Abstract
We made in-vivo measurement of the complex relative permittivity of palm and sole in the frequency range from 100 MHz to 40 GHz with a network analyzer and an open-ended coaxial probe, which was compared with Gabriel in-vitro data for skin tissue to reveal that the in-vivo measurement results are mostly lower than the in-vitro data. For validation, we measured the dielectric constant of Teflon sheet with respect to its thickness from 0.05 mm to 5.00 mm, which showed that the open-ended coaxial probe provides sufficient measurement accuracy for Teflon with a thickness of over 0.5 mm, however, the probe data can be affected by the material beneath the Teflon with a thickness of less than 0.5 mm. This means that the in-vivo palm data derive from the epidermis and the dermis including blood, while the in-vivo sole data come from the epidermis. For further investigation, under the assumption that in-vitro data derive from a mixture of epidermis and blood, we calculated the complex relative permittivity for the compound from the Litchtenecker's law of exponent to show a possibility that due to the inclusion of blood, in-vitro measurement may provide a higher relative permittivity than in-vivo measurement.
