Browsing by Author "Dai, Ming-Zhi"

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A New Gas Sensor of a Thin-Film Diode and Low-Power, Area-Efficient Readout Circuit
(2013)
Chen, Hung-Che
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Chao, Paul C. -P.
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Lin, Wei-Chu
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Sun, Hsiang-Fang
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Dai, Ming-Zhi
The study presents a new gas sensor made of a novel organic diode with vertical nano-junctions and its low-power, area-efficient readout circuit. There are seven parts included in the readout system. First part is a preamplifier, which is composed of trans-impedance to convert the output current of a gas sensor into voltage. Second part is a peak-detect-and-hold circuit. It can detect the maximum voltage and holds its value, the initial value. Third part is a divider, which is used to calculate the ratio of saturation current to initial current. Fourth part is the saturation detector, which is used to detect when the output current of the VNJ-P3HT diode doesn\'t change anymore (that is, the responses are saturated). Fifth part is the auto-reset circuit, which is used to detect when the sensor device starts to react with gas and reset the voltage value of the peak detect-and-hold circuit. Sixth part is a logic gate and a buffer. When the sensor device is reacting with gas and the responses are saturated, the response result is outputted through the logic gate and buffer. Otherwise, the zero is outputted. Seventh part is a micro-processor control unit (MCU). STM32 is the CPU of proposed MCU by ALIENTEK. The ADC of MCU is used to transform the output data of readout circuit. Then the LCD displays the results. The designed circuit is accomplished by Taiwan Semiconductor Manufacturing Company (TSMC) 0.35 mu m 2P4M 3.3V mixed-signal CMOS process.
Achieving a Good Life Time in a Vertical-Organic-Diode Gas Sensor
(2014-09-01)
Dai, Ming-Zhi
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Chen, Yen-Ho
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Chuang, Ming-Yen
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
In this study, we investigate the keys to obtain a sensitive ammonia sensor with high air stability by using a low-cost polythiophene diode with a vertical channel and a porous top electrode. Poly(3-hexylthiophene) (P3HT) and air-stable poly(5,5'-bis(3-dodecyl-2-thienyl)-2,2'-bithiophene) (PQT-12) are both evaluated as the active sensing layer. Two-dimensional current simulation reveals that the proposed device exhibits numerous connected vertical nanometer junctions (VNJ). Due to the de-doping reaction between ammonia molecules and the bulk current flowing through the vertical channel, both PQT-12 and P3HT VNJ-diodes exhibit detection limits of 50-ppb ammonia. The P3HT VNJ-diode, however, becomes unstable after being stored in air for two days. On the contrary, the PQT-12 VNJ-diode keeps an almost unchanged response to 50-ppb ammonia after being stored in air for 25 days. The improved storage lifetime of an organic-semiconductor-based gas sensor in air is successfully demonstrated.
Detecting Breath Ammonia for Non-invasive Diagnostic based on Low-Cost Organic Diode with Vertical Nanojunctions
(2012)
Dai, Ming-Zhi
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Lin, Yi-Lo
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Lin, Hong-Cheng
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Zan, Hsiao-Wen
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Chang, Kai-Ting
We propose a novel solid-state electrical ammonia sensor based on a vertical organic diode with high-density nanopores in the top electrode. The proposed ammonia sensor has a detection limit of 20 ppb, a real-time response, sufficient selectivity, simple structure, high reproducibility, and a low production cost. In addition, we used the proposed sensor to detect the nasal breath of rats directly. After controlling the relative humidity and filtering out the CO2, we successfully obtained repeated real-time, reliable responses. This is the first demonstration of a solid-state sensor having reliable responses to the breath ammonia of an animal. The sensing response between normal and acute groups is significantly different (p < 0.05). These results demonstrated that the proposed ammonia sensor can detect liver that undergoes moderate hepatopathy.
Highly Sensitive Ammonia Sensor with Organic Vertical Nanojunctions for Noninvasive Detection of Hepatic Injury
(2013-03-19)
Dai, Ming-Zhi
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Lin, Yi-Lo
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Lin, Hung-Cheng
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Zan, Hsiao-Wen
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Chang, Kai-Ting
We successfully demonstrate the first solid-state sensor to have reliable responses to breath ammonia of rat. For thioacetamide (TAA)-induced hepatopathy rats, we observe that the proposed sensor can detect liver that undergoes acute-moderate hepatopathy with a p-value less than 0.05. The proposed sensor is an organic diode with vertical nanojunctions produced by using low-cost colloidal lithography. Its simple structure and low production cost facilitates the development of point-of-care technology. We also anticipate that the study is a starting point for investigating sophisticated breath-ammonia-related disease models.
