Ionic Polymer-Metal Composites (IPMCs) are soft actuators, generally referred to as "artificial muscles" which are made out of high polymer gel films of perfluorosulfonic acid chemically plated with gold. These composites bend by applying a low voltage between electrodes on both sides. The actuator is soft and works in water. It bends silently, responds quickly and has a long life. In our previous work, snake-like swimming robots and a 3DOF 2-D manipulator have been developed. In this research we have investigated the bending response of an IPMC artificial muscle in high-pressure water environments, with future applications in deep-sea actuators and robots. The artificial muscles have an advantage over electric motors because they do not need sealing from water, which is difficult in high-pressure water environments. Bending responses of artificial muscles were measured at three different pressure levels, 30MPa, 70MPa and 100MPa. The maximum pressure, 100MPa is the same pressure as the deepest ocean on earth, (10,000m.) From experiments, there was found to be almost no difference with that at normal water pressure of 1Pa. We present detailed results of responses of these artificial muscles including current responses and videos of bending motion with respect to combinations of several different input voltages, frequencies and wave patterns.
Micromechanical model has been developed on the electromechanical response of the ionic polymer metal composites (IPMC). The response function based on the physico-chemical properties of the polymer electrolytes and metals is developed and is applied to that under the control of the electric potential. In the model, the response is attributed to two main effects. One is the electrokinetic effect, that is, the dragged water associated with the flow of counter ion causes the stress in the polymer electrolyte gel. The other is the effect due to the interfacial stress between the polymer electrolyte gel and the electrode. The electromechanical experiments of the IPMC were carried out and their results were compared with the simulation results which were calculated from the response function. The theoretical model can successfully apply to the experimental results, especially to the dependence on the difference of various factors such as ionic change, ionic conductivity, electrode capacitance, dimension of the ionic polymer, etc.
An artificial muscle is an ionic polymer-metal composite (IPMC) which is made out of a high polymer gel film whose surface is plated with gold. Our goal is to realize bio-inspired soft robots, for example, a snake-like swimming robot or multi-degree-of-freedom (DOF) micro-robot manipulator. To realize a snake-like or a multi-DOF bending motion, we cut electrodes on the surface of the actuator in order to control each segment individually. We have developed a variety of motions from this patterned actuator including a snake-like motion. We have also proposed kinematic modeling of the manipulator which simply describes various multi-DOF motions of the artificial muscle. This model is applied to visual feedback control of the manipulator system using a Jacobian control method. For the feedback control, we have developed a visual sensing system using a 1ms high-speed vision system which has a fast enough response to capture the fast actuator motion. We have also made the device swim freely forward and backward by finding the optimal voltage, phase and frequency. In this report, we show some results from simulations of the proposed manipulator control method and experimental results from visual sensing of the bending motion and snake-like swimming of the actuator.