Sheet-Type Sensors and Actuators

Abstract

Recent intensive research and development of organic field-effect transistors (FETs) [1–6] have been motivated by a new class of applications that cannot be easily realized by conventional electronics based on inorganic semiconductors. Organic transistors are mechanically flexible, thin, lightweight, and shock-resistant, because organic devices are manufactured on plastic films at low (ambient) temperature. Furthermore, manufacturing costs of organic transistor circuits would be inexpensive, even for large areas, when they are fabricated using printing technologies and/or roll-to-roll processes. There are two major applications for organic transistors. The first one is a flexible display. This new display includes a paper-like display or an electronic paper, where electric inks, electroluminescent (EL) devices, and liquid crystals or other mediums are powered by organic transistor active matrices [4, 7]. The second one is a radio frequency identification (RFID) tag [8, 9]. An organic transistor-based RFID tag may be printed on packages of products, resulting in an inexpensive and robust electronics. As another application of organic transistors, we demonstrated large-area flexible sensors. The first organic transistor-based large-area sensors are flexible pressure sensor matrices; organic transistor active matrices are used to read out pressure distributions over a large area from a 2-D array of pressure sensor cells. The new pressure sensor can be ideal for electronic artificial skin (e-skin) applications for future generations of robots. The mobility of pentacene that is known as a high-mobility low-molecular weight semiconductor is typically 1 cm2/Vs. This value is about two or three orders of magnitude lower than that of polyor single-crystalline silicon, respectively. Although flexible displays and/or RFID tags require usually high-electronic performance, the