{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T08:24:14Z","timestamp":1776327854730,"version":"3.50.1"},"reference-count":56,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2023,11,30]],"date-time":"2023-11-30T00:00:00Z","timestamp":1701302400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University Politehnica of Bucharest\u2019s PUBART project"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The origin of the photoplethysmography (PPG) signal is a debatable topic, despite plausible models being addressed. One concern revolves around the correlation between the mechanical waveform\u2019s pulsatile nature and the associated biomechanism. The interface between these domains requires a clear mathematical or physical model that can explain physiological behavior. Describing the correct origin of the recorded optical waveform not only benefits the development of the next generation of biosensors but also defines novel health markers. In this study, the assumption of a pulsatile nature is based on the mechanism of blood microcirculation. At this level, two interconnected phenomena occur: variation in blood flow velocity through the capillary network and red blood cell (RBC) shape deformation. The latter effect was qualitatively investigated in synthetic capillaries to assess the experimental data needed for PPG model development. Erythrocytes passed through 10 \u00b5m and 6 \u00b5m microchannel widths with imposed velocities between 50 \u00b5m\/s and 2000 \u00b5m\/s, according to real scenarios. As a result, the length and area deformation of RBCs followed a logarithmic law function of the achieved traveling speeds. Applying radiometric expertise on top, mechanical-optical insights are obtained regarding PPG\u2019s pulsatile nature. The mathematical equations derived from experimental data correlate microcirculation physiologic with waveform behavior at a high confidence level. The transfer function between the biomechanics and the optical signal is primarily influenced by the vasomotor state, capillary network orientation, concentration, and deformation performance of erythrocytes.<\/jats:p>","DOI":"10.3390\/s23239515","type":"journal-article","created":{"date-parts":[[2023,11,30]],"date-time":"2023-11-30T09:37:54Z","timestamp":1701337074000},"page":"9515","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Red Blood Cells\u2019 Area Deformation as the Origin of the Photoplethysmography Signal"],"prefix":"10.3390","volume":"23","author":[{"given":"Lucian","family":"Evdochim","sequence":"first","affiliation":[{"name":"Department of Electronic Devices, Circuits, and Architectures, Faculty of Electronics, Telecommunications and Information Technology, University Politehnica of Bucharest, 060042 Bucharest, Romania"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9048-1853","authenticated-orcid":false,"given":"Eugen","family":"Chiriac","sequence":"additional","affiliation":[{"name":"National Institute for Research and Development in Microtechnologies\u2014IMT Bucharest, 077190 Voluntari, Romania"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4126-7401","authenticated-orcid":false,"given":"Marioara","family":"Avram","sequence":"additional","affiliation":[{"name":"National Institute for Research and Development in Microtechnologies\u2014IMT Bucharest, 077190 Voluntari, Romania"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0028-5347","authenticated-orcid":false,"given":"Lidia","family":"Dobrescu","sequence":"additional","affiliation":[{"name":"Department of Electronic Devices, Circuits, and Architectures, Faculty of Electronics, Telecommunications and Information Technology, University Politehnica of Bucharest, 060042 Bucharest, Romania"}]},{"given":"Drago\u0219","family":"Dobrescu","sequence":"additional","affiliation":[{"name":"Department of Electronic Devices, Circuits, and Architectures, Faculty of Electronics, Telecommunications and Information Technology, University Politehnica of Bucharest, 060042 Bucharest, Romania"}]},{"given":"Silviu","family":"Stanciu","sequence":"additional","affiliation":[{"name":"Laboratory of Cardiovascular Noninvasive Investigations, Dr. Carol Davila Central Military Emergency University Hospital, 010242 Bucharest, Romania"}]},{"given":"Stela","family":"Halichidis","sequence":"additional","affiliation":[{"name":"Department of Clinical Medical Disciplines, Faculty of Medicine, Ovidius University of Constanta, 900527 Constanta, Romania"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1007\/BF01930644","article-title":"Blutdruckversuche an der Maus und Ratte mittels Photozelle","volume":"176","author":"Bonsmann","year":"1934","journal-title":"Naunyn-Schmiedebergs Arch. 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