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Emission from human skin in the sub THz frequency band. Sci Rep 2022; 12:4720. [PMID: 35304510 PMCID: PMC8933490 DOI: 10.1038/s41598-022-08432-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 02/16/2022] [Indexed: 11/09/2022] Open
Abstract
Recently published Radiometric measurements of human subjects in the frequency range 480–700 GHz, demonstrate the emission of blackbody radiation from the body core, rather than the skin surface. We present a detailed electromagnetic simulation of the dermis and epidermis, taking into account the presence of the sweat duct. This complex structure can be considered as an electromagnetic bio-metamaterial, whereby the layered structure, along with the topology of the sweat duct, reveals a complex interference pattern in the skin. The model is capable of accurately representing the skin greyness factor as a function of frequency and this is confirmed by radiometry of living human skin.
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Betzalel N, Ben Ishai P, Einav S, Feldman Y. The AC conductivity of human sweat ducts as the dominant factor in the sub-THz reflection coefficient of skin. JOURNAL OF BIOPHOTONICS 2021; 14:e202100027. [PMID: 33890427 DOI: 10.1002/jbio.202100027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 03/18/2021] [Accepted: 04/05/2021] [Indexed: 06/12/2023]
Abstract
The helical nature of human sweat ducts, combined with the morphological and dielectric properties of skin, suggests electromagnetic activity in the sub-THz frequency band. A detailed electromagnetic simulation model of the skin, with embedded sweat ducts, was created. The model includes realistic dielectric properties based on the measured water content of each layer of skin, derived from Raman Spectroscopy. The model was verified by comparing it to measurements of the reflection coefficient of the palms of 13 volunteers in the frequency band 350-410 GHz. They were subjected to a measurement protocol intended to induce mental stress, thereby also activating the sweat glands. The Galvanic Skin Response was concurrently measured. Using the simulation model the optimal ac-conductivity for each measurement was found. The range of variation for all subjects was found to be from 100 S/m to a maximum value of 6000 S/m with averages of 1000 S/m. These are one order of magnitude increase from the accepted values for water at these frequencies (~100 s/m at 100 GHz). Considering the known biochemical mechanism for inducing perspiration, we conclude that these ac-conductivity levels are probably valid, even though the real time measurements of sweat ac-conductivity levels inside the duct are inaccessible.
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Affiliation(s)
- Noa Betzalel
- The Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Paul Ben Ishai
- The Department of Physics, Ariel University, Ariel, Israel
| | - Sharon Einav
- The Intensive Care Unit, Shaare Zedek Medical Center, Faculty of Medicine, Hebrew University, Jerusalem, Israel
| | - Yuri Feldman
- The Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel
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Physiological Monitoring and Hearing Loss: Toward a More Integrated and Ecologically Validated Health Mapping. Ear Hear 2020; 41 Suppl 1:120S-130S. [DOI: 10.1097/aud.0000000000000960] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Betzalel N, Feldman Y, Ben Ishai P. Response to the comment of Foster et al. titled "Comments on Betzalel et al. "The human skin as a sub-THz receiver-Does 5G pose a danger to it or not?" [Environ. Res. 163 (2018): 208-216]". ENVIRONMENTAL RESEARCH 2020; 182:109016. [PMID: 31863940 DOI: 10.1016/j.envres.2019.109016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Affiliation(s)
- Noa Betzalel
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yuri Feldman
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel
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Betzalel N, Ben Ishai P, Feldman Y. The human skin as a sub-THz receiver - Does 5G pose a danger to it or not? ENVIRONMENTAL RESEARCH 2018; 163:208-216. [PMID: 29459303 DOI: 10.1016/j.envres.2018.01.032] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2017] [Revised: 12/18/2017] [Accepted: 01/23/2018] [Indexed: 06/08/2023]
Abstract
In the interaction of microwave radiation and human beings, the skin is traditionally considered as just an absorbing sponge stratum filled with water. In previous works, we showed that this view is flawed when we demonstrated that the coiled portion of the sweat duct in upper skin layer is regarded as a helical antenna in the sub-THz band. Experimentally we showed that the reflectance of the human skin in the sub-THz region depends on the intensity of perspiration, i.e. sweat duct's conductivity, and correlates with levels of human stress (physical, mental and emotional). Later on, we detected circular dichroism in the reflectance from the skin, a signature of the axial mode of a helical antenna. The full ramifications of what these findings represent in the human condition are still unclear. We also revealed correlation of electrocardiography (ECG) parameters to the sub-THz reflection coefficient of human skin. In a recent work, we developed a unique simulation tool of human skin, taking into account the skin multi-layer structure together with the helical segment of the sweat duct embedded in it. The presence of the sweat duct led to a high specific absorption rate (SAR) of the skin in extremely high frequency band. In this paper, we summarize the physical evidence for this phenomenon and consider its implication for the future exploitation of the electromagnetic spectrum by wireless communication. Starting from July 2016 the US Federal Communications Commission (FCC) has adopted new rules for wireless broadband operations above 24 GHz (5 G). This trend of exploitation is predicted to expand to higher frequencies in the sub-THz region. One must consider the implications of human immersion in the electromagnetic noise, caused by devices working at the very same frequencies as those, to which the sweat duct (as a helical antenna) is most attuned. We are raising a warning flag against the unrestricted use of sub-THz technologies for communication, before the possible consequences for public health are explored.
