IEEE Transactions on Dielectrics and Electrical Insulation
Vol. 13, No. 2; April 2006
1070-9878/06/$20.00 © 2006 IEEE
An RCL Sensor for Measuring Dielectrically Lossy Materials
in the MHz Frequency Range
1. Comparison of Hydrogel Model Simulation with Actual
Hydrogel Impedance Measurements
M.S. Talary, F. Dewarrat, A. Caduff
Solianis Monitoring AG.
8050 Zürich, Switzerland
A.Puzenko, Y. Ryabov,
Department of Applied Physics
The Hebrew University of Jerusalem
Jerusalem 91904, Israel
There is a requirement for the development of non-invasive continuous blood glucose
monitoring devices to meet the clinical demands of the rapidly increasing number of
people currently developing diabetes mellitus. Impedance Spectroscopy is a technology
that meets the requirements of such devices. An NI CGMD is being developed as a
device that couples a sensor to the skin to form an RCL sensor. The reliability of such
an RCL sensor model has been investigated by comparing electrodynamical simulations
to in-vitro measurements of dielectrically “lossy” materials. The sensor has been
modeled and simulated in FEMLAB (Finite Element Modeling Laboratory). In-vitro
measurements are performed on hydrogels, representing the lossy material, by the aid
of a Rohde & Schwarz VNA (vector network analyzer). From the quantitative
agreement of the results we conclude, that the proposed qualitative model is
appropriate for the characterization of the RCL sensor and suggests that more detailed
models can be used to elucidate the behavior of human skin tissue.
Equivalent circuits, circuit simulation, transducers, dielectric
measurements, dielectric materials, skin, medical diagnosis.
mellitus is a metabolic disease that can lead to
uncontrolled glucose excursions.
There is an increasing
interest in the closer monitoring of glycaemic conditions to
reduce the incidence of complications associated with
prolonged hyper or hypo-glycaemic excursions, preferably in a
non-invasive and continuous manner.
Due to the known
specific reactions of blood and tissue cells on a varying
glucose concentration, the electrolyte balance across
membranes of cells in blood and underlying tissue is changed
as a function of glucose.
Dielectric spectroscopy (DS) or
Impedance Spectroscopy (IS), as a more recognized term in
the bio-impedance community, is thought to be sensitive to
these subtle changes.
In this work, we investigate the
feasibility of using DS techniques to monitor changes in
complex human biological systems due to the alteration in
blood glucose levels.
It has been previously reported that a non-invasive, continuous
glucose monitoring device (NI-CGMD) is being developed using
impedance spectroscopy to provide real time monitoring of
glucose levels in human tissue .
This NI-CGMD consists of a
sensor capacitively coupled to the body, a signal generator
operated in a selected frequency range (1 – 200 MHz) and a
microprocessor that controls the operation of the device.