Ionic Polymer-metal Composite Materials Research Articles

Kirigami-inspired self-powered pressure sensor based on shape fixation treatment in IPMC material

Rapid advances in sensing technologies have brought about the fast development of wearable electronics for biomedical applications. Since its conception, over the years, the ionic polymer metal composite (IPMC) is a new man-made material that has demonstrated its great potential for wearable devices due to self-powered sensing capabilities. Here, for the first time, a novel Kirigami technique with unique cut patterns has been employed for designing a stretchable IPMC sensor with enhanced performance. As Nafion itself exhibits the characteristic of shape memory polymer, the Kirigami structure that is built using the IPMC can be buckled up by loading and heating the IPMC above the deformation temperature, T def. To further enhance the memory effect, the Kirigami structure has further been locked by immersing it in potassium hydroxide for the formation of deprotonated Nafion. The voltage output of the proposed IPMC with Kirigami shows a superior performance with 3 times improvement over the conventionally planar electrodes. Dynamic tests with a range of displacements have been performed to validate the sensor design and the robustness of the Kirigami structure. This novel Kirigami-based IPMC sensor has been successfully demonstrated for braille sensing by designing 7 independent electrodes.

Integrated fabrication process with multiple optimized factors for high power density of IPMC actuator

ABSTRACT Ionic polymer-metal composites (IPMCs) are typical smart materials that are commonly used in bionic applications, including soft robots, bionic flapping aircraft, and bionic fish. However, their low output force seriously limits device performance. Stacking of multiple IPMC actuators to improve the overall performance of soft actuators is a strategy that is used in practical applications. Under the energy dissipation condition in the IPMC stacking structure, if each single IPMC in the structure has high power density, the structure will produce excellent performance with high efficiency that can greatly promote wider application of IPMC actuators. To meet this requirement, a method for fabrication process integration with multiple optimized factors was used to obtain IPMC materials in this paper. Carbon nanotube (CNT) doping, isopropyl alcohol-assisted plating, and hot pressing with a mesoscopic structural mold were selected as typical optimization methods for process integration and were initially investigated separately to determine the optimal process parameters. By combining the best process parameters in an integrated process, the IPMC treated by isopropyl alcohol-assisted plating and CNT doping process (No. AC7) showed excellent actuation performance and high work density (~9.71/12.36 gf, ~14.93/31.89 kJ/m3 under 3/4 VDC). The enhanced performance meets the requirements for practical bionic applications.

Characterizing the transduction behavior of ionic polymer-metal composite actuators and sensors via dimensional analysis

Ionic polymer-metal composites (IPMCs) are functional smart materials that exhibit both electromechanical and mechanoelectrical transduction properties, and the physical phenomenon underlying the transduction mechanisms have been studied across the literature extensively. Here we use a new modeling framework to conduct the most comprehensive dimensional analysis of IPMC transduction phenomena, characterizing the IPMC actuator displacement, actuator blocking force, short-circuit sensing current, and open-circuit sensing voltage under static and dynamic loading. The information obtained in this analysis is used to construct nonlinear regression models for the transduction response as univariant and multivariant functions. Automatic differentiation techniques are leveraged to linearize the nonlinear regression models in the vicinity of a typical IPMC description and derive the sensitivity of the transduction response with respect to the driving independent variables. Further, the multiphysics model is validated using experimental data collected for the dynamic IPMC actuator and voltage sensor. With data collected from physical samples of IPMC materials in-lab, the regression models developed under the new computational framework are verified.

Artificial Intelligence-Assisted Throat Sensor Using Ionic Polymer–Metal Composite (IPMC) Material

Throat sensing has received increasing demands in recent years, especially for oropharyngeal treatment applications. The conventional videofluoroscopy (VFS) approach is limited by either exposing the patient to radiation or incurring expensive costs on sophisticated equipment as well as well-trained speech-language pathologists. Here, we propose a smart and non-invasive throat sensor that can be fabricated using an ionic polymer–metal composite (IPMC) material. Through the cation’s movement inside the IPMC material, the sensor can detect muscle movement at the throat using a self-generated signal. We have further improved the output responses of the sensor by coating it with a corrosive-resistant gold material. A support vector machine algorithm is used to train the sensor in recognizing the pattern of the throat movements, with a high accuracy of 95%. Our proposed throat sensor has revealed its potential to be used as a promising solution for smart healthcare devices, which can benefit many practical applications such as human–machine interactions, sports training, and rehabilitation.

