Effect of Thermal Treatment on Preshaped Ionic Polymer Metal Composite (IPMC) Actuators

Compact structure, multifunction, and flexibility are normally considered as incompatible characteristics for legged microrobots. Most robots focused on complex structure of multi-joint legs to attain the multifunction and flexibility, while others had poor flexibility for miniaturization. In the field of underwater monitoring for applications such as pollution detection and video mapping in limited space, underwater microrobots are urgently demanded. To realize these purposes, we have developed several types of microrobots with both compact structure and flexible locomotion. However, they just realized walking, rotating, swimming, or floating motions. Without biomimetic fingers, they could not do some simple operations, such as grasping and carrying any objects to desired place. So, in this paper, we designed a novel type of biomimetic locomotion employing ionic polymer metal composite (IPMC) actuator as one-DOF leg. Then we proposed a new type of underwater microrobot using ten ionic polymer metal composite (IPMC) actuators as legs or fingers, which could realize walking, rotating, floating, and grasping motions. Also, we developed a prototype of this underwater microrobot and carried out some experiments to evaluate its walking and floating speeds. In addition, we used six IPMC actuators as fingers to grasp some small objects and float up. To realize the closed-loop control for the microrobot, we used three proximity sensors to detect and avoid the obstacle while walking.

Identification of an ionic polymer metal composite actuator employing Preisach type fuzzy NARX model and Particle Swarm Optimization

Underwater microrobots are in urgent demand for applications such as pollution detection and video mapping in limited space. Compact structure, multi-functionality, flexibility, and position precision are normally considered incompatible characteristics for underwater microrobots. To accomplish our objectives, we developed several novel bio-inspired biomimetic locomotions with ionic polymer metal composite (IPMC) actuators. IPMC actuator could implement a fast response and high bending deformation, which could be used as artificial muscles to propel robots backwards and forwards with a compact structure. To implement the position precision of IPMC actuator, we proposed an electromechanical model and analyzed the deformation and actuating force of the IPMC equivalent cantilever beam, which were used for the biomimetic locomotion. Then a conventional PID controller for IPMC actuators was designed from the identified model. Based on the IPMC equivalent cantilever beam model, we developed several kinds of underwater microrobots with the compact structure, multi-functionality, flexibility, and position precision.

For the first time, the ionic polymer metal composite (IPMC) actuator is integrated with a radio frequency identification (RFID) tag antenna for achieving frequency reconfiguration in the ultrahigh-frequency (UHF) band. Here, the IPMC movable flap serves as an actuator that can effectively tune the tag resonant frequency. By applying a two-layer-crenelated structure and employing a surface patterned electrode for restraining back relaxation, the deflection of the IPMC actuator can be significantly improved. The IPMC actuator can move in two directions, enabling two-degree frequency tuning. Numerical and experimental data confirm that the tip displacement of the IPMC actuator can be enhanced up to 266% with the use of the two-layer-crenelated structure. The IPMC actuator allows the resonant frequency of the tag antenna to be tuned back by as much as 35 MHz, after deviating due to placing on an unintended object. UHF RFID application is also performed using a portable commercial RFID reader. Good frequency reconfiguration and broad tuning range, along with far read distances, have been achieved with our tunable UHF RFID tag antenna.

Mechanics and electrochemistry of ionic polymer metal composites

Predicting of electro-mechanical behavior of ionic polymer metal composites (IPMCs) is important in many actuator design applications, but a general model for such predictions has not been successfully developed yet. A simple but versatile modeling method based on the concentrated ion boundary layer model was developed to advance the modeling of the bending behavior of IPMCs of different sizes. IPMC beams with different thicknesses and sizes were fabricated by stacking and hot-pressing method, and their mechanical bending characteristics were measured. Finite element analysis of the beams was performed using a concentrated ion boundary layer model that uses a thermal analogy. The calculated deformation and tip blocking force agreed well with the measured values for specimens of different sizes. This study shows that the proposed modeling method is simple but general enough to simulate the deformation characteristics of IPMC actuators of various sizes.

