Investigating structural property of human hair by using infrared free electron lasers

• Published in: Discover Applied Sciences Vol. 6; no. 8; p. 397
• Main Authors: Kawasaki, Takayasu, Nagase, Atsushi, Hayakawa, Ken, Teshima, Fumitsuna, Tanaka, Kiyohisa, Zen, Heishun, Irizawa, Akinori, Sakai, Takeshi, Hayakawa, Yasushi
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 22.07.2024; Springer Nature B.V
• Subjects: Absorption; Absorption spectra; Applied and Technical Physics; Bending; Carboxyl group; Chemical bonds; Chemistry/Food Science; Drying; Earth Sciences; Electron microscopy; Electrons; Energy; Engineering; Environment; Free electron lasers; Hair; Hair stylers; Hydrogen bonds; I.R. radiation; Infrared absorption; Infrared lasers; Infrared spectra; Irradiation; Keratin; Lasers; Materials Science; Melanin; Microscopy; Morphology; Near infrared radiation; Peptide mapping; Photon density; Radiation; Surface structure; Wavelength; Wavelengths; Hair; Keratin; Free electron laser; Infrared ray
• ISSN: 3004-9261; 2523-3963; 3004-9261; 2523-3971
• DOI: 10.1007/s42452-024-06104-9

Intense infrared (IR) rays can heat matters and evaporate waters thermally. One of the possible applications will be hair dryer, although the irradiation effects of IR rays on the hair have not been fully explored. In this study, we first examined the interaction of IR rays at various wavelengths from 3.0 µm (near IR) to 90 µm (far IR) with the surface structure of human hair by using IR free electron lasers (FELs). IR-FEL is an accelerator-based pico-second pulse laser, and the feature is the wavelength-tunability with the high-photon density. When one thread of hair was irradiated by the FEL of 6–7 mJ energy at 60 µm, the cleavage occurred, and the morphological destruction was observed on scanning-electron microscopy images after the irradiations at 70 µm and 6.1 µm (amide I). Synchrotron-radiation infrared microspectroscopy showed that those FEL irradiations decreased a shoulder band at 1710 cm −1 that corresponds to carboxyl group in melanin or fatty acids and increased absorption intensity at 500–600 cm −1 . On the contrary, the FEL at 90 µm little changed either the surface morphology or the infrared absorption spectra. Interestingly, near-IR FELs at 3.0–3.5 µm induced bending of a hair, and 2D mapping of protein secondary conformations revealed that β-sheet was more increased than the other conformations on the surface of the bending area even at low pulse energy (1–3 mJ). As a result, the structural damage of the hair was least at 90 µm, which implies an ideal wavelength for drying hair mildly. Article highlights A unique assessment of hair structure is demonstrated by using accelerator-based infrared laser system. A new far-infrared wavelength for drying hair softly is discovered by this research. Applicability of accelerator-based infrared laser for activities of human life is first shown by this research.