Abstract:
An Electrical Parametric Model of Human Skin and Blood
Glucose Spectroscopy
by
Thumeera Ruwansiri Wanasinghe
Submitted to the Department of Electronic and Telecommunication Engineering,
in partial ful llment of the requirements for the degree of
Master of Science in Engineering
Index Term: Skin impedance model, non-invasive blood glucose measure-
ment, dielectric spectroscopy, compact annular ring slot antenna
Diabetes is well known as a leading cause of death all around the world. Mainly,
invasive methods are used for blood glucose monitoring in the current context.
The monitoring is done either as an inpatient procedures or using home based
measuring devices. Invasive or minimally invasive methods make it di cult when
it comes to frequent measurements required by diabetes patients. It also has other
issues such as the associated pain, phobia, and the spread of diseases like AIDS.
These issues are heightened in the case of home based monitoring devices. As
a result many researchers have attempted to introduce non-invasive measuring
techniques for home based glucose monitoring devices. However none of then have
met the accuracy requirements for medical use.
Dielectric spectroscopy (DS) is one such methods which has been proposed
for non-invasive glycaemia monitoring. In DS, the variation of skin impedance
has been used to derive an index representing blood glucose
uctuation. As a re-
sult of the lack of knowledge of the impedance characteristics of the skin and the
tissue underneath, and its relation to the level of blood glucose, the consistency
and accuracy of the measurements are questionable. The ensuing research pro-
poses a theoretical framework for skin impedance variations with the blood glucose
level and also provides experimental veri cation of the same. This research also
proposes an electrical parametric (impedance) model for human skin and blood
glucose spectroscopy which consists of human skin, electrode-electrolyte interface
and coupling capacitance between transmitter and receiver. Such a mathematical
model of the physiological system will enable us to further analyze the relationship
the physiological parameters have with the
uctuation of the blood glucose levels
for di erent individuals.
Moreover, the thesis analyzes the in
uence from bio-sensor to sensitivity mea-
surements and proposes a concentric annular ring slot antenna (CARSA) as a
possible sensor for non-invasive blood glucose measurement via DS. Compared
to early research of Cada et al. [1], CARSA showed a 13 fold increment of the
measurement sensitivity. Further, it could be seen that, this sensitivity increment
was 40 fold when the e ective length of CARSA decreases from 10 cm to 6.5 cm.
The thesis further highlights the importance of careful design of this sensor and
proposes a rigorous mathematical model of its derivation.
