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RISS 인기검색어
- 검색키워드
- 저자 : Kupnik, Mario (검색결과 2 건)
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A Multichannel Oscillator for a Resonant Chemical Sensor System
Lee, Hyunjoo Jenny,Kwan Kyu Park,Oralkan, Omer,Kupnik, Mario,Khuri-Yakub, Butrus T. IEEE 2014 IEEE transactions on industrial electronics Vol.61 No.10
<P>Vapor detection using highly sensitive miniaturized resonant sensors is of great interest for many applications, including consumer, industrial, and environmental applications. An operational-amplifier-based multichannel oscillator that interfaces with a 50-MHz capacitive micromachined ultrasonic transducer array is presented for chemical sensing applications. The circuit was implemented in a 0.18-μm CMOS technology to reduce power consumption, number of wires, and active area per channel. The presented integrated circuit also addresses the potential-frequency-locking problem between channels by allowing the open-loop gain to be adjustable off-chip. The feasibility of the developed oscillator for the chemical sensing application is demonstrated. Two channels that were operated simultaneously achieved excellent volume sensitivities of 8.5 × 10<SUP>-4</SUP>%/Hz and 3.9 × 10<SUP>-4</SUP>%/Hz, respectively, to relative humidity in N<SUB>2</SUB>.</P>
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CMUT-based resonant gas sensor array for VOC detection with low operating voltage
Park, Sangjun,Yoon, Inug,Lee, Sungwoo,Kim, Hyojung,Seo, Ji-Won,Chung, Yoonyoung,Unger, Alexander,Kupnik, Mario,Lee, Hyunjoo J. Elsevier 2018 Sensors and actuators. B Chemical Vol.273 No.-
<P><B>Abstract</B></P> <P>With the anticipation for a more connected world through the Internet of Things, there is still a strong demand for miniaturized chemical sensors. Here, we report on a miniaturized resonant chemical sensor based on a Capacitive Micromachined Ultrasonic Transducer (CMUT) with a low operating voltage suitable for portable gas sensor applications. Previously reported CMUT chemical sensors required a DC operating voltage (16∼50 V) higher than the supply voltages of common circuits (<I>e.g.,</I> 1.8–5 V). Thus, additional circuitry such as a charge pump circuit often was required as a part of the sensor interface circuits to supply the DC voltage to CMUT. This resulted in additional power consumption and a larger footprint. In this work, the vacuum gap of the CMUT which determines the operating voltage was reduced to 50 nm through the development of a double oxidation process with a high wafer-level yield. We achieved a significantly smaller pull-in voltage (<10 V) for a 500-nm-thick CMUT resonant sensor. The CMUT was operated at approximately 80% of the pull-in voltage (∼8 V) which does not require additional voltage supply to that of the real-time read-out circuitry. Based on the resonant frequency of 6.7 MHz, the theoretical sensitivity of the fabricated CMUT resonant sensor was 0.8 Hz/fg. By coating four different chemically-sensitive polymer layers, we confirmed the operation of the CMUT with low operating voltage as a chemical sensor. Frequency shifts due to the chemical reaction of volatile organic compounds were observed and analyzed through principal component analysis. This work demonstrates the potential of the developed CMUT with low bias voltage as a key component of a portable chemical sensor system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CMUT-based resonant gas sensors with low operating voltage (<8 V) were fabricated. </LI> <LI> The low-voltage CMUT sensor functionalized with PEO exhibited 0.54 Hz/ppm sensitivity to toluene. </LI> <LI> Four CMUT sensors functionalized with different polymers were evaluated against multiple VOCs. </LI> <LI> Discrimination among gases were demonstrated through the use of multiple CMUT sensors. </LI> </UL> </P>
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