Ionic Polymer Metal Composite Strip Research Articles

Electrochemical performance of ionic polymer metal composite under tensile loading

Cracks in polymer composites can lead to premature failure, which can be disastrous for polymer-based energy storage devices. Detecting these cracks is essential to guarantee the reliability and safety of such devices. However, detecting cracks in composite polymers such as ionic polymer metal composites (IPMCs) is a challenging task, which makes it difficult to ensure their performance and safety. The overall goal of this study is to investigate the effect of cracks or damage caused by tensile loading on the mechanical properties and electrochemical characteristics of IPMC based capacitors. During tensile testing, the deformation of the IPMC strips causes changes in the ion distribution and concentration in the polymer matrix, influencing the performance of the material. The measurements were conducted utilizing electrochemical impedance spectroscopy at a room temperature () and frequency range of 10 KHz to 1 Hz. The method utilized in this study proved to be easy and quick with consistent results. The IPMC capacitor was found to increase its capacitance after major cracking in the Pt electrodes from high tensile mechanical loads. Furthermore, at lower frequency range (<100 Hz), the real () and imaginary () part of permittivity increase with the addition of loads. This displays that the dielectric property of the material is affected due to the increasing of the loads. It is concluded that, at frequencies above 100 Hz, the permittivity is weakly load dependent.

Ionic Polymer Metal Composite Based Smart Tongue Using Machine Learning

Ionic polymer metal composite (IPMC)-based new type of taste sensing technology is focused on this study. The developed sensor can sense five taste senses (salty, sweetness, spicy, bitterness, and sourness) artificially. Development of electronic tongue using Nafion-based IPMC strip (Pt-electroded) is the background philosophy for the current finding. Due to the hydrophilic nature of the perfluorinated polymer membrane, IPMC strips while immersed into test solutions, cations like Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , etc., diffused into the polymer layer penetrating through the Pt-electrode surface of the IPMC and rearranged inside the polymer matrix. Bending of IPMC strip produces a small potential difference in millivolt (mV), which is developed across two Pt-electroded sides of IPMC. The output voltage across two electrode sides of IPMC for different taste samples of different concentration shows distinct voltage pattern and is measured in terms of potential difference across the Pt-electrode of IPMC. K-nearest neighbor classification approach of machine learning is useful for the identification of unknown taste agents. The average performance index of the developed machine learning model for the prediction of basic taste is 93.45%. Due to the nontoxic nature of IPMC, taste identification of different food contents would be feasible using this sensing technology.

Design of Laboratory Stand for Displacement Measurement of IPMC Actuators.

The polymer technology based on Electroactive polymers and metal composite ionic polymer has great potential and advantages in many engineering fields. In this paper, a laboratory stand for testing Ionic polymer-metal composites (IPMC) is presented. The laboratory station includes a power supply system and a measuring system for the displacement of IPMC composites. Tests and measurements are carried out using a laser transducer and a camera equipped with image analysis software to determine the IPMC strips displacement. The experimental investigation of IPMCs under different voltage supplies and waveforms, environmental working humidity conditions, temperature, and loading conditions has proved the significant influence of geometric dimension and the effect of increased stress on the displacement value. For materials powered by a higher voltage value, an increased deflection value was noted. In case of displacement, longer is the sample, higher is the displacement value. The length of the sample under load, affects adversely its performance, resulting in an increase in the load on the sample. For samples of a thick size, a more stable movement with and without load can be noticed.

Taste Sensor Using Ionic Polymer Metal Composite

The usage of ionic polymer metal composite (IPMC) being an electroactive polymer is prevalent in different engineering applications. IPMC are synthetic composite nanomaterials which show artificial muscle behavior under applied voltage or electric impetus. When an electrical potential is applied across the two membranes, the positively charged conjugated and hydrated cations migrate toward the negative electrode. This migration creates an osmotic pressure gradient across the membrane; hence, the strip gets deformed or bent. On the other hand, IPMC strips are capable of generating electrical potential under the action of stretching or bending (thereby acting as a sensor). In this letter, the authors report the pragmatic application of the IPMC strip to study a taste sensor. The sensing characteristics of IPMC strips are applied to sense five general tastes (sweet, sour, bitter, salty, and spicy). Primarily, IPMCs are immersed into individual solutions and kept for 15 min for doping action. Thus, different solutions having distinct concentration of ions will lead to distinct identifications. In this present investigation, the authors have instigated the IPMC strip as a sensor; when an IPMC strip is bent or deformed, an analogous voltage in the range of millivolts is generated across the membranes. Second, clammy IPMCs are bent in the clockwise and again in the counterclockwise direction (10°) to record the corresponding voltage. A set of experimental data was collected, which divulged unique characteristics for different solutions pertinent to different tastes. Thus, IPMC strips are able to recognize different taste senses.