Longitudinal size effects on electrical and actuation behaviors of ionic polymer-metal composite

The structural characteristics of ionic polymer-metal composite (IPMC) were analyzed, and the effects of IPMC length ranging from 1 to 5 cm (with a width of 0.5 cm) were evaluated in terms of electrical parameters and actuation behavior. It has been concluded that the electrical parameters of IPMC materials (including capacitance, electrode resistance in thickness-direction, and internal resistance) decrease, and the bending strain of the setpoint increases as the length increases. The simulation of the current response of IPMC to 2 V DC voltage shows that the error between simulated peak current using 1 cm-IPMC parameters and the measured value is 8.23 times higher than that of 5 cm-IPMC. The strain of the set point on 5 cm-IPMC sample is 5.65 times bigger than that of the 1 cm-IPMC sample.

A hyperelastic porous media framework for ionic polymer-metal composite actuators and sensors: thermodynamically consistent formulation and nondimensionalization of the field equations

Ionic polymer-metal composites (IPMCs) are smart materials that exhibit large deformation in response to small applied voltages, and conversely generate detectable electrical signals in response to mechanical deformations. The study of IPMC materials is a rich field of research, and an interesting intersection of material science, electrochemistry, continuum mechanics, and thermodynamics. Due to their electromechanical and mechanoelectrical transduction capabilities, IPMCs find many applications in robotics, soft robotics, artificial muscles, and biomimetics. The current literature is sparce in multiphysics models that account for large deformations, coupled ion-solvent transport, the porous structure of the membrane, and lossy electrodes under finite-strains. This study addresses this by developing a new, hyperelastic porous media modeling framework for IPMCs using the principles of continuum thermodynamics and multiphasic materials. This framework compactly captures the broadest strokes of IPMC modeling methodologies, summarizing them in the form of general constitutive requirements placed on thermodynamic potential describing the polymer skeleton. A simple IPMC model is derived under this framework which captures the finite-strain deformation of a hyperelastic material, accounting for the coupled ion-solvent transport through the porous polymer, and resistive electrodes deforming with the skeleton. The resulting governing equations are further cast into a generalized nondimensional formulation, and an expansive set of unique dimensionless -groups are derived for IPMC actuator and sensor devices. This new framework and the nondimensional formulation lay the groundwork for future research and an expansive characterization of IPMC transduction phenomena via dimensional analysis.

Dynamic modeling of biomimetic undulatory ribbon fin underwater propulsor actuated by IPMC

Abstract In this paper, electro-mechanical dynamic modeling of a biomimetic propulsor based on undulating ribbon fin is proposed. Kinematics of the system is considered as the sinusoidal undulating motion of the ribbon fin which is guided by the actuating ionic polymer metal composite material. This is a smart material that actuates when an input voltage is applied and composed of a simple RC circuit. Elongated body theory is used to produce system dynamics considering the kinematics and also the hydrodynamic parameters like drag is undertaken as the application aspect is underwater environment. The proposed model has been used to evaluate the speed and thrust of the biomimetic system. Also, the thrust efficiency can be obtained for the different input frequencies. The proposed model may contribute to the understanding of an undulating ribbon fin inspired by IPMC for the underwater locomotion.

A Study of the Movement, Structural Stability, and Electrical Performance for Harvesting Ocean Kinetic Energy Based on IPMC Material

The movement of water in the oceans generates a vast store of kinetic energy, which has led to the development of a wide variety of offshore energy harvesters all over the world. In our energy harvester, we used ionic polymer-metal composites (IPMCs) to convert the ocean energy into electricity. This paper presents a simulated model of an IPMC-based electrochemical kinetic energy harvesting system installed in the ocean and produced using the computational fluid dynamics (CFD) method. The simulation processes focused on the movement and structural stability of the system design in the ocean for the protection of the IPMC module against possible damage, which would directly affect the power output. Furthermore, the experimental tests under real marine conditions were also studied to analyze the electrical harvesting performance of the IPMC system. These results showed that the use of IPMC materials has many advantages as they are soft and durable; as a result, they can respond faster to wave parameters such as frequency, amplitude, and wavelength.

