise arvutustes. Taaskord on lõplikud võrrandid koos tuletuskäiguga esitatud. Lisaks on analüüsitud suur hulk simulatsiooni tulemusi arvutusprobleemi suurust ja kulutatud arvutusaega silmas pidades ja sellest lähtuvalt leitud parim adaptiivuse algoritm seda liiki probleemide jaoks. On ka näidatud kuidas meetod võimaldab arvutusdomeeni geomeetriat arvesse võtta – domeeni pikkuse ja laiuse suhtest tulenevad ääreefektid on automaatselt arvutustes käsitletud. Kokkuvõtteks, käesolevas töös on detailselt kirjeldatud kuidas kasutades uudne hp-FEM meetod koos adaptiivsete algoritmide ja väljapõhise võrguga võimaldab Nernst-Planck-Poisson-Navier probleemi lahendada efektiivselt, samal ajal hoides lahenduse arvutusvea etteseatud piirides.Ionic polymer-metal composites (IPMC) have been studied during the past two decades for their potential to serve as noiseless mechanoelectrical and electromechanical transducers. The advantages of IPMC over other electroactive polymer actuators are low voltage bending, high strains (>1%), and an ability to work in wet environments. The main focus has been on the electromechanical transduction property – the material’s ability to exhibit large bending deformation in response to a low (typically 1...5 V) applied voltage. However, lately research on the mechanoelectrical transduction properties of the material has gained more attention. In order to describe both deformation in response to applied voltage (electromechanical transduction) and induced voltage in response to applied deformation (mechanoelectrical transduction) properties of IPMC, an advanced physics based model of the material is necessary. Ongoing research has been focused on creating such model where real measurable quantities can be imposed as boundary conditions in order to reduce the number of unknown parameters required for calculations. In this dissertation, a physics based model that is based on novel hp-FEM (finite element method) is proposed. From the fundamental aspect, previously proposed and validated physics based model consisting of a system of Poisson-Nernst-Planck-Navier’s equations is described in detail and used in IPMC deformation calculations. From the mathematical aspect, a novel hp-FEM method was researched to model the equations efficiently. The main focus of this disseration is on the mathematical aspect. Full derivation of the equations with an in-depth study of the benefits of using higher order FEM with automatic adaptivity is presented. The explicit weak form of the Poisson-Nernst-Planck system for Newton’s method is presented. Thereafter, a brief overview of the adaptive multi-mesh hp-FEM is introduced and the residual vector and Jacobian matrix of the system is derived and implemented using hp-FEM library Hermes. It is shown how such problem benefits from using individual meshes with mutually independent adaptivity mechanisms. To begin with, a model consisting of only the Poisson-Nernst-Planck system is solved using different adaptivity algorithms. For instance, it is demonstrated that the problem with set of constants that results Debye’s length in the nanometer scale can be successfully solved. What makes it even more remarkable is the fact that the calculation domain size is in the millimeter scale. Based on those results, the complete Poisson-Nernst-Planck-Navier’s system of equations is studied for IPMC electromechanical transduction calculations. Again, the entire mathematical derivation including weak forms, the residual vector and Jacobian matrix are presented. Thereafter, a number of simulations are analyzed in terms of problem size and consumed CPU time. The best automatic adaptivity mode for such problem is determined. It is also shown how hp-FEM helps to keep the problem geometrically scalable. Additionally, it is demonstrated how employing a PID controller based time step adaptivity helps to reduce the total calculation time. Overall, by using hp-FEM with adaptive multi-mesh configuration the Nernst-Planck-Poisson-Navier’s problem size in IPMC deformation calculations is reduced significantly while a prescribed precision of the solution is maintained

Development, Analysis, and Comparison of Electromechanical Properties and Electrode Morphology of Ionic Polymer Metal Composites