The ionic polymer metal composite (IPMC) actuator is one of the most promising smart actuators that possesses unique advantages and is suitable for underwater applications. However, there are challenges to employ it directly in such applications for precise tracking. The IPMC suffers from high nonlinearity due to the existence of inherent creep and hysteresis phenomena. Furthermore, the IPMC actuator is always subject to uncertainty and external disturbance due to the working environment. Therefore, to cope with the aforementioned restrictions and to make the IPMC applicable for real-life applications, designing a high-accuracy tracking control technique is an urgent demand. In this article, a new integral nonlinear hyperplane-based sliding mode controller is dedicated for an underwater IPMC actuator. The proposed controller employs an adaptive tuning law in the discontinuous part to overcome any prerequisite for knowing the upper bound of the model uncertainty and external disturbance. Extensive experiments have been carried out to verify practical effectiveness of the proposed controller in comparison with conventional nonsingular terminal sliding mode in terms of fast convergence, accurate tracking, and the robust performance.

This paper presents dynamic modeling of an innovative contractible ionic polymer-metal composites (IPMC) actuator with a helical configuration. The helical shaped IPMC actuator is fabricated through the thermal treatment of an IPMC strip, which is helically coiled on a glass rod. This type of a soft actuator can be used to realize not only bending motion but also torsional and longitudinal motion. For the first time, an explicit analytical expression is developed for the computation of mode shapes and dynamic responses of a helical IPMC actuator based on the intrinsic equations of the naturally curved and twisted beam. The numerical transfer-matrix method is used to solve the systems of 12 linear ordinary differential equations with boundary conditions. In particular, the effect of the structural parameters on the performance of the helical IPMC actuator is evaluated, using experimental results and an analytical model. The validation of the proposed model is achieved through comparison with computational results using a commercial finite-element (FE) program as well as experimental results. The present experimental and theoretical results show that diameter, among the structural parameters, plays an important role in the actuation performance of a helical IPMC actuator. The proposed modeling is general and can also be used in solving other cylindrical or noncylindrical helical IPMC actuators with different cross-sectional shapes as well as various end conditions.

An ionic polymer-metal composite (IPMC) actuator is one of polymer-based soft actuators. It is produced by chemically plating gold or platinum on both surface of a perfluorosulfonic acid membrane which is known as an ion-exchange membrane. It is able to be activated by a simple driving circuit and generate a large deformation under a low applied voltage (0.5-3 V). However, individual difference and characteristics changes from environmental conditions should be considered for realizing a stable or precise control. To solve these problems, we applied a stochastic ON/OFF controller to an integrated IPMC actuator with parallel connections. The controller consists of a central controller and distributed controllers. The central controller broadcasts a control signal such as an error signal to distributed controllers uniformly. The distributed controllers switch the ON/OFF states based on the broadcasted signal stochastically. The central controller dose not measure the states of each IPMC actuator, and the control signals is calculated by using the output signal of the integrated actuator and reference signal. The validity of the applied method was investigated through numerical simulations and experiments.

This paper reports a microreservior-based drug delivery device that is activated by ionic polymer metal composite (IPMC) actuator. The actuator is fabricated with Nafion 117 membrane and plated with silver layer electrodes. To fit with biocompatible properties, the device body, including the drug reservoir, was constructed using polydimethylsiloxane (PDMS) material. Experimental measurement of the fabricated IPMC actuator shows a maximum deflection displacement of 0.076 ~ 0.077 mm at two consecutive actuation cycles. To study the concentration of the drug released from the developed device, fluorescent dye was loaded in the reservoir and the released intensity was measured using well plate reader. An increase of the fluorescent intensity shows that IPMC actuator successfully unseals the microreservoir and achieves the targeted application.

Ionic Polymer Metal Composite (IPMC) actuators have shown promise as miniature underwater propulsors due to their high flexibility, reduced weight, and low activation voltage and power consumption. In this second of two papers, we discuss numerical simulations of the flow of a viscous fluid generated by a two-dimensional cantilever IPMC actuator vibrating along its fundamental mode shape. We compute the thrust produced by the actuator as a function of its oscillation frequency and maximum tip displacement and show that it is correlated to vortex shedding. We find that vorticity production is prominent at the IPMC tip and increases as the oscillation frequency increases. We analyze the lateral force and the moment exerted by the IPMC on the surrounding fluid. Further, we study the power transferred by the vibrating IPMC to the encompassing fluid. The findings are validated via comparison with the experimental results presented in part 1 of this series.