LABEL-FREE SENSOR
(2010-09-23)
Meng, Hsin- Fei
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Hong, Sheng-Fu
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Chao, Yu-Chiang
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Liu, Chien-Cheng
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Liu, Wen-Hsing
A label-free sensor is disclosed. The label-free sensor comprises a substrate, a first electrode formed on the substrate, a second electrode formed on the substrate and spaced away from the first electrode, and a semiconductor layer formed on the substrate and is in contact with the first electrode and the second electrode, wherein the semiconductor layer has a plurality of probe groups, which are bonded to the semiconductor layer by functionalization, for sensing a coupling-specific substance, which has bonding specificity with the probe groups. The semiconductor layer of the label-free sensor of the present invention is bonded with probe groups, and the detection of detected object is performed in instant, quick, rapid, and sensitive manner by measuring variation in electric current, thereby avoiding the use of the fluorescent reading equipment for reading fluorescent signals.
Polymer hot-carrier transistor with low bandgap emitter
(2008-03-03)
Chao, Yu-Chiang
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Xie, Ming-Hong
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Dai, Ming-Zhi
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Meng, Hsin-Fei
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Horng, Sheng-Fu
Vertical polymer hot-carrier transistor using the low bandgap material poly(3-hexylthiophene) as both the emitter and the collector are studied. The common emitter current gain is shown to depend on the LiF thickness and the emitter thickness, with maximal value at 31. Current density as high as 31 mA/cm(2) is achieved when collector voltage is -10 V. For the device using blend of poly(3-hexylthiophene) and high bandgap polymer poly(9-vinylcarbazole) as the emitter, the current density rises sharply to 428 mA/cm(2). The brightness of 3000 cd/m(2) is obtained as a polymer light-emitting diode is driven by the transistor with the same area. The transistor can be operated at 100 kHz. (c) 2008 American Institute of Physics.
Polymer Infrared Proximity Sensor Array
(2011-04-01)
Chen, En-Chen
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Shih, Cheng-Yang
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Dai, Ming-Zhi
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Yeh, Han-Cheng
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Chao, Yu-Chiang
A near-infrared proximity sensor array is achieved by integrating a polymer light-emitting diode and a polymer photodetector (PD). A green emission is converted into deep red peaked at 670 nm by the inorganic phosphor Intematix R670 with quantum efficiency of over 20%. A bandpass filter is used to select a spectral tail of phosphor luminescence with a wavelength above 700 nm. The emissive polymer is green polyfluorene. The infrared PD contains a thick film of a blend of poly(3-hexylthiophene) and (6,6)-phenyl-C61-butyric acid methyl ester up to a thickness of 8 mu m. Position of a moving object at a distance of 10 cm is detected in real time by the array with dynamic images displayed on the computer screen.
Porous Organic TFTs for the Applications on Real-Time and Sensitive Gas Sensors
(2011-08-01)
Zan, Hsiao-Wen
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Dai, Ming-Zhi
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Hsu, Ting-Yu
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Lin, Hung-Cheng
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Meng, Hsin-Fei
A pentacene-based organic thin-film transistor (OTFT) with a porous active layer is demonstrated for the first time. The porous OTFT exhibits a fast, sensitive, and reversible response to ammonia gas with a detection limit as 500 ppb, whereas the OTFT without porous structure has a slow response and a poor recovery behavior. The sensing mechanism dominated by the dissociation of hydroxyl groups of the polymer dielectric layer is raised and discussed. The proposed device is the first OTFT-based ammonia sensor with reversible response and high sensitivity in low parts-per-million range. It is promising for the development of a diagnostic breath analysis system.
Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors
(2011-06-20)
Zan, Hsiao-Wen
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Li, Chang-Hung
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Yeh, Chun-Cheng
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Dai, Ming-Zhi
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Meng, Hsin-Fei
An organic sensing layer is capped onto an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction with the a-IGZO film. Oxidizing or reducing vapor molecules act like electron acceptors or electron donors to change the potential of the organic layer and the current of a-IGZO TFT. A sensitive and reversible response to 100 ppb ammonia and 100 ppb acetone is obtained at room temperature. This letter opens a route to develop low-cost large-area bio/chemical sensor arrays based on the emerging a-IGZO TFT technology. (C) 2011 American Institute of Physics. [doi:10.1063/1.3601488]