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The demand for flexible and stretchable devices has been increasing in multiple fields, such as healthcare, energy harvesting, and artificial intelligence. In this study, we report a novel method to fabricate flexible and stretchable devices by integrating a kirigami sheet with an elastomer, both stretchable. Owing to the flatness of the kirigami sheet under no stress, electrodes can be patterned using a printing technique, which can enable large size and mass production. Kirigami sheets form three-dimensional shapes under stress/strain. The integration of kirigami and elastomers is carried out by placing a liquid elastomer on the three-dimensional structure. A biaxially stretchable light-emitting device was fabricated by patterning the electrode on a kirigami sheet and placing a light-emitting elastomer on top of it. This study reports the fabrication method, fabricated device on activation, and stretchability. [ABSTRACT FROM AUTHOR]

Flexible devices have been studied to realize IoT or novel wearable devices. The data that flexible devices deal with can include personal information when application areas further expand. A security system for flexible devices becomes more important in this case. In this study, we investigate the thermal stability of an organic flexible security system. The security system utilizes fabrication variation of a chip, and it is called a physically unclonable function (PUF). As a result, the bit error rate of the organic PUF is 1.8% and the index of ID uniqueness (i.e., randomness) has an almost theoretical value of 0.48. The generated ID remains even after annealing at 100 °C for 97 h by using CYTOP encapsulation. X-ray diffraction measurement implies that degradation of PUF characteristics partially derives from structure changes of the organic n-type semiconductor thin film after annealing. [ABSTRACT FROM AUTHOR]

We developed a tunable wedge prism by electrowetting actuation. Our prism can shift the field of view to the left or to the right and is useful for small cameras and endoscopes because its field of view can be changed without the need for large instruments. It consists of two plates that face each other, and a liquid is sandwiched between them. The liquid and plates form a wedge when the angle between the plates is changed. We used electrowetting to change the angle between the plates. The wedge prism is small because the liquid driven by electrowetting works as a prism. In addition, the prism produces a clear field of view because its optical flatness is determined by the flatness of the plates. [2007-0079] Index Terms--Electrostatic devices, microelectromechanical devices, optical device fabrication.

Currently, electronic components having wavy structures are being actively studied because such wavy structures exhibit stretchability through flattening under stretching. The buckling of a thin film on an elastomer is an easy and inexpensive approach of creating a wavy structure and has attracted considerable attention. Despite its simplicity and easiness, the requirement of stretchers during film deposition limits fabrication methods, such as spin-coating and printing methods, and hinders their application in industry. Here, we eliminated the requirement of stretchers during film deposition by utilizing plastic deformation of the thin film and extending methods of developing a wrinkle structure. We used poly-3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS), the most widely used conductive polymer, as a thin film and adopted its stretchable wrinkle structure for stretchable electronic devices. The stretchability and durability of PEDOT:PSS were enhanced by sandwiching the PEDOT:PSS layer between two Parylene layers. The PEDOT:PSS layer was conductive at a stretch of up to 170%, and the change in resistance was less than 10% after 4000 cyclic loads. Additionally, we demonstrated a new concept of a flexible and stretchable light emitting device using the proposed Parylene/PEDOT:PSS/Parylene multi-layer and functionalized polydimethylsiloxane. [ABSTRACT FROM AUTHOR]

It is often postulated that quasistatic cracks propagate along the direction allowing fracture for the lowest load. Nevertheless, this statement is debated, in particular for anisotropic materials. We performed tearing experiments in anisotropic brittle thin sheets that validate this principle in the case of weak anisotropy. We also predict the existence of forbidden directions and facets in strongly anisotropic materials, through an analogy with the description of equilibrium shapes in crystals. However, we observe cracks that do not necessarily follow the easiest direction but can select a harder direction, which is only locally more advantageous than neighboring paths. These results challenge the traditional description of fracture propagation, and we suggest a modified, less restrictive criterion compatible with our experimental observations. [ABSTRACT FROM AUTHOR]

