Simple model for synchronization of two Belousov-Zhabotinsky gels interacting mechanically.

A Belousov-Zhabotinsky (BZ) gel is a unique biomimetic system that undergoes autonomous volume oscillations induced by the redox oscillation of the BZ reaction. In a previous study, researchers reported that the oscillations of two BZ gels coupled by compression were synchronized by a mechanical interaction. They mathematically explained the synchronization behavior using a phase oscillator model. As a different approach to the previous study, a physicochemical investigation of the phenomenon will lead to a better understanding of the functional biological rhythms essential for life. In this study, we construct a simple phenomenological model to understand the synchronization of BZ gels. The model consists of two parts. One is the dynamics of the chemical reactions in the BZ gels. We use a phenomenological model based on the Oregonator for the BZ reaction. The other is the dynamics of the mechanical deformation of the BZ gel. Using approximations, we extract the parameters essential for the synchronization of a mechanical interaction. Thus, we can derive a novel equation for the deformation dynamics of mechanically coupled BZ gels. By combining these two parts, we perform numerical calculations. This allows us to find that the synchronization of the two BZ gels is less likely to occur under stronger compression. We explain this trend through one physicochemical parameter in our model: the volume fraction of the BZ gel in the reduced state.

Pocketable and Smart Electrohydrodynamic Pump for Clothes.

Seamlessly fusing fashion and functionality can redefine wearable technology and enhance the quality of life. We propose a pocketable and smart electrohydrodynamic pump (PSEP) with self-sensing capability for wearable thermal controls. Overcoming the constraints of traditional liquid-cooled wearables, PSEP with dimensions of 10 × 2 × 1.05 cm and a weight of 10 g is sufficiently compact to fit into a shirt pocket, providing stylish and unobtrusive thermal control. Silent operation coupled with the unique self-sensing ability to monitor the flow rate ensures system reliability without cumbersome additional components. The significant contribution of our study is the formulation and validation of a theoretical model for self-sensing in EHD pumps, thereby introducing an innovative functionality to EHD pump technology. PSEP can deliver temperature changes of up to 3 °C, considerably improving personal comfort. Additionally, the PSEP system features an intuitive, smartphone-compatible interface for seamless wireless control and monitoring, enhancing user interaction and convenience. Furthermore, the ability to detect and notify users of flow blockages, achieved by self-sensing, ensures an efficient and long-term operation. Through its blend of compact design, intelligent functionality, and stylish integration into daily wear, PSEP reshapes the landscape of wearable thermal control technology and offers a promising avenue for enhancing personal comfort in daily life.

Effect of Diversity Education on Young Adolescents in Japan: Toward the "Do No Harm" Principle.

This study evaluated the impact of a semi-structured diversity education program on young adolescents, which included five 45-min sessions facilitated by schoolteachers using an instructors' manual. The study compared changes in knowledge and attitude related to diversity, self-esteem, and mental health among participants before and after the program. The participants were 776 junior high school students. Self-esteem and mental health conditions were assessed with the Rosenberg Self-Esteem Scale (RSES) and Kessler 6-Item Psychological Distress Scale (K6). The ratio of those who answered the knowledge and attitude questions correctly increased significantly for most questions, while the ratio decreased significantly for two questions. The RSES scores improved significantly after the program, but the difference was very small. Mental health, as measured by K6, became significantly worse after the program. A logistic regression analysis indicated that lower K6 scores before the program and worse academic grades had significantly higher odds ratios; being a girl, not having a disability, and having close friends were associated with worse K6 scores after the program. Further, this indicates the importance of developing processes based on evidence and the "nothing about us without us" principle.

Artificial temperature-compensated biological clock using temperature-sensitive Belousov-Zhabotinsky gels.

The circadian rhythm is a fundamental physiological function for a wide range of organisms. The molecular machinery for generating rhythms has been elucidated over the last few decades. Nevertheless, the mechanism for temperature compensation of the oscillation period, which is a prominent property of the circadian rhythm, is still controversial. In this study, we propose a new mechanism through a chemically synthetic approach (i.e., we realized temperature compensation by the Belousov-Zhabotinsky (BZ) gels). The BZ gels are prepared by embedding a metal catalyst of the BZ reaction into the gel polymer. We made the body of BZ gels using a temperature-sensitive polymer gel, which enabled temperature compensation of the oscillation by using temperature dependence of volume. Moreover, we constructed a simple mathematical model for the BZ oscillation in temperature-sensitive gels. The model can reproduce temperature compensation of BZ gels, even though all reactions are temperature sensitive according to the Arrhenius rule. Our finding hints that a soft body coupling may be underlying temperature-compensated biological functions, including circadian rhythms.

Periodical propagation of torsion in polymer gels.

Gel actuators have potential in soft robotics. Although gel actuators can realize various motions like contraction, expansion, and bending, most require external inputs such as batteries and circuits. Herein we propose a periodical torsional motion hydrogel driven by chemical energy from the Belousov-Zhabotinsky (BZ) reaction. Our BZ gel system exhibits autonomous motion without a battery. The elastic moduli of the redox states of the BZ gel are investigated using stress-strain analysis. An experimental system, which integrates the BZ gel and two PDMS (dimethylpolysiloxane) rotators, is designed to evaluate torsion angles. The experimental pre-twist angle dependence of the rotary motion is compared with a theoretical rotation model. The results agree qualitatively. This study should contribute to the development of soft actuators without external components.

Electrochemical Dual Transducer for Fluidic Self-Sensing Actuation.

An electrochemical dual transducer (ECDT) based on a chemical reaction is a new fluidic machine for self-sensing actuation. Recently, incorporating sensors has enhanced the multifunctionality of soft robots with fluidic machines such as pumps or compressors. However, conventional fluidic systems have limitations such as heavy weight, noise, bloat, and complexity. In our previous research, we adopted small-sized, lightweight, and quiet electrohydrodynamic pumps for soft robots. In this paper, we propose a new ECDT by exploring the possibility of an electrohydrodynamic (EHD) pump to sense the flow of the working fluid. The current in the ECDT is proportional to 1/3 of the inflowing velocity. We also clarify its mechanism, mathematical model, range of detectable flow rate, sensitivity factor, relaxation time, response speed, and pumping characteristics. The advantages of the ECDT are their small size, light weight, simple fabrication process, extensibility of the sensing range, and sensitivity. We also demonstrate a suction cup driven by the ECDT, which can detect, hold, and release objects. We expect a bidirectional ECDT will realize a small, multifunctional, and straightforward fluidic system.