Deivid Pugal

A self-oscillating ionic polymer-metal composite bending actuator

This paper presents an electromechanical model of an ionic polymer-metal composite (IPMC) material. The modeling technique is a finite element method (FEM). An applied electric field causes the drift of counterions (e.g., Na+), which, in turn, drags water molecules. The mass and charge imbalance inside the polymer is the main cause of the bending motion of the IPMC. The studied physical effects have been considered as time dependent and modeled with FEM. The model takes into account the mechanical properties of the Nafion polymer as well as the thin coating of the platinum electrodes and the platinum diffusion layer. The modeling of the electrochemical reactions, in connection with the self-oscillating behavior of an IPMC, is also considered. Reactions occurring on the surface of the platinum electrode, which is immersed into formaldehyde (HCHO) solution during the testing, are described using partial differential equations and also modeled using FEM. By coupling the equations with the rest of the model, ...

Visualization of the cation migration in ionic polymer-metal composite under an electric field

Ionic polymer-metal composites (IPMCs) exhibit a large dynamic bending deformation due to the redistribution of counter-ions inside the polymer. It has not been possible to get the high resolution data of the cation migration. The images obtained so far have only validated the versatile actuation model. The actuation model states that the electrically induced cation movement contributes to the volumetric stress change in the membrane. In this work, a visualization of the cation migration using the fluorescent microscopy is created. The results demonstrated in this letter help to understand the underlying mechanism of the IPMC transduction.

Design of a semiautonomous biomimetic underwater vehicle for environmental monitoring

This paper describes a preliminary prototype of a fishlike biomimetic underwater robot. The goal is to develop a semiautonomous vehicle for environmental monitoring in shallow waters. We describe the vehicle and discuss the environmental factors that have influenced the design. Experimental results illustrate the performance of the prototype.

Self-oscillating electroactive polymer actuator

To drive the electroactive polymer (EAP) materials and subsequently control their strain generation, the need for power electronics and driving circuits has been eminent. In this letter the authors demonstrate a spontaneous actuation of an electroactive polymer that requires only dc power to produce its ac responses. Such a dc-to-ac response of the EAP was achieved by the deposition of an effective electrocatalyst, i.e., platinum, on an ionomer, Nafion™. The coated ionomer was immersed into an acidic formaldehyde solution. An applied dc voltage will produce current oscillations in the system, and therefore oscillating bending of the actuator.

Finite element simulations of the bending of the IPMC sheet

This paper presents a electro-mechanical model of an IPMC sheet. The model is developed using Finite Element method. The physical bending of an IPMC sheet due to the drift of counter-ions (e.g Na+) and water in applied electric field are simulated. Our model establishes a cause-effect relationship between the charge imbalance of the counter-ions and the mechanical bending of the IPMC sheet. The model takes into account the mechanical properties of the Nafion polymer as well as the platinum coating. As the simulations are time dependent, a transient model is used and some additional parameters, such as damping coefficients, are included. In addition to electro-mechanical model, electrochemical reactions are introduced. Equations describing periodic adsorption and desorption of CO and OH on a platinum electrode of an IPMC muscle immersed into formaldehyde solution are coupled to mechanical properties of the proposed model. This permits us to simulate self-oscillatory behavious of an IPMC sheet. The simulation results are compared to experimental data.

An advanced finite element model of IPMC

This paper presents an electro-mechanical Finite Element Model of an ionic polymer-metal composite (IPMC) material. Mobile counter ions inside the polymer are drifted by an applied electric field, causing mass imbalance inside the material. This is the main cause of the bending motion of this kind of materials. All foregoing physical effects have been considered as time dependent and modeled with FEM. Time dependent mechanics is modeled with continuum mechanics equations. The model also considers the fact that there is a surface of platinum on both sides of the polymer backbone. The described basic model has been under developement for a while and has been improved over the time. Simulation comparisons with experimental data have shown good harmony. Our previous paper described most of the basic model. Additionally, the model was coupled with equations, which described self-oscillatory behavior of the IPMC material. It included describing electrochemical processes with additional four differential equations. The Finite Element Method turned out to be very reasonable for coupling together and solving all equations as a single package. We were able to achieve reasonably precise model to describe this complicated phenomenon. Our most recent goal has been improving the basic model. Studies have shown that some electrical parameters of an IPMC, such as surface resistance and voltage drop are dependent on the curvature of the IPMC. Therefore the new model takes surface resistance into account to some extent. It has added an extra level of complexity to the model, because now all simulations are done in three dimensional domain. However, the result is advanced visual and numerical behavior of an IPMC with different surface characteristics.

