Ionic Polymer Metal Composite Research Articles

Novel IP2C sensors with flexible electrodes based on plasma-treated conductive elastomeric nanocomposites

Ionic polymer-metal composites (IPMC) are devices composed of metallic electrodes and an ionomeric polymer membrane in a ‘sandwich’ architecture and. Their main property is electromechanical actuation or sensing based on the movement of ions. Metallic electrodes are commonly used for their high electrical conductivity, malleability, and chemical resistance. However, the high cost of noble metals, such as platinum, long manufacturing time, and fatigue failure limit their application. Therefore, the replacement of metallic electrodes with conductive elastomeric nanocomposites (CENs) was evaluated to reduce the costs and complexity of manufacturing the device and increase its working life. In this work, carbon nanotubes were used as the conductive fillers. The dispersion to achieve high electrical conductivity was carried out directly in the synthetic or natural polyisoprene rubber latex assisted by surfactant and high-power sonication. To improve the adhesion between the elastomeric electrode and the ionic membrane (Nafion), plasma treatment with atmospheric air was applied as a surface modifier. This treatment improved the hydrophilicity and adhesion of the rubbers by forming oxygenated groups and increasing the surface nanoroughness. In this way, ionomeric polymer–polymer composite (IP2C) devices were fabricated using Nafion and plasma-modified CENs, this type of electrode is unprecedented in the literature for this application. These devices showed displacement and strain sensing capacity at levels close to the conventional IPMC in all tested frequency ranges and applied accelerations. Notably, the IP2C obtained better resolution at low frequencies than the control.

Perspective on the development and application of ionic polymer metal composites: from actuators to multifunctional sensors

This perspective discusses the development of IPMC matrixes and their applications, from actuating to multifunctional sensing.

Current research status of ionic polymer–metal composites in applications of low-voltage actuators

Bending response images of an IPMC actuator under the same DC voltage and recovery process diagram after removing the voltage.

Application‐Oriented Modeling of Soft Actuator Ionic Polymer–Metal Composites: A Review

Compared to conventional actuators, the soft ionic polymer–metal composite (IPMC) actuator has significant advantages in specific applications, and the mathematical model of IPMC actuators is essential to comprehending and applying IPMCs. Due to the inherent characteristics of IPMCs and the impact of the manufacturing and measurement processes, it is challenging to developa reliable model. This article provides a comprehensive overview of the developments in IPMC actuator modeling. In particular, three types of models are examined and contrasted: the nonphysical identification model, the partial‐physical model, and the physical‐based model. In order to comprehend the current state of numerous IPMC actuator models, the characteristics, evolution, and functions of each type of model are discussed. Afterward, the evolution of the IPMC actuators’ applications is discussed. Finally, promising research directions for IPMC actuator models are identified that can more effectively facilitate the development of IPMC‐based devices.

The effects of ethanol content on the electrical response of IPMC for drinking perception

Ionic polymer metal composite (IPMC) is a kind of smart material that integrates functions of actuating and sensing. In this paper, we demonstrated a new sensing function of IPMC to detect the concentration of ethanol by investigating the effects of ethanol content on the electrical response of IPMC. Benefiting from the ion migration effect in the Nafion matrix, the voltage of IPMC varies with different ethanol concentrations. It was found that the response process of IPMC to ethanol solution can be divided into a rapid response stage caused by concentration difference and a slow response stage caused by uneven mechanical stress. The voltage change caused by the concentration difference was defined as the response voltage, and the sensitivity of the IPMC sensor to ethanol concentration was 4.39 mV. We have demonstrated the good cyclability and stability of IPMC to ethanol by experiments. Furthermore, the IPMC sensor was applied to respiratory monitoring after drinking. It has been proven that the IPMC sensor can monitor the changes in alcohol concentration after drinking, which is of great significance for the prevention of stroke after drinking.

Ionic Polymer-Metal Composites: From Material Engineering to Flexible Applications.