A micro-structure supported on a droplet is subjected to capillary force and aligned dependent on its shape. If the droplet's boundary conditions at the bottom and the micro-structure are non-circular, capillary torque is exerted on the structures. The direction of torque is determined by the boundary conditions and the position of the structure. By changing the boundary conditions continuously, rotational motion of a plate was achieved. The boundary conditions of the droplet were controlled by electrowetting. We patterned electrodes in an annular shape on the plate supporting the droplet. By changing the voltage-applied electrodes, the boundary conditions were changed and the plate is rotated. The droplet and the plate worked as a capillary motor with this method. We report the relationship between the characteristics of the capillary motor and its rotational motion. We sandwiched a 3.0-μL water droplet between two plates and achieved a rotational motion of 720 rpm at maximum. [ABSTRACT FROM AUTHOR]

The author focuses on career education, with emphasis on employment support for youth, in Japan. He cites the low unemployment rate in the working environment for Japanese youth before the collapse of the bubble-economy in 1992. A plan called Plan for Promoting Youth Employment (PPYE) offers ways on how to address youth unemployment, including the development of youth labor market and job creation for youth through business start-ups.

Two-dimensional ridge structures are induced by equi-biaxial compression with large equi-biaxial pre-stretch in a thin film by using a micro-fluidics technique. Whereas wrinkles tend to be uniformly distributed, ridges are localized. The wrinkle-to-ridge transition is unstable (subcritical), resulting in large amplitude changes. The nature and morphology of the ridges is studied and quantified by experiments and numerical simulations., Engineering and Applied Sciences

Wrinkles on thin film/elastomer bilayer systems provide functional surfaces. The aspect ratio of these wrinkles is critical to their functionality. Much effort has been dedicated to creating high-aspect-ratio structures on the surface of bilayer systems. A highly prestretched elastomer attached to a thin film has recently been shown to form a high-aspect-ratio structure, called a ridge structure, due to a large strain induced in the elastomer. However, the prestretch requirements of the elastomer during thin film attachment are not compatible with conventional thin film deposition methods, such as spin coating, dip coating, and chemical vapor deposition (CVD). Thus, the fabrication method is complex, and ridge structure formation is limited to planar surfaces. This paper presents a new and simple method for constructing ridge structures on a nonplanar surface using a plastic thin film/elastomer bilayer system. A plastic thin film is attached to a stress-free elastomer, and the resulting bilayer system is highly stretched one- or two-dimensionally. Upon the release of the stretch load, the deformation of the elastomer is reversible, while the plastically deformed thin film stays elongated. The combination of the length mismatch and the large strain induced in the elastomer generates ridge structures. The morphology of the plastic thin film/elastomer bilayer system is experimentally studied by varying the physical parameters, and the functionality and the applicability to a nonplanar surface are demonstrated. Finally, we simulate the effect of plasticity on morphology. This study presents a new technique for generating microscale high-aspect-ratio structures and its potential for functional surfaces.

Capillary force makes a liquid droplet's surface have the minimum area. If the droplet is sandwiched between two plates, it exerts capillary force on the plates. The magnitude of the force depends on the shape of the sandwiched droplet, which is in turn determined by the shape of the plates and the volume of the liquid. The liquid's shape, however, is hard to determine analytically. In this paper, the torque caused by a droplet sandwiched between two noncircular plates is experimentally and theoretically analyzed. We patterned a magnetic material on the surface of the plates and used it to apply a magnetic force to the plates. The torque on the plates was measured. The torque caused by capillary force was calculated by observing the equilibrium between the capillary force and magnetic force. We obtained approximate theoretical solutions for the liquid's shape and torque and verified that they were in accordance with the experimental results. The experimental and theoretical results presented in this paper are useful for designing microdevices or self-assemblies actuated by capillary force.