A Rod-Shaped Ionic Polymer-Metal Composite for Use as an Active Catheter-Platform

“Catheterization” is becoming one of the important medical operations since it engages minimally invasive medical procedures. It is a common practice that a catheter is inserted into body-cavities to administrate diversified medical functions such as diagnosis and surgery. Current method to deal with catheters is based upon the manual mechanisms that are time consuming and, sometimes, involving high risk to the patient. In this work, we explore the use of a promising electroactive polymer (EAP), called ionic polymer-metal composite (IPMC) as a material for use in active catheter-platforms. The configuration of our interest is a rod-shaped IPMC with 2-DOF electromechanical actuation capability. The desired functionality was achieved by fabricating inter-digitated electrodes. Firstly, the 3-D Finite Element (FE) model was introduced as a design tool to optimize the important parameters including electrode configurations. The FE model is based upon the physical transport processes — field induced migration and diffusion of ions. Secondly, based upon the FE modeling we fabricated an initial prototype exhibiting desired electromechanical output. The prototype of rod-shaped IPMC has a diameter of 1 mm and a 20 mm length. We have successfully demonstrated that the 2-DOF bending of the fabricated IPMC is feasible.Copyright

IPMC mechanoelectrical transduction: its scalability and optimization

Ionic polymer‐metal composite (IPMC) mechanoelectrical transduction is described with a system of partial differential equations—the Poisson equation, the Nernst‐Planck equation, and the Navier equations for the displacements. Modeling of this system of four equations is challenging due to the differences in the physical fields—namely, one physical field can be very smooth while others have steeper gradients. When using the conventional finite element method (FEM), the problem size in terms of number of degrees of freedom can be very large. Additionally, it is challenging to find an optimal mesh due to the fact that the physical fields are time dependent. Last but not least, due to the coupled nature of the system, it is necessary to have a way to estimate the error to ensure the desired accuracy of the solutions. In this work, we propose a novel hp-FEM modeling method for solving the system of equations. hp-FEM is a modern version of the FEM that is capable of exponential convergence. It is also demonstrated how the multi-meshing reduces the problem size while maintaining the prescribed error limit. The solution domain that describes IPMC can be scaled without a significant increase in the number of degrees of freedom and solution time. Additionally, PID controller based time step optimization is incorporated. The model is implemented in Hermes, which is a free hp-FEM solver. (Some figures may appear in colour only in the online journal)

IPMC: recent progress in modeling, manufacturing, and new applications

The current paper presents the latest advancements in manufacturing, modeling and applications of ionic polymer-metal composite (IPMC) materials at University of Nevada, Reno. The paper highlights the newest techniques used in making the novel IPMCs. This includes the dimension control and patterning the electrodes so that the multiaxial bending of the material can be achieved. The novel concept of strain sensing and also more energy efficient actuation is discussed. Moreover, we have been working on improving the modeling of IPMC. The focus has been creating a physical model for design purposes. This has lead to developing a first full scale 3-dimensional model of IPMC material. Additionally, electrode effect has been presented and new techniques have been explored to take the Finite Element (FE) modeling of IPMC to the next level.

Modeling the transduction of IPMC in 3D configurations

The Finite Element Analyze (FEA) methods have proven to be applicable for modeling the basic transduction sheets(cantilevers) of ionic polymer-metal composite (IPMC). Physical models can simulate ion transport and corresponding strain. More complicated models also add the effect of the electrode, both surface and electrochemical ones. In this work we propose a FEA model for IPMC materials of different shapes. The new model is three dimensional. When dealing with 3D transduction, the electrode surface geometrical properties of IPMC becomes more important as well. For instance, there are several ways how to attach the electrodes to a cylindrical IPMC to get various deformation modes. The proposed model considers the electrode placement and provides sufficiently accurate transduction estimate for more complicated IPMC structures.