@article{zhou_dieffenderfer_aleem_lee_misra_2024, title={A Novel Monolithic MEMS Array for E-Nose Applications}, volume={8}, ISSN={["2475-1472"]}, url={https://doi.org/10.1109/LSENS.2024.3355902}, DOI={10.1109/LSENS.2024.3355902}, abstractNote={In this letter, we present a novel monolithic microelectromechanical syste-ms (MEMS) matrix array that can be adapted for electronic nose (E-nose) applications. The proposed MEMS array consists of four heater rows and four sensing electrode columns, arranged in crossbars and resulting in 16 intersections, which sit on top of suspended membranes created by frontside isotropic dry etching. Power supply, fine-tuning, and wireless communication are integrated on a custom printed circuit board. Thin films of metal oxide are deposited on this matrix array via atomic layer deposition. The achieved E-nose is low power, ultrasensitive, fast, scalable, reliable, and repeatable. It responds to different volatile organic compounds (VOCs) through the identification of optimal operating temperature. For nitrogen dioxide, ethanol, and carbon monoxide (CO), optimal temperatures and measured lower detection limits are ∼150 °C, 6.67 ppb, ∼250 °C, 50 ppb, and ∼350 °C, 1 ppm, respectively. Calculated theoretical detection limits are orders of magnitude lower. At optimal conditions, response/recovery time is <1 min. By tuning temperature profiles, this E-nose can inherently separate VOCs in mixtures. The proposed array is a versatile platform, compatible with back end of line complementary metal–oxide–semiconductor (CMOS) technology.}, number={2}, journal={IEEE SENSORS LETTERS}, author={Zhou, Yilu and Dieffenderfer, James and Aleem, Mahaboobbatcha and Lee, Bongmook and Misra, Veena}, year={2024}, month={Feb} }
 @article{dieffenderfer_brewer_noonan_smith_eichenlaub_haley_jacks_lobaton_neupert_hess_et al._2023, title={A Wearable System for Continuous Monitoring and Assessment of Speech, Gait, and Cognitive Decline for Early Diagnosis of ADRD}, ISSN={["1558-4615"]}, DOI={10.1109/EMBC40787.2023.10339986}, abstractNote={Early detection of cognitive decline is essential to study mild cognitive impairment and Alzheimer’s Disease in order to develop targeted interventions and prevent or stop the progression of dementia. This requires continuous and longitudinal assessment and tracking of the related physiological and behavioral changes during daily life. In this paper, we present a low cost and low power wearable system custom designed to track the trends in speech, gait, and cognitive stress while also considering the important human factor needs such as privacy and compliance. In the form factors of a wristband and waist-patch, this multimodal, multi-sensor system measures inertial signals, sound, heart rate, electrodermal activity and pulse transit time. A total power consumption of 2.6 mW without any duty cycling allows for more than 3 weeks of run time between charges when 1500 mAh batteries are used.Clinical Relevance— Much earlier detection of Alzheimer’s disease and related dementias may be possible by continuous monitoring of physiological and behavioral state using application specific wearable sensors during the activities of daily life.}, journal={2023 45TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY, EMBC}, author={Dieffenderfer, James and Brewer, Alec and Noonan, Maxwell A. and Smith, Madeline and Eichenlaub, Emily and Haley, Katarina L. and Jacks, Adam and Lobaton, Edgar and Neupert, Shevaun D. and Hess, Thomas M. and et al.}, year={2023} }
 @article{wu_nichols_foster_martin_dieffenderfer_enomoto_lascelles_russenberger_brenninkmeyer_bozkurt_et al._2023, title={An Exploration of Machine Learning Methods for Gait Analysis of Potential Guide Dogs}, url={https://doi.org/10.1145/3637882.3637883}, DOI={10.1145/3637882.3637883}, abstractNote={Gait analysis is important for guide dog organizations, as ideal guide dogs have a smooth and efficient gait, where they can also easily shift between and maintain various gaits. Gait quality and natural traveling speed are two of the multiple factors important in matching a guide dog to its visually impaired handler. Gait evaluation typically includes subjective visual observation of the dog or objective assessments obtained from special-designed equipment. Guide dog organizations need a