Basic design of a biomimetic underwater soft robot with switchable swimming modes and programmable artificial muscles

A biomimetic underwater robot was designed utilizing ionic polymer-metal composite (IPMC) artificial muscles. The actuators were controlled by thermal and electrical inputs, taking advantage of both the shape-memory and electromechanical behavior of the material, to achieve multiple swimming modes in the proposed robot. The design was inspired by the pectoral fish swimming modes, such as stingrays, knifefish, and cuttlefish. The robot was actuated by two soft fins which consisted of multiple embedded IPMC actuators connected with an Eco-Flex membrane. Through electromechanical actuation, a traveling wave was generated on the soft fin. The deformation and the blocking force of the IPMCs on the fin were measured to characterize the actuators. An experimental setup was also designed in a flow channel to measure the thrust force of the robot under different frequencies and traveling wave numbers in a captive state. Experiments determined a peak thrusting force of 12 mN at a frequency of 0.5 Hz and wave number of 1, and twisting deformations of 30° were obtained. Additionally, shape-memory was utilized to change the swimming mode of the robot from Gymnotiform to Mobuliform. The designed underwater robot utilizes IPMC materials with multi-input control, enabling high deformability, with available maneuverability and agility in future studies.

Tunable Contact of Epidermal Electronics With Skin Based on Ionic Polymer–Metal Composite Material

Epidermal electronics mounted on the body provides the robust and noninvasive interfaces to monitor the electrophysiological signals of human body. The contact characteristic of the epidermal electronics with the skin affects the accuracy of the measured signals. In this paper, ionic polymer–metal composite is used to regulate the interface force for the consistency of the contact performance. The patterns of the ionic polymer–metal composite are designed for the flexibility and the contact characteristic of the epidermal electronics with the skin. This study provides an approach for the adjustment of the contact characteristic, which is very valuable for the longtime accurate monitoring of the epidermal electronics attached on the skin.

A moisture and electric coupling stimulated ionic polymer-metal composite actuator with controllable deformation behavior

Ionic polymer-metal composite (IPMC) actuator can generate large and rapid deformation based on ion migration under a relatively low driving voltage. Under full hydrated conditions, the deformation is always prone to relaxation. At room humidity conditions, the deformation increases substantially at the early stage of actuation, and then decreases gradually. Generally, most researchers considered that the change of water content or relative humidity mainly leads to the deformation instabilities, which severely limits the practical applications of IPMC. In this Letter, a novel actuation mode is proposed to control the deformation behavior of IPMC by employing moisture as an independent or collaborative incentive source together with the electric field. The deformation response is continuously measured under electric field, electric field-moisture coupling stimulus and moisture stimulus. The result shows that moisture can be a favorable driving factor for IPMC actuation. Such an electric field-moisture coupling stimulus can avoid the occurrence of deformation instabilities and guarantee a superior controllable deformation in IPMC actuation. This research provides a new method to obtain stable and large deformation of IPMC, which is of great significance for the guidance of material design and application for IPMC and IPMC-type iEAP materials.

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.

Ocean-based electricity generating system utilizing the electrochemical conversion of wave energy by ionic polymer-metal composites

In this research we used an energy harvesting system based on ionic polymer–metal composites (IPMCs) to absorb the kinetic energy of the ocean waves and generate electricity. The experimental results showed that IPMC materials have many advantages, including softness and durability; they also respond rapidly to wave parameters such as frequency, amplitude, and wavelength. In addition, the 296-day recorded data showed that the average power density generated each day remained stable at approximately 245μW/m2, the degradation of the IPMC's electrical performance in long-term operation being trivial.

