Kenji Omote

Bio: Kenji Omote is an academic researcher from Daikin. The author has contributed to research in topics: Fullerene & Endohedral fullerene. The author has an hindex of 12, co-authored 87 publications receiving 788 citations. Previous affiliations of Kenji Omote include Yamagata University & Tokyo University of Science.

Temperature dependence of elastic, dielectric, and piezoelectric properties of “single crystalline’’ films of vinylidene fluoride trifluoroethylene copolymer

Abstract: Elastic, dielectric, and piezoelectric constant matrix elements of a “single crystalline’’ (SC) film of vinylidene fluoride trifluoroethylene copolymer, P(VDF/TrFE), in which the orthorhombic [001] and [110] axes of fully extended chain crystals are preferentially oriented parallel to the stretching axis and normal to the surface, respectively, were measured at temperatures ranging from 10 K to the Curie point (402–404 K) by using a piezoelectric resonance method. All of the electromechanical coupling factors (k31, k32, k33, k24, and k15) are larger than those of conventional lamellar crystalline films. Some of the matrix elements for a P(VDF/TrFE) single crystal are derived from the measured values of constant matrix elements for the SC film. Some features characteristic of the SC film are revealed. The SC film has a large Young’s modulus for the stretching direction (1/s11) (121 GPa at 10 K). The properties related to the molecular motions along the chain axis, such as 1/s11, shear stiffness constant c55, shear piezoelectric constant e15, etc., exhibit strong relaxations around 250 K. The origin of these relaxations in the crystalline phase is discussed.

Formation of ‘‘single crystalline films’’ of ferroelectric copolymers of vinylidene fluoride and trifluoroethylene

Abstract: We find that a highly double‐oriented film of practically unlimited size can be obtained from a uniaxially drawn film of P(VDF/TrFE) by crystallization in the paraelectric phase with its surfaces free from any constraint other than tensile stress along the chain axis. The c axis (the chain axis) and the [110] axis in the orthorhombic system of the poled crystalline film are parallel to the stretching axis and perpendicular to the film plane, respectively. Contrary to conventional crystalline polymer films, the present film has no amorphous region and no lamellar crystal. The film exhibits highly anisotropic characteristics in optical, mechanical, and piezoelectric properties.

Touch panel and transparent piezoelectric sheet

Abstract: PROBLEM TO BE SOLVED: To provide a transparent piezoelectric sheet capable of adopting a different position detection type touch panel, and capable of using an existing touch panel manufacturing device and an existing touch panel itself as those are. SOLUTION: The transparent piezoelectric sheet includes the first transparent plane electrode 22 arranged on one face of a sheet-like transparent piezoelectric layer, and the second transparent plane electrode 23 arranged on the other face of the sheet-like transparent piezoelectric layer, the first transparent plane electrode has the first transparent plane electrode part 221, and the second transparent plane electrode has the second transparent plane electrode part 231. The present invention uses the transparent piezoelectric sheet with a contour of the first transparent plane electrode part including a contour of the second transparent plane electrode part in top view, or with the contour of the second transparent plane electrode part including the contour of the first transparent plane electrode part in top view, combinedly with a resistance film type or an electrostatic capacitance type touch panel. COPYRIGHT: (C)2010,JPO&INPIT

Transparent piezoelectric sheet-with-A-frame, touch panel, and electronic device each having the transparent piezoelectric sheet

Abstract: A transparent piezoelectric sheet-with-a-frame includes a transparent piezoelectric sheet and a frame covering a peripheral edge portion of the transparent piezoelectric sheet. The transparent piezoelectric sheet includes one transparent piezoelectric film including an organic polymer, one first transparent plate electrode placed on a first main surface of the transparent piezoelectric film and having a first transparent plate electrode portion, and one second transparent plate electrode placed on a second main surface of the transparent piezoelectric film and having a second transparent plate electrode portion. An outline of the second transparent plate electrode portion is positioned inside an outline of the first transparent plate electrode portion as seen in a plan view. The outline of the first transparent plate electrode portion completely coincides with the frame, and the outline of the second transparent plate electrode portion does not at all coincide with the frame as seen in the plan view.

Transparent piezoelectric sheet, and transparent piezoelectric sheet-with-a-frame, touch panel, and electronic device each having the transparent piezoelectric sheet

Abstract: A transparent piezoelectric sheet includes a quadrilateral-shaped transparent piezoelectric film and a first transparent plate electrode. The quadrilateral-shaped transparent piezoelectric film includes an organic polymer. The quadrilateral-shaped transparent piezoelectric film has entire main surfaces that are piezoelectric. The first transparent plate electrode is layered on part of a first main surface of the main surfaces of the transparent piezoelectric film. One to three sides of the four sides of the quadrilateral shape of the transparent piezoelectric film and area(s) of the first main surface adjacent thereto are not covered by the first transparent plate electrode.

