The Experts below are selected from a list of 6951 Experts worldwide ranked by ideXlab platform
Tatsuo Okada - One of the best experts on this subject based on the ideXlab platform.
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Dielectrophoretic fabrication and characterization of a ZnO nanowire-based UV Photosensor
Nanotechnology, 2006Co-Authors: Junya Suehiro, Shin Ichiro Hidaka, Mitsuhiro Higashihata, Makoto Ueda, Nobutaka Nakagawa, Kiminobu Imasaka, Tatsuo OkadaAbstract:Wide-gap semiconductors with nanostructures such as nanoparticles, nanorods, nanowires are promising as a new type of UV Photosensor. Recently, ZnO (zinc oxide) nanowires have been extensively investigated for electronic and optoelectronic device applications. ZnO nanowires are expected to have good UV response due to their large surface area to volume ratio, and they might enhance the performance of UV Photosensors. In this paper, a new fabrication method of a UV Photosensor based on ZnO nanowires using dielectrophoresis is demonstrated. Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized materials in non-uniform electric fields. ZnO nanowires, which were synthesized by nanoparticle-assisted pulsed-laser deposition (NAPLD) and suspended in ethanol, were trapped in the microelectrode gap where the electric field became higher. The trapped ZnO nanowires were aligned along the electric field line and bridged the electrode gap. Under UV irradiation, the conductance of the DEP-trapped ZnO nanowires exponentially increased with a time constant of a few minutes. The slow UV response of ZnO nanowires was similar to that observed with ZnO thin films and might be attributed to adsorption and photodesorption of ambient gas molecules such as O(2) or H(2)O. At higher UV intensity, the conductance response became larger. The DEP-fabricated ZnO nanowire UV Photosensor could detect UV light down to 10 nW cm(-2) intensity, indicating a higher UV sensitivity than ZnO thin films or ZnO nanowires assembled by other methods.
Domenico Caputo - One of the best experts on this subject based on the ideXlab platform.
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Sensors - Integration of Amorphous Silicon Photosensors with Thin Film Interferential Filter for Biomolecule Detection
Lecture Notes in Electrical Engineering, 2017Co-Authors: Domenico Caputo, Augusto Nascetti, Emanuele Parisi, Mario Tucci, Giampiero De CesareAbstract:This work presents a thin film device, combining, on the same glass substrate, Photosensors and long-pass interferential filter to achieve a compact and efficient sensor for biomolecule detection. The Photosensors are amorphous silicon stacked structures, while the interferential filter is fabricated alternating layers of silicon dioxide and titanium dioxide, directly grown over the Photosensors. The system has been optimized to effectively detect the natural fluorescence of Ochratoxin A, a highly toxic mycotoxin present in different food commodities. In particular, the long-pass interferential filter has been designed to reject the wavelengths arising from the excitation source (centered at 330 nm) thus transmitting the OTA emission spectrum (centered at 470 nm). Experimental results show that the filter strongly reduces the Photosensors quantum efficiency below 420 nm, while keeps it nearly constant at higher wavelength.
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Amorphous silicon Photosensors for food quality control applications
Lecture Notes in Electrical Engineering, 2015Co-Authors: Domenico Caputo, Riccardo Scipinotti, Augusto Nascetti, G. De Cesare, Corrado Fanelli, Alessandra RicelliAbstract:In this paper we present an innovative, low cost and portable detection system for food quality control based on Thin Layer Chromatography method. The operating principle relies on the real-time monitoring of the chromatographic run through the measurement of the photocurrent induced in amorphous silicon (a-Si:H) Photosensors by naturally fluorescent molecules present in the investigated sample. The integration in the system of the array of a-Si:H Photosensor allows to achieve a sensitive and compact system without external optics for focusing the fluorescent light. The presented system was designed for detection and quantification of Ochratoxin A (OTA), a toxin due to food contamination by fungi. Tests for the detection of OTA were successfully performed achieving a minimum detectable quantity of 0.2 ng for both red wine extract and OTA standard solutions. Taking into account a 90 % of extraction efficiency and a volume of 2 µl which can be spotted on the HPTLC plate, we infer that a volume of only 5.5 ml of red wine is necessary to compare OTA level with the law limit.
