Optimization of Skin Impedance Sensor Design with Finite Element Simulations

Impedance spectroscopy is a measurement technique that has been investigated in a wide variety of medical applications. An example is the measurement of the dielectric properties of the skin and underlying tissue using sensors placed in contact with human skin with capacitive fringing field electrodes. Electrodes with different characteristic geometries measure biophysical properties at separate penetration depths in the tissue and have therefore different sensitivities to e.g. physiological processes in the tissue. When the measured depth is in the dermis layer, the time series of the measured impedance at specific frequencies can be related to the effect of glucose changes. The aim of this work is to use finite element methods (FEM) for optimizing the sensor design to maximise its sensitivity to the dielectric changes of the dermis layer. This is achieved by evaluating FEM simulations for different electrode widths and distances to ground and searching for the geometries at which the information coming from the dermis layer reach a maximum. Experimental data supports the conclusions drawn from the simulation output.