Verification of Beam Models for Ionic Polymer-Metal Composite Actuator

Ionic Polymer-Metal Composite (IPMC) can work as an actuator by applying a few voltages.A thick IPMC actuator,where Nafion-117 membrane was synthesized with polypyrrole/alumina composite filler,was analyzed to verify the equivalent beam and equivalent bimorph beam models.The blocking force and tip displacement of the IPMC actuator were measured with a DC power supply and Young's modulus of the IPMC strip was measured by bending and tensile tests respectively.The calculated maximum tip displacement and the Young's modulus by the equivalent beam model were almost identical to the corresponding measured data.Finite element analysis with thermal analogy technique was utilized in the equivalent bimorph beam model to numerically reproduce the force-displacement relationship of the IPMC actuator.The results by the equivalent bimorph beam model agreed well with the force-displacement relationship acquired by the measured data.It is confirmed that the equivalent beam and equivalent bimorph beam models are practically and effectively suitable for predicting the tip displacement,blocking force and Young's modulus of IPMC actuators with different thickness and different composite of ionic polymer membrane.

Constitutive relationship of ionic polymer-metal composite and static response character of its cantilever setup to voltage

As a new ionic polymer-metal composite(IPMC) for artificial muscle,the mechanical performance parameters and the relationship between the deformation and the electrical parameters of the IPMC were studied. With the digital speckle correlation method,the constitutive relationship of the IPMC was confirmed. With non-contact photography measurement,a cantilever setup was designed to confirm the relationship between the deformation of the IPMC film and the applied voltage. The relationship curve of tip displacement of the IPMC cantilever setup vs the voltage was achieved. The results indicate that the IPMC is isotropic,its elastic modulus is 232 MPa and Poisson ratio is 0.163. The curve achieved from the test of the tip displacement of the IPMC cantilever setup shows that the tip displacement reaches the maximum when the stimulated voltage is 5 V. And the tip displacement descends largely when the frequency of the applied voltage is between 30 mHz and 100 mHz.

Soft actuator based on ion-exchange polymer-metal composite

Ion-exchange polymer-metal composite （IPMC） is a new electroactive material. It has large deformation and high force weight ratio in the presence of low voltage （〈1.5 V）. In this study a soft actuator known as artificial muscle based on IPMC was prepared. The IPMC actuator is composed of a perfluorinated ion-exchange membrane and platinum plated on both sides of the membrane by chemical means. Experiences and some key points are introduced in preparation of the IPMC. Electromechanical behaviors of the actuator are investigated, Factors related to the actuator performance are discussed.

Neural Network Approach to Modelling the Behaviour of Ionic Polymer-Metal Composites in Dry Environments

Ionic polymer-metal composites (IPMCs) are especially interesting electroactive polymers because they show large a deformation in the presence of a very low driving voltage (around 1 - 2 V) and several applications have recently been proposed. Normally a humid environment is required for the best operation, although some IPMCs can operate in a dry environment, after proper encapsulation or if a solid electrolyte is used in the manufacturing process. However, such solutions usually lead to increasing mechanical stiffness and to a reduction of actuation capabilities. In this study we focus on the behaviour of non-encapsulated IPMCs as actuators in dry environments, in order to obtain relevant information for design tasks linked to the development of active devices based on this kind of smart material. The non-linear response obtained in the characterisation tests is especially well-suited to modelling these actuators with the help of artificial neural networks (ANNs). Once trained with the help of characterisation data, such neural networks prove to be a precise simulation tool for describing IPMC response in dry environments.