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Amorphous silicon Photosensors integrated in microfluidic structures as a technological demonstrator of a “true” Lab-on-Chip system
Sensing and Bio-Sensing Research, 2015Co-Authors: Domenico Caputo, Riccardo Scipinotti, Augusto Nascetti, Annalisa De Angelis, Nicola Lovecchio, Giampiero De CesareAbstract:Abstract In this paper we present a compact technological demonstrator including on the same glass substrate an electrowetting-on-dielectrics (EWOD) system, a linear array of amorphous silicon Photosensor and a capillary-driven microfluidic channel. The proposed system comprises also a compact modular electronics controlling the digital microfluidics through the USB interface of a computer. The system provides therefore both on-chip detection and microfluidic handling needed for the realization of a ‘true’ Lab-on-Chip. The geometry of the Photosensors has been designed to maximize the radiation impinging on the Photosensor and to minimize the inter-site crosstalk, while the fabrication process has been optimized taking into account the compatibility of all the technological steps for the fabrication of the EWOD system, the Photosensor array and the microfluidics channels. As a proof of the successful integration of the different technological steps we demonstrated the ability of the a-Si:H Photosensors to detect the presence of a droplet over an EWOD electrode and the effective coupling between the digital and the continuous microfluidics, that can allow for functionalization, immobilization and recognition of biomolecules without external optical devices or microfluidic interconnections.
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Multiwell cartridge with integrated array of amorphous silicon Photosensors for chemiluminescence detection: development, characterization and comparison with cooled-CCD luminograph
Analytical and Bioanalytical Chemistry, 2014Co-Authors: Mara Mirasoli, Martina Zangheri, Gridelli Cesare, Luca Cevenini, Riccardo Scipinotti, Domenico Caputo, Augusto Nascetti, Aldo RodaAbstract:We propose a disposable multiwell microcartridge with integrated amorphous silicon Photosensors array for bio- and chemiluminescence-based bioassays, where the enzymatic reactions and the detection unit are coupled on the same glass substrate. Each well, made in a polydimethylsiloxane (PDMS) unit, hosts an enzymatic reaction that is monitored by one Photosensor of the array. Photosensors were characterized in terms of their dark current background noise and response to different wavelengths of visible light in order to determine their suitability as detection devices for chemical luminescent phenomena. Calibration curves of the Photosensors’ response to different luminescent systems were then evaluated by using the chemiluminescent reactions catalyzed by alkaline phosphatase and horseradish peroxidase and the bioluminescent reaction catalyzed by firefly luciferase. Limits of detection in the order of attomoles for chemiluminescence enzymes and femtomoles for luciferase and sensitivities in the range between 0.007 and 0.1 pA pmol^−1 L were reached. We found that, without the need of cooling systems, the analytical performances of the proposed cartridge are comparable with those achievable with state-of-the-art thermoelectrically cooled charge-coupled device-based laboratory instrumentation. In addition, thanks to the small amount of generated output data, the proposed device allows the monitoring of long-lasting reactions with significant advantages in terms of data-storage needs, transmission bandwidth, ease of real-time signal processing and limited power consumption. Based on these results, the operation in model bioanalytical assays exploiting luminescent reactions was tested demonstrating that a-Si:H Photosensors arrays, when integrated with PDMS microfluidic units, provide compact, sensitive and potentially low-cost microdevices for chemiluminescence and bioluminescence-based bioassays with a wide range of possible applications for in-field and point-of-care bio-analyses.
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Amorphous silicon Photosensors for on-chip detection in digital microfluidic system
Sensors and Actuators A: Physical, 2014Co-Authors: Domenico Caputo, Augusto Nascetti, G. De Cesare, Riccardo ScipinottiAbstract:Abstract In this paper we present the integration, on a single glass substrate, of amorphous silicon photodiodes with an electrowetting-on-dielectric (EWOD) system as a technological demonstrator for achieving a compact, stand alone Lab-on-Chip (LoC) system. The EWOD system comprises a thin film of indium tin oxide (ITO) acting as actuation electrodes and a 1 μm-thick polydimethylsiloxane (PDMS) layer acting as both insulation and hydrophobic layer. The a-Si:H Photosensors are ITO/p-type/intrinsic/n-type/metal stacked structures, aligned with the transparent EWOD electrodes, to detect optical signals generated inside (or modulated by) the liquid droplets handled by the digital microfluidic system. The fabrication process has been designed and performed taking into account the compatibility of all the technological steps of the Photosensor and EWOD structures fabrication. The successful integration has been demonstrated checking the correct geometry of EWOD electrodes and measuring the optoelectronic performances of the a-Si:H Photosensors at the end of the system fabrication. The correct operation and potentiality of the presented device has been assessed monitoring a photodiode current when a water droplet is moved forward and backward over the EWOD electrodes aligned with the Photosensors.
