Medical Engineering Defense, Musab Jilani

The application of microfabrication techniques to enzyme electrodes has enabled not only greater control over enzyme geometry but also the possibility of monolithic low-power fully wireless implantable biosensors with sensor-on-CMOS construction. Such efforts must be guided by a strong grasp of the theory of diffusion-limited electrochemistry of the products of enzymatically catalyzed reactions. Low power requirements demand a full understanding of sensor turn-on transients and the reduced device size changes diffusion dynamics and increases the importance of considerations such as oxygen recycling from the reaction at the working electrode. This work presents the development of sophisticated finite element simulations of enzyme electrodes incorporating full two-substrate enzyme kinetics, a dynamic simulation of the sensor environment, and a full treatment of oxygen recycling.

It also presents an advancement in empirical methods through the development of an automated wafer-scale measurement system enabling the testing of up to twenty sensors in parallel still on the wafer on which they were fabricated. The combination of rapid in-vitro verification with effective in-silico simulation promises to greatly speed up the design iteration process. We explore some results studied theoretically and empirically through the use of these tools, in particular the determination of the impact of enzyme geometry on sensor response. These results additionally show the potential of thin-film deposition via spin-coating and vapor deposition crosslinking to enable the kind of fast response-time electrodes that are needed for achieving monolithic wireless implantable biosensors.