A cellular model of the electrical characteristics of skin

Abstract

The dielectric properties of skin are of particular interest in the fields of Functional Electrical Stimulation (FES), diagnostic procedures such as Electrocardiogram and cancer treatment. This thesis is concerned primarily with the effect of hydration and electroporation on skin impedance when signals used in FES are applied. Skin impedance has typically been represented by an equivalent circuit of varying complexities in the literature; however this approach does not incorporate the effects of hydration and electroporation. Alternatives to this include simulation of skin cells undergoing electrical stimulation and direct experimentation either in vitro or in vivo. This thesis aims to expand the current understanding in this field with particular focus on the effects of hydration and electroporation through simulation. The stratum corneum (SC) has the most dominant impact on overall impedance of skin, particularly at low frequencies, and therefore was the focus for all of the simulations.

The models representing individual cells showed strong agreement with experimental data in the literature in terms of their impedance when exposed to a variety of frequencies and input voltages. Expanding these models to include a greater number of cells continued to generate agreement with experimental data from the literature. When the conductivity of the SC cells were altered to represent the effect of hydration, the simulations showed a substantial reduction in impedance from 53kΩ to 27kΩ, which can be represented as a double exponential decay. A further model was produced with a cell membrane conductivity dependent upon the voltage across the membrane to represent the presence of electropores. The results showed that when signals typically used in FES are applied, electropores are formed. The presence of electropores causes a decrease in skin impedance from 76kΩ to 22kΩ.

More information

Identifiers

Catalogue record

Export record