Flexible and printed organic electronics technology has garnered increasing attention and resources in research and development because of its potential use in low-cost, environmentally friendly electronic devices. We successfully fabricated pseudo-CMOS inverters using p-type organic thin-film transistor (OTFT) devices and NAND logic gates. The inverters exhibited ideal characteristics at low operating voltages and high gains. Using our newly developed n-type organic semiconductor (OSC) material (TU-3) and a commonly used p-type OSC material (diF-TES-ADT), we successfully demonstrated a CMOS inverter that employed a stacked TFT device construction. Based on this CMOS inverter design, an operational amplifier, ring oscillators, and D-flip flop circuits were also fabricated. To realize very short-channel OTFT devices and higher-performance integrated circuits, we employed the reverse-offset printing method to form narrow channel lengths of less than 10μm, which resulted in good electrical characteristics. Pressure sensors based on ferroelectric polymer (PVDF-TrFE) materials are excellent at detecting vital signs in the human body. We previously succeeded in precisely detecting pulse waves with a wearable patch-type sensor, which was fabricated on a plastic film substrate using printing methods. Our goal was to develop a smart sensor device that can be connected wirelessly to the Internet and that combines printed integrated circuits and one or more sensors. More recently, we developed flexible hybrid electronic (FHE) devices that use silicon-based LSI die for signal processing and wireless communication circuits and that are integrated onto a flexible plastic film substrate.
Printing enables the mass production of products at a low cost. In the field of printed electronics, thickness, thin lines, and uniform thickness are all required. Screen printing has long been used in printed electronics because it is the only means by which large areas can be printed in a stable manner. However, screen printing can only be used for printing on flat objects and thus cannot handle three dimensions. By contrast, pad printing has long been adopted as a three-dimensional printing method. In pad printing, the printing thickness is thinner than in screen printing because intaglio is used. Screen pad printing enables printing that is equivalent to screen printing on three-dimensional objects. In an experiment conducted in this study, screen printing was first performed on a silicone rubber blanket. The printing pad then removed the paste from the blanket and transferred it to a substrate. Much thicker prints (as compared to when using intaglio) were then transferred to three-dimensional objects. In the experiment, conduction was obtained when the level differences were 85 degrees or less.
With the high resolution of printed circuit boards, screen-printing technology has been improved. Screen printing can produce high-resolution circuit patterns, which was previously possible only through the photo imageable method. Here, we describe the trends and future of etching resist ink, solder resist ink, metal paste, and photo emulsion for screen printing.
The rapid increase in the global usage of consumer electronic products has accelerated the consumption of non-renewable resources and generated excessive electronic waste (e-waste). E-waste threatens human health and the environment, particularly in developing countries. Accordingly, the need to develop green electronic devices that originate from natural resources and are human and environmentally friendly has increased. Wood-derived nanocellulose paper has recently received considerable attention as a promising substrate for green electronics because of its renewability and biodegradability. In this study, we investigate green paper electronics based on nanocellulose paper while considering transparent conductive and electronic paper as well as nonvolatile paper memory and paper sensors. These paper electronic devices provide high device performance as well as excellent flexibility, biodegradability, and disposability, thus opening new doors for future green electronics.
A implantable neural interface that can record and control neural activities has been researched and developed as a sensor for the purpose of diagnosis, treatment, and elucidation of serious neurological diseases such as Parkinson's disease, epilepsy, etc. Recently, we have developed a neural interface using a stretchable transparent wiring comprised with Au-plated Ag nanowires. The neural interface realized long-term implantation in the rat's brain, and simultaneous optogenetic stimulation and electrocorticogram recording on the marmoset's cerebral cortex. In this paper, we describe overview of the wiring technologies using the Ag nanowires toward realization of high transparency, conductivity, stretchability, and electrochemical durability. Moreover, a miniaturization technology of Ag nanowire based transparent wiring is described in the aim of not only to improve the spatial resolution of the implantable sensor but also to integrate it in flexible electronics such as display, touch panel, solar cell, wearable sensor, etc. In the future, our developed wiring technologies under solution process will enable to realize a stretchable and transparent electronics with fabrication area from fine scale (several tens to several hundreds of μm) to large scale (several tens cm).
In Japan, the print publication market has declined over the past 14 years. However, the market for electronic publications (e-publications) has recently expanded. The objective of this study is to offer suggestions for accelerating both print publication and e-publication use by consumers. For this purpose, we constructed five hypotheses concerning the differences in awareness and behaviors of two groups of consumers: those who use only print publications (P-users) and those who use both print publications and e-publications (E-users). We conducted a consumer survey and analyzed consumer responses to verify the hypotheses. Our results indicated the following: 1) Both types of users prefer to go to bookstores and physically select books. E-users purchase print publications more often through the Internet than do P-users. 2) E-users evaluate the advantages of e-publications higher than P-users do, whereas many P-users cannot actually identify the advantages of e-publications. 3) E-users use print publications and e-publications according to the genres of the publications. 4) Print publications are often read thoroughly, whereas e-publications are often read by users while they participate in another activity. The results of these analyses enabled us to provide suggestions for promoting the use of both print publications and e-publications.