ConspectusIonic polymer-metal composites (IPMCs) are one kind of artificial muscles that can realize energy conversions in response to external stimulus with merits of lightweight, scalability, quick response, and flexibility and have been treated as an important platform in artificial intelligence, such as bionic robotics, smart sensors, and micro-electromechanical systems. It is well-known that IPMC devices are mainly composed of one electrolyte layer laminated with symmetric electrode layers and realize energy conversion based on ion migration and redistribution inside the devices. However, several critical issues have greatly impeded the practical applications of IPMC devices, including metal electrode cracks, metal-polymer interface detachment, and water loss in the electrolyte. In the past decade, our group and collaborators have made attempts to address the mentioned critical issues with the purpose of accelerating practical applications of IPMC devices. First, in order to address the metal electrode cracks, we have developed various electrode materials to replace the metal electrode material, such as black phosphorus and graphdiyne. These materials display superior electrical and mechanical properties with enhanced material stability without cracking. Second, to address metal-polymer interface detachment, we have designed robust interfaces for IMPC devices with vertical array structures. The as-prepared interfaces present high ionic conductivity with excellent mechanical stability under bending states. As a result, the IPMC devices deliver high working stability exceeding a million cycles under air conditions. Third, in order to avoid water loss in the electrolyte, especially at ambient conditions, we have developed ionogel electrolytes containing highly stable ionic liquids as active ion sources. The ionogel electrolytes effectively prevent water loss in conventional water-containing electrolytes, just like Nafion electrolytes and greatly improve the working stability of IPMC devices. After addressing the key issues of IPMC devices, we finally obtained many high-performing IPMC devices and explored various intelligent applications of them. For instance, we have demonstrated the smart functions of IPMC devices as sensitive strain sensors, such as sign language recognition, handwriting detection, and human muscle monitoring. In addition, we have developed bionic flying robots with a vibration frequency as high as 30 Hz with the aid of high-performance IPMC actuators. A medical catheter based on IPMC actuators has been put forward by our group and can realize multiple degrees of freedom deformation under a low driving voltage of 2.5 V, which presents great potential for application in medical instruments. Lastly, a perspective on critical challenges and future research directions on IPMC materials and devices is highlighted for accelerating practical application.

Electrochemo-poromechanics of ionic polymer metal composites: identification of the model parameters

We propose a procedure to identify the parameters of a model for the multiphysics response of ionic polymer metal composites (IPMCs). Aiming at computational efficiency and accuracy, the procedure combines analytical structural mechanics and fully-coupled electrochemo-poromechanics, additionally resorting to an evolutionary algorithm. Specifically, we consider the finite-deformation electrochemo-poromechanical theory recently developed by our group, which couples the linear momentum balance, the mass balances of solvent and mobile ions, and the Gauss law. Remarkably, the theory constitutively accounts for the cross-diffusion of solvent and mobile ions. This, in conjunction with a generalised finite element implementation that we have recently proposed, allows us to accurately capture the boundary layers of ions and solvent concentrations occurring at the membrane–electrode interfaces, which govern the IPMC behaviour in actuation and short-circuit sensing. Thus, we can explore the IPMC behaviour under external actions consistent with applications and obtain accurate predictions with a reasonable computational cost for wide ranges of model parameters. We focus on experimental data from the literature that are concerned with Nafion™-Pt IPMCs of variable membrane thickness and subjected to peak voltage drop across the electrodes ranging from 2 to 3.5 V (under alternating current). Importantly, the considered tests deal with both the tip displacement of cantilever IPMCs and the blocking force of propped-cantilever IPMCs. Overall, the adopted theory and the proposed procedure allow unprecedented agreement between predictions and experimental data, thus marking a step forward in the IPMC characterisation.

