Diabetes mellitus, commonly known as Diabetes is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced. Diabetes is a major health problem worldwide in the world we know today. The management of diabetes requires extensive monitoring of blood sugar (glucose) over a long period of time. This in turn requires large numbers of testing, hence the accuracy and price of every test is a common concern.
In this work we look into the feasibility of compact, economical extended field effect transistor (EGFET) glucose sensors made by inexpensive electrodeposition method.
Sensing films for EGFET were fabricated using ZnO nanorods using a three electrode electrodeposition method and then coated with immobilized glucose oxidase enzyme. Different morphologies and crystalinity of ZnO nanorods were examined to find the optimum sensitivity to glucose concentration variations. Samples of nanorod arrays with diameter ranging from 50~500nm were fabricated, the samples are checked for morphology and crystallinity via scanning electron microscope and X-ray diffraction, the sample is also checked for impurities using energy-dispersive X-ray spectroscopy . Glucose oxidase are then immobilized on the nanorod array and connected to the gate of a commercial MOSFET to perform the glucose concentration sensing. Most samples exhibit a sensing limitation down to approximately 10-8 mole, in which some achieve sensitivity of up to 7.8 μA/p[g]. The reaction time of the sensing film is dependent on the amount of enzyme immobilized; reaction time of fewer than 20 second can be achieved.
The sensitivity of the EGFET is found to be highly correlated to the morphology of the nanorod array, decrease in nanorod diameter resulted in the increase in sensitivity. In addition, samples with moderate crystalinity show better sensitivity; this may be due to excess dangling bonds in which defects expose to the surface. Thus causing more sites for the bonding of H+ , which can be seen as having a higher capacity for the sensing of glucose. However the nature of nanorods with too small diameter proves to be poor in crystalinity, this causes the in loss conductivity, which inevitably lead to the loss of sensing signal.

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