In the present paper, equivalent beam and equivalent bimorph beam models for IPMC(ionic Polymer-Metal Composite) actuators are described. Physical properties of an IPMC, such as Young's modulus and electro-mechanical coupling coefficient. are determined from the rule of mixture, bimorph beam equations, and measured force-displacement data of a cantilevered IPMC actuator. By using a beam equation with estimated physical properties, actuation displacements of a cantilevered IPMC actuator was calculated and a good agreement between the computed tip displacements and the measured data was observed. Finite element analysis(FEA) combined with the estimated physical properties was used to reproduce the force-displacement relationship of an IPMC actuator. Results from the FEA agreed well with the measure data. The proposed models might be used for modeling of IPMC actuators with complicated shapes and boundary conditions.

Simple and highly efficient microvalve systems based on an ionic polymer-metal composite (IPMC) diaphragm actuator have been developed. The microvalve system that was fabricated in this work operates when open and close voltage is applied, due to the phenomena of lithium ion flux and the subsequent electro-osmotic drag of water to the cathode. IPMC was prepared by compositing with platinum nanoparticles on both sides of Nafion thin film. SEM images of the IPMC showed the high density and uniform size distribution of the Pt nanoparticles in the interpenetrating layer to ensure the proper performance of an IPMC actuator. The displacement of the IPMC for the microvalve was measured with a laser displacement meter. The application of open and close voltage made the operation of the valve faster. The fluorescence images of the flow in the fabricated IPMC-based microvalve system showed the successful operation of flow control in the microfluidic channel. The IPMC-based microvalve system shows a potential of IPMC for application as an actuator in microfluidic systems.

Ionic Polymer Composite Material (IPMC) is a flexible material and has revealed many advantages to encourage the scientists and researchers to investigate its characteristics for practical applications in various fields. The ongoing research can be divided into two branches. One deals with the improvement of the material properties to make it more useful and reliable while the other involves the exploration of new application areas. In this paper, Firstly, a new application of IPMC is suggested to actuate a rigid link that can mimic a bionic knee joint for a grass hopper manipulator. Secondly, forward kinematic model is proposed for the manipulator by employing geometric coordinate system method. Lastly, wolfram mathematica software is employed for the simulation of the model. The simulation results based on the model are found very encouraging to lure the article team to carry on the research idea for manufacturing and testing for the comparison of both types of results.

In this paper, model-based precision force and position control of an ionic polymer metal composite (IPMC) is presented. A 23.8 mm × 3.4 mm × 0.16 mm IPMC strip was used as an actuator in a cantilever configuration. Open-loop force and position responses of an IPMC are not repeatable, and hence closed-loop precision control is of critical importance to ensure proper functioning, repeat-ability and reliability. After feedback controllers were designed and implemented with empirically obtained fourth-order plant transfer functions, the overshoot decreased from 460 to 2.8 per cent and the settling time was reduced from 37.5 to 3.22 s in force control. In position control the overshoot decreased from 333 to 20.3 per cent and the settling time was reduced from 21.5 to 2.56 s. Microscale precision force and position control capabilities of the IPMC actuator were also demonstrated experimentally. An 8 μN force resolution was achieved with a force noise of 0.5μN r.m.s., and the position resolution was 6 μm with a position noise of 2.5 μm r.m.s. The maximum force and tip displacement achieved with the IPMC actuator under closed-loop control were 2 mN and 5 mm respectively. The IPMC actuator could follow various commanded force and position trajectories such as sinusoidal and trapezoidal position profiles, and a velocity profile with a 3 mm/s maximum velocity. A novel hybrid force and position control strategy demonstrated its utility in practical micromanipulalion applications where the actuator force must be limited to prevent damaging micro-objects. High-precision control of the IPMC at low force level proved its potential for micromanufacturing and micromanipulation applications such as robotic and biomedical microgrippers.