Frangiskos V. Topalis - One of the best experts on this subject based on the ideXlab platform.
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Multi-criteria decision analysis to select the optimum position and proper field of view of a Photosensor
Energy Conversion and Management, 2014Co-Authors: Lambros T. Doulos, Aris Tsangrassoulis, Frangiskos V. TopalisAbstract:Abstract The lack of knowledge concerning the commissioning of a daylight responsive system constitutes a serious impediment to their widespread use. Furthermore, installation details and tools regarding their Photosensor position and field of view (FOV) are insufficient. This paper presents a decision making method capable to estimate the best position of a Photosensor on the ceiling and its proper FOV based on multiple criteria analysis. The criteria used are (a) the correlation of the lighting levels between the working plane and the ceiling, (b) the corresponding energy savings and (c) the lighting adequacy which is defined as the percentage for occupied time with total illuminance exceeding design illuminance (i.e 500 lux EN 12464-1, 2011) and is strongly affected by the control algorithm. A number of simulations with variable FOV and position of Photosensors were performed in order to clarify the calculation procedure of the proposed methodology. Three different typical room geometries have been used with variable window sizes and orientation. Furthermore a prototype Photosensor with variable FOV through the use of a telescopic cylinder was constructed and placed in a scale room (1:10) in order to verify the results of simulations. The verification was based on a set of experimental procedures concerning measurements of the spatial response of the prototype Photosensor (for various FOVs) and measurements of ceiling/workplane illuminance inside the scaled room for various combinations of position and FOV of the Photosensor. The proposed methodology can be used as a tool for the determination of the optimum operation of a daylight responsive system with Photosensors.
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The role of spectral response of Photosensors in daylight responsive systems
Energy and Buildings, 2008Co-Authors: Lambros T. Doulos, Aris Tsangrassoulis, Frangiskos V. TopalisAbstract:Abstract Lighting control technologies using Photosensors have a great potential for energy savings in areas with high levels of daylight. Although the proper application of these controls can exploit this potential, unfortunately, it has been accomplished in a small percentage of new projects. One reason is the difficulty in justification of energy savings, which in turn, is directly linked with the simulation of the behaviour of these lighting controls. The core of these systems is the Photosensor, which adjusts the electric light output in proportion to the amount of the daylight that detects, using its spatial and spectral response. The aim of this study is to quantify the impact of Photosensor spectral response on its illuminance values, by taking into account various daylight spectra as these are modified due to various types of coloured glazing. Five commercial Photosensors were selected and their spectral response was measured. In addition, spectral transmittance of 16 commercial types of glazing was measured as well. Using these data, a set of simulations were performed using three colour channels in a typical office room and the relative differences in illuminance – and thus energy savings – among the Photosensors are presented. The results show that differences are significant ranging from 36 to 118%, a fact that can affect the estimated payback period of a lighting control system.
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Reviewing the role of Photosensors in lighting control systems
2007Co-Authors: Lambros T. Doulos, Aris Tsangrassoulis, Frangiskos V. TopalisAbstract:The application of innovative technologies of automatic control in lighting systems gains daily the interest of engineers, constructors and users. The main purpose of these applications is the energy savings. Daylight control is a form of automatic control that replaces the manual control of the users. The core of this system is the Photosensor, which creates a signal in proportion to the amount of the daylight that detects, using its spatial and spectral response. The signal of the Photosensor can be combined with dimming electronic ballasts which adjust the electric light output giving a great potential for energy savings in areas with high levels of daylight. Nevertheless, the daylight responsive systems are widely misunderstood and they have been characterized hastily as problematic systems. The lack of knowledge and comprehension of these systems is a great withdraw against their widespread use and a lost opportunity for energy savings. In this present study becomes effort to overcome these difficulties clarifying the operation procedures of the Photosensors and their function as part of the lighting system. Also the characteristics that influence their operation are presented with advices for their optimum placement in spaces of application.