method to easily collect and analyze objective data of gait information. In this work, we explored how various machine learning models could learn and analyze gait patterns from inertial measurements data that were collected during two different data collection experiments using a wearable sensor device. We also evaluated how well each machine learning model could generalize behavior patterns from various dogs under different environments. Additionally, we compared how sensor placement locations could affect gait prediction performance by attaching the sensor device to the dog’s neck and back area respectively. The tested machine learning models were able to classify different gaits in the range of 42% to 91% in terms of accuracy, and predict various gait parameters with an error rate ranging from 14% to 29% depending on the setup. Furthermore, we also observed that using behavior data collected from the neck region contains more movement information than the back area. By performing a cross-dataset generalization test on the machine learning models, we found that even with performance drop, the models were able to learn gait-specific behavior patterns that are generalizable for different dogs. Although the results were preliminary, the proposed gait analysis exploration still showed promising potential for studying behavior patterns of candidate guide dogs.}, journal={TENTH INTERNATIONAL CONFERENCE ON ANIMAL-COMPUTER INTERACTION, ACI 2023}, author={Wu, Yifan and Nichols, Colt and Foster, Marc and Martin, Devon and Dieffenderfer, James and Enomoto, Masataka and Lascelles, B. Duncan X. and Russenberger, Jane and Brenninkmeyer, Gerald and Bozkurt, Alper and et al.}, year={2023} }
 @article{pozdin_dieffenderfer_2022, title={Towards Wearable Health Monitoring DevicesY}, volume={12}, ISSN={["2079-6374"]}, DOI={10.3390/bios12050322}, abstractNote={Humans have searched far beyond our planet to understand the fundamental principles and mechanisms of life [...]}, number={5}, journal={BIOSENSORS-BASEL}, author={Pozdin, Vladimir A. and Dieffenderfer, James}, year={2022}, month={May} }
 @article{latif_dieffenderfer_tanneeru_lee_misra_bozkurt_2021, title={Evaluation of Environmental Enclosures for Effective Ambient Ozone Sensing in Wrist-worn Health and Exposure Trackers}, ISSN={["1930-0395"]}, DOI={10.1109/SENSORS47087.2021.9639530}, abstractNote={The ambient environmental conditions, most notably ozone concentration, play a critical role in exacerbating asthma related symptoms. Wearable devices offer a great potential for asthma care and management by tracking health and environmental status. Wearable devices in the form factor of a wristband using ultra-low power ozone sensors can provide a localized, real-time, and vigilant monitoring of users’ ambient environment. This work presents a preliminary investigation of environmental enclosures for such a custom designed wrist-worn wearable device for asthma. Enclosure design plays an important role in ensuring optimal environmental and gas sensor operation. In this study, we studied openings along the sidewall of the wrist-worn device covered with commercially available expanded polytetrafluoroethylene-based membranes to provide the required air flow while ensuring resistance to water.}, journal={2021 IEEE SENSORS}, author={Latif, Tahmid and Dieffenderfer, James and Tanneeru, Akhilesh and Lee, Bongmook and Misra, Veena and Bozkurt, Alper}, year={2021} }
 @article{ring_burbank_mills_ivins_dieffenderfer_hernandez_2021, title={Validation of an app-based portable spirometer in adolescents with asthma}, volume={58}, ISSN={["1532-4303"]}, DOI={10.1080/02770903.2019.1702201}, abstractNote={Abstract Objectives Objective measurements of asthma impairment could aid teens in recognition of changes in asthma status over time. Ready access to a conventional spirometer is not realistic outside of the clinical setting. In this proof-of-concept study, we compared the performance of the VitalFlo mobile spirometer to the nSpire KoKo® sx1000 spirometer for accuracy in measuring Forced Expiratory Volume in one second (FEV1) and Forced Vital Capacity (FVC) in adolescents with asthma. Methods Two hundred forty pulmonary function measurements were collected from 48 adolescents with persistent asthma from the University of North Carolina’s pediatric allergy and pulmonology subspecialty clinics. Participants performed spirometry with the nSpireKoKo® sx1000 spirometer and the VitalFlo spirometer during their clinic visits. 