{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T18:59:24Z","timestamp":1771700364552,"version":"3.50.1"},"reference-count":49,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2022,11,1]],"date-time":"2022-11-01T00:00:00Z","timestamp":1667260800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["NNX16AQ99A"],"award-info":[{"award-number":["NNX16AQ99A"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000104","name":"National Aeronautics and Space Administration","doi-asserted-by":"publisher","award":["#1849525"],"award-info":[{"award-number":["#1849525"]}],"id":[{"id":"10.13039\/100000104","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Science Foundation Graduate Research Fellowship","award":["NNX16AQ99A"],"award-info":[{"award-number":["NNX16AQ99A"]}]},{"name":"National Science Foundation Graduate Research Fellowship","award":["#1849525"],"award-info":[{"award-number":["#1849525"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Modern wearable devices show promising results in terms of detecting vital bodily signs from the wrist. However, there remains a considerable need for a device that can conform to the human body\u2019s variable geometry to accurately detect those vital signs and to understand health better. Flexible radio frequency (RF) resonators are well poised to address this need by providing conformable bio-interfaces suitable for different anatomical locations. In this work, we develop a compact wearable RF biosensor that detects multisite hemodynamic events due to pulsatile blood flow through noninvasive tissue\u2013electromagnetic (EM) field interaction. The sensor consists of a skin patch spiral resonator and a wearable transceiver. During resonance, the resonator establishes a strong capacitive coupling with layered dielectric tissues due to impedance matching. Therefore, any variation in the dielectric properties within the near-field of the coupled system will result in field perturbation. This perturbation also results in RF carrier modulation, transduced via a demodulator in the transceiver unit. The main elements of the transceiver consist of a direct digital synthesizer for RF carrier generation and a demodulator unit comprised of a resistive bridge coupled with an envelope detector, a filter, and an amplifier. In this work, we build and study the sensor at the radial artery, thorax, carotid artery, and supraorbital locations of a healthy human subject, which hold clinical significance in evaluating cardiovascular health. The carrier frequency is tuned at the resonance of the spiral resonator, which is 34.5 \u00b1 1.5 MHz. The resulting transient waveforms from the demodulator indicate the presence of hemodynamic events, i.e., systolic upstroke, systolic peak, dicrotic notch, and diastolic downstroke. The preliminary results also confirm the sensor\u2019s ability to detect multisite blood flow events noninvasively on a single wearable platform.<\/jats:p>","DOI":"10.3390\/s22218389","type":"journal-article","created":{"date-parts":[[2022,11,2]],"date-time":"2022-11-02T08:15:12Z","timestamp":1667376912000},"page":"8389","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["A Flexible Near-Field Biosensor for Multisite Arterial Blood Flow Detection"],"prefix":"10.3390","volume":"22","author":[{"given":"Noor","family":"Mohammed","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Massachusetts Amherst, Amherst, MA 01003, USA"},{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"}]},{"given":"Kim","family":"Cluff","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"}]},{"given":"Mark","family":"Sutton","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"}]},{"given":"Bernardo","family":"Villafana-Ibarra","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"}]},{"given":"Benjamin E.","family":"Loflin","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"},{"name":"Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8673-6902","authenticated-orcid":false,"given":"Jacob L.","family":"Griffith","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"},{"name":"J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 32611, USA"}]},{"given":"Ryan","family":"Becker","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"},{"name":"Department of Biomedical Engineering, Duke University, Durham, NC 27708, USA"}]},{"given":"Subash","family":"Bhandari","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"},{"name":"Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14850, USA"}]},{"given":"Fayez","family":"Alruwaili","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"},{"name":"Department of Biomedical Engineering, Rowan University, Glassboro, NJ 08028, USA"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9436-466X","authenticated-orcid":false,"given":"Jaydip","family":"Desai","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Wichita State University, Wichita, KS 67260, USA"}]}],"member":"1968","published-online":{"date-parts":[[2022,11,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1393","DOI":"10.1109\/TBCAS.2019.2945575","article-title":"A Noninvasive, Electromagnetic, Epidermal Sensing Device for Hemodynamics Monitoring","volume":"13","author":"NMohammed","year":"2019","journal-title":"IEEE Trans. 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