Riccardo Scipinotti - One of the best experts on this subject based on the ideXlab platform.
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Amorphous silicon Photosensors for food quality control applications
Lecture Notes in Electrical Engineering, 2015Co-Authors: Domenico Caputo, Riccardo Scipinotti, Augusto Nascetti, G. De Cesare, Corrado Fanelli, Alessandra RicelliAbstract:In this paper we present an innovative, low cost and portable detection system for food quality control based on Thin Layer Chromatography method. The operating principle relies on the real-time monitoring of the chromatographic run through the measurement of the photocurrent induced in amorphous silicon (a-Si:H) Photosensors by naturally fluorescent molecules present in the investigated sample. The integration in the system of the array of a-Si:H Photosensor allows to achieve a sensitive and compact system without external optics for focusing the fluorescent light. The presented system was designed for detection and quantification of Ochratoxin A (OTA), a toxin due to food contamination by fungi. Tests for the detection of OTA were successfully performed achieving a minimum detectable quantity of 0.2 ng for both red wine extract and OTA standard solutions. Taking into account a 90 % of extraction efficiency and a volume of 2 µl which can be spotted on the HPTLC plate, we infer that a volume of only 5.5 ml of red wine is necessary to compare OTA level with the law limit.
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Amorphous silicon Photosensors integrated in microfluidic structures as a technological demonstrator of a “true” Lab-on-Chip system
Sensing and Bio-Sensing Research, 2015Co-Authors: Domenico Caputo, Riccardo Scipinotti, Augusto Nascetti, Annalisa De Angelis, Nicola Lovecchio, Giampiero De CesareAbstract:Abstract In this paper we present a compact technological demonstrator including on the same glass substrate an electrowetting-on-dielectrics (EWOD) system, a linear array of amorphous silicon Photosensor and a capillary-driven microfluidic channel. The proposed system comprises also a compact modular electronics controlling the digital microfluidics through the USB interface of a computer. The system provides therefore both on-chip detection and microfluidic handling needed for the realization of a ‘true’ Lab-on-Chip. The geometry of the Photosensors has been designed to maximize the radiation impinging on the Photosensor and to minimize the inter-site crosstalk, while the fabrication process has been optimized taking into account the compatibility of all the technological steps for the fabrication of the EWOD system, the Photosensor array and the microfluidics channels. As a proof of the successful integration of the different technological steps we demonstrated the ability of the a-Si:H Photosensors to detect the presence of a droplet over an EWOD electrode and the effective coupling between the digital and the continuous microfluidics, that can allow for functionalization, immobilization and recognition of biomolecules without external optical devices or microfluidic interconnections.
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Multiwell cartridge with integrated array of amorphous silicon Photosensors for chemiluminescence detection: development, characterization and comparison with cooled-CCD luminograph
Analytical and Bioanalytical Chemistry, 2014Co-Authors: Mara Mirasoli, Martina Zangheri, Gridelli Cesare, Luca Cevenini, Riccardo Scipinotti, Domenico Caputo, Augusto Nascetti, Aldo RodaAbstract:We propose a disposable multiwell microcartridge with integrated amorphous silicon Photosensors array for bio- and chemiluminescence-based bioassays, where the enzymatic reactions and the detection unit are coupled on the same glass substrate. Each well, made in a polydimethylsiloxane (PDMS) unit, hosts an enzymatic reaction that is monitored by one Photosensor of the array. Photosensors were characterized in terms of their dark current background noise and response to different wavelengths of visible light in order to determine their suitability as detection devices for chemical luminescent phenomena. Calibration curves of the Photosensors’ response to different luminescent systems were then evaluated by using the chemiluminescent reactions catalyzed by alkaline phosphatase and horseradish peroxidase and the bioluminescent reaction catalyzed by firefly luciferase. Limits of detection in the order of attomoles for chemiluminescence enzymes and femtomoles for luciferase and sensitivities in the range between 0.007 and 0.1 pA pmol^−1 L were reached. We found that, without the need of cooling systems, the analytical performances of the proposed cartridge are comparable with those achievable with state-of-the-art thermoelectrically cooled charge-coupled device-based laboratory instrumentation. In addition, thanks to the small amount of generated output data, the proposed device allows the monitoring of long-lasting reactions with significant advantages in terms of data-storage needs, transmission bandwidth, ease of real-time signal processing and limited power consumption. Based on these results, the operation in model bioanalytical assays exploiting luminescent reactions was tested demonstrating that a-Si:H Photosensors arrays, when integrated with PDMS microfluidic units, provide compact, sensitive and potentially low-cost microdevices for chemiluminescence and bioluminescence-based bioassays with a wide range of possible applications for in-field and point-of-care bio-analyses.
