Ionic polymer-metal composites (IPMC) actuators are popular because they can be driven at a low voltage, possess excellent responsiveness, and can perform soft motions similar to that of living creatures. Conventional IPMC soft robots are manufactured by cutting and assembling IPMC sheets. However, using this conventional process to stably manufacture three-dimensional (3D)-shaped soft robots is difficult. To mitigate this problem, we propose a new method for fabricating 3D IPMC actuators in which several surface electrodes are separately fabricated from a single ion-exchange membrane. We refer to our proposal as the simultaneous 3D forming and patterning (SFP) method. Unlike the conventional IPMC fabrication process, the SFP method requires only one step to fix the ion-exchange membrane to contact masks. First, we briefly describe IPMC actuators, before introducing the proposed SFP method in detail. Next, we describe our investigations of the patterning resolution for the surface electrode using the proposed method. We fabricated two soft robot prototypes using the proposed method. The first robot is a starfish-type soft robot. Its surface electrode can be patterned in a plane using the proposed method, and independent driving is possible by applying voltage individually to the divided electrodes. The second prototype is a sea anemone-type soft robot, wherein surface electrodes can be patterned on a 3D curved surface to form a 3D shape.

Among the various pneumatic actuators, thin McKibben muscles are particularly attractive owing to their high performance in terms of high contraction ratio, high flexibility, and productivity. One of the challenges for thin McKibben muscles and other pneumatic actuators is the fact that they generally need air hoses and air sources like compressors. This necessarily leads to bulky systems. To solve this problem, we propose and study a new approach to driving pneumatic actuators that exploits electrolysis/synthesis of water by a polymer electrolyte fuel cell (PEFC). This method could in-principle have high applicability to thin McKibben muscles. However, one challenge must still be addressed for the realization of an electrically driven thin McKibben muscle: the development of a tube-shaped soft PEFC. This paper proposes an electrically driven thin McKibben muscle with a tube-shaped soft PEFC realized through a flowing non-electrolytic plating method. First, the proposed thin McKibben muscle is briefly described. Then, a novel method for plating a tube-shaped soft PEFC using reflux is introduced, and its fundamental operation is tested. After the evaluation of the PEFC, we report a prototype realization of the proposed thin McKibben muscle. The developed prototype has a length of over 170 mm, a diameter of 4 mm, and high flexibility for bending. Finally, we elaborate on a driving experiment through which fundamental characteristics were experimentally evaluated. The prototype thin McKibben muscle succeeded in electrically controlling contraction and expansion motion with a flexible and bendable structure.

Ionic polymer-metal composite (IPMC) actuators are expected as artificial muscles for bio-mimetic soft robots. The IPMC gel first bends quickly and then bends back slowly when a constant voltage is applied to the sample. The latter phenomenon, referred to as the stress relaxation, can be modeled by electrostress diffusion coupling theory. The theory can predict the behavior of the actuator for the different species of counterions. In order to describe the actuator dynamics as a system with inputs and outputs, this paper proposes a linear state space model based on the electrostress diffusion coupling theory. The model consists of the three systems, the electrical, the electro-mechanical, and the mechanical systems. The results of the simulation and the experiment demonstrate the validity of the model.

Bucky gel actuator is a novel electro-active polymer (EAP), which is a low-voltage driven dry soft actuator. Its device has a bimorph structure with polymer-supported bucky gel electrodes and a polymer-supported ionic gel electrolyte. It can be fabricated by layer-by-layer casting, to form any shape easily. In addition, the bucky gel device generates electromotive force when bending, and then it also can be used as a sensor. Since sensor and actuator functions exist in a same device, flexible and miniature integrated actuator-sensor systems for soft robotics can be constructed easily. In this study, we conduct some experiments to verify the possibility of the bucky gel actuator/sensor. Feedback controls of the actuator are demonstrated and the characteristics of the sensor are investigated. By utilizing both functions of the actuator and the sensor, feedback control based on the sensor signal is demonstrated.

We constructed a snake-like swimming robot using IPMC actuator, and verified swimming motion based on numerical simulation and experiments. In applying periodic inputs with appropriate frequency and phase shift, the snake-like robot is capable of smooth propulsion. It is known that IPMC has a sensor function that IPMC films generate electromotive voltage when bending or being deformed. By using the sensor function into the snake-like robot, it is considered that autonomous propulsive motion can be realized by feedback of the sensor signal. In this paper, we consider the autonomous locomotion of the snakelike swimming robot with IPMC actuator/sensor, and verify the realization of swimming motion by feedback of the sensor signal. Furthermore, the efficiency of the autonomous locomotion is investigated

We are studying about robotic application of ionic polymer-metal composite (IPMC). The characteristics of IPMC highly depend on the type of counter-ions, and it is considered that the performance of the actuators can be improved by combining the actuators with several types of counter-ions and applying an integrated control. IPMC has also a sensor function, as the IPMC film generates electromotive force when it is deformed. It has possibility to be integrated into IPMC actuator with soft actuation. In this paper, we consider an integrated design of IPMC actuator/sensor, and investigate a control of the combined IPMC actuators using Hinfincontrol and the construction of IPMC sensor system

