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In this study, we devised an evaluation method and a quantitative index for the radial distribution of the out‐of‐plane deformation of kirigami structures with a slit pattern on concentric circles. The concentric kirigami structure was deformed in the out‐of‐plane direction by pulling the center of the structure, and the out‐of‐plane deformation distribution in the radial direction was changed by changing the distance between the slits in the radial direction of the circle and the length on the circumference of the circle. We used a single quantitative index to express the radial distribution of out‐of‐plane deformation. If the design of the kirigami structure can be freely determined from the quantification index, it can significantly contribute to the realization of useful devices which uses the concentric kirigami structure. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Heat‐shrinkable films commonly serve as active materials for self‐folding owing to their capability to fold all hinges upon heating. For origami‐based electronic devices, the self‐folding of the metal layer is necessary. Nevertheless, the self‐folding angle is low owing to the high bending stiffness of metal layers and the low adhesion of heat‐shrinkable films. Here, we introduce a bilayer self‐folding technique that effectively suppresses delamination of the shrink layer, thereby achieving a high folding force and angle. A polyolefin film mechanically fixed on the metal substrate serves to inhibit delamination, regardless of the adhesive properties of the shrink layer. This is achieved by applying adhesives within holes fabricated on the shrink layer. Conventional methods using an adhesive layer to fix the shrink layer lead to delamination at temperatures above 100°C, resulting in a decrease in self‐folding angles. In contrast, our novel fixing method yields a folding angle of 161° at 140°C, with a shrinkage rate of 69%. To demonstrate the versatility of our proposed technique, we self‐fold various origami structures, including Miura‐ori, scissors, cranes, and tessellation with chip LEDs. The introduced method broadens the range of substrate materials suitable for self‐folding and offers new possibilities for the development of origami devices. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Recently, a new technology has come to the fore, namely four-dimensional (4D) printing. Conventional research has, however, mostly been in a glass state after a shape change such as self-folding of 4D printing, because the heat shrinkage or shape memory effect of polymers is used. Therefore, the 4D printed hinges are rigid and cannot be folded or unfolded after 4D printing below the glass transition temperature of the shape memory polymer (SMP). Hence, in this study, we proposed a hybrid hinge structure that is elastic and can be largely deformed as an origami structure even after 4D printing. On the hybrid hinge, a soft elastomer hinge was arranged beside the rigid 4D printing hinges to achieving the elastic folding deformation after self-folding. We confirmed that the samples recovered to almost their original shape without failure after 500 cycles of folding. They exhibited high durability and elasticity. Finally, the usefulness of the hybrid hinge was demonstrated by fabricating a miura-ori and an origami compliant mechanism gripper, which could be deformed as origami structure below the glass transition temperature of the SMP. We believe that our 4D printing method can be applied for developing self-folding actuators and robots, which require origami deformation. [Display omitted] • A hybrid hinge composed of 4D printed hinges and an elastomer hinge was proposed to realize hinge elasticity. • The effect of the hybrid hinge structure on the self-folding angle was evaluated experimentally and analytically. • The hybrid hinges have large deformability and were unbroken and resilient even after 500 cycles of repeated folding. • A miura-ori structure that can be folded and unfolded after self-folding is demonstrated. • An origami gripper using a compliant mechanism that can be gripped and released was realized. [ABSTRACT FROM AUTHOR]

SUMMARY We demonstrated coloring elements with high ratio change of the coloring area by using bending deformation of electroactive hydrogel. By using the nondimensional deflection α of a gel, we showed that the response time for the color change and the thickness of the coloring element can be designed. We fabricated a 3 × 3 dot-matrix display with α of 0.56 and evaluated the performance of the coloring element. As a result, the coloring area ratios in black state and colored state were 7.64 ± 4.6% and 92.1 ± 4.6%, respectively. The response times were 12 s from blank state to colored state, and 13 s from colored state to blank state. [ABSTRACT FROM AUTHOR]

Microchannels made of fluoropolymers show potential merits due to their excellent solvent resistance, but such channels have not been widely used because of the complexity to fabricate them. This communication describes a method to prototype microfluidic devices using fluoropolymer films. The fabrication requires only two steps; cutting fluoropolymer films with a desktop cutting plotter and applying heat and pressure to laminate them. The method is rapid, simple, and low-cost. The conditions for heat press were identified for two common fluoropolymers: polytetrafluoroethylene and fluorinated ethylene propylene. The laminated films were confirmed to remain sealed with an internal pressure of at least 300 kPa. The fabricated devices were tested for the resistance to a set of organic solvents that would not be compatible with typical devices fabricated in polydimethylsiloxane. To highlight the potential of the fluoropolymer devices fabricated in this method, generation of droplets in a continuous stream of organic solvent using a T-junction channel was demonstrated. Our method offers a simple avenue to prototype microfluidic devices to conduct experiments involving organic solvents such as organic chemistry and in-channel synthesis of microparticles. [ABSTRACT FROM AUTHOR]

This paper presents a thermal-based skin moisture sensor that is insusceptible to thin coating materials on skin. To realize this sensor, numerical simulations are performed to evaluate the influence of surface-coating materials, such as Vaseline moisturizer, on the heat transfer from a heat source in the sensor to the skin. The simulation results show that the influence of the thin Vaseline layer on the temperature change of the heat source is negligible, but the existence of air gaps between the sensor and the skin drastically interrupts the heat transfer. Considering the simulation results, the thermal-based skin moisture sensor is designed and fabricated with a microelectromechanical systems (MEMS) pressure sensor to avoid heat transfer interruption due to air gaps. The measurement results of water content in a water-absorbing polymer, covered with a 10-μm-thick polyethylene film, show that the moisture sensor can assess the water content of materials that are covered with a thin layer. Finally, we demonstrate the hydration measurement of skin with Vaseline coating. The measurement results confirm the potential of the moisture sensor to measure the water content of skin covered with moisturizing substances. [ABSTRACT FROM AUTHOR]