In this study, we fabricated a novel wearable vibration sensor for insects and measured their wing flapping. An analysis of insect wing deformation in relation to changes in the environment plays an important role in understanding the underlying mechanism enabling insects to dynamically interact with their surrounding environment. It is common to use a high-speed camera to measure the wing flapping; however, it is difficult to analyze the feedback mechanism caused by the environmental changes caused by the flapping because this method applies an indirect measurement. Therefore, we propose the fabrication of a novel film sensor that is capable of measuring the changes in the wingbeat frequency of an insect. This novel sensor is composed of flat silver particles admixed with a silicone polymer, which changes the value of the resistor when a bending deformation occurs. As a result of attaching this sensor to the wings of a moth and a dragonfly and measuring the flapping of the wings, we were able to measure the frequency of the flapping with high accuracy. In addition, as a result of simultaneously measuring the relationship between the behavior of a moth during its search for an odor source and its wing flapping, it became clear that the frequency of the flapping changed depending on the frequency of the odor reception. From this result, a wearable film sensor for an insect that can measure the displacement of the body during a particular behavior was fabricated.
A high energy-density laminate cell with high safety and durability was realized. The energy-density of over 250 Wh/kg was obtained using high nickel-content cathode material of NCM811. Sufficient robustness against nail penetration test was also obtained in 60 Ah cell adopting a high heat-resistant separator and a heat-suppressing electrolyte (HSE). Moreover, a long durability of over 1000 charge/discharge cycles has been obtained by optimizing the surface conditions of the NCM811-based cathode electrodes with the S-based electrolyte additives. 1. Introduction Recently, the needs of high energy-density LIBs for EV have increased. Ensuring the safety characteristics and long duration are strongly required for high energy-density LIBs. For the next generation of EV, long cruising range is one of the most important elements in the market demand. Other than EV, there is expectation of high energy-density cells for realizing compactness of the battery system.High energy-density LIBs of around 250 Wh/kg have already been developed using cylindrical cells of lower than 5 Ah in cell-capacity in recent years [1]. It is considered that the cylindrical cells are suitable for higher energy-density but difficult to realize larger capacity. And its durability and safety characteristics have not been mentioned in detail. On the other hand, the laminate cells have been considered that they are suitable for larger capacity because of the flexibility of cell-design and its higher heat radiation. However, as the cell-capacity becomes larger, the safety generally becomes more disadvantageous. Furthermore, the thermal instability of higher nickel-content cathode becomes more serious for securing the safety [2]. Therefore, there has been an obstacle to realize the laminate LIBs for large cell-capacity with high energy-density. In this study, the method that can achieve high energy-density and high safety is presented. The characteristics of 60 Ah laminate cells using this method are also shown. 2. Results and Discussion 60 Ah laminate cells with high energy-density of over 250 Wh/kg, keeping high safety, were realized. Such a high energy-density cell was obtained featuring a high nickel-content cathode material based on NCM811. The nail penetration tests under the penetrating-speed of 10 mm/s with the nails of 3 mm in diameter were carried out. The results were no-fire and no-smoke even when the cell-capacity was up to 60 Ah (The photo inset in Fig.1). It was caused by the combination of a high heat-resistant separator and an HSE. It was found that the hard-short area was not increased, because of the small shrinkage of the separator near the penetrated nail. These effects enable us to secure sufficient robustness against the nail penetration test for 60 Ah laminate cells with high energy-density of over 250 Wh/kg. The safety tests except for nail penetration tests were also acceptable for the demand of application.Cycle performances were tested for the obtained cells. The result showed 90% of capacity retention after 1000 cycles at 25 deg. C. (Fig. 1). This result was obtained by optimizing the surface conditions of the cathode electrodes using the S-based electrolyte additives. The cell resistance was not increased after 1000 cycles. By impedance analysis, it was found that the charge-transfer resistances for the cathode electrodes were not increased. This result suggests that the specific S-based electrolyte additives effectively prevent the surface deterioration of NCM811 by forming surface film on cathodes, as well as anodes. 3. Conclusion In conclusion, 60 Ah laminate cells with high energy-density of over 250 Wh/kg were successfully realized, featuring NCM811-based cathode, optimized surface conditions for electrodes, and the combination of the heat-resistant separator and the HSE. The cell-series using such novel materials and process integration technologies can be applicable for wide-range applications, such as large-capacity EV, ESS, and also high-current power-supply devices attached to E-assisted vehicles, UPS, robots, and drones. References [1] V. Muenzel, A. F. Hollenkamp, A. I. Bhatt, J. D. Hoog, M. Brazil, D. A. Thomas, and I. Mareels, J. Electrochem. Soc., 162, A1592-A1600 (2015) [2] G. Kimand and J. R. Dahn, J. Electrochem. Soc., 161, A1394-A1398 (2014) Figure 1
The goal of our research is to give the robot environmental adaptability. As a result of pursuing accuracy, the conventional robot is rigid and sturdy, and can operate at high speed with high precision in a well-known space. In contrast, these systems have difficulty in unknown or unstructured environments. We thought that the "flexibility" of living things is the key to solve this problem for robots of the future. Living things process a variety of stimuli, act accordingly, and sometimes change their bodies to adapt to the environment. We defined the "flexibility" of a living being as its intelligence, movement, and body. Muscle cells are one of the candidate materials that enable "flexible" robots. It has been reported that myoblasts, the material of muscle cells, fuse by induction of differentiation, and their properties change depending on the growth environment. Therefore, muscle cells have not only physically flexible but also environmental adaptability. Furthermore, the advent of 3D printing technology in recent years has enabled us to freely create three-dimensional structures and has greatly contributed to the development of conventional robots. In fact, the development of an actuator composed of muscle cells (muscle-cell based actuator) with a 3D printer has been reported. On the other hand, only a part of the robot has been replaced with cells, and the production requires the knowledge and skills of some engineers, so it has not been put to practical use. Previous studies have reported that muscle cells can be used as pressure sensors. For this reason, muscle cells seem to become all the CPUs, sensors, and actuators that compose a robot. However, their hierarchical structure and performance are unclear for a muscle-cell robot. Thus, we aim to establish 4D printing technology that can embed dynamic elements (like muscle cells) into artificial objects. In this study, we defined 4D printing technology as printing technology that adds dynamic elements of cells to 3D printing. For the establishment of 4D printing technology, we examined the method of arranging muscle cells and selected gel working as a scaffold for muscle cells in this report. We tried two methods of cell arrangement. One is the attachment method and the other is the embedding method. The attachment method is first printing only the gel and then spreading the cells on the surface of the gel. The embedding method is to print the gel containing the cells. We also used two gels, GelMA (CELLINK) and Collagen 1A (Nitta Gelation) and evaluated adhesion (whether cells can stay in the gel), printability, differentiation, and shape retention. These experiments were performed under four conditions combined with the cell arrangement methods and the gel. As a result, cells could not be arranged evenly by the attachment method, whereas the embedding method did not have that problem. Collagen 1A was seem to be better for the gel, because it contributed to cell differentiation and shape maintenance, but it had slightly lower printing properties than GelMA. Finally, we examined whether the gel with printed myoblast functions as a muscle-cell based actuator. It was observed that the gel containing muscle cells contracted in response to electrical stimulation. These data suggested that printed myoblast by a 3D printer functions as an actuator. We concluded that our method can produce functional muscle cells. Towards establishing 4D printing technology, we will investigate the arrangement and function of the printed cells to be printed. We plan to clarify the optimal combination for creating sensors, actuators, and CPUs, which are the components of a muscle cell robot, by constructing a robot changing the combination of the structure and processing method of cells.
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