A 3D analytical ion transport model for ionic polymer metal composite actuators in large bending deformations

Ionic polymer metal composites (IPMCs) are a kind of soft electroactive polymer composites. An IPMC strip commonly has a thin polymer membrane coated with a noble metal as electrodes on both sides. Whenever an electric voltage is applied to the IPMC, it bends and whenever it is deformed, a low voltage is measurable between its electrodes, hence IPMC is an actuator as well as a sensor. They are well known for their promising features like low density, lightness, high toughness and remarkable stimulus strain, also, they have the potential for low-voltage operation while exhibiting acceptable large bending deformation. In this paper, a three-dimensional (3D), dynamic and physics-based model is presented analytically and experimentally for IPMC actuators. The model combines the ion transport dynamics within the IPMC and the bending dynamics of it as a beam under an electrical stimulation. In particular, we present an analytical model to create a relation between the input voltage and the output tip displacement of an IPMC actuator for large bending deformations. Experimental results show that the proposed model captures well the tip displacement.

Harvesting Energy From an Ionic Polymer–Metal Composite in a Steady Air Flow

Abstract The paper presents the results of an investigation of a possibility for energy harvesting from a flexible material such as an ionic polymer–metal composite (IPMC) placed in a steady flow of air characteristic of conditions typical to a densely urbanized area. As electro-active devices require dynamic loading to produce current, their response is usually evaluated in unsteady and turbulent flows, where an electro-active polymer follows the movement of the medium surrounding the device. In our study, we examine the flow conditions at which flutter sets the IPMC strip in motion. Although flutter is often perceived as an unfavorable phenomenon for aerodynamic applications and civil structures, it may be beneficial for harvesting wind energy. Of particular interest is that this phenomenon may occur in a steady flow, which potentially expands the range of favorable flow conditions for energy harvesting. In the paper, the air speed at which flutter occurs and the speed range at which flutter is sustained are provided along with the estimated amount of power produced in an IPMC sample of specified dimensions.

An investigation of multimodal sensing capabilities of ionic polymer-metal composites

This paper presents the novel multimodal sensing capabilities of ionic polymer metal composites (IPMCs) for measuring linear and rotational deformations. Two IPMC samples with Gold (Au) and black Platinum (Pt) electrodes were manufactured, and their responses under twisting and axial compression/tension were investigated. To perform consistent and rigorous experiments to study the multimodal sensing capabilities of the IPMC samples, an experimental test bed was developed that enabled the application of twisting, axial compression, and axial tension to the IPMC strips both in a separate and combined manner, while recording their generated voltage responses. Through rigorous experiments, this study demonstrates the unique sensing capabilities of IPMCs to create distributed nanosensing over the entire body of the IPMC sample. Upon various types of deformations, IPMCs were shown to generate unique and distinct output voltage signals that were highly correlated with the type of motions induced. In particular, the strongest correlations of more than 0.9 were found between the IPMCs’ responses and the applied mechanical stimuli in the twisting and axial compression modes, while moderate correlations were observed in the axial tension mode. These results provide a proof-of-concept for the future use of IPMCs as flexible and versatile sensors for measuring linear and rotational motions in applications such as wearable soft robotics.

Behavior Identification of IPMC Actuators Using Laguerre-MLP Network With Consideration of Ambient Temperature and Humidity Effects on Their Performance

In this paper, we propose a model for ionic polymer metal composite (IPMC) actuators that its superiority over the other models is its capability to make a confident prediction about the bending displacement of all points along the IPMC strip in large bending displacements, without using previous data of the output and also with consideration of the effects of the ambient conditions on its performance. To achieve this aim, we used a nonautoregressive model named as Laguerre-multilayer perceptron network. Moreover, the effect of ambient temperature and humidity changes in the range of biomedical applications of IPMC was investigated using variance analysis of experimental data and also these ambient conditions were applied to the proposed model as operating points. This model was described in detail and validated by experimental results.