High performance piezoelectric devices based on aligned arrays of nanofibers of poly(vinylidenefluoride-co-trifluoroethylene)

Abstract: Multifunctional capability, flexible design, rugged lightweight construction and self-powered operation are desired attributes for electronics that directly interface with the human body or with advanced robotic systems. For these applications, piezoelectric materials, in forms that offer the ability to bend and stretch, are attractive for pressure/force sensors and mechanical energy harvesters. Here, we introduce a large area, flexible piezoelectric material that consists of sheets of electrospun fibres of the polymer poly[(vinylidenefluoride-co-trifluoroethylene]. The flow and mechanical conditions associated with the spinning process yield free-standing, three-dimensional architectures of aligned arrangements of such fibres, in which the polymer chains adopt strongly preferential orientations. The resulting material offers exceptional piezoelectric characteristics, to enable ultra-high sensitivity for measuring pressure, even at exceptionally small values (0.1 Pa). Quantitative analysis provides detailed insights into the pressure sensing mechanisms, and establishes engineering design rules. Potential applications range from self-powered micro-mechanical elements, to self-balancing robots and sensitive impact detectors.

From vinylidene fluoride (VDF) to the applications of VDF-containing polymers and copolymers: recent developments and future trends.

Abstract: After an introduction reporting the properties and the applications of fluoropolymers, a first part deals with i) the main routes to produce vinylidene fluoride (VDF) monomer, ii) its homopolymerization, and iii) the advantages and uses of polyvinylidene fluoride (PVDF). In a second section, this review, illustrated by numerous examples, extensively reports the synthesis, properties and applications of the copolymers based on VDF with non-halogenated, fluorinated, commercially available or synthesized comonomers. These comonomers exhibit XYC=CZ-Sp-R structures where X, Y, and Z represent H, F, and CF3 groups, Sp a spacer and R a function such as OH, OAc, SAc, CO2R' (R' being a H atom or an alkyl group), CN, P(O)(OR')2 and SO3H. According to the nature and to the amount of the comonomer, the copolymers can be thermoplastic, elastomeric or thermoplastic elastomers. Introducing reactive R side groups brings complementary properties such as hydrophily, ionic exchange or surface properties, or further crosslinking of the resulting copolymers. Then, the kinetics of radical copolymerization of VDF with M comonomers led to the assessment of the reactivity ratios which are compared. Hence, a reactivity series of these M comonomers with respect to a macroradical terminated by VDF is proposed. Usually, these copolymers exhibit random structures but only three comonomers produced alternating copolymers with VDF: hexafluoroisobutylene, F2C=CFCO2CH3, and H2C=C(CF3)CO2R. The controlled radical copolymerizations of VDF with other comonomers (such as chlorotrifluoroethylene, 3,3,3-trifluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether or-trifluoromethacrylic acid) either in the presence of xanthates, borinates or iodo-compounds are also reported. In addition, new VDF-containing copolymers exhibit well-defined architectures, such as block and graft copolymers. They can be synthesized either by conventional techniques or by controlled radical copolymerization. Chemical modifications of PVDF and poly(VDF-co-monomer) copolymers are also presented. Several properties and applications (such as surfactants, dielectrical polymers, thermoplastic elastomers, fuel cell and ultrafiltration membranes, or polycondensates, the fluorinated segments of which bringing softness and thermal stability) of these VDF-containing copolymers will illustrate this review.

A Hybrid Piezoelectric Structure for Wearable Nanogenerators

Abstract: A hybrid-fiber nanogenerator comprising a ZnO nanowire array, PVDF polymer and two electrodes is presented. Depending on the bending or spreading action of the human arm, at an angle of ∼90°, the hybrid fiber reaches electrical outputs of ∼0.1 V and ∼10 nA cm(-2) . The unique structure of the hybrid fiber may inspire future research in wearable energy-harvesting technology.

History and recent progress in piezoelectric polymers

Abstract: Electrets of carnauba wax and resin have exhibited good stability of trapped charges for nearly 50 years. Dipolar orientation and trapped charge are two mechanisms contributing to the pyro-, piezo-, and ferroelectricity of polymers. Since the 1950s, shear piezoelectricity was investigated in polymers of biological origin (such as cellulose and collagen) as well as synthetic optically active polymers (such as polyamides and polylactic acids). Since the discovery of piezoelectricity in poled polyvinylidene fluoride (PVDF) in 1969, the pyro-, piezo-, and ferroelectricity were widely investigated in a number of polar polymers, such as copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylcyanide and vinylacetate, and nylons. Recent studies involve submicron films of aromatic and aliphatic polyureas prepared by vapor deposition polymerization in vacuum and the piezoelectricity of polyurethane produced by the coupling of electrostriction and bias electric fields. Gramophone pickups using a piece of bone or tendon were demonstrated in 1959. Microphones using a stretched film of polymethyl glutamate were reported in 1968. Ultrasonic transducers using elongated and poled films of PVDF were demonstrated in 1972. Headphones and tweeters using PVDF were marketed in 1975. Hydrophones and various electromechanical devices utilizing PVDP and its copolymers have been developed during the past 30 years. This paper briefly reviews the history and recent progress in piezoelectric polymers.

Metal oxide semiconductor thin-film transistors for flexible electronics

Abstract: The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular, the realization of large-area digital circuitry like flexible near field communication tags and analog integrated circuits such as bendable operational amplifiers is presented. The last topic of this review is devoted for emerging flexible electronic systems, from foldable displays, power transmission elements to integrated systems for large-area sensing and data storage and transmission. Finally, the conclusions are drawn and an outlook over the field with a prediction for the future is provided.