In the medical field and in industry application, a novel type of micro biped robot with multi DOF that can swim smoothly in water or aqueous medium has urgently been demanded. The fish-like microrobot is one of the micro and miniature devices, which is installed with sensing and actuating elements. This paper describes the new structure and motion mechanism of a hybrid type of underwater microrobot using ICPF actuator, and discusses the swimming and floating possibility of the microrobot in water. Characteristic of the underwater microrobot is measured by changing the frequency and the amplitude of input voltage. The experimental results indicate that the swimming speed of proposed underwater microrobot can be controlled by changing the frequency of input voltage; the moving direction (upward or downward) can be controlled by changing the amplitude and the frequency of input voltage

Ionic polymer-metal composite (IPMC), which is one of the electro-active polymer actuators, is expected as artificial muscles for robots. An interesting property of IPMC is that it requires water to work, therefore it is suitable for underwater robots. In this paper, we developed an underwater robot which mimics rajiform swimming, that is the swimming form of a ray fish. Fins are designed using sixteen IPMCs. For autonomous operation, miniaturization of the electrical devices such as a micro controllers and small amplifiers are performed. A simple traveling wave control input is employed to generate moment on the fin. In the experiment, propulsion speed is measured under various control parameters. Furthermore, incremental wave of the fin is observed although the amplitude of the control input is spatially uniform. We also discuss this phenomenon from the point of view of interaction between elasticity of the actuator and fluid dynamics

In this paper, to deal with the locomotion in underwater environment, we designed a novel type of leg, inspired by stick insect legs. The biomimetic leg is composed of two segments of ICPF (ionic conducting polymer film) actuators with a 2-DOF motion. It has simple structure, simple control method, and good localization characteristic. We designed and developed a prototype microrobot with 3 units of the legs. The dimension of the microrobot is 48*20*17 mm3and its dried weight is 0.65 g. We have measured the speeds with different control signals. The experimental results show that it can arrive at a speed of 4.7 mm/s with a control signal of 5 Hz and 10 V. And results indicate that the novel type leg has a good speed performance and localization in aquatic environment. The microrobot using ICPF actuators has powerful applications in the biomedical and naval fields

We describe a two-dimensional (2-D) multi-degree-of-freedom (DOF) robot manipulator made from a soft polymer gel actuator, which we call an artificial muscle. The independent voltage control of three segments of patterned electrodes on the artificial muscle enables independent partial bending motions of each segment and realizes a multi-DOF control of the manipulator. We introduce the kinematic modeling of these multi-DOF bending motions and propose visual feedback control of the artificial muscle. For high-speed visual feedback, we have developed a visual sensing system with a 1ms sampling rate. Finally, we show the experimental results of the visual sensing and kinematic modeling of the bending motions of the manipulator.

Ionic polymer metal composite (IPMC) is one of the most promising EAF actuators for applications, and slave good property of response and durability. The characteristics of IPMC materials depend on a type of counter ion. In applying to mechanical systems such as a robot, there exist possibilities to change the properties of the dynamics by changing the counter ions according to environment or purpose adequately. In this paper, we consider swimming of a snake-like robot with IPMC actuator, and demonstrate a smooth swimming motion. Then, we also verify the doping effects by experiments.

In the medical field and in industry application, a new type of a novel type of micro biped robot with multi DOF that can swim smoothly in water or aqueous medium has urgently been demanded. The fish-like microrobot is one of the micro and miniature devices, which is installed with sensing and actuating elements. This paper describes the new structure and motion mechanism of an underwater microrobot using ICPF actuator, and discusses the swimming possibility of the microrobot in water. Characteristic of the underwater microrobot is measured by changing the frequency and the amplitude of input voltage. The experimental results indicate that the swimming speed of proposed underwater micro robot can be controlled by changing the frequency of input voltage; the moving direction (upward or downward) can be controlled by changing the amplitude and the frequency of input voltage.

In this paper, we propose a new prototype model of a micro pump using ICPF (Ionic Conducting Polymer Film) actuator as the servo actuator. This micro pump consists of two active one-way valves that make use of the same ICPF actuator. The overall size of this micro pump prototype is 12 mm in diameter and 20 mm in length. The actuating mechanisms are as follows: (1) the ICPF actuator as the diaphragm is bent into anode side by application of electricity. Then the volume of the pump chamber increases, resulting in the inflow of liquid from the inlet to the chamber; (2) by changing the current direction, the volume of the pump chamber decreases, resulting the liquid flow from the chamber to the outlet; and (3) the ICPF actuator is put on a sine voltage, the micro pump provides liquid flow from the inlet to the outlet continuously. Characteristic of the micropump is measured. The experimental results indicate that the micro pump has the satisfactory responses.

It is our purpose to develop an underwater microrobot that has the characteristics of flexibility, driven by a low voltage, good response and safety in body. We propose a prototype model of an underwater microrobot utilizing an ICPF (ionic conducting polymer film) actuator as the servo actuator to realize swimming motion with 3 DOF. A biomimetic fish-like microrobot using an ICPF actuator as a propulsion tail fin and a buoyancy adjuster for a microrobot swimming structure in water or aqueous medium has been developed. The overall size of the underwater microrobot prototype shaped as a fish is 45mm in length, 10 mm in width and 4 mm in thickness. There is a pair of fins and a buoyancy adjuster. The characteristics of the underwater microrobot is measured by changing the frequency and amplitude of input voltage. The experimental results indicate that the swimming speed of the proposed underwater micro robot can be controlled by changing the frequency of input voltage; the moving direction (upward or downward) can be controlled by changing the amplitude and the frequency of input voltage.