Search

[Abstract] Organic sensor array was fabricated on a curved plastic film substrate of which Gauss curvature was finite. In this work, we proposed soft robot finger as one of the test cases of curved surface device that has artificial tactile sense by detecting slight deformation induced by touching an object. We made curved surface sensor array by thermal molding of planer device array on thin plastic film. Observed electrical current in each sensor pixel reflected strain distribution and time response induced by external slight displacement applied.

In recent years, organic flexible devices have been investigated extensively and sub-millimeter bending stability of organic thin film devices has been achieved by placing the active layer of the transistor on a neutral strain surface. Around the neutral strain surface, an organic thin film has a high bending durability because the in-plane tensile and compressive strain cancel each other. However, this type of highly flexible device is also destroyed or undergoes irreversible degradation when subjected to hard bending, and the breaking point is very difficult to detect experimentally. Therefore, we performed a finite element analysis of a flexible device and found a possible breaking point at the boundary between the contact electrode and the organic layer. This was the result of a strain concentration at the boundary due to the difference in Young's modulus of the organic semiconductor and Au. In addition, the shear stress is concentrated around the edge of the Au electrode. These results indicate that the most likely breaking point for this type of flexible transistor is a rupture of the organic layer at the interface with the Au electrode.

High throughput printing processes have been developed for the fabrication of organic flexible sheet devices. However, printing processes inevitably use toxic solvents to prepare inks of organic semiconductors. Here we propose a novel and complementary method for the preparation of flexible sheet electronics. A thermal pressing method has several advantages, such as (i) being solvent-free, (ii) resulting in flexible device with structural durability against bending, (iii) making simultaneous sealing available to prevent physical or atmospheric damage, and (iv) providing seamless application to roll-to-roll processes by combination with toner technology. We have demonstrated that the characteristics of a flexible organic field-effect transistor (OFET) fabricated by the thermal press process were not degraded during or after the bending test until a bending radius of 2 mm was achieved, which is sufficient for the concept of a rolled-up type flexible sheet display.

Organic transistors have attracted considerable interest because they are lightweight, flexible, inexpensive, and highly efficient over large areas. As a result of these characteristics, organic transistors are expected to find use in a variety of applications, including electronic barcodes, displays, and sensors. Until now, their performance has been inferior to inorganic transistors because of their lower mobility values (typical mobility ranges are 1–10 and 500–10 000 cm Vs for organic and inorganic semiconductors, respectively). Attempts to enhance the performance of organic transistors have relied on decreasing the length and increasing the cross-sectional area through which the charge carriers travel. In the case of an organic thin-film transistor (OTFT), which is the most popular type of organic transistor (Fig. 1a), it is necessary to decrease the channel length and increase the channel width by fine patterning the source and drain electrodes. Nanometer-scale devices can be fabricated if state-of-the-art lithographic techniques are used prior to organic-film growth. However, this type of process is not practical for fabricating low-cost, largescale flexible electronics. One approach to resolving this issue is to employ a verticaltype transistor (Fig. 1b). The carrier pathway in a verticaltype transistor is perpendicular to the substrate, and the current is dispersed over a wide area in the device. A static induction transistor (SIT), which is frequently referred to as a solidstate triode, is one of the simplest vertical-type transistors. SITs were first developed using inorganic semiconductors

Organic thin-film transistors (OTFTs) are emerging as aninexpensive alternative to amorphous silicon devices becauseof their many attractive features, such as a simple fabricationprocess, low cost, and mechanical flexibility. Recently, the per-formance of OTFTs has been significantly improved by modi-fying the dielectric surface and/or source and drain (S/D) elec-trodes

The Hurtley reaction for preparation of benzochromenone (III) is optimized and manufacturing costs are reduced.

We propose a double heterojunction organic light-emitting diode (OLED) using a zinc oxide (ZnO) film, which works as a transparent and electron injection layer. The crystal structure of the ZnO films as a function of Ar/O2 flow ratio and the basic characteristics of the OLED depending on the ZnO sputtering conditions are investigated. Excellent characteristics of the novel OLED were obtained, as high as 470 cd/m2 at 22 V and 7.6 mA/cm2. The results obtained here demonstrate that the vertical organic light-emitting transistor (OLET) using a ZnO layer as an electron injection layer is promising as a key element for flexible sheet displays. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 49–55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20151

Organic semiconductor transistors are expected for flexible displays, information tags, and the like. However, organic transistors have some disadvantages of current density and speed of operation, because of their high resistivity and low carrier mobility. To improve their performance, it is valuable to analyze the mechanism of operation. We have compared characteristics of lateral- and vertical-type transistors using pentacene evaporated films. The pentacene lateral-type FET characteristics showed large variation due to fabrication parameters such as deposition rate, substrate temperature, and film thickness. It was found that evaporated pentacene thin films have large grain gaps, which disturb carrier flow along the channel formed pentacene film/SiO2 interface direction and make FET characteristics unstable. It is assumed that pentacene films are not suitable lateral-type transistors. Accordingly, we have fabricated vertical-type organic static induction transistors (SITs) using pentacene evaporated films. The pentacene SITs show high-speed operation (cutoff frequency of 7.5 kHz) at relatively low voltages. Further optimization of SIT structure will improve the device performance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10500

Reactions of substituted acetone derivatives with acrylic acid esters (>200 mol %) in the presence of t-BuOK (200 mol %) in t-BuOH-THF (1:1 by volume) turned out to proceed as a cascade process consisting of the first Michael addition, the second Michael addition, and the last Claisen reaction to afford 4,4-disubstituted cyclohexane-1,3-diones. Only more substituted enolates play the role of a Michael donor in this cascade process, and therefore the ketone took up two alkoxycarbonylethyl groups on the same carbon bearing more substituents. Such intermediates were followed by intramolecular Claisen reactions leading to cyclohexane-1,3-diones bearing quaternary stereogenic centers at C(4), which bears an alkoxycarbonylethyl group and the substituent of the starting acetone derivatives. Thus-obtained 4,4-disubstituted cyclohexane-1,3-diones were successfully employed for total syntheses of intricate alkaloids of biological interest such as (+)-aspidospermidine, (±)-galanthamine, (±)-lycoramine, and (±)-mesem...

A novel fabrication technique for making plastic electronics has been developed by applying an ultrasonic welding method that is already widely used in cutting, molding, and joining plastic sheets and parts for many industrial products. One major use of ultrasonic welding is the assembly of blood transfusion bags and other medical supplies, because the inert plastic parts can be joined and sealed without any adhesive agent and within a very short processing time. In this study, the same method is applied to make plastic electronics. The successful fabrication of organic TFTs is shown without affecting the gate insulator layer and the self-assembled monolayer (SAM) of pentafluorobenzenethiol (PFBT). We therefore demonstrate that ultrasonic welding can also be used to fabricate plastic electronics. Using this process, for example, one could add electronic functionality not only on the surface of a blood transfusion bag, but also in or through the welding margin at the fringe of the bag.