On the thrust performance of an ionic polymer-metal composite actuated robotic fish: Modeling and experimental investigation

In this paper, we theoretically predict and experimentally measure the thrust efficiency of a biomimetic robotic fish, which is propelled by an ionic polymer-metal composite （IPMC） actuator. A physics-based model that consists of IPMC dynamics and hydrodynamics was proposed, and simulation was conducted. In order to test the thrust performance of the robotic fish, a novel experimental apparatus was developed for hydrodynamic experiments. Under a servo towing system, the IPMC fish swam at a self-propelled speed where external force is averagely zero. Experimental results demonstrated that the theoretical model can well predict the thrust efficiency of the robotic fish. A maximum thrust efficiency of 2.3x10-3 at 1 Hz was recorded experi- mentally, the maximum thrust force was 0.0253 N, recorded at 1.2 Hz, while the maximum speed was 0.021 m/s, recorded at 1.5 Hz, and a peak power of 0.36 W was recorded at 2.6 Hz. Additionally, the optimal actuation frequency for the thrust efficiency was also recorded at the maximum self-propelled speed. The present method of examining the thrust efficiency may also be applied to the studies of other types of smart material actuated underwater robots.

Bio-inspired robotic manta ray powered by ionic polymer-metal composite artificial muscles

The manta ray(Manta birostris)is the largest species of rays that demonstrates excellent swimming capabilities via large-amplitude flapping of its pectoral fins.In this article,we present a bio-inspired robotic manta ray using ionic polymer–metal composite(IPMC)as artificial muscles to mimic the swimming behavior of the manta ray.The robot utilizes two artificial pectoral fins to generate undulatory flapping motions,which produce thrust for the robot.Each pectoral fin consists of an IPMC muscle in the leading edge and a passive polydimethylsiloxane membrane in the trailing edge.When the IPMC is actuated,the passive polydimethylsiloxane membrane follows the bending of the leading edge with a phase delay,which leads to an undulatory flapping motion on the fin.Characterization of the pectoral fin has shown that the fin can generate flapping motions with up to 100%tip deflection and 40◦twist angle.To test the free-swimming performance of the robot,a light and compact on-board control unit with a lithium ion polymer battery has been developed.The experimental results have shown that the robot can swim at 0.067 BL/s with portable power consumption of under 2.5 W.

Ionic polymer-metal composite mechanoelectric transduction:effect of impedance

Ionic polymer–metal composites(IPMCs)are commonly used as soft actuators due to their electromechanical response.However,the reverse phenomenon,i.e.IPMC’s ability to generate charge on application of mechanical strain(mechanoelectric response),is not very well understood.The concept of mechanoelectric transduction and its dependence on complex IPMC architecture comprising of electrode,polymer and composite layer is illustrated with a phenomenological model.The impedance model takes into account the charge transport inside the polymer and layer properties in terms of their impedances.The model lucidly indicates the significance of capacitance in IPMC transduction.The impedance model is used for studying IPMC step and frequency response and the effect of IPMC capacitance on its application as energy harvester.

Wireless actuation and control of ionic polymer-metal composite actuator using a microwave link

The ionic polymer–metal composite(IPMC),a type of electroactive polymer(EAP)actuator,has created a unique opportunity to design robots that mimic the motion of biological systems due to its soft structure and operation at a low voltage.Although this polymer actuator has strong potential for a next-generation artificial muscle actuator,it has been observed by many researchers that supplying actuation voltages in multiple locations is challenging.In robotic applications,a tethered operation is prohibited and the battery weight can be critical for actual implementation.In this research,the remote unit can provide necessary power and control signals to the target mobile robot units actuated by IPMCs.This research addresses a novel approach of using a wireless power link between the IPMC and a remote unit using microstrip patch antennas designed on the electrode surface of the IPMC for transmitting the power.Frequency modulation of the microwave is proposed to selectively actuate a particular portion of the IPMC where the matching patch antenna pattern is located.This approach can be especially useful for long-term operation of small-scale locomotion units and avoids problems caused by complex internal wiring often observed in various types of biologically inspired robots.

