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The annelid provides a biological solution of effective locomotion adaptable to a large variety of unstructured environmental conditions. The undulated locomotion of the segmented body in the annelid is characterized by the combination of individual motion of the muscles distributed along the body, which has been of keen interest in biomimetic investigation. In this paper, we present an annelid-like robot driven by soft actuators based on dielectric elastomer. To mimic the unique motion of the annelid, a novel actuation method employing dielectric elastomer is developed. By using the actuator, a three-degree-of-freedom actuator module is presented, which can provide up-down translational motion, and two rotational degree-of-freedom motion. The proposed actuation method provides advantageous features of reduction in size, fast response and ruggedness in operation. By serially connecting the actuator modules, a micro-robot mimicking the motion of the annelid is developed and its effectiveness is experimentally demonstrated.

This paper presents a comprehensive review of the use of ionic polymer-metal composite (IPMC) materials as mechanoelectrical transducers. Recently increasing emphasis has been put on the research of IPMCs as displacement or velocity sensors for various applications. This has resulted in various theories and models to describe the mechanoelectrical transduction phenomenon. The paper gives an overview of the proposed transduction principles, developed models and the latest applications. In more detail, the history of IPMC materials, the physics and the electrochemistry behind the mechanoelectrical transduction, different black-box and gray-box models, and novel real-world mechatronics-related applications are discussed throughout the paper. However, despite the latest advancements in the research of IPMC transduction, there is still a certain amount of controversy regarding some of the IPMC sensorial properties. For instance, it has been noticed by several authors that there is a signal delay when bending an IPMC. The general understanding of the physical principles about regular IPMC mechanoelectrical transduction is rather good. In the last section of the paper novel results are presented for copper-coated IPMC materials. Apparently the electrochemistry behind the transduction for copper-coated IPMCs is significantly different. Besides ionic diffusion, chemical reactions on the electrodes also occur and dominate the actuation process. Experimental results show some promising opportunities for designing new copper-coated IPMC-based sensors.

Among ElectroActive Polymers(EAPs) the dielectric elastomer actuator is regarded as one of the most practically applicable in the near future. So far, its effect on the actuation phenomena has not been discussed sufficiently, although its strong dependency on prestrain is a significant drawback as an actuator. Recent observations clarifies that prestrain has the following pros and cons: prestrain plays an important role in generating large strain, whereas it rather contributes to the reduction of the strain. Prestrain provides the advantages of improving the response speed, increase of the breakdown voltage, and removing the boundary constraint caused by the inactive actuation area of the actuator. On the contrary, the elastic forces by prestrain makes the deformation smaller and the induced stress relaxation is severely detrimental as an actuator. Also, the permittivity decreases as prestrain goes up, which adds an adverse effect because the strain is proportional to the permittivity. In the present work, a comprehensive study on the effects of prestrain is performed. The key parameters affecting the overall performances are extracted and it is experimentally validated how they work on the actuation performance.

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