Gold nanowire mesh electrode for electromechanical device

Ionic polymer-metal composite (IPMC) actuators were prepared with Nafion film as the ionic polymer and gold nanowire (Au-NW) mesh film as the metal electrodes by hot-pressing, which shortened preparation time within 1 h. As a reference, IPMC actuator consisting of Nafion film and gold foil (Au-foil) was also prepared. Au-NW mesh film can be an electrode with thinner (about 150 nm) and lower surface resistivity (about 0.5 Ω sq−1) than the conventional electrode prepared by electroless plating. Larger contact area of the Au-NW mesh electrode than the Au-foil electrode resulted in better actuation performance (60% larger peak-to-peak displacement in actuation). It was confirmed that the transformation behavior of Au-NWs differed depending on the external stimuli condition. Namely Au-NWs transformed to Au nanoparticles in the case of the heat stimulus only. Meanwhile, Au-NWs transformed to plates in the case of the heat and pressure stimuli. While higher temperature improved the adhesion of Au-NW mesh electrode to the Nafion surface, it induced the transformation of nanowire to plates. The IPMC actuator that the Au-NW mesh electrodes were hot-pressed at 90 ºC exhibited the highest capacitance and the largest peak-to-peak displacement in actuation. This research expanded the application field of gold nanowires to the electromechanical devices.

Applications of a Novel Tunable Piezoelectric Vibration Energy Harvester.

Conversion of ambient energy to usable electrical energy is attracting attention from researchers since providing a maintenance-free power source for the sensors is critical in any IoT (Internet of Things)-based system and in SHM (structural health monitoring). Continuous health monitoring of structures is advantageous since the damage can be identified at inception and the necessary action taken. Sensor technology has advanced significantly, and MEMS (microelectromechanical systems)-based low-power sensors are available for incorporating into large structures. Relevant signal conditioning and transmission modules have also evolved, making them power-efficient and miniaturized. Various micro wireless sensor nodes (WSN) have also been developed in recent years that require very little power. This paper describes the applications of a novel tunable piezoelectric vibration energy harvester (PVEH) for providing autonomous power to low-power MEMS sensors for use in IoT and remote SHM. The novel device uses piezoelectric material and an ionic polymer-metal composite (IPMC) and enables electrical tuning of the resonant frequency using a small portion of the power generated.

Development of ionic polymer metal composite actuator by EB graft-polymerization

Ionic polymer-metal composites (IPMC) actuators were fabricated by applying ionic exchange groups such as sulfonic acids and carboxylic acids using EB graft-polymerization to two types of fluorine-based copolymers (Poly (tetrafluoroethylene-co-hexafluoropropylene): FEP and Poly (ethylene-co-tetrafluoroethylene): ETFE) as base materials, and then forming electrodes with Pt-Pd by sputtering. The physical properties of the obtained graft membrane and the evaluation as an actuator were performed. It was suggested that the acrylic acid graft membrane is preferable for PEM as components of IPMC actuator, because the ion conduction mechanism is a vehicle mechanism in which oxonium ions pass through formed hydrated clusters in PEM. In the case of operation at 10 V, IPMC actuator based on the acrylic acid-grafted FEP and ETFE showed similar or larger displacement than that based on conventional membrane. The grafted ETFE, which has high mechanical properties, is superior to the grafted FEP used in the actuators. Therefore, it was found that the ETFE grafted with acrylic acid is preferable for the IPMC actuator.

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.

Adaptive Pseudoinverse Control for Constrained Hysteretic Nonlinear Systems and its Application on Dielectric Elastomer Actuator

Flexible smart material actuators, such as dielectric elastomer actuators (DEA) and ionic polymer metal composites, have shown greatly potential applications in the field of soft biomimetic robots and rehabilitation robots due to their human-like muscle softness, large stretch, and high energy density characteristics. In this article, a fuzzy logic system (FLS) and barrier Lyapunov function (BLF) based adaptive pseudoinverse control scheme is proposed for a class of state-constrained hysteretic nonlinear systems, where all the states are always strictly limited in each constrained set. The main features of this article are: 1) the hysteresis nonlinearity in the actuators is considered and mitigated by the proposed pseudoinverse control algorithms, which implies that the direct hysteresis inverse model is not required, instead a searching mechanism of the actual control signal from the temporary control signal; 2) the all-state-constrained control problem of the Preisach hysteresis model is overcome when the control signal is coupled in the double integral functions with the aid of an FLS, BLFs, and the proposed hysteresis pseudoinverse algorithms; and 3) the DEA-based motion control platform is constructed, and the experiments are conducted to validate the effectiveness of our proposed control scheme.

