Spectroscopy of excised skin patches exposed to THz and far-IR radiation

Alireza Lajevardipour; Zoltan Vilagosh; Dominique Appadoo; Jeffrey Davis; Saulius Juodkazis; Andrew Wood

doi:10.1364/BOE.424267

Spectroscopy of excised skin patches exposed to THz and far-IR radiation

Biomed Opt Express. 2021 Jul 1;12(7):4610-4626. doi: 10.1364/BOE.424267.

Authors

Alireza Lajevardipour^{1

2}, Zoltan Vilagosh^{1

2}, Dominique Appadoo³, Jeffrey Davis⁴, Saulius Juodkazis^{4

5}, Andrew Wood^{1

2}

Affiliations

¹ Department of Health Sciences and Biostatistics, School of Health Sciences, Swinburne University of Technology, Hawthorn, Vic 3122, Australia.
² Australian Centre for Electromagnetic Bioeffects Research, Swinburne University of Technology, Hawthorn, Vic 3122, Australia.
³ ANSTO-Australian Synchrotron, THz/Far-IR Beamline, Clayton, Vic 3168, Australia.
⁴ Optical Sciences Centre, School of Science, Swinburne University of Technology, Hawthorn, Vic 3122, Australia.
⁵ World Research Hub Initiative (WRHI), School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.

Abstract

Applications of far infrared (Far-IR) and terahertz (THz) radiation in areas such as healthcare and security are fast-growing. As a consequence, humans and the environment are becoming more exposed to mm-wave and Far-IR radiation than previously. We examined typical skin-care and sunscreen ingredients and propitiatory products with transmission FTIR, ATR-FTIR and THz-time domain spectroscopy (THz-TDS) methods using fresh and dehydrated toad and fresh human skin samples for their absorption properties in these frequency ranges. The skin hydration compounds glycerol and sorbitol have comparable absorption characteristics to physiological bulk water. Products containing these and similar hydrating compounds have significant Far-IR absorption characteristics. The sunscreen ingredients ZnO (20 micron), TiO₂ (mesh 325), and graphene platelet demonstrate a generally poor Far-IR absorbance, with TiO₂ displaying some frequency-specific absorption in the 3-6 THz and 12 THz regions. The Far-IR absorbance of proprietary sunscreens was, however, shown not to be significant. The absorption properties of melanin, collagen, bound water, and other constituents are significant in dehydrated skin samples but are not of the same order of importance as the hydrating agents examined.