This paper discusses a time-domain analysis of the exact transfer function of Zhu’s multiphysics model of IPMC sensors. The authors recently derived the exact transfer function that describes the output voltage of Zhu’s IPMC sensor model. This paper shows that some time-domain constants such as the peak voltage and the steady-state voltage of a step response can be derived from the transfer function. It is shown that the values estimated from the exact transfer function agree with the numerical simulation in the time domain by COMSOL.
This talk discusses analytical simplification of a multi-physics model for ionic polymer-metal composite (IPMC) sensors. Some methods including finite element method, and assumed mode method based on separation of variables are introduced. For the finite-element or the assumed-mode simulation, we have built in-house MATLAB programs. The obtained approximated models are represented by ordinary differential equations, and the computational cost is greatly reduced by the proposed simplifications. The magnitudes of the error in the approximated models for open-circuit voltage are kept acceptable level within at most 2%, although the computational time is greatly reduced to 1/100 to 1/1000.
An Ionic Polymer-Metal Composite (IPMC) has characteristics as a sensor as well as an actuator. Zhu has recently proposed a multi-physical model representing sensor voltage of a deformed IPMC. This paper discusses approximation methods aiming at fast simulation or control system design. First, we linearize the nonlinear partial differential equations (PDEs) of Zhu’s model. Next, this paper considers two types of spatial discretization methods, Finite Difference Method and Finite Element Method. We have found that it is not necessary to use a large number of sample points or finite elements for simulating the sensor voltage.
In this paper, we designed and demonstrated an IPMC actuated wing for mimicking flapping motion of a butterfly. Unlike other insects, such as dragonfly, housefly, mosquito etc. with high frequency of vibration (>30Hz on flying), the flapping times of butterfly wing is less than ten times. That’s to say, the frequency of butterfly wing is lower than 10Hz. So it is feasible that utilizing IPMC actuator with excellent advantage of low frequency response to imitate the flapping motion of butterfly. Firstly, to improve the frequency response of IPMC actuator, we fabricated the strip shaped IPMC with the thickness less than 100μm and Au electroplating was employed in the preparation process. Secondly, IPMC actuated wing and biomimetic butterfly fully made of IPMC were designed and fabricated. Finally, we measured and evaluated the deformations, block forces and lift forces of the flapping wing. Experimental results demonstrated that thin IPMC exhibits a large flapping with light weight, which is more suitable for flapping wing.
This paper presents the design, fabrication, and testing of a novel 6 legged terrestrial walking robot inspired by the movements of an ant, while the ionic polymer-metal composite(IPMC) is used as the leg actuators. This terrestrial walking robot (size: 34 mm × 20mm ×28 mm, weight: 2.43g) is able to move in open air independently. The legs of the robot are made of a spatial two-degree-of-freedom (2DOF) IPMC actuator structure which shows great characteristics in movement and load-carrying capability. The different dimension of the IPMC actuator and the parameters of the leg structure are tested and optimized to cater the demand of different part of the leg structures. The robot is controlled by a microprocessor, an on-board lithium battery is used as the power and the square wave signal is employed to drive the 6 independent leg structures.
To date, water-based ionic polymer metal composite (IPMC) is just regarded as a kind of electroactive material, whereas humidity is traditionally regarded as a disadvantageous factor, the change of which negatively influences the performance of the IPMC. However, the deformation of the IPMC is greatly sensitive to ambient humidity, and can be enhanced dramatically by changing the humidity. In this study, 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 is continuously recorded under electric field and electric field-moisture coupling stimulus. These results are consistent with the view that the bending properties of the IPMC are a result of the balance of osmotic pressure and electrostatic stress in the membrane, which is greatly dependent on the change of humidity. Therefore, development of the coupling-drive mode is of great significance for the guidance of material design and application for the IPMC.
Ionic polymer-metal composites (IPMCs) generate electrical potential under deformation and can be used as sensors. Recently, Zhu et al. have proposed a sensor model which describes distribution of cations, water molecules and electrical potential under bending deformation. In this paper, we discuss a simplification of the multi-physical sensor model, which is represented by a set of nonlinear partial differential equations. The nonlinear partial differential equations are simplified and approximated into a set of linear ordinary differential equations, i.e., a state-space equation model. At the end, the simplified model is validated by comparing the simulation results with those of the partial differential equation model.
Ionic Polymer-Metal Composite (IPMC) actuators have been attracting a growing interest in extensive applications, which consequently raises the demands on the accuracy of its theoretical modeling. For the last few years, rough landscape of the interface between the electrode and the ionic membrane of IPMC has been well-documented as one of the key elements to ensure a satisfied performance. However, in most of the available work, the interface morphology of IPMC was simplified with structural idealization, which lead to perplexity in the physical interpretation on its interface mechanism. In this paper, the quasi-random rough interface of IPMC was described with fractal dimension and scaling parameters. And the electro-chemical field was modeled by Poisson equation and a properly simplified Nernst–Planck equation set. Then, by simulation with Finite Element Method, a comprehensive analysis on he inner mass and charge transportation in IPMC actuators with different fractal interfaces was provided, which may be further adopted to instruct the performance-oriented interface design for ionic electro-active actuators. The results also verified that rough interface can impact the electrical and mechanical response of IPMC, not only from the respect of the real surface increase, but also from mass distribution difference caused by the complexity of the micro profile.