Development of an ionic polymer-metal composite stepper motor using a novel actuator model

A novel ionic polymer–metal composite(IPMC)actuated stepper motor was developed in order to demonstrate an innovative design process for complete IPMC systems.The motor was developed by utilizing a novel model for IPMC actuators integrated with the complete mechanical model of the motor.The dynamic,nonlinear IPMC model can accurately predict the displacement and force actuation in air for a large range of input voltages as well as accounting for interactions with mechanical systems and external loads.By integrating this geometrically scalable IPMC model with a mechanical model of the motor mechanism an appropriate size IPMC strip has been chosen to achieve the required motor specifications.The entire integrated system has been simulated and its performance verified.The system has been built and the experimental results validated to show that the motor works as simulated and can indeed achieve continuous 360
rotation,similar to conventional motors.This has proven that the model is an indispensable design tool for integrated IPMC actuators into real systems.This newly developed system has demonstrated the complete design process for smart material actuator systems,representing a large step forward and aiding in the progression of IPMCs towards wide acceptance as replacements for traditional actuators.

Modeling Ionic Polymer-Metal Composites with Space-Time Adaptive Multimesh hp-FEM

We are concerned with a model of ionic polymer-metal composite(IPMC)materials that consists of a coupled system of the Poisson and Nernst-Planck equations,discretized by means of the finite element method(FEM).We show that due to the transient character of the problem it is efficient to use adaptive algorithms that are capable of changing the mesh dynamically in time.We also show that due to large qualitative and quantitative differences between the two solution components,it is efficient to approximate them on different meshes using a novel adaptive multimesh hp-FEM.The study is accompanied with numerous computations and comparisons of the adaptive multimesh hp-FEMwith several other adaptive FEM algorithms.

Improving electromechanical output of IPMC by high surface area Pd-Pt electrodes and tailored ionomer membrane thickness

In this study,we attempt to improve the electromechanical performance of ionic polymer–metal composites(IPMCs)by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness.With proper electroless plating techniques,a high dispersion of palladium particles is achieved deep in the ionomer membrane,thereby increasing notably the interfacial surface area of electrodes.The membrane thickness is increased using 0.5 and 1 mm thick ionomer films.For comparison,IPMCs with the same ionomer membranes,but conventional Pt electrodes,are also prepared and studied.The electromechanical,mechanoelectrical,electrochemical and mechanical properties of different IPMCs are characterized and discussed.Scanning electron microscopy-energy dispersive X-ray(SEM-EDS)is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt IPMCs.Our experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt electrodes are superior in mechanoelectrical transduction,and show significantly higher blocking force compared to conventional type of IPMCs.The blocking forces of more than 0.3 N were measured at 4V DC input,exceeding the force output of typical Nafion®117-based Pt IPMCs more than two orders of magnitude.The newly designed Pd-Pt IPMCs can be useful in more demanding applications,e.g.,in biomimetic underwater robotics,where high stress and drag forces are encountered.

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

Ionic polymer-metal composites(IPMCs)are typical smart mate-rials 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 struc-ture has high power density,the structure will produce excel-lent 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 opti-mized factors was used to obtain IPMC materials in this paper.Carbon nanotube(CNT)doping,isopropyl alcohol-assisted plat-ing,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 opti-mal process parameters.By combining the best process para-meters 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/m^(3) under 3/4 VDC).The enhanced performance meets the requirements for practical bionic applications.

An artificial lateral line system using IPMC sensor arrays

Most fish and aquatic amphibians use the lateral line system,consisting of arrays of hair-like neuromasts,as an important sensory organ for prey/predator detection,communication,and navigation.In this paper a novel bio-inspired artificial lateral line system is proposed for underwater robots and vehicles by exploiting the inherent sensing capability of ionic polymer-metal composites(IPMCs).Analogous to its biological counterpart,the IPMC-based lateral line processes the sensor signals through a neural network.The effectiveness of the proposed lateral line is validated experimentally in the localization of a dipole source(vibrating sphere)underwater.In particular,as a proof of concept,a prototype with body length(BL)of 10 cm,comprising six millimeter-scale IPMC sensors,is constructed and tested.Experimental results have shown that the IPMC-based lateral line can localize the source from 1-2 BLs away,with a maximum localization error of 0.3 cm,when the data for training the neural network are collected from a grid of 2 cm by 2 cm lattices.The effect of the number of sensors on the localization accuracy has also been examined.

