Sonja Huclova et al 2012 J. Phys. D: Appl. Phys. 45 025301 doi:10.1088/0022-3727/45/2/025301
Sonja Huclova1, Daniel Erni2 and Jürg Fröhlich1
Show affiliationsHuman skin consists of several layers with distinct dielectric properties. Physiological processes leading to changes in dielectric properties of the specific layers can potentially be non-invasively monitored employing dielectric spectroscopy. So far no comprehensive skin and underlying tissue model is available for this purpose in the frequency range between 1 and 100 MHz. Focusing on this dispersion-dominated frequency region, different multilayer skin models are investigated. First, with sublayers obtained from two-phase mixtures, second, three-phase mixtures of shelled cell-like ellipsoids and finally, multiphase mixtures obtained from numerical models of single cells generated using a flexible surface parametrization method. All models are numerically evaluated using the finite-element method and a fringing field sensor on the top of the multilayer system serving as a probe. Furthermore, measurements with the sensor probing skin in vivo were performed. The validity of the models was tested by removing the uppermost skin layer, the stratum corneum (SC). It was found that only a three-phase mixture (extracellular medium, cell membrane and cytoplasm) at least can qualitatively reproduce the measured dispersion still occurring without the SC if the model is set up without a priori knowledge of the dispersive behaviour as e.g. a Cole–Cole fit to measured data. Consequently, microstructural features of tissue have to be part of any accurate skin model in the MHz region.
87.10.-e General theory and mathematical aspects
87.18.-h Biological complexity
87.19.R- Mechanical and electrical properties of tissues and organs
02.70.Dh Finite-element and Galerkin methods
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
Issue 2 (18 January 2012)
Received 18 June 2011, in final form 14 November 2011
Published 16 December 2011
Sonja Huclova et al 2012 J. Phys. D: Appl. Phys. 45 025301