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The Artificial Pancreas 425

Fig. 10 Schematic representation of a microdialysis SCGM system. (Based on
Schoemaker, M., Andreis, E., R€ oper, J. Kotulla, R., Lodwig, V., Obermaier, K., Stephan, P.,
Reuschling, W., Rutschmann, M., Schwaninger, R., Wittmann, U., Rinne, H.,
Kontschieder, H., Strohmeier, W., 2003. The SCGM1 system: subcutaneous continuous glu-
cose monitoring based on microdialysis technique. Diabetes Technol. Ther. 5: 599–608.)

made of a highly oxygen-permeable silicon tube. The fluid then passes
through the sensor where the H 2 O 2 is oxidized on an electrode in the
normal fashion to produce a small current proportional to the glucose
concentration in the dialysate. The electrode consists of a screen-printed
three-electrode system with an Ag/AgCl RE, a WE, and a carbon counter
electrode. Calibration ensures that the measured current is converted to the
correct blood glucose level. Finally, the fluid is collected in the waste bag
(Schoemaker et al., 2003).

3.5 Noninvasive Glucose Monitoring
The glucose monitoring techniques discussed so far leave a lot to be desired.
The standard lancet and strip methods are expensive in terms of consumables
and boring to administer resulting in repeated measurements being skipped.
Subcutaneous sensors that measure glucose concentration in interstitial fluid
are limited by patient discomfort, onerous calibration procedures, and bio-
fouling. These limitations have led to a strong research drive to find a
completely noninvasive glucose monitoring method. The methods investi-
gated so far are mostly based on measuring the optical properties of interstitial
fluid, the aqueous humor in the anterior chamber of the eye, or the