@article{seok_mahmud_kumar_adelegan_yamaner_oralkan_2019, title={A Low-Power Wireless Multichannel Gas Sensing System Based on a Capacitive Micromachined Ultrasonic Transducer (CMUT) Array}, volume={6}, ISSN={["2327-4662"]}, url={https://doi.org/10.1109/JIOT.2018.2861330}, DOI={10.1109/JIOT.2018.2861330}, abstractNote={Detection of volatile organic compounds (VOCs), challenged by their diversity and similarity, is gaining much attention due to concerns about adverse health effects they cause, along with intensifying development efforts in wireless sensor nodes. Precise identification of volatiles may be subject to the sensitivity and selectivity of a sensor itself and the proximity of the sensor to the source, necessitating power-efficient and portable/wearable sensing systems. The metal-oxide sensors, commonly employed for detection of VOCs, are not power efficient, due to the required heating element, and lack the selectivity, thus reporting only the total VOC level. In this paper, we present a complete low-power wireless gas-sensing system based a capacitive micromachined ultrasonic transducer array, which is known to have several advantages such as high mass sensitivity, easy implementation of a multielement structure, and high selectivity upon polymer coating. We took a holistic approach to designing the sensing elements and the custom integrated circuit (IC) as well as to operating the system, resulting in a small self-contained sensor node (38-mm detect-weight diameter and 16-mm detect-weight height). The chemical-sensing capability of the system has been validated with ethanol, achieving 120-ppb limit-of-detection while the sensor array, including the IC and the power management unit, consuming 80- $\mu \text{W}$  average power with power cycling by actively taking measurements for 3 s detect-weight per minute. The presented system will eventually provide a ubiquitous tool to identify VOCs with the help of multivariate data analysis.}, number={1}, journal={IEEE INTERNET OF THINGS JOURNAL}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Seok, Chunkyun and Mahmud, Marzana Mantasha and Kumar, Mohit and Adelegan, Oluwafemi Joel and Yamaner, Feysel Yalcin and Oralkan, Omer}, year={2019}, month={Feb}, pages={831–843} }
 @inproceedings{seok_mahmud_adelegan_zhang_oralkan_2016, title={A battery-operated wireless multichannel gas sensor system based on a capacitive micromachined ultrasonic transducer (CMUT) array}, DOI={10.1109/icsens.2016.7808803}, abstractNote={This paper reports on the design and implementation of a complete battery-operated wireless system for a mechanically resonant gas sensor based on a capacitive micromachined ultrasonic transducer (CMUT) array. A custom-designed front-end integrated circuit (IC) with eight inputs and a serial peripheral interface (SPI) was tightly integrated with a CMUT array. The power consumption of the front-end is 10 μW with a duty cycle of 1:60 corresponding to 1-s measurement time every minute. For the completeness of the system, a power management unit (PMU) was designed and interfaced with the described custom IC along with a wireless module. For multichannel operation, time-division multiplexing was adopted to minimize power consumption and prevent potential frequency locking between different channels. Multichannel wireless data acquisition with the described system was demonstrated by loading unfunctionalized sensor channels with humidity in human breath.}, booktitle={2016 ieee sensors}, author={Seok, C. and Mahmud, M. M. and Adelegan, O. and Zhang, X. and Oralkan, Omer}, year={2016} }
 @inproceedings{tanneeru_mills_lim_mahmud_dieffenderfer_bozkurt_nagle_lee_misra_2016, title={Room temperature sensing of VOCS by atomic layer deposition of metal oxide}, DOI={10.1109/icsens.2016.7808786}, abstractNote={This work demonstrates room temperature sensing of volatile organic compound (VOC) — acetone via an ultrathin film metal oxide sensing layer. Atomic layer deposition (ALD) enables a high quality ultrathin film with precise thickness control. The 14nm ultrathin SnO2 thin film was deposited by ALD resulting in VOCs sensing at room temperature. The ultra-low power consumption (less than 50nW) and the room temperature operation of these devices make them compatible with wearable devices for real-time health and environment monitoring.}, booktitle={2016 ieee sensors}, author={TANNEERU, AKHILESH and Mills, S. and Lim, M. and Mahmud, M. M. and Dieffenderfer, J. and Bozkurt, A. and Nagle, T. and Lee, B. and Misra, V.}, year={2016} }
 @inproceedings{mahmud_kumar_zhang_yamaner_nagle_oralkan_2015, title={A capacitive micromachined ultrasonic transducer (CMUT) array as a low-power multi-channel volatile organic compound (VOC) sensor}, booktitle={2015 ieee sensors}, author={Mahmud, M. M. and Kumar, M. and Zhang, X. and Yamaner, F. Y. and Nagle, H. T. and Oralkan, O.}, year={2015}, pages={181–184} }
 @inproceedings{kumar_seok_mahmud_zhang_oralkan_2015, title={A low-power integrated circuit for interfacing a capacitive micromachined ultrasonic transducer (CMUT) based resonant gas sensor}, DOI={10.1109/icsens.2015.7370639}, abstractNote={In this work we present a complete end-to-end interface for a capacitive micromachined ultrasonic transducer (CMUT) intended for low-power gas sensing applications. A prototype chip was designed in a 0.18-μm BiCMOS process. Different blocks (a BJT-based Colpitts oscillator, an inverter-based oscillator, a sine-to-square wave converter, a digital frequency counter, and a parallel-to-serial converter) required for the complete system are discussed, designed, and tested for their standalone performance. Consequently, a complete system interfaced with a 3.6-MHz CMUT and providing a digital frequency output is presented. With duty cycling for one measurement per minute the system consumed 10 μW power.}, booktitle={2015 ieee sensors}, author={Kumar, M. and Seok, C. and Mahmud, M. M. and Zhang, X. and Oralkan, Omer}, year={2015}, pages={1781–1784} }