Conformable, flexible, large-area networks of pressure and thermal sensors with organic transistor active matrixes

Abstract

Skin-like sensitivity, or the capability to recognize tactile information, will be an essential feature of future generations of robots, enabling them to operate in unstructured environments. Recently developed large-area pressure sensors made with organic transistors have been proposed for electronic artificial skin (E-skin) applications. These sensors are bendable down to a 2-mm radius, a size that is sufficiently small for the fabrication of human-sized robot fingers. Natural human skin, however, is far more complex than the transistor-based imitations demonstrated so far. It performs other functions, including thermal sensing. Furthermore, without conformability, the application of E-skin on three-dimensional surfaces is impossible. In this work, we have successfully developed conformable, flexible, large-area networks of thermal and pressure sensors based on an organic semiconductor. A plastic film with organic transistor-based electronic circuits is processed to form a net-shaped structure, which allows the E-skin films to be extended by 25%. The net-shaped pressure sensor matrix was attached to the surface of an egg, and pressure images were successfully obtained in this configuration. Then, a similar network of thermal sensors was developed with organic semiconductors. Next, the possible implementation of both pressure and thermal sensors on the surfaces is presented, and, by means of laminated sensor networks, the distributions of pressure and temperature are simultaneously obtained.electronic artificial skin ͉ large-area sensor O rganic field-effect transistors (1-3) and their integrated circuits (4-6) have attracted considerable attention because of attributes that complement silicon-based large-scale integrations, devices that are high-performance but expensive. Organic transistors can be manufactured on plastic films at low (ambient) temperatures; therefore, they are mechanically flexible (7) and potentially inexpensive to manufacture. Two major applications drive recent studies of organic transistors. The first includes flexible displays such as paper-like displays or e-paper, in which electric inks or other media are driven by organic transistor active matrixes (8, 9). The second comprises radio frequency identification tags (10). The printable features (11-15) of organic transistors should facilitate the implementation of radio frequency identification on packages.We have recently demonstrated another promising application: a flexible pressure sensor matrix (16,17), in which organic transistor active matrixes are used to read out pressure data from sensors. This new pressure sensor (16, 17) could be very suitable for electronic artificial skin (E-skin), which will be an essential feature of robots, enabling them to operate in unstructured environments (18). Although the mobility of organic semiconductors is known to be about two or three orders of magnitude less than that of poly-and single-crystalline silicon, the slower speed is tolerable for most applications of large-area sensors. For E-skin ...

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