3D Printing of Layered Structures of Metal-Ionic Polymers: Recent Progress, Challenges and Opportunities.

Layered Structures of Metal Ionic Polymers, or Ionic Polymer-Metal Composites (IPMCs) are formed by a membrane of an ionic electroactive materials flanked by two metal electrodes on both surfaces; they are devices able to change their shape upon application of an electrical external stimulus. This class of materials is used in various fields such as biomedicine, soft robotics, and sensor technology because of their favorable properties (light weight, biocompatibility, fast response to stimulus and good flexibility). With additive manufacturing, actuators can be customized and tailored to specific applications, allowing for the optimization of performance, size, and weight, thus reducing costs and time of fabrication and enhancing functionality and efficiency in various applications. In this review, we present an overview of the newest trend in using different 3D printing techniques to produce electrically responsive IPMC devices.

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.

High water content electrically driven artificial muscles with large and stable deformation for soft robots

Ionic-polymer metal composites (IPMCs) actuators show great potential for soft robots due to their large deformations and fast responses at low voltage. However, realizing large and stable deformation remains a challenge since the existence of back relaxation phenomena. Herein, we report high-performance IPMCs actuators fabricated via solution-casting and isopropanol-assisted electroless plating methods. The actuator exhibits extremely large bending deformation (125°) and ultrafast initial response speed (1.09 % s−1 bending strain rate) within one second of the start time under the DC voltage of 3 V. Furthermore, the actuator exhibits no significant back relaxation, even when it lifts objects 11 times heavier and holds up for more than 695 s. The outstanding properties of the actuator are demonstrated by various soft robots, including a guide-grapple robot and a microarchitecture for robotic metamaterials, and a finite element simulation approach is proposed to model the robotic metamaterials. This study offers a viable means for developing high-performance artificial muscles without back relaxation for promising applications in biomedical devices, robotic metamaterials, and soft robotics.

Resonant frequency tuning of a novel piezoelectric vibration energy harvester (PVEH)

It is imperative to provide autonomous power supplies for the sensor nodes in structural health monitoring. Piezoelectric vibration energy harvesters (PVEH) can generate power to meet this. Here, studies on a novel PVEH design integrating ionic polymer metal composites (IPMC), for electrical tuning of resonant frequency of the harvester have been discussed. The device for which a patent is pending, has two sections. Macro fiber composite (MFC) is bonded on the root section and the extension beam is impacted by IPMC. Net power output was achieved with varying conditions. This article also discusses theoretical analysis of results and next-generation devices.

Preparation and performance research of porous and Venus flytrap-shaped IPMC

Ionic polymer–metal composite (IPMC) is a new type of artificial muscle material. It is often used as the driver of bionic micro animals and plants because of its low driving voltage, large deformation and high sensitivity. The water uptake (WUP) of IPMC is an important factor affecting its driving performance. Considering this, a series of porous IPMCs with different content of nano Fe3O4 were prepared by particle leaching and electroless plating. Owing to the existence of a porous structure, the transportation channels of water molecules are greatly increased, which improves the WUP and driving performance of the IPMC. Combined with the inspiration of the stoma’s natural plant body structure, porous IPMC (P-IPMC) was applied to the bionic Venus flytrap (VF) actuator. The experimental results show that when the nano Fe3O4 content is between 0.1 wt% and 0.5 wt%, the performance of P-IPMC is better than that of non-porous IPMC (NP-IPMC). From the performance response of the NP-VF and P-VF actuators, P-VF can meet the requirements of a similar shape and motion state to the natural flytrap at a voltage value of 4 V, which is better than the driving performance of NP-VF. This paper lays a foundation for the improvement of driving performance and the diversified use of IPMC.

