In this paper, we examine the development of tailored 3D-structured (engineered) polymer-metal interfaces to create enhanced ionic polymer-metal composite (eIPMC) sensors towards soft, self-powered, high sensitivity strain sensor applications. First, a physics-based chemoelectromechanical model is developed to predict the sensor behavior of eIPMCs by incorporating structure microfeature effects in the mechanical response of the material. The model incorporates electrode surface properties, such as microscale feature thickness, size and spacing, to help define the mechanical response and transport characteristics of the polymer-electrode interface. Second, two novel approaches are described to create functional samples of eIPMC sensors using fused deposition manufacturing and inkjet printing technologies. Sample eIPMC sensors are fabricated for experimental characterization. Finally, experimental results are provided to show superior performance in the sensing capabilities compared to traditional sensors fabricated from sheet-form material. The results also validate important predictive aspects of the proposed minimal model.

Underwater robots with buoyancy control capability are highly desirable in deep ocean exploration for underwater environment monitoring and intelligent collection. In this paper, a prototype of buoyancy control device powered by ionic polymer metal composite (IPMC) is developed. An IPMC is used for enhancing the water electrolysis of tap water and separating the gases produced. The produced hydrogen and oxygen gases are stored in two separate chambers. Collection of these gases increase the volume of water displaced by the device, hence, increases its buoyancy. Two solenoid valves are used to control the release of gases to decrease the device’s buoyancy. Using a dynamic model developed in our previous work, the parameters of the model are identified through an open-loop test. A PID controller is then designed for close-loop depth control. The PID controller uses the error in depth to estimate the desired gas generation/releasing rate. It then calculates the duty cycle of the pulse-width modulation (PWM) signal used for driving the solenoid valves. The closed-loop depth control is verified both through simulation and real-time experiment, showing satisfactory results.

For the development and application of various robots, researchers have been looking for adequate materials for external structures and actuators. Ionic polymer metal composite (IPMC), is a type of ionic electroactive polymer (EAP), and this material can exhibit large deflection with low external voltages (∼5 V). This smart material can work in an aquatic environment without the impact from the aquatic pressure, so a swimming robot is one of popular applications of IPMC. Recently, several models in various methods have been found to simulate output deflection. For example, some typical models based on cantilever beams or system identification tools have been used to provide models of IPMC systems. In this paper, however, an electrical model with equivalent passive elements based on existing internal properties is introduced in order to model the system directly. On the other hand, the surface metallic electrodes and the internal Nafion ® membrane can be modeled as equivalent resistors according to the properties. Finally, a novel linear time-variant (LTV) modeling method that is different from conventional models is introduced and applied to an IPMC electrical model, built on the basis of the internal environment such as surface resistance, thickness, and water distribution related to the unique working principle of IPMC. Eventually, most of the equivalent elements will change with time in operation, so this electrical model will be revised and describe the entire system more accurately.

Ionic polymer metal composite (IPMC), categorized as an ionic electroactive polymer (EAP), can exhibit conspicuous deflection with low external voltages (∼5 V). This material has been commonly applied in robotic artificial muscles since reported in 1992 because it can be fabricated in various sizes and shapes. Researchers developed numerous IPMC models according to its deflection in response to the corresponding input stimulation. In this paper, an IPMC strip is modeled (1) as a cantilever beam with a loading distribution on the surface, and (2) with system identification tools, such as an autoregressive with exogenous (ARX)/autoregressive moving average with exogenous (ARMAX) model and an output-error (OE) model. Nevertheless, the loading distribution is non-uniform due to the imperfect surface conductivity. Finally, a novel linear time-variant (LTV) modeling method is introduced and applied to an IPMC electrical model on the basis of the internal environment such as surface resistance, thickness, and water distribution related to the unique working principle of IPMC. A comparison between the simulated and the experimental deflections demonstrates the benefits and accuracy of the LTV electrical model.

Low power consumption and activation voltage combined with high flexibility and minimal weight make Ionic Polymer Metal Composites (IPMCs) well-suited for miniaturized underwater propulsion systems. In this series of papers, we comprehensively discuss the flow field induced by an IPMC strip vibrating in a quiescent aqueous environment by performing complementary physical experiments and numerical simulations. The experimental results are presented in this paper. Planar particle image velocimetry is used to measure the time-averaged flow field of a vibrating IPMC. The momentum transferred to the fluid is computed to estimate the mean thrust generated by the vibrating actuator. We find that the mean thrust increases with the Reynolds number, defined by the maximum tip speed and IPMC length, and is only marginally affected by the relative vibration amplitude. Detailed understanding of the flow environment induced by a vibrating IPMC can guide the optimization of IPMC-based propulsion systems for bio-mimetic robotic swimmers.

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.

Reported are advances made in connection with modeling of ionic polymeric metal composite (IPMC) plates undergoing large deformation under an imposed dynamic electric field. Analysis, design and prototyping of sensing or/and actuating plates made with IPMCs requires analytical models of the utilized materials and structures. This paper presents recent advances made towards the development of a computational implementation of a general theory for describing such systems in a way that allows accurate prediction of their behavior within their state space. Continuum mechanics, irreversible thermodynamics, and electrodynamics are utilized to derive the general four dimensional multi-physics field equations of materials used for artificial muscle applications. These applications are particularly important in terms of creating data sheets, thin data keyboards as well as flat speakers made with IPMC plates. The system of governing partial differential equations describing the state evolution of large deflection IPMC plates is derived. The system of these electro-hygro-thermally modified Von-Karman non-linear equations are solved numerically through an adaptive finite element approach through perspectives of geometrical and material nonlinearities. The preliminary results are presented for the case of finite deformation of an IPMC plate.

In this paper, we study the free-locomotion of a miniature bio-mimetic underwater vehicle inspired by carangiform swimming fish. The vehicle is propelled by a vibrating Ionic Polymer Metal Composite (IPMC) attached to a compliant passive fin. The IPMC vibration is remotely controlled through the vehicle’s onboard electronics that consists of a small-sized battery pack, an H-Bridge circuit, and a wireless module. The planar motion of the vehicle body is described using rigid-body dynamics. Hydrodynamic effects, such as added mass and damping, are included in the model to enable a thorough description of the vehicle’s surge, sway, and yaw motions. The time-varying actions exerted by the vibrating IPMC on the vehicle body, including thrust, lift, and moment, are estimated by combining force and vibration measurements with reduced order modeling based on modal analysis. The model predictions are validated through experimental results on the planar motion of the fish-like robotic swimmer.