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Amorphous silicon Photosensors for on-chip detection in digital microfluidic system
Sensors and Actuators A: Physical, 2014Co-Authors: Domenico Caputo, Augusto Nascetti, G. De Cesare, Riccardo ScipinottiAbstract:Abstract In this paper we present the integration, on a single glass substrate, of amorphous silicon photodiodes with an electrowetting-on-dielectric (EWOD) system as a technological demonstrator for achieving a compact, stand alone Lab-on-Chip (LoC) system. The EWOD system comprises a thin film of indium tin oxide (ITO) acting as actuation electrodes and a 1 μm-thick polydimethylsiloxane (PDMS) layer acting as both insulation and hydrophobic layer. The a-Si:H Photosensors are ITO/p-type/intrinsic/n-type/metal stacked structures, aligned with the transparent EWOD electrodes, to detect optical signals generated inside (or modulated by) the liquid droplets handled by the digital microfluidic system. The fabrication process has been designed and performed taking into account the compatibility of all the technological steps of the Photosensor and EWOD structures fabrication. The successful integration has been demonstrated checking the correct geometry of EWOD electrodes and measuring the optoelectronic performances of the a-Si:H Photosensors at the end of the system fabrication. The correct operation and potentiality of the presented device has been assessed monitoring a photodiode current when a water droplet is moved forward and backward over the EWOD electrodes aligned with the Photosensors.
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Amorphous Silicon Photosensors for Detection of Ochratoxin a in Wine
IEEE Sensors Journal, 2012Co-Authors: Domenico Caputo, Augusto Nascetti, G. De Cesare, Corrado Fanelli, Alessandra Ricelli, Riccardo ScipinottiAbstract:The presence of ochratoxin A (OTA) in different food commodities deserves great attention because of its toxic and carcinogenic effects on humans and animals. In this paper, we report on the detection of OTA both in standard solutions and in contaminated samples of red wine by using amorphous silicon Photosensors. The method relies on the excitation by ultraviolet radiation of the toxin molecules and on the absorption of the toxin reemitted light by the Photosensor. The device is a p-i-n stacked structure, whose electro-optical characteristics have been optimized in order to maximize the Photosensor responsivity and the limit of detection. For standard solutions, we found minimum detected OTA amount to be equal to 0.1 ng, while for contaminated red wine samples the technique coupled with very simplified and rapid extraction procedures has allowed the detection of OTA at the 1-ppb level.
Zong-syun Chen - One of the best experts on this subject based on the ideXlab platform.
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Transparent ZnO Nanowire-Network Ultraviolet Photosensor
IEEE Transactions on Electron Devices, 2011Co-Authors: Shi-ming Peng, Sheng-joue Young, Chi-nan Tsai, Jhih-hong Hong, Zong-syun ChenAbstract:This paper demonstrates the fabrication of transparent ultraviolet (UV) Photosensors with a self-assembling ordered ZnO nanowired network. The average optical transmission of the entire networked Photosensor structure in the visible range of the spectrum is about 70%. At an applied bias of 5 V and 340-nm irradiation, the photoresponsivity and the ratio of UV-to-visible rejection was 175.58 and 207.63 A/W for the transparent UV Photosensors. For a bandwidth of 100 Hz and an applied bias of 5 V, the noise equivalent power and normalized detectivity of the devices were 2.32 × 10-10 W and 4.36 × 108 cm · Hz0.5/W , respectively.