Shunsuke Nagahama

Signal transmission with magnetic powdery wire in a pipeline

In this paper, we discuss a signal transmission function of an artificial circulatory system. We proposed a biomimetic circulatory system so as to imitate the homeostatic function of the human circulation system [1]. The following blood functions were imitated in the system: (1) clotting, (2) energy supply, and (3) motor cooling. However, the circulatory system has other functions, for example, signal transduction by hormones. Thus, we propose adding a signal transmission function to our artificial circulatory system. The proposed function was realized with iron powder and a magnetic field. Particles of iron powder aligned along the direction of the magnetic field lines and formed as a wire. We defined this as a magnetic powdery wire (MPW). The MPW has a self-repairing function. When the wire collapsed, iron powder was transferred to the MPW, and it was repaired. As a result of a signal transmission experiment, we confirmed that the pulse signals were transmitted properly. In the experiment, we observed a time lag in the rise time and fall time on the pulse waveforms. We hypothesized that this was because the wire consisted of iron powder, and the magnetic field became similar to that of a coil. As a result of the self-repairing experiment, we confirmed that the wire repaired itself after being broken and transmitted pulse signals properly. These results demonstrate that our system is able to transmit information and self-repair with iron powders and a magnetic field. Additionally, the observed phenomenon will be the basis for a new device.

The development of magnetic powdery sensor

In this work, we developed a contact-type displacement sensor called the magnetic powdery sensor (MPS) that consists of magnets and iron powder. The self-repairing functions of the components of robots, such as wires, sensors, and actuators, have an important role in extending the life of robots. To realize the self-repairing functions of such components, we proposed a magnetic powdery wire (MPW) in our earlier research. The success of this study led us to consider other components of robots where the repairing mechanism could to be applied, leading to the development of the MPS. The key features of the MPS are its simple structure and self-repairing capability. The MPS is implemented with two sets of parallel Acrylonitrile-Butadiene-Styrene (ABS) plates with a magnet fixed at the center. The distance between the plates varies between 7 mm and 23 mm, and their magnetic fields are in the same direction. We implemented the MPS by dispersing iron powder between the plates. The resistance decreases as the distance between the plates reduces. Through experimental results, we confirmed that the displacement can be measured by the MPS and that the MPS has self-repairing capability. As the sensor part of the MPS is composed of iron powder, it can be repaired in the same way as the MPW. These results demonstrate that the life of the magnetic powdery displacement sensor can be extended.

Synthesis of high-strength and electronically conductive triple network gels with self-healing properties by the restraint method

In this study, we synthesized a self-healing electrically conductive gel based on Agar/hydrophobically associated polyacrylamide (HPAAm) by a restraint-assisted method. Recently, self-healing conductive materials based on such gels have been widely researched. However, as gels are generally weak, the gel-based materials are also often low in strength. Therefore, in this study, we applied the restraint method for adding pyrrole to Agar/HPAAm, which is a self-healing high-strength gel. The synthesized product was a high-strength conductive gel with self-healing abilities. Tensile tests confirmed that the swelling of the synthesized gel caused a low tensile breaking stress. Additionally, electrical conductivity measurements showed that the conductivity was increased by the addition of polypyrrole. These measurements were also carried out after the gel underwent self-healing. 30% of the strength and 54% of the conductivity of the undamaged gel were recovered, indicating the good self-healing performance of the gel proposed in this research.

Development of a dipping wire method to improve the abrasion resistance of a plastic wire

In this study, the concept of a self-repairing wire for tendon-driven robots was proposed. A wire in a tendon-driven robot is worn by friction between the tendon and pulley and also between the tendon and guide rail. A worn tendon may lead to breakage of the tendon and makes it difficult to control the robot. In this study, a method to continuously protect the wire surface was proposed to inhibit tendon abrasion. A polymer layer was formed around the catalyst by coating the surface of the wire with a catalyst and supplying liquid resin to the surface. The layer protected the wire from abrasion and the wire re-formed itself when it was worn by abrasion. Specifically, when the wire was abraded, the catalysts reacted with the liquid resin to re-form the coating. In the study, three experiments were conducted and the results confirmed that the wire was protected from abrasion by re-coating itself.