With smart materials and adaptive structures being nudged into mainstream technology progressively, the smart composites are donning a predominant role as indispensable structures. Among these, the Ionic Polymer Metal Composites (IPMC), with their large bending deformation and relaxation characteristics at very low voltages are attractive as transducers in many areas of application. The actuation and sensing properties of IPMC have been sought after for various engineering functions. The paper focuses on manufacturing various types of IPMC. Combining the ionic polymer with platinum electrodes, gold sputter coated electrodes and multi-walled carbon nanotube Bucky paper electrodes to create enhanced IPMCs, comparative analysis of different manufacturing methodologies discussing the electrode morphology using scanning electron microscopy and energy dispersive X-ray spectroscopy techniques is studied. A comparison of the uniformity of the electrode plating obtained from the different processes is studied while the research also concentrates on making use of different ionic solutions to change the anions within the polymer membrane for comparison such as to determine the most suited ion content within the solid electrolyte for effective IPMC actuation. A COMSOL multiphysics model is attempted in this thesis, which effectively describes a multiphysics modeling approach for the IPMC. This new functionally graded material is tested for its bending deformation, blocking force and the current consumption to prove the electro-mechanical efficiency of the platinum, gold and Bucky paper IPMC. By studying the electromechanical properties of this smart composite actuator based on its actuation under different electric excitations, we can draw conclusions subsequently from the results of the comparison

Novel Configurations of Ionic Polymer-Metal Composites (IPMCs) As Sensors, Actuators, and Energy Harvesters

This dissertation starts with describing the IPMC and defining its chemical structure and fundamental characteristics in Chapter 1. The application of these materials in the form of actuator, sensor, and energy harvester are reported through a literature review in Chapter 2. The literature review involves some electromechanical modeling approaches toward physics of the IPMC as well as some of the experimental results and test reports. This chapter also includes a short description of the manufacturing process of the IPMC. Chapter 3 presents the mechanical modeling of IPMC in actuation. For modeling, shear deformation expected not to be significant. Hence, the Euler-Bernoulli beam theory considered to be the approach defining the shape and critical points of the proposed IPMC elements. Description of modeling of IPMC in sensing mode is in Chapter 4. Since the material undergoes large deformation, large beam deformation is considered for both actuation and sensing model. Basic configurations of IPMC as sensor and actuator are introduced in Chapter 5. These basic configurations, based on a systematic approach, generate a large number of possible configurations. Based on the presented mechanisms, some parameters can be defined, but the selection of a proper arrangement remained as an unknown parameter. This mater is addressed by introducing a decision-making algorithm. A series of design for slit cylindrical/tubular/helical IPMC actuators and sensors are introduced in chapter 5. A consideration related to twisting of IPMCs in helical formations is reported through some experiments. Combinations of these IPMC actuators and sensors can be made to make biomimetic robotic devices as some of them are discussed in this chapter and the following Chapters 6 and 7. Another set of IPMC actuator/sensor configurations are introduced as a loop sensor and actuator that are presented subsequently in Chapter 6. These configurations may serve as haptic and tactile feedback sensors, particularly for robotic surgery. Both of these configurations (loop and slit cylindrical) of IPMCs are discussed in details, and some experimental measurements and results are also carried out and reported. The model for different inputs is studied, and report of the feedback is presented. Various designs of these configurations of IPMC are also presented in chapter 7, including their extension to mechanical metamaterials and soft robots

Theoretical and Experimental Investigation on the Multiple Shape Memory Ionic Polymer-Metal Composite Actuator

Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. The ionic polymer-metal composite (IPMC) is an emerging smart material in actuation and sensing applications, such as biomimetic robotics, advanced medical devices and human affinity applications. Here, we report a Multiple Shape Memory Ionic Polymer-Metal Composite (MSM-IPMC) actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. Theoretical and experimental investigation on the MSM-IPMC actuator were performed. To date, the effect of the surface electrode properties change on the actuating of IPMC have not been well studied. To address this problem, we theoretically predict and experimentally investigate the dynamic electro-mechanical response of the IPMC thin-strip actuator. A model of the IPMC actuator is proposed based on the Poisson-Nernst-Planck equations for ion transport and charge dynamics in the polymer membrane, while a physical model for the change of surface resistance of the electrodes of the IPMC due to deformation is also incorporated. By incorporating these two models, a complete, dynamic, physics-based model for IPMC actuators is presented. To verify the model, IPMC samples were prepared and experiments were conducted. The results show that the theoretical model can accurately predict the actuating performance of IPMC actuators over a range of dynamic conditions. Additionally, the charge dynamics inside the polymer during the oscillation of the IPMC are presented. It is also shown that the charge at the boundary mainly affects the induced stress of the IPMC. This study is beneficial for the comprehensive understanding of the surface electrode effect on the performance of IPMC actuators. In our study, we introduce a soft MSM-IPMC actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of our knowledge, this MSM-IPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability. The shape memory properties of MSM-IPMC were theoretically and experimentally studied. We presented the multiple shape memory properties of Nafion cylinder. A physics based model of the IPMC was proposed. The free energy density theory was utilized to analyze the shape properties of the IPMC. To verify the model, IPMC samples with the Nafion as the base membrane was prepared and experiments were conducted. Simulation of the model was performed and the results were compared with the experimental data. It was successfully demonstrated that the theoretical model can well explain the shape memory properties of the IPMC. The results showed that the reheat glass transition temperature of the IPMC is lower than the programming temperature. It was also found that the back-relaxation of the IPMC decreases as the programming temperature increases. This study may be useful for the better understanding of the shape memory effect of IPMC. Furthermore, we theoretically modeled and experimentally investigated the multiple shape memory effect of MSM-IPMC. We proposed a new physical principle to explain the shape memory behavior. A theoretical model of the multiple shape memory effect of MSM-IPMC was developed. Based on our previous study on the electro-mechanical actuation effect of IPMC, we proposed a comprehensive physics-based model of MSM-IPMC which couples the actuation effect and the multiple shape memory effect. It is the first model that includes these two actuation effects and multiple shape memory effect. Simulation of the model was performed using finite element method. To verify the model, an MSM-IPMC sample was prepared. Experimental tests of MSM-IPMC were conducted. By comparing the simulation results and the experimental results, both results have a good agreement. The multiple shape memory effect and reversibility of three different polymers, namely the Nafion, Aquivion and GEFC with three different ions, which are the hydrogen, lithium and sodium, were also quantitatively tested respectively. Based on the results, it is shown that all the polymers have good multiple shape memory effect and reversibility. The ions have an influence on the broad glass transition range of the polymers. The current study is beneficial for the better understanding of the underlying physics of MSM-IPMC. A biomimetic underwater robot, that was actuated by the MSM-IPMC, was developed. The design of the robot was inspired by the pectoral fish swimming modes, such as stingrays, knifefish and cuttefish. The robot was actuated by two soft fins which were consisted of multiple IPMC samples. Through actuating the IPMCs separately, traveling wave was generated on the soft fin. Experiments were performed for the test of the robot. The deformation and the blocking force of the IPMCs on the fin were measured. A force measurement system in a flow channel was implemented. The thrust force of the robot under different frequencies and traveling wave numbers were recorded. Multiple shape memory effect was performed on the robot. The robot was capable of changing its swimming modes from Gymnotiform to Mobuliform, which has high deformability, maneuverability and agility

Ionic Electroactive Polymer Devices: Physics-Based Modeling with Experimental Investigation and Verification