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Affiliation(s)
- Noa Betzalel
- Department of Applied Physics, The Rachel and Selim Benin School of Engineering and Computer Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel
| | - Paul Ben Ishai
- Department of Applied Physics, The Rachel and Selim Benin School of Engineering and Computer Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel; Department of Physics, Ariel University, Ariel 40700, Israel
| | - Yuri Feldman
- Department of Applied Physics, The Rachel and Selim Benin School of Engineering and Computer Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel.
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Vorobyov A, Daskalaki E, Hennemann C, Decotignie JD. Human physical condition RF sensing at THz range. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:2067-2070. [PMID: 28268737 DOI: 10.1109/embc.2016.7591134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The skin response to high radio frequency has been associated with the human physical condition and most prominently with the stress. The objective of this study is to investigate the possibility to detect mental and light physical stress through the measurement of skin reflectance in the mm-wave/sub-THz band. Two frequency bands have been considered, 75-110 GHz (Band-I) and 325-500 GHz (Band-II), while the measurements have been performed in the three different locations, the arm, the dorsal side of the hand and the fingertip. The measurement setup is discussed in detail and the reflectance spectrum is demonstrated. The results illustrate a difference in skin reflectance under rest and stress in Band-II which ranges from 3.5 dB at the finger to 7 dB at the hand. The outcomes of this study indicate the feasibility of stress detection through skin reflectance measurement and serve as a suggestion for deeper exploration of higher frequency bands.
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Tripathi SR, Miyata E, Ishai PB, Kawase K. Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region. Sci Rep 2015; 5:9071. [PMID: 25766116 PMCID: PMC4357862 DOI: 10.1038/srep09071] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 02/17/2015] [Indexed: 11/09/2022] Open
Abstract
It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 ± 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings.
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Affiliation(s)
| | - Eisuke Miyata
- Nagoya University, Furo-cho, Chikusa Ku, Nagoya 464-8603, Japan
| | - Paul Ben Ishai
- The Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel
| | - Kodo Kawase
- Nagoya University, Furo-cho, Chikusa Ku, Nagoya 464-8603, Japan
- RIKEN, 519-1399 Aramakiaoba, Aoba, Sendai 980-0845, Japan
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Hayut I, Ben Ishai P, Agranat AJ, Feldman Y. Circular polarization induced by the three-dimensional chiral structure of human sweat ducts. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:042715. [PMID: 24827286 DOI: 10.1103/physreve.89.042715] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Indexed: 06/03/2023]
Abstract
The upper part of the human eccrine sweat ducts, embedded within the epidermis layer, have a well-defined helical structure. It was recently suggested that, as electromagnetic entities, the sweat ducts interact with sub-mm waves [Y. Feldman et al., Phys. Rev. Lett. 100, 128102 (2008)]. Although correlation between changes in the reflectance spectrum in this frequency range and physiological activities has been shown, a direct link between the electromagnetic reflection and the helical structure itself has remained to be established. The fact that the sweat ducts manifest natural homochirality is henceforth used to produce this link. We report the detection of circular polarization asymmetry in the electromagnetic reflection from the human skin at sub-THz frequencies in vivo. We compare the results to numerical simulations and to measurements of a fabricated metamaterial. We argue that the observed circular dichroism can be interpreted uniquely as the signature of the helical structure itself. By twisting reflected electromagnetic waves, the human skin exhibits properties which are usually discussed only in the framework of metamaterial science.
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Affiliation(s)
- Itai Hayut
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Paul Ben Ishai
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Aharon J Agranat
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Yuri Feldman
- Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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