Influence of Humidity and Actuation time on Electromechanical Characteristics of Ionic Polymer-Metal Composite Actuators

This paper experimentally investigates the effects of humidity and actuation time on the electromechanical properties of Ionic Polymer-Metal Composites (IPMC) to improve the practical applications of using the IPMCs as soft biomimetic sensors and actuators. The experiments are conducted in both the open atmosphere (uncontrolled environment at room temperature) and inside a controlled environmental chamber under different input voltages (in term of wave shape, value, and frequency). Results show that the IPMC’s electromechanical properties, namely the deformation capacity and electrical resistance, highly depend on the water content (in the IPMC strip and environment) and the duration of actuation. The Deflection and current of the tested IPMC samples can be represented by an exponential time function were an exponent value decreases with increasing the humidity. IPMC deformation capacity decreases while material electrical resistance increases during activation session. Increasing relative humidity to more than 50% reduces the drying effect on the IPMC deformation capacity and resistance. Also, the IPMC material shows a relaxation behavior for a step voltage input, which can be related to the back immigration of the hydrated cations from the anode to the cathode due to higher pressure at the anode side of the IPMC strip.

Nonlinear analysis of ionic polymer–metal composite beams using the von Kármán strains

In this study, nonlinear analysis of ionic polymer–metal composite (IPMC) strips using the Euler–Bernoulli beam theory with the von Kármán nonlinear strain is presented. The governing equations are derived using a variational formulation based on a thermodynamic framework. The nonlinear extensions to the linear theory are made in such a way that the resulting form of the coupling between deformation and solvent concentration remains simple. A hybrid finite element–finite volume numerical solution and a operator-split time stepping scheme are formulated for obtaining numerical solutions of the transient electromechanical response. The model is phenomenological, but it is capable of simulating the transient response of IPMC strips under general loading conditions, and it would be useful in the design of mechanisms with IPMC strips as components. The results of the nonlinear analysis are compared with the corresponding linear results for a cantilever beam like IPMC strip. Significant differences in simulation results of tip deflection, solvent concentration, and beam configurations are observed between the linear and the nonlinear beam theory. The differences are due to coupling between the bending and the axial stiffness as properly formulated in the proposed nonlinear theory.

SDRE controller considering Multi Observer applied to nonlinear IPMC model

Ionic Polymer Metal Composite (IPMC) is an electroactive polymer (EAP) and a promising candidate actuator for various potential applications mainly due to its flexible, low voltage/power requirements, small and compact design, and lack of moving parts. Although widely used in industry, this material requires accurate numerical models and knowledge of optimal control methods. This paper presents State-Dependent Riccati Equation (SDRE) approach as one of rapidly emerging methodologies for designing nonlinear controllers. Additionally, the present paper describes a novel method of Multi HGO Observer design. In the proposed design, the calculated position of the IPMC strip accurately tracks the target position, which is illustrated by the experiments. Numerical results and comparison with experimental data are presented and the effectiveness of the proposed control strategy is verified in experiments.

An electrical model with equivalent elements in a time-variant environment for an ionic-polymer-metal-composite system

Ionic polymer metal composite (IPMC) is a kind of ionic electroactive polymer (EAP) smart material that can exhibit conspicuous deflection with low external voltages (~ 5 V). It can be cut in various sizes and shapes, and used and applied in robots and artificial muscles with the capability in aquatic operation. An IPMC strip can be modeled as a cantilever beam with a loading distribution on the surface. Nevertheless, the loading distribution is non-uniform due to the imperfect surface conductivity that causes four different imaginary loading distributions employed in our structural model. The difference can be up to 5 times (3:8 mm to 19 mm). In this paper, a novel linear time-variant (LTV) model is introduced and applied to model an IPMC system. This modeling method is different from previous linear time-invariant (LTI) models because the internal environment of IPMC may be unsteady due to mobile cations with water molecules. In addition, the influence of surface conductivity is simulated and proven based on this model. Finally, by applying this novel modeling method, hysteresis that exists in IPMC and affects the relationship between the output deflection and the corresponding input voltage, such as 0:1-, 0:2-, and 0:3-rad/s sinusoidal waves, has been shown and simulated.

