The effect of viscoelasticity on ink ejection from inkjet heads has been attracting attention recently. It is expected that the pressure propagation inside the head and the deformation speed and frequency during ejection are large, but there are no commercially available viscoelasticity measuring devices that can evaluate ink under these conditions. On the other hand, viscoelasticity measuring methods using pulsed ultrasound can evaluate bulk physical properties and sample surface properties at megahertz high frequencies. Here, we have demonstrated that it is possible to distinguish between samples of different manufacturers and compositions for commercially available inkjet inks with small viscosity terms, which was previously considered difficult to achieve with conventional methods. Unlike actual machine evaluation, the high-frequency viscoelasticity measuring method is simple and is therefore expected to accurately obtain ink physical properties, and therefore to provide useful parameters for inkjet ejection analysis.

Surfactant, when added to water-based inks, alters the dynamic surface tension, depending on the surface age. The interval time is considered to be equivalent to the surface age. In this study, a test liquid composed of glycerin and propylene glycol with a surfactant was used to vary the interval time until a drop for observation was ejected after refresh pulses. The jetting condition, which is defined as the time from the start of jetting until satellites coalesce into a sphere, was observed to change. Meanwhile, surface tension was measured by observing the oscillations of ink droplets in flight, using satellite collisions with the main drop under double pulse driving. The results showed that the Ohnesorge number, calculated from the measured dynamic surface tension, can be related to changes in satellite coalescence time during jetting.

This paper introduces ultra-flexible organic photonic devices for continuous physiological monitoring. It presents an ultra-flexible SpO₂ meter that directly attatch to the skin for single-point measurements and a conformable, high-resolution sheet-type image sensor for multipoint sensing. These devices can take static biometric data like fingerprints and vein image, as well as dynamic data such as pulse waves. This technology has the potential to measure biological information previously difficult to obtain, which is valuable for applications such as anesthesia and vital sign monitoring.

Ultrathin flexible organic photovoltaics （OPVs） have attracted growing attention as lightweight and conformable energy harvesters for wearable and soft electronic systems. Unlike conventional photovoltaics, ultrathin OPVs, typically below 10 μm in total thickness, exhibit remarkable bendability and mechanical durability, enabling integration with curved and dynamic surfaces. This review highlights recent advances in device architecture, efficiency improvement strategies, and mechanical durability against repeated deformation. Particular emphasis is placed on structural design principles, such as neutral mechanical plane engineering and alternative flexible electrodes, as well as evaluation protocols for bending stability and fatigue resistance. By focusing on efficiency and mechanical durability, this paper maps a pathway toward practical deployment of ultrathin OPVs as conformable and reliable power sources, bridging materials innovation with system-level design for flexible energy technologies.

The production of perovskite solar cells (PSCs) is moving beyond spin coating. Among various methods for fabricating large-area PSCs, inkjet printing is emerging as a promising alternative due to its low material waste and high precision. This work reports a method for inkjet printing an electron transport layer for PSCs using an industrial inkjet head capable of printing large areas. By analyzing the physical properties of the ink (Ohnesorge number) and optimizing the waveform, stable single-drop formation was achieved, enabling reliable ink ejection of the DI-water-based SnO₂ ink. The printed film was post-treated at an optimal drying temperature to successfully suppress the coffee ring effect and banding defects caused by swath, leading to a uniform SnO₂film. As the DPI increased, it was confirmed that the film surface became flatter and the density increased. The surface-enhanced electron transport layer (ETL) induced uniform nucleation and crystal growth in the upper perovskite layer, ultimately achieving a significant improvement in the device's photovoltaic performance. With high-DPI Inkjet printing, a device with power conversion efficiency (PCE) of 17.42 % is achieved.

This study presents a simple, low-cost method for selective patterning of perovskite films during spin-coating by locally modifying substrate wettability using UV ozone treatment and a rectangular mask. This technique enables simultaneous film formation and patterning, reducing precursor usage by approximately 25 %. However, pronounced edge bead formation occurred near the boundaries between treated and untreated regions, causing film thickness non-uniformity and voids. These microstructural defects led to a reduction in open-circuit voltage (Voc), especially in certain cells. The results identified substrate design, particularly the placement of ITO etch lines, as a key factor influencing liquid behavior. By optimizing etch line positions, edge bead formation was suppressed and Voc was recovered. These findings highlight the importance of integrating substrate design into process control and demonstrate the potential of this method for scalable coating techniques such as slot-die and bar coating, supporting future industrial applications of perovskite solar modules.

Aerosol printing (AP) has emerged as a versatile direct-write additive manufacturing technique capable of depositing fine-resolution features on planar and non-planar substrates. While widely adopted for applications ranging from electronic interconnects to sensors and 3D microstructures, its continuous jetting nature necessitates reliable shuttering mechanisms for discrete feature fabrication. This review highlights the evolution of shuttering strategies in AP, spanning mechanical external shutters, pneumatic shutters, internal rotary valve systems, and advanced internal pneumatic shutters. Each approach is examined with respect to its operating principle, advantages, and limitations. By critically analyzing prior work alongside recent advances, this review provides insights into the role of shuttering in overcoming process challenges and advancing the capability of AP for next-generation manufacturing.

Gas barrier technology for water vapor is utilized across various industries. In this study, a reaction was used to form dense SiN_x films with soluble Polysilazane (PHPS: perhydropolysilazane) as a precursor and with irradiation of 172 or 222 nm light to fabricate water vapor barrier films. In 172 nm light irradiation, the high absorption coefficient of PHPS caused photodensification at the film surface, resulting in high water vapor barrier performance (one unit: 2.2×10^-4 g/m²/day, three units: 5.0×10^-5 g/m²/day). Conversely, the irradiation with 222 nm light resulted in densification inside the film due to PHPS's low absorption coefficient. The resulting barrier performance was low, suggesting that this was caused by the absence of localized densification. Nevertheless, combining 172 nm and 222 nm light improved both crack resistance and barrier performance. This achievement represents significant technology capable of resolving the trade-off between photodensification and crack resistance.

This study aims to redefine the intrinsic value of the creative process itself. It presents part of the outcomes from the KISEKI ART Project, jointly developed by Wacom Co., Ltd., Preferred Networks, Inc. (PFN), and CELSYS, Inc. Guided by the philosophy that “the trajectory of creation is also art,” Wacom seeks to capture the invisible moments within artistic creation—countless brushstrokes, corrections, and serendipitous gestures—using its digital ink technology, and to analyze and visualize them through PFN's AI technology. This enables the visualization of the artist's inner processes and expressive variations, offering creators new insights into their own work. Furthermore, this study identifies and extracts the unique brushstroke characteristics inherent to each creator, defining them as “Emon,” or pictorial fingerprints. Emon symbolizes the individuality, energy, and sensitivity embedded in the act of creation, positioning the creative process itself as a form of art. Through this approach, the research explores how the fusion of art and technology can rediscover creative trajectories as cultural and intellectual assets, and expand the possibilities of human creative experience.