2022 Fiscal Year Research-status Report
Human sweat ducts as helical antenna: Prospects for practical applications
| Project/Area Number |
21K04174
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| Research Institution | Shizuoka University |
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Principal Investigator |
トリパティ サロジ 静岡大学, 工学部, 准教授 (20648729)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | terahertz / skin / sweat duct / sweat / helix |
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| Outline of Annual Research Achievements |
Previous studies have indicated that the interaction between terahertz (THz) waves and human skin occurs at a specific frequency due to the presence of a helical structure sweat duct in the epidermis of skin. When the sweat duct is filled with sweat, it acts as a low Q helical antenna, and the frequency of the duct is determined by both the morphological characteristics (such as the diameter of the sweat duct) and the dielectric properties of the skin and sweat. To investigate this further, we measured both the refractive index and absorption coefficient of sweat collected from various parts of the human body. Additionally, we designed a low-cost terahertz wave quarter wave plate that allows us to study the polarization-dependent terahertz reflection of the skin.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
We conducted an in-depth study of the dielectric properties of the human sweat duct range by using attenuated total reflection terahertz time domain spectroscopy in the frequency band of 200 GHz to 2.5 THz. Our findings revealed that both the real and imaginary part of the dielectric permittivity decreases with an increase in frequency. To describe these dielectric properties of sweat in the terahertz frequency region, we presented a dielectric model which reveal the presence of relaxation processes related to sodium and calcium ions concentrations in sweat. Additionally, we designed and experimentally demonstrated a bamboo terahertz quarter wave plate capable of producing both right and left circular polarized terahertz waves in the sub-terahertz frequency range.
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| Strategy for Future Research Activity |
In the upcoming academic year, we will utilize a system called attenuated total reflection terahertz time domain spectroscopy to measure the reflectance of terahertz waves from the skin of individuals experiencing mental stress. To assess the level of stress, we will measure heart rate variability and photoplethysmography using a specific measurement protocol. The collected data will be analyzed using machine learning algorithms such as random forest and support vector machine to classify the terahertz signal from human skin. Our final goal is to develop a method for understanding human stress using terahertz time domain spectroscopy.
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| Causes of Carryover |
A part of the budget was not utilized due to the COVID-19 pandemic travel restrictions, which made it impossible to attend the international conference. The unused budget will be carried forward to the next year and allocated towards attending both national and international conferences.
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| Remarks |
In this paper, we reported a method to enhance the ellipticity of a circular polarizer made of chiral metamaterials.
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