Powder electroluminescent (EL) devices have been put to practical use as auxiliary light sources because of their superior environmental resistance and ease of fabrication compared to other surface emitting devices. Recently, changes in dielectric constant due to adsorption of water molecules have been observed as changes in EL intensity against the backdrop of their excellent environmental resistance. However, this system cannot distinguish a decrease in EL intensity due to the degradation of the device. In this paper, we aim to realize a powder EL device in which changes in the absorption spectrum of the cobalt complex due to changes in humidity can be detected as changes in the emission color.

With the replacement and new introduction of digital printing in the analog printing market, its influence is gradually expanding into the cosmetics sector. This study attempts to elucidate the challenges of applying digital print technology to makeup by using a commercially available inkjet cosmetic printer. We specifically focused on the fact that traditional digital printing primarily involves adding color to a white base and has not extensively explored techniques for correcting flaws in the print substrate. From this perspective, we evaluated the technology of the Opte inkjet cosmetic printer, which corresponds to base makeup, confirming the importance of (1) preventing pigment sedimentation, (2) avoiding ink bleeding, (3) ensuring print image opacity, and (4) ensuring the safety and environmental compatibility of the materials used. These issues remain active areas of research even in the latest inkjet digital printing technology, reaffirming the expectation that advancements in digital printing will further the application of inkjet technology in the cosmetics field.

This paper introduces reagent immobilization technique on microchannel devices using inkjet technology and an example of its application to single-step bioassays. Inkjet technology allows precise ejection of a fixed volume of reagent solution, so it has been used not only for conventional printers, but also for the development of disposable analytical devices using paper substrates, which have been progressed in recent years. In this paper, two types of reagents that react with each other are independently immobilized at different positions within the channel in a microchannel device made of silicone rubber PDMS (poly (dimethylsiloxane)). Here a technology to create a single-step bioassay device, that can obtain a fluorescent signal according to the concentration of the analyte in a single step by simply introducing a sample solution, is introduced. The analytical performance of diagnostic marker protein analysis, enzyme inhibitor analysis, etc. using this technique will be discussed as well as prospects.

The COVID-19 pandemic has underscored the value and necessity of self-administered diagnostic tests. One example of an analytical platform beneficial for self-diagnostic applications is microfluidic paper-based analytical devices (μPADs), which have gained significant attention in the field of analytical chemistry. Due to their ability to reduce costs and simplify assay operation, μPADs hold considerable promise for practical application. The fact of μPADs being built on paper or paper-like substrates makes printing technologies attractive tools for highly reproducible mass production of devices. Among available printing methods, drop-on-demand inkjet printing stands out for its unique ability to flexibly deposit assay reagents in high-resolution patterns, such as letters. This review introduces μPADs for intuitive semi-quantitative analysis, fabricated by taking advantage of inkjet printing technology. These devices overcome some of the difficulties with analyte quantification, a challenge in colorimetry-or luminescence-based μPADs.

Bioprinting is a technology for fabricating 3D structures containing living cells using digital data and bioink containing cells. When sufficiently developed, this technology is expected to make it possible to fabricate functional 3D structures that reproduce the local arrangement and functional structure of cells in living tissues and organs, which has been difficult to achieve with existing tissue engineering technologies. The fabrication of such structures is expected to revolutionize drug development and transplantation medicine. This paper focuses on bioprinting technology to fabricate jelly-like gel structures and outlines the main printing methods, as well as bioprinting based on ink solidification using a peroxidase enzyme reaction and bioprinting based on ink solidification using a photocatalyst that functions by visible light irradiation.

Flexible sensor system with good wearability and noninvasive vital recording function is of great interest toward remote monitoring for medical and healthcare applications. From skin surfaces, physical and chemical parameters of body can be noninvasively detected such as electrocardiogram (ECG), body temperature, and chemical substances in sweat. Here, our efforts toward the low-cost, disposable, and long-term stable multimodal flexible sensor sheet are introduced. In particular, the device design with kirigami structure for high signal-to-noise ratio monitoring of ECG and good wearability is discussed, and its real-time wireless monitoring is demonstrated. Another topic is to develop a sweat sensor for dehydration monitoring. Based on the systematic studies of each sensor, wireless sensor system is developed, and using the sensor system, demonstrations as proof of concepts are conducted. Although there are still many challenges to move forward to realizing practical sensor system, these efforts may contribute to the field of flexible and wearable electronics for the remote healthcare and medical applications.

Wearable biosensors that detect physiological indicators in body fluids such as sweat, saliva, and tears are being developed for early detection and prevention of diseases. These devices can be worn in daily life and during exercise to diagnose exercise efficiency and health status, and are useful for health monitoring. In this paper, we review wearable biosensors and biofuel cells based on printing technology, especially screen printing. First, the development of porous carbon materials with controlled nano-/mesopores/macropores as electrode materials were described. Carbon material with controlled pore structure (MgOC) using magnesium oxide as a template is introduced. Next, wearable biosensors and biofuel cells printed with MgOC are described. In particular, sensors for monitoring body fluid components such as glucose in urine and lactate in sweat are introduced.

The coming of the 6G era, in which people, items, and services will be seamlessly connected via the Internet, will require innovations in imaging technology. Innovations in molecular design are required for the liquid crystal materials and organic semiconductor materials that have supported imaging technology up to now. In particular, it is essential to establish molecular design strategies to create flexible and tough devices with improved mechanical properties by releasing stress while maintaining electronic properties. This chapter focuses on synthesizing semiconducting polymers and developing flexible/stretchable semiconducting polymer materials, from the fundamentals to applications. With the progress of control technologies for the regioregularity, molecular weight, and molecular weight distribution of semiconducting polymers, such polymers have attracted attention for their high performance and multifunctionality. Thus, the creation of new organic electronics material platforms is highly expected in the near future.