The primary focus of this study is to examine, understand, and model ionic electroactive polymer based systems in attempt to further develop this field of study. Physics-based modeling is utilized, as opposed to empirical modeling, to achieve a deeper insight to the underlying physics. The ionic electroactive polymer system of primary interest in this study is ionic polymer-metal composite (IPMC) devices. Other similar devices, such as anion-exchange membrane (AEM) type actuators and flow battery systems are also investigated using the developed model. The underlying physics are in the studies of transport phenomenon for describing the ionic flow within the polymer membrane, solid mechanics for describing deformation of the given devices, electric potential and electric currents physics for the voltage across the devices, and ion exchange along with chemical reaction in case of flow batteries. Specific details of these systems are analyzed, such as geometrical and electrode effects. The results in modeling IPMC actuators and sensors have been used to experimentally validate the modeling framework and have provided keen insight to the underlying physics behind these transduction phenomena. The developed models will benefit researchers in these fields and are expected to provide a better understanding of these systems. This study provides a framework for design and fabrication of advanced, highly integrated, ionic migration and exchange polymer-composite devices. In particular, this work focuses on finite element simulations of ionic electroactive polymers using COMSOL Multiphysics versions 4.3 through 5.2, with primary focus on ionic polymer-metal composite devices. The basic framework model for IPMCs is of greatest importance and is the initial focus of this work. This is covered in Chapter 3 in detail with experimental comparison of results. Other aspects of interest are geometrical and electrode effects of IPMCs, which are discussed in Chapter 3 and Chapter 4. Applications of the modeling framework, such as in modeling other electroactive polymer actuators is covered in Chapter 5 and Chapter 6, which includes simulations of electrodeless artificial cilia actuators in lithium chloride (LiCl) electrolyte, discussion and modeling of all-Vanadium oxidation reduction (redox) flow battery devices, fluid-structure interactions with IPMCs, and discussion of implementing the modeling framework for anion type IPMCs. Two publications from Journal of Applied Physics and one paper accepted for publication from the Marine Technology Society Journal are included herein, with publisher permission. These papers focus directly on topics of interest to this work. They underwent several revisions and are included in full or large excerpt form to provide the most accurate description and discussion of these topics. The author of this dissertation is first author and did much of the work of one of the three papers; specific author contributions for the other two papers are detailed before each paper is presented, in which the author of this dissertation was primarily responsible for finite element simulations, discussion, and revisions. Chapter 7 and Chapter 8 contain conclusions and recommendations for future work, respectively

Ionic polymer-metal composite (IPMC) sensors

Ionic polymer-metal composites (IPMCs) which are fabricated from an ionomeric membrane, infused with mobile counterions and sandwiched between two thin noble metal electrodes, offer an outstanding capability to transform electrical energy into mechanical energy and vice versa which makes them an appropriate candidate for actuators and sensors. The purpose of this dissertation is to characterize and model IPMCs in sensory mode, develop a new fabrication procedure to improve their flexibility and humidity dependence and take advantage of IPMCs’ exceptional properties in the fabrication of several biomedical instruments to measure some physiological signals such as plantar pressure distribution, blood pulse and tactile forces. For this aim, some IPMC dynamic pressure sensors in bending, compression and shear modes of deformation are designed based on streaming potential hypothesis, fabricated utilizing direct assembly process (DAP) and calibrated in a standard shock pressure tube which provides a broad evaluation of the linearity, sensitivity and reliability of IPMC sensors. Also, to develop a reliable model of applicable sensors that could be used for real-time purposes, three explicit, dynamic, physics-based, rational transfer functions are derived by solving IPMC governing partial differential equation (PDE) in Laplace domain for compression, shear and bending modes. Derived models not only have terms of fundamental material parameters and sensor dimensions but also offer simplicity. Next, to resolve the fragility of electrodes and strong humidity dependence, IPMCs with highly flexible electrodes using sputtered gold thin film and coated with a waterproof acrylic material are fabricated. Conducting some experiments over a period of time shows the improved reliability evidently. In order to develop a self-powered flexible insole, eight circular IPMC pressure sensors are fabricated and fixed on the measuring insole at some specific anatomic areas. The fabricated smart insole is utilized for the real-time plantar pressure distribution analysis of a subject during static stance and gait cycle during walking and running. Produced colormaps based on measured signals are realistic and show a good agreement with those from commercial smart insoles. Finally, IPMCs are developed for monitoring blood pulse wave and as a flexible touch sensor and recorded signals are discussed