@article{li_mills_flewwellin_herzberg_bosari_lim_jia_jur_2021, title={Influence of Armband Form Factors on Wearable ECG Monitoring Performance}, volume={21}, ISSN={["1558-1748"]}, DOI={10.1109/JSEN.2021.3059997}, abstractNote={In the current state of innovation in wearable technology, there is a vast array of biomonitoring devices available to record electrocardiogram (ECG) in users, a key indicator of cardiovascular health. Of these devices, armband form factors serve as a convenient all-in-one platform for integration of electronic systems; yet, much of the current literature does not address the appropriate electrode location nor contact pressures necessary to achieve reliable system level ECG sensing. Therefore, this paper will elucidate the role of electrode location and contact pressure on the ECG sensing performance of an electronic textile (E-textile) armband worn on the upper left arm. We first carry out an ECG signal characterization to validate the ideal armband electrode placement necessary to measure high quality signals without sacrificing practical assembly of the armband. We then model and experimentally quantify the contact pressure between the armband onto the upper arm as a function of armband size, a critical parameter dictating skin-electrode impedance and ECG signal quality. Finally, we evaluate how the size of the armband form factor affects its ECG sensing performance. Our experimental results confirm that armbands exhibiting modeled contact pressures between 500 Pa to 1500 Pa can acquire ECG signals. However, armband sizes exhibiting experimental contact pressures of 1297 ± 102 Pa demonstrate the best performance with similar signal-to-noise ratios (SNR) compared to wet electrode benchmarks. The fundamental design parameters discussed in this work serve as a benchmark for the design of future E-textile and wearable form factors with efficient sensing performance.}, number={9}, journal={IEEE SENSORS JOURNAL}, author={Li, Braden M. and Mills, Amanda C. and Flewwellin, Tashana J. and Herzberg, Jacklyn L. and Bosari, Azin Saberi and Lim, Michael and Jia, Yaoyao and Jur, Jesse S.}, year={2021}, month={May}, pages={11046–11060} }
 @article{lee_lim_misra_2021, title={Wearable skin vapor sensing system for continuous monitoring of various health and lifestyles}, ISSN={["1930-0395"]}, DOI={10.1109/SENSORS47087.2021.9639471}, abstractNote={This work demonstrates a battery powered wearable monitoring system to measure the volatile organic compounds (VOCs) emanating from human skin. The portable system consists of gas sensors, Wi-Fi and Bluetooth enabled MCU, temperature and humidity sensors on a 33mm x 30mm PCB board. The developed system includes 5 sensors to detect and quantify the VOCs from skin as well as to measure the ambient VOC level. The results show that the developed system is able to distinguish the total VOCs between intermittent fasting and alcohol intake. This wearable sensing system enables detection of VOCs in real-time as well as monitoring of personalized VOC exposures for various lifestyles.}, journal={2021 IEEE SENSORS}, author={Lee, Bongmook and Lim, Michael and Misra, Veena}, year={2021} }
 @article{lim_mills_lee_misra_2018, title={Investigation of O-3 Adsorption on Ultra-Thin ALD SnO2 by QCM}, volume={18}, ISSN={["1558-1748"]}, url={https://doi.org/10.1109/JSEN.2018.2815698}, DOI={10.1109/jsen.2018.2815698}, abstractNote={This paper investigates the properties of room temperature adsorption of O3 on ultra-thin ALD SnO2. Adsorption is characterized by gravimetric measurements on QCM and frequency shift is converted to mass calculations. Both Langmuir and Freundlich isotherm parameters are calculated for O3 on Au, as-deposited SnO2, and annealed SnO2. Of the samples, annealed SnO2 shows the greatest mass shift and calculated number of adsorption sites. The surface resistivity is estimated to transduce the adsorbed quantity into conductometric respsonse; $\mathrm {\Delta }{R}_{s}=4.037e5\,\,\mathrm {\Omega /sq}$ for an O3 saturated as-deposited ALD SnO2 surface and $\mathrm {\Delta }{R}_{s}=4.859e3\,\,\mathrm {\Omega /sq}$ for the annealed ALD SnO2.}, number={9}, journal={IEEE SENSORS JOURNAL}, author={Lim, Michael and Mills, Steven and Lee, Bongmook and Misra, Veena}, year={2018}, month={May}, pages={3590–3594} }