Effect of surface roughening method on performance of IPMC artificial muscle

Ionic Polymer Metal Composite (IPMC) is a new kind of ionic Electro-active Polymer (EAP) composed of a perfluorinated polymer membrane coated with a noble metal (usually use Pt and Au) on both sides, which behaves like biological muscle bends towards the anode (in the case of cation exchange membrane) under the influence of an applied electric field. Since it has several advantages such as large deformation, light weight, flexibility, bio-compatibility and low driving voltage compared with shape memory alloy materials and piezoelectric ceramic, IPMC, also termed “artificial muscle”, can be widely applied to the actuators, sensors, biomimetic materials and medical engineering. As a kind of composite materials composed of polymer and metal, the performance of IPMC is closely related to the construction between polymer membrane and metal electrode. Surfaces roughening treatment of the Nafion membranes is employed in order to improve the construction way of the interfaces between polymer membranes and metal electrodes, which is a significant method to improve the electromechanical properties of IPMC materials. In this paper, a controllable and directional surface treatment for IPMC was developed. A surface roughening device included friction head, membrane jig and fixed stage was demonstrated for the IPMC membranes based on linear reciprocating motion of the UMT-2 friction-abrasion testing machine. Compared with manual surfaces roughening treatment, mechanical surface roughening treatments under 20, 50 and 80 N three kinds of load was used. The same preparation process was guaranteed to prepare IPMC on the basis of Nafion membranes with different surfaces roughening methods. The surface morphology of the Nafion membranes was observed using digital microscope. The cross-sectional and metal electrodes of the IPMC were observed using scanning electron microscopy (SEM). The surface roughness of the roughened membranes were measured with surface profiler. The effect of different roughening treatments methods and loading condition on the displacement and blocking force of IPMC artificial muscle were investigated using home-built apparatus. Compared with IPMC with manual surfaces roughening treatment, the IPMC with 20 N roughening load shows the best actuation performance of displacement, and the IPMC with 50 N roughening load shows the best actuation performance of blocking force. Mechanical roughening method can exclude the human factors in the manual roughening process, and produce controllable loading strength and direction, making the polishing cracks uniform in depths and directions. Compared with manual surfaces roughening treatment, the compactness constructed of the interfaces between polymer membranes and metal electrodes can be improved by the mechanical surface roughening treatments, the adsorption capability and deposition thickness of the Pt particles were increased. Thus, the flat and dense electrode with uniform cracks was obtained, which definitely reduced the surface resistance and enhance the blocking force and displacement of IPMC. The denser and thicker electrodes can prevent water leakage and extend the effective operating time of IPMC artificial muscle in the air. This research can improve the stability of the preparation process, which lays a solid foundation for the standardization of preparation process of IPMC. Also, the actuation performance of IPMC was enhanced, guaranteeing the further development and application of IPMC artificial muscle.

A self-strain feedback tuning-fork-shaped ionic polymer metal composite clamping actuator with soft matter elasticity-detecting capability for biomedical applications

This paper presents a smart tuning-fork-shaped ionic polymer metal composite (IPMC) clamping actuator for biomedical applications. The two fingers of the actuator, which perform the clamping motion, can be electrically controlled through a unique electrode design on the IPMC material. The generated displacement or strain of the fingers can be sensed using an integrated soft strain-gage sensor. The IPMC actuator and associated soft strain gage were fabricated using a micromachining technique. A 13.5×4×2mm3 actuator was shaped from Nafion solution and a selectively grown metal electrode formed the active region. The strain gage consisted of patterned copper foil and polyethylene as a substrate. The relationship between the strain gage voltage output and the displacement at the front end of the actuator's fingers was characterized. The equivalent Young's modulus, 13.65MPa, of the soft-strain-gage-integrated IPMC finger was analyzed. The produced clamping force exhibited a linear increasing rate of 1.07mN/s, based on a dc driving voltage of 7V. Using the developed actuator to clamp soft matter and simultaneously acquire its Young's modulus was achieved. This demonstrated the feasibility of the palpation function and the potential use of the actuator in minimally invasive surgery.