Nonlinear dynamics of curved IPMC actuators undergoing electrically driven large deformations

The nonlinear dynamics of curved ionic polymer-metal composite(IPMC)actuators having large tip displacement and periodical jumping locomotion was investigated experimentally.Through snap-through phenomena,the actuator generates much larger tip displacement and shows abrupt jumps in the transitions of upswings and downswings with low input energy.Two curved IPMC cantilever actuators having two different constant curvatures of 0.01 mm^(−1) and 0.02 mm^(−1) were fabricated through thermal treatment from flat IPMCs,simultaneously with no residual stress.As-fabricated IPMC actuators were tested to evaluate the effect of initial curvature under static and dynamic electrical excitations.Unlike the case of the flat IPMC actuator,asymmetric characteristics in step and harmonic responses were investigated in the curved IPMC actuators.Also,at relatively higher input voltage,snap-through phenomena were observed with much larger transverse displacements and periodical abrupt jumps of the instant speed.This revealed jumping movements between the multiple equilibrium points.The results show that optimum curvatures for better bending performance of curved cantilever IPMCs exist and that this snap-through mechanism could be applied to IPMC actuators by considering their soft and flexible properties and the geometric structures.

A compliant surgical robotic instrument with integrated IPMC sensing and actuation

Robotic assisted surgery is becoming widely adopted by surgeons for a number of reasons,which include improved instrumentation control and dexterity as well as faster patient recovery times and cosmetic advantages.Robotic assisted surgery is currently one of the fastest growing applications in robotics.Although the traditional robotic actuators which are currently used have advanced performance which can,in some aspects,surpass that of humans,they simply do not have the capabilities and diversity required to meet the demand for new applications in robotic surgery.Novel transducers which have advanced capabilities and which allow safe operation in delicate environments are needed.Ionic polymer-metal composites(IPMCs)have extensive desirable characteristics when compared with traditional actuators and as their transduction mechanisms can mimic biological muscle they have much potential for future advanced biomedical and surgical robotics.In this research,a complete two degree-of-freedom(2DOF)surgical robotic instrument has been developed,which with the attachment of surgical tools(scalpel,etc.)has the ability to undertake surgical procedures.The system integrates an IPMC sensor and actuator at each joint.A gain scheduled(GS)controller,which is tuned with an iterative feedback tuning(IFT)algorithm,has been developed to ensure an accurate and adaptive response.The main advantages of this device over traditional devices are the improved safety through a natural compliance of the joints as well as the mechanical simplicity which ensures ease of miniaturisation for minimally invasive surgery(MIS).The components of the system have been tested and shown to have the capabilities required to operate the device for certain surgical procedures,specifically a device work envelope of 1600 mm^(2),compliance of 0.0668 m/N while still maintaining enough force to cut tissue,IPMC sensor accuracy between 3-22%and a control system which has shown to guarantee zero steady state error.

Evaluation of dehydration loss and investigation of its effect on bending response of segmented IPMC actuators

Efforts were made to estimate and analyze the effect of dehydration on the bending response of segmented ionic polymer-metal composite(IPMC)actuators.An experiment was conducted with an IPMC actuator to study the variation of bending characteristics with input voltage.Based on the experimental data,the Cobb-Douglas production method was used to obtain the dehydration factor in terms of input voltage and time.The motion of the patches was restricted to planar in two dimensions.A single-patch IPMC actuator was then modeled following the Euler-Bernoulli approach incorporating loss due to dehydration.A forward kinematics model for the segmented actuators was formulated after constituting the homogeneous coordinate transformation matrix,assuming it is a serial link multi-degree of freedom manipulator.An energy-based dynamic model of the patches was derived using the Lagrange principle.Simulations were performed for single and two segmented IPMC patches to demonstrate the bending response for various input voltages.The results demonstrate the gradual reduction of bending response of an actuator owing to moisture loss.