Evaluating Platinum‐Based Ionic Polymer Metal Composites as Potentiometric Sensors for Dissolved Ozone in Ultrapure Water Systems

AbstractMonitoring the content of dissolved ozone in purified water is often mandatory to ensure the appropriate levels of disinfection and sanitization. However, quantification bears challenges as colorimetric assays require laborious off‐line analysis, while commercially available instruments for electrochemical process analysis are expensive and often lack the possibility for miniaturization and discretionary installation. In this study, potentiometric ionic polymer metal composite (IPMC) sensors for the determination of dissolved ozone in ultrapure water (UPW) systems are presented. Commercially available polymer electrolyte membranes are treated via an impregnation‐reduction method to obtain nanostructured platinum layers. By applying 25 different synthesis conditions, layer thicknesses of 2.2 to 12.6 µm are obtained. Supporting radiographic analyses indicate that the platinum concentration of the impregnation solution has the highest influence on the obtained metal loading. The sensor response behavior is explained by a Langmuir pseudo‐isotherm model and allows the quantification of dissolved ozone to trace levels of less than 10 µg L−1. Additional statistical evaluations show that the expected Pt loading and radiographic blackening levels can be predicted with high accuracy and significance (R2adj.&gt; 0.90,p&lt; 10−10) solely from given synthesis conditions.

Nafion-Pt IPMC electroactive behavior changes in response to environmental nonequilibrium conditions

Electroactive polymers (EAPs) continue to gain attention for their potential to offer unique and versatile solutions in the soft robotic and flexible electronic industries. Ionic polymer-metal composites (IPMCs) are a class of ionic-type EAPs which can be configured as capacitor actuators with very low voltage requirements (⩽5 V AC or DC). Their compact, portable, and lightweight properties, coupled with a biomimetic bending actuation response make them ideal for human-machine integrated technologies such as medical implants, active skins, and artificial muscles. This work tested the IPMC’s actuation and electrical response in varying saturation conditions (70% RH, 85% RH, 95% RH, and DI water liquid immersion) and voltage application schemes (direct current voltage (DCV) cycled, continuously applied, and relaxation responses upon voltage removal). This information was then used to establish actuation and back-relaxation response patterns through repetitive testing for statistical certainty. These demonstrated maximized actuation in water vapor conditions where the IPMC’s dielectric permittivity is maximized (), and the dissipation factor is minimized (). The response trends in vapor conditions are gradual but yield larger actuation ranges with increasing hydration. Liquid immersion restricts the IPMC’s range of motion but produces a sharper response pattern. These trends were validated against previously published IPMC actuator models. All of this creates a more pragmatic perspective on the potential of this technology which aids in the advancement of this material’s evolution towards viable real-world application configurations which capitalize on the material’s natural responses.

Analysis of a Soft Bio-Inspired Active Actuation Model for the Design of Artificial Vocal Folds

AbstractPhonation results from the passively induced oscillation of the vocal folds in the larynx, creating sound waves that are then articulated by the mouth and nose. Patients undergoing laryngectomy have their vocal folds removed and thus must rely on alternative sources of achieving the desired vibration of artificial vocal folds. Existing solutions, such as voice prostheses and the Electrolarynx, are limited by producing sufficient voice quality, for instance. In this paper, we present a mathematical analysis of a physical model of an active vocal fold prosthesis. The inverse dynamical equation of the system will help to understand whether specific types of soft actuators can produce the required force to generate natural phonations. Hence, this is referred to as the active actuation model. We present the analysis to replicate the vowels /a/, /e/, /i/, and /u/ and voice qualities of vocal fry, modal, falsetto, breathy, pressed, and whispery. These characteristics would be required as a first step to design an artificial vocal folds system. Inverse dynamics is used to identify the required forces to change the glottis area and frequencies to achieve sufficient oscillation of artificial vocal folds. Two types of ionic polymer-metal composite (IPMC) actuators are used to assess their ability to produce these forces and the corresponding activation voltages required. The results of our proposed analysis will enable research into the effects of natural phonation and, further, provide the foundational work for the creation of advanced larynx prostheses.