Doctoral Dissertations

Date of Award

12-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical Engineering

Major Professor

Syed Kamrul Islam

Committee Members

Benjamin J. Blalock, Jeremy Holleman, Mohamed Mahfouz

Abstract

Implantable micro- and nano- sensors and implantable microdevices (IMDs) have demonstrated potential for monitoring various physiological parameters such as glucose, lactate, CO2 [carbon dioxide], pH, etc. Potentiostats are essential components of electrochemical sensors such as glucose monitoring devices for diabetic patients. Diabetes is a metabolic disorder associated with insufficient production or inefficient utilization of insulin. The most important role of this enzyme is to regulate the metabolic breakdown of glucose generating the necessary energy for human activities. Diabetic patients typically monitor their blood glucose levels by pricking a fingertip with a lancing device and applying the blood to a glucose meter. This painful process may need to be repeated once before each meal and once 1- 4 hour after meal. Patients may need to inject insulin manually to keep the blood glucose level at 3.9-6.7 mmol [mili mol] /liter.

Frequent glucose measurement can help reduce the long term complication of this disease which includes kidney disease, nerve damage, heart and blood vessel diseases, gum disease, glaucoma and etc. Having an implanted close loop insulin delivery system can help increase the frequency of glucose measurement and the accuracy of insulin injection. The implanted close loop system consists of three main blocks: (1) an electrochemical sensor in conjunction with a potentiostat to measure the blood glucose level, (2) a control block that defines the level of insulin injection and (3) an implanted insulin pump.

To provide a continuous health-care monitoring the implantable unit has to be powered up using wireless techniques. Minimizing the power consumption associated with the implantable system can improve the battery life times or minimize the power transfer through the human body. The focus of this work is on the design of low-power potentiostats for the implantable glucose monitoring system.

This work addresses the conventional structures in potentiostat design and the problems associated with these designs. Based on this discussion a modification is made to improve the stability without increasing the complexity of the system. The proposed design adopts a subthreshold biasing scheme for the design of a highly-stabilized, low-power potentiostats.

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