Ryuma Niiyama

An instant color‐changing shield was devised for pneumatic structures. The inspiration from the inflammatory response of the human immune system led to the fabrication of a rapid damage‐detecting and instant repairing system using an exothermal reaction between anhydrous sodium acetate and water. With the addition of a thermochromic pigment, this exothermal behavior was converted into a thermochromic reaction. A mixture of anhydrous sodium acetate and thermochromic solution consisting of water and the thermochromic pigment was quantitatively analyzed for colorimetric and thermographic variations with multiple mixing ratios. Compressive strength using gradually formed sodium acetate trihydrate was measured and evaluated based on the quantity of the thermochromic solution contacted with anhydrous sodium acetate. An X‐ray diffractogram analysis was utilized for the elucidation of the chemical transition from anhydrous sodium acetate powder to aggregated sodium acetate trihydrate particles, which leads to the development of a rigid protective layer for inflatable structures. For a thermochromic shield, a combination of the thermochromic solution and anhydrous sodium acetate powder was prepared in the form of a three‐layered attachable patch and tested with a pneumatically inflatable part. We believe that the adoption of the exothermic and thermochromic reactions for the damage‐detecting and instant repairing system would be able to contribute to further applications for pneumatic structures.

A multipurpose chemochromic protector is proposed with a hydrogel made from a mixture of sodium chloride, starch, and water, and the deposition of a copper layer on the nylon polyethylene film surrounding the hydrogel. This hydrogel is found to be chemically stable, water-retaining, shock-absorbent, biocompatible, cost-effective, and highly reactive with copper enough to realize its chemochromic characteristics. The varying chemical compositions of the hydrogel show that the presence of poly(acrylic acid) (PAA) inside can enhance the damage-detecting and recovery capabilities of the protector. The compressive strength measurement reveals that the hydrogel becomes effectively solidified with the formation of copper chloride and the evaporation of water molecules to cover the damaged areas. In the shear strength experiment, the PAA-included hydrogel is proven to have the high adhesiveness necessary for the recovery of the protector. The damage-detecting and recovery experiment successfully presents the copper-specific chemochromic properties of the protector, implying that the addition of PAA intensifies the color changes of the hydrogel as well as its increased stiffness in the damaged areas. The chemochromically operating surface protector with a simple fabrication process, intuitive measurement, and an alternative working mechanism would be able to promote related studies and contribute to the development of additional protective measures such as for diverse protective clothing, miscellaneous robotic structures, and numerous space applications.

The extension of the lifespan of soft robots necessitates the establishment of an effective self‐healing system accompanied by rapid damage detection. Inspired by the mechanisms of bleeding and blood coagulation, a novel damage‐detecting and self‐healing modular skin is developed for inflatable structures. This alternative structural material is realized using a liquid conductive polymer composed of an elastomer, conductive particles, and a dispersant. Encapsulated in a thin layer, this conductive polymer is found to be capable of both damage detection through generating an electric current and subsequent self‐healing through its solidification in the damaged area. The repeated and reproducible generation of electric current is confirmed both prior to and subsequent to the infliction of damage to the patch. A comparison of conductive polymers with distinct mixing ratios reveals that the changes in electric current following the solidification on the patches are different. The applicability of the modular skins is confirmed by their conduciveness to assembly for various curvatures and larger areas of inflatable structures. The proposed modular skins feature an easy fabrication process, a simple chemical mechanism, and high adaptability to inflatable structures, thus displaying considerable potential for pioneering a new methodology for effective damage detection and self‐healing systems in inflatable robots.

Ostrich neck-inspired manipulators have attracted attention in the field of bio-inspired robotics. They achieve unique movements that are difficult for conventional robots, owing to their flexibility. However, it is difficult to mimic the length, mass, and actuation redundancy of ostrich necks. This is because the longer and heavier the robotic arm, the greater is the load on the joints. Furthermore, if a robotic arm exhibits actuation redundancy, its structure and control become more complex. In this study, we developed a hybrid RobOstrich manipulator with both intrinsic and extrinsic actuations. This is the third-generation of the RobOstrich series. The manipulator consists of a servomotor attached to each joint that performs intrinsic actuation and two servomotors on the base that perform extrinsic actuation through wires. We conducted an experiment to reproduce the rolling pattern, which is a unique movement of the ostrich neck, to verify the effect of hybrid actuation. The results indicated that the joint angle error and required torque were reduced by applying hybrid actuation.

Safe physical human-robot collaboration is possible with soft robots due to their inherent compliance and low inertia. Soft bodies inherently possess passive compliance, providing adaptability in collaborative tasks because of their deformations; however, the same features add complexity to modeling and dynamic control. We focus on motion generation for a 3 degrees of freedom (3DOF) inflatable robot arm, which consists of soft inflatable body links and rigid joints. This research explores the limitations of relying solely on soft robot compliance for completing contact-based tasks. Our goal is to generate adaptive motion for contact-based tasks by exploiting the compliance of soft links. We compare contact-based tasks involving an inflatable robot with and without a learning model. Improved performance is achieved when soft robot compliance is augmented with imitation learning. The combination of soft robot compliance and the adaptability of the machine learning model demonstrates the potential for collaborative robots to safely interact with humans and their surroundings.

Extra or supernumerary robotic limbs are actively exploited in the field of body augmentation. The science of self-recognition of additional body parts is an interesting subject. Although the field is primarily led by psychological studies in virtual reality, which facilitate flexible experimental designs, we believe that assessments employing real robots are also essential. In this study, we investigated the sense of body ownership and agency of a dual-arm wearable robotic arm using an inexpensive and safe inflatable structure. We report the results of functional near-infrared spectroscopy (fNIRS) analysis of brain activity during the use of the robotic arm. The questionnaire results from the experiment, which involved a button-touching task, revealed that both the sense of ownership and sense of agency were significantly higher in the goal-oriented collaborative experience compared to the non-goal-oriented condition. This indicates that humans feel ownership of and agency toward an autonomous robot or a remote-controlled robotic arm operated by another person. The analysis of the fNIRS data included a two-factor analysis of variance for the learning and trial phases. While there was no main effect for the conditions within each phase, a significant interaction was observed between the two brain regions of the right angular gyrus and right postcentral gyrus.