Energy harvesting from limit cycle oscillation of a cantilever plate in low subsonic flow by ionic polymer metal composite

In this work, energy harvesting from limit cycle oscillation of low aspect ratio rectangular cantilever plates in low subsonic flow by ionic polymer metal composite is considered. The plate is modeled in according to classic plate theory with Von-Karman strain–displacement relations for modeling large deflections due to midplane stretching. Aerodynamics flow is modeled based on modified vortex lattice aerodynamics model. Linear and nonlinear aeroelastic characteristics of the considered model are accurately examined and the effects of ionic polymer metal composite energy harvesting properties on flutter margin and limit cycle oscillation amplitudes are investigated. The obtained results show that output power of [Formula: see text] is generated when the flow velocity reaches to [Formula: see text] , and position of ionic polymer metal composite on the plate has great effect on the amount of power produced. The extraction of energy from plate vibration in conjunction with large strain characteristics of ionic polymer metal composite materials produces static deflection of plate. This static deflection produces stiffness hardening of the entire system, accordingly reduces the amplitude of limit cycle oscillation. Obtained results show that ionic polymer metal composite actuator has more influence on limit cycle oscillation of plate, while its effect on flutter instability is negligible.

Biomimetic Applications of Ionic Polymer Metal Composites (IPMC) Actuators - A Critical Review

Biomimetic is the field of engineering in which biological creatures and their functions are investigated and are used as the basis for the design and manufacturing of machines. Ionic Polymer Metal Composite (IPMC) is a smart material which has demonstrated a meaningful bending and tip force after the application of a low voltage. It is light-weighted, flexible, easily actuated, multi-directional applicable and requires simple manufacturing. Resultantly, IPMC has attracted scientists and researchers to analyze it further and consider it for any industrial and biomimetic applications. Presently, the research on IPMC is bi-directional oriented. A few groups of researchers are busy to find out the causes for the weaknesses of the material and to find out any remedy for them. The second class of scientists is exploring new areas of applications where IPMC material can be used. Although, the application zone of IPMC is ranging from micropumps diaphragms to surgical holding devices, this paper provides an overview of the IPMC application in biomimetic and biomedical field.

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.

Design of an IPMC diaphragm for micropump application

Micropumps have gained a great potential to be applied as biomedical devices and micro systems. Because of low driven voltage, flexible operation, and self sensing ability, the ionic polymer metal composite (IPMC) material has been used as diaphragm of micropumps. This paper presents a novel design of IPMC diaphragm which helps to produce larger deformation and increase the durability of IPMC actuator. Unlike the conventional design of using a single piece of IPMC material clamped at all edges, we use several IPMC actuators (clamped at single edge) to drive elastic thin films. By eliminating the edge constrains for IPMC actuators, the new diaphragm can provide significantly larger deformation. Moreover, new design separates the IPMC from the pumping fluid and thus allows solvent to cover the IPMC and maintain long operating duration.An incorporation of physical induced stress model of IPMC actuators and the visual ANSYS environment is proposed to analyze the characteristic of the proposed diaphragms in comparison with the conventional one. Experiments have also been carried out to demonstrate the effectiveness of proposed model. Experimental results show that the new diaphragm design can produce deformation up to 0.4mm and maintain stable operation over 35min corresponding to a 3V–0.05Hz input signal, while the conventional design can produce only 0.2mm in deformation and the pumping performance decreases rapidly after 8min.

A review on IPMC material as actuators and sensors: Fabrications, characteristics and applications

In this paper we present a comprehensive review of ionic polymer metal composite (IPMC) covering fundamentals of IPMC; from fabrication processes to control and applications. IPMC is becoming an increasingly popular material among scholars, engineers and scientists due to its inherent property of low activation voltage, large bending strain, i.e., transformation electrical energy to mechanical energy, and properties to be used as bidirectional material, i.e., it can be used as actuators and sensors. Among the diversity of electro active polymers (EAPs), recently developed IPMCs are good candidates for use in bio-related application because of their biocompatibility. Yet, the challenge remains in controlling a somewhat complicated material as mechanical, electrical and chemical properties interact with each other in the ionic polymer. Several IPMC fabrication processes, their mechanical characteristics and performance, a number of recent IPMC applications and pertaining mathematical modeling have been reported in this paper. Also we have attempted to present concisely the control of IPMC and effects of various factors in the performance of IPMC. The applications of IPMC have been growing, and recently more sophisticated IPMC actuator applications have been performed. This indicates that the IPMC actuators hold potential for more sophisticated control application. Extensive references are provided for more indepth explanation.