An experimental study of force control of an IPMC actuated two-link manipulator using time-delay control

This study focuses on the force control of an ionic polymer metal composite (IPMC) actuator and a two-link manipulator actuated by the IPMC. As a polymer actuator that transforms electric energy into mechanical energy, IPMC has been applied to various mechanical devices. The time-varying property of IPMC makes it difficult to control the tip force of an IPMC actuator with a strip form, which requires a force control scheme with considerable robustness. In this study, time-delay control (TDC), which has shown exceptional robustness in various control systems, was applied to the force control of an IPMC actuator and a two-link manipulator actuated by IPMC strips. The experiments demonstrated that TDC could control the tip force of an IPMC strip so that, in spite of its time-varying characteristics, it closely follows the designed reference force with exceptional robustness. Moreover, the contact force of a two-link manipulator actuated by IPMC strips could be successfully controlled with the TDC law including the kinematic relation of the manipulator.

Shape estimation of IPMC actuators in ionic solutions using hyper redundant kinematic modeling

Ionic Polymer Metal Composites (IPMCs) has established itself as an ionomer rendering wide-ranging applications spanning the paradigm of robotics to medical appliances, thereby drawing significant research interests. Prior studies to characterize IPMCs have been conducted over several years but efforts on its kinematic modeling have remained inchoate. The bending profile of IPMC changes when placed in different ionic solutions. The IPMC trace along with its tip location characterizes its complete behavior upon low level actuation. This article aims at identifying the bending patterns of an IPMC actuator, decomposing it as a 20-link hyper-redundant serial manipulator. The Tractrix based inverse kinematics engine is used to study the polymer profile in distilled water, 1.5N LiCl and NaCl solutions respectively. The proposed algorithm yields a natural curve (Tractrix) which resembles the profile traced by an actuated IPMC strip — enabling its use in potential applications which would require a foresight of the actuator workspace.

Miniaturized Terrestrial Walking Robot Using PVDF/PVP/PSSA Based Ionic Polymer–Metal Composite Actuator

This paper presents a design and fabrication of millimeter scale walking robot using ionic polymer–metal composite (IPMC) actuator as the robot's leg for walking in terrestrial environment. A small scale of new IPMC actuator based on poly-vinylidene fluoride (PVDF)/polyvinyl pyrrolidone (PVP)/polystyrene sulfuric acid (PSSA) blend membrane was fabricated and employed in this study to sustain and drive the walking robot with sufficient force and displacement. The PVDF/PVP/PSSA based IPMC actuator with a polymer mixture ratio of 15/30/55 shows improved performances than Nafion based IPMC actuator. To enhance a traction force of the walking robot and to increase the life time of IPMC actuators, the IPMC strips are covered with a thin PDMS (polydimethylsiloxane) layer. A miniaturized terrestrial walking robot (size: 18 × 11 × 12 mm, weight: 1.3 g) with a light weight robot's body which can support 2-, 4-, or 6-IPMC-leg models was designed and implemented the walking motion on the ground at the maximum speed of 0.58 mm/s.

Simultaneous parametric optimization of IPMC actuator for compliant gripper

Ionic Polymer Metal Composite (IPMC) exhibits artificial muscle behavior while subjected to change in voltage, frequency and doping solutions. Here, an attempt has been made to actuate a miniscule compliant gripper by a pair of IPMC strips. To obtain substantial displacement and force to actuate the compliant gripper, a full factorial experimental layout was laid by considering three levels of voltage (1.5 V-3 V-4.5 V), frequencies (0.1 Hz-0.01 Hz-0.001 Hz) and doping solutions (KCl, NaCl and Distilled Water). Grey Relational Analysis was adopted to turn multi-objectives (force and displacement) into a single objective and the best parametric combination was found as ds-1-f+1-v+1 [KCl 1.5 (N)-0.001 Hz-4.5 V]. Response Surface Modeling (RSM) and ANOVA was adopted to correlate the force and displacement in terms of the process parameters (Voltage and Frequency). At the optimized parametric condition, IPMC strips provided actuating force and displacement of 4.8 mN and 3.24 mm respectively. A small compliant two-jaw gripper was modeled in CATIA V5-R20 and through ANSYS 14.0, it was observed that, at 1.5 mm gripper thickness, each jaw-tip flexed by 1.56 mm. Afterwards, the gripper was fabricated with PDMS material and IMPCs were able to flex each jaw by 0.87 mm. The gripper was observed to grip objects with maximum of 1.247 gms of weight.

