1,720,987 research outputs found
Inkjet printed arrays of pressure sensors based on all-organic field effect transistors
No full textIn this paper we propose totally flexible organic field effect transistors (OFETs) assembled on plastic films as sensors for mechanical variables. First mechanical sensors for pressure and bending detection are presented. A sharp and reversible sensitivity of the output current of the device to an elastic deformation induced by means of a mechanical stimulus on the device channel has been observed and suggested the idea of employing arrays of such sensors for detecting the deformation applied onto a planar surface. Second the possibility of using similar devices for bio- and chemo-detection is described. By exploiting the properties of the basic structure, the device can be combined with any kind of substrate to detect for instance the pressure applied by people walking or standing on a functionalized carpet. This emerging technology seems to be promising for applications in the field of remote and non invasive monitoring of elderly and disabled people
Electrical characteristics of ink-jet printed, all-polymer electrochemical transistors
No full textWe report on the fabrication and characterization of inkjet-printed, all-Organic Electro-
Chemical Transistors (OECTs) entirely realized by a conducting polymer, namely
poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonic acid) (PEDOT:PSS).
The transistors utilized saline as the electrolyte and exhibited output characteristics typical
for operation in depletion regime. The transfer characteristics could be tuned on the basis
of device geometry, with the ratio between the area of the channel and the area of the gate
electrode determining the transconductance. This work paves the road for the low-cost,
print-on-demand fabrication of circuits for applications in bio-sensors and disposable
electronics
Direct X-ray photoconversion in flexible organic thin film devices operated below 1 v
No full textThe application of organic electronic materials for the detection of ionizing radiations is very appealing thanks to their mechanical flexibility, low-cost and simple processing in comparison to their inorganic counterpart. In this work we investigate the direct X-ray photoconversion process in organic thin film photoconductors. The devices are realized by drop casting solution-processed bis-(triisopropylsilylethynyl)pentacene (TIPS-pentacene) onto flexible plastic substrates patterned with metal electrodes; they exhibit a strong sensitivity to X-rays despite the low X-ray photon absorption typical of low-Z organic materials. We propose a model, based on the accumulation of photogenerated charges and photoconductive gain, able to describe the magnitude as well as the dynamics of the X-ray-induced photocurrent. This finding allows us to fabricate and test a flexible 2 × 2 pixelated X-ray detector operating at 0.2 V, with gain and sensitivity up to 4.7 × 10 4 and 77,000 nC mGy 1 cm 3, respectively
Solid State Organic X-Ray Detectors Based on Rubrene Single Crystals
No full textIn this work we report the results on the investigation of rubrene single crystals as solid state direct ionizing radiation detectors. With the aim to understand how electrical properties, and in particular a large charge carrier mobility, affect the radiation detection process in organic semiconducting single crystals, we compare the detection performance of rubrene-based devices with those of 1,5-dinitronaphthalene (DNN)-based ones. DNN has been recently proven to be a stable and reliable X-ray direct detector, operating at very low voltages, in air and at room temperature, with a carrier mobility values about two orders of magnitude lower than rubrene. We demonstrate here that the large charge carrier mobility of rubrene crystals does not result in a better X-rays detection performance. In fact, rubrene devices are shown to be less performing than DNN as detectors, with lower sensitivity to X-rays, poorer stability and reproducibility, and longer rise and decay times of the signa
Inkjet printing of transparent, flexible, organic transistors
No full textTwo different types of all-organic, transparent transistors, namely Organic Thin Film Transistors (OTFTs) and
Organic Electrochemical Transistors (OECTs), were fabricated on transparent, flexible plastic substrates by
means of inkjet printing. In OTFTs the source, drain and gate electrodes were inkjet printed using a poly
(3,4ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS ) solution, while a thermally sublimated
layer of Parylene C acted as gate dielectric. Two kinds of organic semiconductors were used as active layers:
6,13-bis(triisopropylsilylethynyl) pentacene for p-type and N1400 for n-type OTFTs. For OECTs, all electrodes
were also realized by inkjet printing deposition of a PEDOT:PSS solution. Electrical output characteristics of
both kinds of devices are reported, demonstrating that the performances of our devices may be compared to
those of transistors fabricated employing different realization techniques
A deeper insight into the operation regime of all-polymeric electrochemical transistors
No full textAll-Organic Electrochemical Transistors (OECTs) realized by employing Poly(3,4-EthyleneDiOxyThiophene) doped with Poly(Styrene Sulfonate) as conductive polymer show a dependence of their behavior on the gate to channel area ratio. This peculiarity has been investigated and the working mechanism has been explained in view of the behavior of the ionic component of the device. In particular, taking into account the current theory of OECT behavior, we have focused our attention on the role of the gate, trying to clarify if these devices may be considered as working in Faradaic or capacitive regime
Organic bendable and stretchable field effect devices for sensing applications
No full textIn this paper we propose a detailed investigation on the electrical response of Organic Field Effect Transistors (OFETs) assembled on flexible plastic substrates to mechanical deformations. We will demonstrate that, by applying a surface deformation by an external mechanical stimulus we are inducing morphological and structural changes in the organic semiconductor, giving rise to a marked, reproducible and reversible variation of the device output current. We will show how the intrinsic properties of the employed active layers play a crucial role in determining the final sensitivity to the mechanical deformation. Finally we will also demonstrate that the fabricated flexible system can be successfully employed for different applications that go from the detection of biomechanical parameters (joints motion, breath rate, etc.) in the wearable electronics field, to tactile transduction for the realization of artificial “robot skins”
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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