The Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel.
The Department of Physics, Ariel University, Ariel, Israel.
J Biophotonics. 2021 Jul;14(7):e202100027. doi: 10.1002/jbio.202100027. Epub 2021 Apr 30.
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.
人的汗管呈螺旋状，加上皮肤的形态和介电特性，表明皮肤在亚太赫兹频段存在电磁活动。创建了一个包含嵌入式汗管的皮肤详细电磁模拟模型。该模型基于拉曼光谱法测量的皮肤各层的实际含水量，包含了基于真实介电特性。通过将模型与 13 名志愿者手掌在 350-410GHz 频段的反射系数测量值进行比较，验证了该模型。志愿者接受了旨在引起精神压力从而激活汗腺的测量方案。同时测量了皮肤电反应。使用仿真模型找到了每种测量的最佳交流电导率。发现所有受试者的变化范围均在 100 S/m 至 6000 S/m 之间，平均值为 1000 S/m。与这些频率下（~100GHz 时为 100 S/m）水的公认值相比，这些值增加了一个数量级。考虑到引起出汗的已知生化机制，我们得出结论，即使无法实时测量管内汗液的交流电导率水平，这些交流电导率水平也是合理的。