Accurate Dynamic Modeling of Helical Ionic Polymer-Metal Composite Actuator Based on Intrinsic Equations

This paper presents dynamic modeling of an innovative contractible ionic polymer-metal composites (IPMC) actuator with a helical configuration. The helical shaped IPMC actuator is fabricated through the thermal treatment of an IPMC strip, which is helically coiled on a glass rod. This type of a soft actuator can be used to realize not only bending motion but also torsional and longitudinal motion. For the first time, an explicit analytical expression is developed for the computation of mode shapes and dynamic responses of a helical IPMC actuator based on the intrinsic equations of the naturally curved and twisted beam. The numerical transfer-matrix method is used to solve the systems of 12 linear ordinary differential equations with boundary conditions. In particular, the effect of the structural parameters on the performance of the helical IPMC actuator is evaluated, using experimental results and an analytical model. The validation of the proposed model is achieved through comparison with computational results using a commercial finite-element (FE) program as well as experimental results. The present experimental and theoretical results show that diameter, among the structural parameters, plays an important role in the actuation performance of a helical IPMC actuator. The proposed modeling is general and can also be used in solving other cylindrical or noncylindrical helical IPMC actuators with different cross-sectional shapes as well as various end conditions.

Time-delay control of ionic polymer metal composite actuator

This paper presents the control of an ionic polymer metal composite (IPMC) strip, which is an electro-active polymer actuator. IPMC can produce mechanical bending motion in response to an electrical excitation. Although IPMC has many beneficial properties, such as low power consumption, large deformation, and bi-directional actuation, it is very challenging to control because of its time-varying and nonlinear properties. Time-delay control (TDC) was applied to an IPMC strip in order to obtain a robust and precise tracking performance. The TDC scheme has shown good tracking performance with exceptional robustness in many other applications, in addition to having a simple and efficient structure and design process. A first-order filter was applied to the control input to reduce the sensor noise. An anti-windup scheme was also used because of its inherent integral effect. The simulation and experimental results of an IPMC strip controlled by TDC showed good performance in the steady state and transient responses. Furthermore, the control output responses tracked the desired model even when the IPMC parameters varied in repetitive experiments. In addition, it was shown through Nyquist analysis that the stability of the IPMC strip controlled by TDC is always maintained with the time-varying parameters. These results demonstrate that the TDC law applied to a time-varying and nonlinear IPMC provides robustness in performance and stability, while yielding precise transient and steady state tracking performance.

Single active finger IPMC microgripper

This paper presents a new design for a single active finger ionic polymer metal composite (IPMC) microgripper. This design has one stationary finger and one actuating finger. The gripper is tested in comparison with a two fingered gripper (2FG) on its ability to perform pick and place operations. The grippers each use IPMC strips in three widths: 1.25 mm, 2.5 mm and 5.0 mm. The single fingered gripper shows success rates of 86.2%, 89.2%, and 75% respectively versus 78.5%, 93.9% and 75% for a 2FG. The single fingered gripper performance is nearly equivalent to that of a 2FG. Even though a single finger produces half the force, its ability to carry objects is as good as or better than a 2FG. In addition, the stationary finger is considerably stiffer than an active IPMC finger, which helps in positional accuracy. Using half the IPMC, the single fingered gripper is the economical choice.

A room-temperature processed parylene-patterned helical ionic polymer–metal composite spring actuator with selectable active region

This paper presents a novel helical ionic polymer metal composite (IPMC) spring actuator. A room-temperature fabrication process is developed to selectively grow in situ nickel metal electrode on a coiled Nafion strip, which is patterned with parylene as a masking layer to delineate the inactive region. This method allows the helical spring actuator to be shaped in a near-constant temperature environment and minimizes the residual stress effect on the Nafion polymer, compared to other processes using thermal treatment. The developed process ensures that short-circuiting never occurs between the outer and inner electrodes of the actuator, and the active region can be designed via parylene patterning. The motion of the fabricated spring actuator is measured, and the maximal displacement reaches 1 mm at the endpoint of the spring under a 0.1 Hz 6 V square wave actuation. A microtensile experiment is performed for characterizing the stress and strain relation. The resulting Young’s moduli of the Nafion and fabricated IPMC strips are 183 and 227 MPa, respectively. Analysis based on Castigliano’s theorem is executed to derive equations related to the moment, force output, strain energy, and displacement of an arbitrary point of the fabricated spring actuator. Results show the produced moment, force, and strain energy of the operated spring actuator are in the level of 1.5 μN m, 300 mN, and 20−100 μJ, respectively.