Shingo Iba

Bio: Shingo Iba is an academic researcher from University of Tokyo. The author has contributed to research in topics: Field-effect transistor & Transistor. The author has an hindex of 13, co-authored 25 publications receiving 4185 citations.

A large-area, flexible pressure sensor matrix with organic field-effect transistors for artificial skin applications

Abstract: It is now widely accepted that skin sensitivity will be very important for future robots used by humans in daily life for housekeeping and entertainment purposes Despite this fact, relatively little progress has been made in the field of pressure recognition compared to the areas of sight and voice recognition, mainly because good artificial “electronic skin” with a large area and mechanical flexibility is not yet available The fabrication of a sensitive skin consisting of thousands of pressure sensors would require a flexible switching matrix that cannot be realized with present silicon-based electronics Organic field-effect transistors can substitute for such conventional electronics because organic circuits are inherently flexible and potentially ultralow in cost even for a large area Thus, integration of organic transistors and rubber pressure sensors, both of which can be produced by low-cost processing technology such as large-area printing technology, will provide an ideal solution to realize a practical artificial skin, whose feasibility has been demonstrated in this paper Pressure images have been taken by flexible active matrix drivers with organic transistors whose mobility reaches as high as 14 cm2/V·s The device is electrically functional even when it is wrapped around a cylindrical bar with a 2-mm radius

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.

Integration of organic FETs with organic photodiodes for a large area, flexible, and lightweight sheet image scanners

Abstract: A large-area, flexible, and lightweight sheet image scanner has been successfully manufactured on a plastic film by integrating high-quality organic transistors and organic photodetectors. The effective sensing area of the integrated device is 5/spl times/5 cm/sup 2/; the resolution, 36 dots per inch (dpi); and the total number of sensor cells, 5184. The pentacene transistors with top contact geometry have a channel length of 18 /spl mu/m and mobility of 0.7 cm/sup 2//Vs. Organic photodetectors composed of copper phthalocyanine and 3,4,9,10-perylene-tetracarboxylic-diimide distinguish between black and white parts on paper based on the difference in their reflectivity. Since this new area-type image-capturing device does not require any optics or mechanical scanning devices, the present sheet image scanners are mechanically flexible, lightweight, shock resistant, and potentially inexpensive to manufacture; therefore, they are suitable for human-friendly mobile electronics.

Bending experiment on pentacene field-effect transistors on plastic films

Abstract: We have fabricated very flexible pentacene field-effect transistors with polyimide gate dielectric layers on plastic films with a mobility of 0.3cm2∕Vs and an on/off ratio of 105, and have measured their electrical properties under various compressive and tensile strains while changing the bending radius of the base plastic films systematically. We have found that the change in source-drain current with bending radius is reproducible and reversible when the bending radius is above 4.6mm, which corresponds to strains of ∼1.4±0.1%. Furthermore, the change in source-drain current does not depend on the direction of strain versus direction of current flow.

High mobility of pentacene field-effect transistors with polyimide gate dielectric layers

Abstract: Polyimide gate dielectric layers cured at 180 °C have been employed to fabricate high-quality pentacene field-effect transistors on polyethylenenaphthalate-based films. The surface roughness (root-mean square) of gate dielectric layers characterized by atomic force microscopy is only 0.2 nm, while that of the base film is 1 nm. The transistors with pentacene channel layers deposited on 990 nm polyimide gate dielectric layers attain the on/off ratio of 106 and mobility of 0.3 cm2/V s. Furthermore, by decreasing the thickness of polyimide gate dielectric layers down to 540 nm, the mobility is enhanced up to 1 cm2/V s.

Materials and mechanics for stretchable electronics

Abstract: Recent advances in mechanics and materials provide routes to integrated circuits that can offer the electrical properties of conventional, rigid wafer-based technologies but with the ability to be stretched, compressed, twisted, bent, and deformed into arbitrary shapes. Inorganic and organic electronic materials in microstructured and nanostructured forms, intimately integrated with elastomeric substrates, offer particularly attractive characteristics, with realistic pathways to sophisticated embodiments. Here, we review these strategies and describe applications of them in systems ranging from electronic eyeball cameras to deformable light-emitting displays. We conclude with some perspectives on routes to commercialization, new device opportunities, and remaining challenges for research.

Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes

Abstract: Transparent films of carbon nanotubes can accommodate strains of up to 150% and demonstrate conductivities as high as 2,200 S cm−1 in the stretched state.

A stretchable carbon nanotube strain sensor for human-motion detection

Abstract: Thin films of single-wall carbon nanotube have been used to create stretchable devices that can be incorporated into clothes and used to detect human motions.

Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers

Abstract: The development of an electronic skin is critical to the realization of artificial intelligence that comes into direct contact with humans, and to biomedical applications such as prosthetic skin. To mimic the tactile sensing properties of natural skin, large arrays of pixel pressure sensors on a flexible and stretchable substrate are required. We demonstrate flexible, capacitive pressure sensors with unprecedented sensitivity and very short response times that can be inexpensively fabricated over large areas by microstructuring of thin films of the biocompatible elastomer polydimethylsiloxane. The pressure sensitivity of the microstructured films far surpassed that exhibited by unstructured elastomeric films of similar thickness, and is tunable by using different microstructures. The microstructured films were integrated into organic field-effect transistors as the dielectric layer, forming a new type of active sensor device with similarly excellent sensitivity and response times.

An ultra-lightweight design for imperceptible plastic electronics

Abstract: Electronic devices have advanced from their heavy, bulky origins to become smart, mobile appliances. Nevertheless, they remain rigid, which precludes their intimate integration into everyday life. Flexible, textile and stretchable electronics are emerging research areas and may yield mainstream technologies. Rollable and unbreakable backplanes with amorphous silicon field-effect transistors on steel substrates only 3 μm thick have been demonstrated. On polymer substrates, bending radii of 0.1 mm have been achieved in flexible electronic devices. Concurrently, the need for compliant electronics that can not only be flexed but also conform to three-dimensional shapes has emerged. Approaches include the transfer of ultrathin polyimide layers encapsulating silicon CMOS circuits onto pre-stretched elastomers, the use of conductive elastomers integrated with organic field-effect transistors (OFETs) on polyimide islands, and fabrication of OFETs and gold interconnects on elastic substrates to realize pressure, temperature and optical sensors. Here we present a platform that makes electronics both virtually unbreakable and imperceptible. Fabricated directly on ultrathin (1 μm) polymer foils, our electronic circuits are light (3 g m(-2)) and ultraflexible and conform to their ambient, dynamic environment. Organic transistors with an ultra-dense oxide gate dielectric a few nanometres thick formed at room temperature enable sophisticated large-area electronic foils with unprecedented mechanical and environmental stability: they withstand repeated bending to radii of 5 μm and less, can be crumpled like paper, accommodate stretching up to 230% on prestrained elastomers, and can be operated at high temperatures and in aqueous environments. Because manufacturing costs of organic electronics are potentially low, imperceptible electronic foils may be as common in the future as plastic wrap is today. Applications include matrix-addressed tactile sensor foils for health care and monitoring, thin-film heaters, temperature and infrared sensors, displays, and organic solar cells.