119 simulated FVC maneuvers were conducted on both devices to standardize measurements. Pearson correlations, Bland-Altman procedure, and two-sample comparison tests were performed to assess the relationship between the two spirometers. Results VitalFlo measurements were significantly highly correlated with nSpireKoKo® spirometer values for FEV1, (r 2=0.721, [95% CI, 0.749 ± 0.120], P < 0.001) and moderately for FVC (r 2= 0.617, [95% CI, 0.640 ± 0.130], P < 0.001) measurements. There were no statistically significant differences of the mean FEV1 (M = 0.00764, SD = 0.364, t(59)=0.16, P = 0.87) and FVC measurements (M = 0.00261, SD = 0.565, t(59)=0.036, P = 0.97.) between the VitalFlo and nSpireKoKo® systems. Both devices demonstrated significantly high correlation when comparing the automated FVC (r 2 = 0.997, [95% CI, 1.00 ± 0.00974], P < 0.001) measurements. Bland-Altman plots did not demonstrate significant bias between devices for both FEV1 (0.00764 L) and FVC (0.00261 L) measurements. Conclusions Lung function measurements from the VitalFlo mobile spirometer were comparable to a commercially-available spirometer commonly used in clinical settings. This validated app-based spirometer for home use has the potential to improve asthma self-management.}, number={4}, journal={JOURNAL OF ASTHMA}, author={Ring, Brian and Burbank, Allison J. and Mills, Katherine and Ivins, Sally and Dieffenderfer, James and Hernandez, Michelle L.}, year={2021}, month={Mar}, pages={497–504} }
 @article{dieffenderfer_goodell_mills_mcknight_yao_lin_beppler_bent_lee_misra_et al._2016, title={Low-Power Wearable Systems for Continuous Monitoring of Environment and Health for Chronic Respiratory Disease}, volume={20}, ISSN={2168-2194 2168-2208}, url={http://dx.doi.org/10.1109/JBHI.2016.2573286}, DOI={10.1109/jbhi.2016.2573286}, abstractNote={We present our efforts toward enabling a wearable sensor system that allows for the correlation of individual environmental exposures with physiologic and subsequent adverse health responses. This system will permit a better understanding of the impact of increased ozone levels and other pollutants on chronic asthma conditions. We discuss the inefficiency of existing commercial off-the-shelf components to achieve continuous monitoring and our system-level and nano-enabled efforts toward improving the wearability and power consumption. Our system consists of a wristband, a chest patch, and a handheld spirometer. We describe our preliminary efforts to achieve a submilliwatt system ultimately powered by the energy harvested from thermal radiation and motion of the body with the primary contributions being an ultralow-power ozone sensor, an volatile organic compounds sensor, spirometer, and the integration of these and other sensors in a multimodal sensing platform. The measured environmental parameters include ambient ozone concentration, temperature, and relative humidity. Our array of sensors also assesses heart rate via photoplethysmography and electrocardiography, respiratory rate via photoplethysmography, skin impedance, three-axis acceleration, wheezing via a microphone, and expiratory airflow. The sensors on the wristband, chest patch, and spirometer consume 0.83, 0.96, and 0.01 mW, respectively. The data from each sensor are continually streamed to a peripheral data aggregation device and are subsequently transferred to a dedicated server for cloud storage. Future work includes reducing the power consumption of the system-on-chip including radio to reduce the entirety of each described system in the submilliwatt range.}, number={5}, journal={IEEE Journal of Biomedical and Health Informatics}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Dieffenderfer, James and Goodell, Henry and Mills, Steven and McKnight, Michael and Yao, Shanshan and Lin, Feiyan and Beppler, Eric and Bent, Brinnae and Lee, Bongmook and Misra, Veena and et al.}, year={2016}, month={Sep}, pages={1251–1264} }
