{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,21]],"date-time":"2026-05-21T09:43:55Z","timestamp":1779356635826,"version":"3.51.4"},"reference-count":15,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2019,12,10]],"date-time":"2019-12-10T00:00:00Z","timestamp":1575936000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Ministry of Science and ICT","award":["NRF-2018R1A4A1025704"],"award-info":[{"award-number":["NRF-2018R1A4A1025704"]}]},{"name":"Ministry of Science and ICT","award":["NRF-2016M 3A9F1941328"],"award-info":[{"award-number":["NRF-2016M 3A9F1941328"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The multi-wavelength photoplethysmography sensors were introduced to measure depth-dependent blood volume based on that concept that the longer the light wavelength, the deeper the penetration depth near visible spectrum band. In this study, we propose an omnidirectional optical sensor module that can measure photoplethysmogram while using multiple wavelengths, and describe implementation detail. The developed sensor is manufactured by making a hole in a metal plate and mounting an LED therein, and it has four wavelength LEDs of blue (460 nm), green (530 nm), red (660 nm), and IR (940 nm), being arranged concentrically around a photodetector. Irradiation light intensity was measured by photoluminescent test, and photoplethymogram was measured with each wavelength simultaneously at a periphery of the human body such as fingertip, earlobe, toe, forehead, and wrist, in order to evaluate the developed sensor. As a result, the developed sensor module showed a linear increase of irradiating light intensity according to the number of LEDs increases, and pulsatile waveforms were observed at all four wavelengths in all measuring sites.<\/jats:p>","DOI":"10.3390\/s19245441","type":"journal-article","created":{"date-parts":[[2019,12,10]],"date-time":"2019-12-10T10:52:41Z","timestamp":1575975161000},"page":"5441","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":34,"title":["Design of Multi-Wavelength Optical Sensor Module for Depth-Dependent Photoplethysmography"],"prefix":"10.3390","volume":"19","author":[{"given":"Sangjin","family":"Han","sequence":"first","affiliation":[{"name":"Department of Biomedical engineering, Chonnam National University, Yeosu 59626, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Donggeun","family":"Roh","sequence":"additional","affiliation":[{"name":"Department of Biomedical engineering, Chonnam National University, Yeosu 59626, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junyung","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Biomedical engineering, Chonnam National University, Yeosu 59626, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8095-356X","authenticated-orcid":false,"given":"Hangsik","family":"Shin","sequence":"additional","affiliation":[{"name":"Department of Biomedical engineering, Chonnam National University, Yeosu 59626, Korea"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,12,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"R1","DOI":"10.1088\/0967-3334\/28\/3\/R01","article-title":"Photoplethysmography and its application in clinical physiological measurement","volume":"28","author":"Allen","year":"2007","journal-title":"Physiol. Meas."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1433","DOI":"10.1088\/0031-9155\/33\/12\/008","article-title":"Estimation of optical pathlength through tissue from direct time of flight measurement","volume":"33","author":"Delpy","year":"1988","journal-title":"Phys. Med. Biol."},{"key":"ref_3","unstructured":"Ingle, J.D., and Crouch, S.R. (1988). Spectrochemical Analysis, Prentice Hall College Book Division."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"13012","DOI":"10.1039\/C6DT01428C","article-title":"Upconverting nanoparticles for the near infrared photoactivation of transition metal complexes: New opportunities and challenges in medicinal inorganic photochemistry","volume":"45","author":"Ruggiero","year":"2016","journal-title":"Dalton Trans."},{"key":"ref_5","unstructured":"Liu, J., Li, Y., Ding, X.-R., Dai, W.-X., and Zhang, Y.-T. (2015, January 25\u201329). 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Sensors, 19.","DOI":"10.3390\/s19040789"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/24\/5441\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:41:01Z","timestamp":1760190061000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/24\/5441"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,12,10]]},"references-count":15,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2019,12]]}},"alternative-id":["s19245441"],"URL":"https:\/\/doi.org\/10.3390\/s19245441","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,12,10]]}}}