 @inproceedings{lim_malhotra_mills_muth_lee_misra_2016, title={Metal oxide gas sensing characterization by low frequency noise spectroscopy}, DOI={10.1109/icsens.2016.7808835}, abstractNote={This work demonstrates a new method for selective identification of low ppb concentrations of O3. Atomic layer deposited thin film SnO2 was used as a sensing layer. SnO2 sensitized quartz crystal microbalances (QCM) demonstrate expected mass loading behavior as well as unique frequency domain response towards synthetic air, O3, and NO2 at room temperature. Power spectral densities (PSD) of the response of each gas were calculated and contain peaks at different normalized frequencies. These PSD peaks are found to have significant differences in magnitude for each analyte and provide evidence of selective room temperature adsorption of gases on SnO2.}, booktitle={2016 ieee sensors}, author={Lim, M. and Malhotra, A. and Mills, S. and Muth, J. and Lee, B. and Misra, Veena}, 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} }
 @article{lim_mills_lee_misra_2015, title={Application of AlGaN/GaN Heterostructures for Ultra-Low Power Nitrogen Dioxide Sensing}, volume={4}, ISSN={["2162-8769"]}, DOI={10.1149/2.0101510jss}, abstractNote={Ultra-low power room temperature NO2 sensors are demonstrated using AlGaN/GaN. The chemically stable semiconductor was sensitized to increase the sensitivity to enable ultra-low power, low ppb level detection without additional heaters. Sensors were sensitized by two methods, ultra-thin ALD SnO2 and surface enhancement by ICP-RIE in BCl3 gas. Both sensitization techniques demonstrate room temperature response, while the unsensitized sensors did not respond. At room temperature, surface enhanced sensors show a significant increase in sensitivity compared to SnO2 sensitized sensors. Sensitized sensors have fast response times and ultra-low power consumption to enable wearable monitoring systems with high spatial resolution of NO2. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0101510jss] All rights reserved.}, number={10}, journal={ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY}, author={Lim, Michael and Mills, Steven and Lee, Bongmook and Misra, Veena}, year={2015}, pages={S3034–S3037} }
 @article{mills_lim_lee_misra_2015, title={Atomic Layer Deposition of SnO2 for Selective Room Temperature Low ppb Level O-3 Sensing}, volume={4}, ISSN={["2162-8769"]}, DOI={10.1149/2.0111510jss}, abstractNote={This work demonstrates ultra-low power ozone sensors for real time, continuous, and portable monitoring. Atomic Layer Deposition (ALD) of SnO2 enables precise control of ultrathin film thickness on the order of the Debye length to enhance sensitivity at room temperature. Correlation between ozone concentration and the rate of resistance change is used to maintain fast response times and ultraviolet (UV) illumination hastens recovery. ALD SnO2 ultrathin film sensors realize room temperature operation with highly selective detection of 50 ppb ozone with average power consumption of 150 μW making them well suited for real time, portable environmental monitoring systems. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0111510jss] All rights reserved.}, number={10}, journal={ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY}, author={Mills, Steven and Lim, Michael and Lee, Bongmook and Misra, Veena}, year={2015}, pages={S3059–S3061} }
 @inproceedings{misra_lee_manickam_lim_pasha_mills_bhansali_2015, title={Ultra-low power sensing platform for personal health and personal environmental monitoring}, DOI={10.1109/iedm.2015.7409687}, abstractNote={The vision of the NSF Center on Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) is to develop nano-enabled technologies to achieve a paradigm shift towards long-term health and wellness management. To achieve this, the center is building self-powered, wearable and multimodal sensing systems for correlation of environmental exposures to physiological parameters. This paper presents the latest advances in environmental and personal health sensors that have ultra-low power consumption and are highly selective and sensitive to enable real time, continuous, and wearable platforms.}, booktitle={2015 IEEE International Electron Devices Meeting (IEDM)}, author={Misra, Veena and Lee, B. and Manickam, P. and Lim, M. and Pasha, S. K. and Mills, S. and Bhansali, S.}, year={2015} }