 @inproceedings{keller_wilkins_reynolds_dieffenderfer_hood_daniele_bozkurt_tunc-ozdemir_2016, title={Nanocellulose electrodes for interfacing plant electrochemistry}, booktitle={2016 ieee sensors}, author={Keller, K. and Wilkins, M. and Reynolds, J. and Dieffenderfer, J. and Hood, C. and Daniele, M. A. and Bozkurt, A. and Tunc-Ozdemir, M.}, 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{dieffenderfer_wilkins_hood_beppler_daniele_bozkurt_2016, title={Towards a sweat-based wireless and wearable electrochemical sensor}, booktitle={2016 ieee sensors}, author={Dieffenderfer, J. and Wilkins, M. and Hood, C. and Beppler, E. and Daniele, M. A. and Bozkurt, A.}, year={2016} }
 @article{brugarolas_latif_dieffenderfer_walker_yuschak_sherman_roberts_bozkurt_2016, title={Wearable Heart Rate Sensor Systems for Wireless Canine Health Monitoring}, volume={16}, ISSN={["1558-1748"]}, DOI={10.1109/jsen.2015.2485210}, abstractNote={There is an increasing interest from dog handlers and veterinarians in an ability to continuously monitor dogs' vital signs (heart rate, heart rate variability, and respiratory rate) outside laboratory environments, with the aim of identifying physiological correlations to stress, distress, excitement, and other emotional states. We present a non-invasive wearable sensor system combining electrocardiogram (ECG), photoplethysmogram (PPG), and inertial measurement units (IMU) to remotely and continuously monitor the vital signs of dogs. To overcome the limitations imposed by the efficiently insulated skin and dense hair layers of dogs, we investigated the use of various styles of ECG electrodes and the enhancements of these by conductive polymer coatings. We also studied the incorporation of light guides and optical fibers for an efficient optical coupling of PPG sensors to the skin. Combined with our parallel efforts to use IMUs to identify dog behaviors, these physiological sensors will contribute to a canine-body area network to wirelessly and continuously collect data during canine activities with a long-term goal of effectively capturing and interpreting dogs' behavioral responses to environmental stimuli that may yield measurable benefits to handlers' interactions with their dogs.}, number={10}, journal={IEEE SENSORS JOURNAL}, author={Brugarolas, Rita and Latif, Tahmid and Dieffenderfer, James and Walker, Katherine and Yuschak, Sherrie and Sherman, Barbara L. and Roberts, David L. and Bozkurt, Alper}, year={2016}, month={May}, pages={3454–3464} }
 @inproceedings{dieffenderfer_goodell_bent_beppler_jayakumar_yokus_jur_bozkurt_peden_2015, title={Wearable wireless sensors for chronic respiratory disease monitoring}, DOI={10.1109/bsn.2015.7299411}, abstractNote={We present a wearable sensor system consisting of a wristband and chest patch to enable the correlation of individual environmental exposure to health response for understanding impacts of ozone on chronic asthma conditions. The wrist worn device measures ambient ozone concentration, heart rate via plethysmography (PPG), three-axis acceleration, ambient temperature, and ambient relative humidity. The chest patch measures heart rate via electrocardiography (ECG) and PPG, respiratory rate via PPG, wheezing via a microphone, and three-axis acceleration. The data from each sensor is continually streamed to a peripheral data aggregation device, and is subsequently transferred to a dedicated server for cloud storage. The current generation of the system uses only commercially-off-the-shelf (COTS) components where the entire electronic structure of the wristband has dimensions of 3.1×4.1×1.2 cm3 while the chest patch electronics has a dimensions of 3.3×4.4×1.2 cm3. The power consumptions of the wristband and chest patch are 78 mW and 33 mW respectively where using a 400 mAh lithium polymer battery would operate the wristband for around 15 hours and the chest patch for around 36 hours.}, booktitle={2015 IEEE 12th International Conference on Wearable and Implantable Body Sensor Networks (BSN)}, author={Dieffenderfer, J. P. and Goodell, H. and Bent, B. and Beppler, E. and Jayakumar, R. and Yokus, M. and Jur, J. S. and Bozkurt, A. and Peden, D.}, year={2015} }