An ionic polymer material can generate electrical potential and function as a bio-sensor under a non-uniform deformation. Ionic polymer-metal composite (IPMC) is a typical flexible ionic polymer sensor material. A multi-physical sensing model is presented at first based on the same physical equations in the physical model for IPMC actuator we obtained before. Under an applied bending deformation, water and cation migrate to the direction of outside electrode immediately. Redistribution of cations causes an electrical potential difference between two electrodes. The cation migration is strongly restrained by the generated electrical potential. And the migrated cations will move back to the inner electrode under the concentration diffusion effect and lead to a relaxation of electrical potential. In the whole sensing process, transport and redistribution of charge and mass are revealed along the thickness direction by numerical analysis. The sensing process is a revised physical process of the actuation, however, the transport properties are quite different from those of the later. And the effective dielectric constant of IPMC, which is related to the morphology of the electrode-ionic polymer interface, is proved to have little relation with the sensing amplitude. All the conclusions are significant for ionic polymer sensing material design.
Ionic Polymer Metal Composites (IPMCs), as one of the most promising smart materials, can produce a large
deformation for low voltage in the range of 0-5V. Since the materials were found, IPMCs have often been studied as
actuators for their large deformation and inherent flexibility. Recently, IPMCs are applied to the optical lens-driving
system. In this paper, we design miniature optical lens actuators for the focusing requirements. And two kinds of the
driving structure, the petal-shaped and annular structure, are proposed. Then, the preparation processes of IPMCs and the
actuators are presented and five kinds of petal-shaped and annular actuators are manufactured and their performances are
tested, respectively. Finally, the performances of the actuators with different parameters are analyzed by an equivalent
thermal model with FEA software.
A multi-physical model of ionic polymer metal composites (IPMCs) is presented in this paper when they deform under
an applied voltage. It is composed of two parts, which describe the dynamic electro-transport and the large deformation
respectively. The first part describes the ion and water molecule transport, the equations of which are derived using the
thermodynamics of irreversible process. Besides the gradient of the electric potential and the concentration usually
considered in the previous models of IPMCs, the hydrostatic pressure gradient is confirmed to be one of the main factors
induced the mass transport. The second states the eigen strain induced by the redistribution of ion and water molecule
and reveals the stress field from micro to macro scale by the method of micromechanics. The elastic stress balanced with
the eigen-stress including the hydrostatic pressure can influence the distribution of ion and water molecule reversely. To
explore the reasonable mechanisms of the relaxation phenomena, various kinds of eigen-stresses are discussed here and
preliminary numerical results evaluating deformation are given based on the classical Na+ Nafion type IPMC. It's
obtained that the osmotic pressure is an indispensable eigen-stress to explain the complicated deformation.
IPMC was considered as a polyelectrolyte membrane sandwiched between two flat electrodes in most of its theoretical
models. However, structural idealization (ignorance of the interface) may lead to problematic predictions; therefore a
proper model to characterize IPMC structures is expected for a more sophisticated electrochemistry or deformation
theory. This paper proposed a geometrical model for the electroless-plated palladium-electroded IPMC (Pd-IPMC),
where it's treated as a composite containing three distinguished layers: upper electrode, interface layer, and the substrate
membrane. Especially, fractal dimension was adopted to describe the rough contact surface between the upper electrode
and the substrate membrane. And the interface was determined by the volume fraction of the palladium particles. Based
on this model, we estimated the elastic modulus of Pd electrode, and the value was found to be far less than Pd metal.
Furthermore, we estimated the tensile elastic modulus of Pd-IPMC, the result agrees well with the experimental one,
which proved the applicability of the structure model.
The electrode of Ionic polymer-metal composites (IPMCs) is the key to understand their working mechanisms and
mechano-electrical properties; however, there is little experimental report on the electrode morphologies and their
forming mechanisms. In this paper, several typical IPMC samples with different electrode morphologies are fabricated
by combining various process steps. The influence of the process steps, such as roughing treatment, immersing reduction
and chemical plating, on the electrode surface and cross-section morphologies is investigated by SEM study, where the
reaction principles are employed to explain that how the metal particles generate and grow at different directions of the
electrode. The current and deformation responses of the samples are measured at the present of a voltage to characterize
the mechano-electrical properties. Then it is concluded that immersing reduction is only suitable as a pre-deposition
process step, and chemical plating is necessary for IPMC with desirable performance.
In this paper, we study the electro-stress in dielectric elastomer (DE) undergoing large deformation
subjected to a high voltage. The electrostriction is investigated and evaluated by the free-energy model
when the dielectric permittivity does not remain constant in actuation. We investigate the nominal and
true electric fields as the DE stretched with the electrostriction involved or not, and the stable domain
for safe actuation is provided.
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