 @article{uzsák_dieffenderfer_bozkurt_schal_2014, title={Social facilitation of insect reproduction with motor-driven tactile stimuli}, volume={281}, ISSN={0962-8452 1471-2954}, url={http://dx.doi.org/10.1098/rspb.2014.0325}, DOI={10.1098/rspb.2014.0325}, abstractNote={Tactile stimuli provide animals with important information about the environment, including physical features such as obstacles, and biologically relevant cues related to food, mates, hosts and predators. The antennae, the principal sensory organs of insects, house an array of sensory receptors for olfaction, gustation, audition, nociception, balance, stability, graviception, static electric fields, and thermo-, hygro- and mechanoreception. The antennae, being the anteriormost sensory appendages, play a prominent role in social interactions with conspecifics that involve primarily chemosensory and tactile stimuli. In the German cockroach (Blattella germanica) antennal contact during social interactions modulates brain-regulated juvenile hormone production, ultimately accelerating the reproductive rate in females. The primary sensory modality mediating this social facilitation of reproduction is antennal mechanoreception. We investigated the key elements, or stimulus features, of antennal contact that socially facilitate reproduction inB. germanicafemales. Using motor-driven antenna mimics, we assessed the physiological responses of females to artificial tactile stimulation. Our results indicate that tactile stimulation with artificial materials, some deviating significantly from the native antennal morphology, can facilitate female reproduction. However, none of the artificial stimuli matched the effects of social interactions with a conspecific female.}, number={1783}, journal={Proceedings of the Royal Society B: Biological Sciences}, publisher={The Royal Society}, author={Uzsák, Adrienn and Dieffenderfer, James and Bozkurt, Alper and Schal, Coby}, year={2014}, month={May}, pages={20140325} }
 @inproceedings{dieffenderfer_beppler_novak_whitmire_jayakumar_randall_qu_rajagopalan_bozkurt_2014, title={Solar powered wrist worn acquisition system for continuous photoplethysmogram monitoring}, DOI={10.1109/embc.2014.6944289}, abstractNote={We present a solar-powered, wireless, wrist-worn platform for continuous monitoring of physiological and environmental parameters during the activities of daily life. In this study, we demonstrate the capability to produce photoplethysmogram (PPG) signals using this platform. To adhere to a low power budget for solar-powering, a 574nm green light source is used where the PPG from the radial artery would be obtained with minimal signal conditioning. The system incorporates two monocrystalline solar cells to charge the onboard 20mAh lithium polymer battery. Bluetooth Low Energy (BLE) is used to tether the device to a smartphone that makes the phone an access point to a dedicated server for long term continuous storage of data. Two power management schemes have been proposed depending on the availability of solar energy. In low light situations, if the battery is low, the device obtains a 5-second PPG waveform every minute to consume an average power of 0.57 mW. In scenarios where the battery is at a sustainable voltage, the device is set to enter its normal 30 Hz acquisition mode, consuming around 13.7 mW. We also present our efforts towards improving the charge storage capacity of our on-board super-capacitor.}, booktitle={2014 36th annual international conference of the ieee engineering in medicine and biology society (embc)}, author={Dieffenderfer, J. P. and Beppler, E. and Novak, T. and Whitmire, E. and Jayakumar, R. and Randall, C. and Qu, W. G. and Rajagopalan, R. and Bozkurt, A.}, year={2014}, pages={3142–3145} }
 @inproceedings{dieffenderfer_bair_bozkurt_2013, title={Towards a smart bandage with functional near infrared spectroscopy capability}, DOI={10.1109/biowireless.2013.6613659}, abstractNote={This paper presents our efforts towards a smart bandage with incorporated miniaturized wireless functional near infrared spectroscopy system as a sensor node for wearable body area networks. The built prototype was used to successfully transmit deoxygenation of forearm muscle tissue during pressure cuff induced ischemia through an established Bluetooth link. The system can run over 4 hours continuously sampling at 150 Hz with provided 90mAh lithium polymer batteries and transmit data to distances more than 75 meters.}, booktitle={Ieee topical conference on biomedical wireless technologies networks and}, author={Dieffenderfer, J. and Bair, M. C. and Bozkurt, A.}, year={2013}, pages={13–15} }