Graduate Exam Abstract

William Tedjo

Ph.D. Final
July 30, 2019, 12:00 pm - 2:00 pm
Scott 301 Odyssey Design Studio
A Biosensor System with an Integrated CMOS Microelectrode Array for High Spatio-temporal Electrochemical Imaging

Abstract: The ability to view biological events in real-time has contributed significantly to research in life sciences.
While optical microscopy is important to observe anatomical and morphological changes, it is equally
important to capture real-time two-dimensional chemical activities that drive the bio-sample behaviors.
Furthermore, it is well known that physiological events related to oxygen concentration gradients
provide valuable information to determine the state of metabolizing biological cells. This work presents
a chemical imaging system employing a custom-designed CMOS microchip with 16,064 surface
microelectrode array at 27.5µm spatial resolution and up to 4Hz temporal resolution. Utilizing a three-
electrode system configuration, the system is capable of imaging low oxygen concentration (18.3µM,
0.58mg/L, or 13.8mmHg) with a sensitivity of 8.21pA/µM (R=0.98). A microfluidic support system allows
convenient bio-sample handling and delivery to the MEA surface for sensing. In vitro oxygen imaging
experiments were performed using bovine cumulus-oocytes-complexes cells with custom software
algorithms to analyze its flux density and oxygen consumption rate. Finally, the imaging results are
processed and presented as two-dimensional heatmaps, representing the dissolved oxygen
concentration in the immediate proximity of the cell. The two-dimensional images and analysis of
oxygen consumption provide a unique insight into the spatial and temporal dynamics of cell

Adviser: Dr. Tom Chen
Co-Adviser: N/A
Non-ECE Member: Dr. Stuart Tobet
Member 3: Dr. Jesse Wilson
Addional Members: Dr. George Collins

[1] Tedjo, W., Catandi, G., Obeidat, Y., Carnevale, E., Chen, T., 2019. Design of a Microelectrode Sensor Array for High-Resolution Imaging of Oxygen Consumption in Small Biological Samples. Biosens. Bioelectron. (submitted in July 2019 - under review)

[2] Tedjo, W., Chen, T., 2019. An Integrated Biosensor System with High-Density Microelectrode Array for Real-Time Electrochemical Imaging. IEEE Trans. on Biomedical Circuits and Systems. (submitted May 2019 - under review)

[3] Obeidat, Y., Evans, A., Tedjo, W., Chicco, A., Carnevale, E., Chen, T., 2018. Monitoring Oocyte/Embryo Respiration Using Electrochemical-Based Oxygen Sensors. Sensors Actuators B Chem.

[4] Tedjo, W., Nejad, J.E., Feeny, R., Yang, L., Henry, C.S., Tobet, S., Chen, T., 2018. Electrochemical biosensor system using a CMOS microelectrode array provides high spatially and temporally resolved images. Biosens. Bioelectron. 114, 78-88.

[5] Tedjo, W., Feeny, R., Eitel, C., Schwerdtfeger, L., Willett, S., Henry, C., Tobet, S., Chen, T., 2016. Design of an integrated microelectrode array system for high spatiotemporal resolution chemical imaging, in: 2016 IEEE Biomedical Circuits and Systems Conference (BioCAS). IEEE, pp. 46-49.

Program of Study:
ECE 534 – Analog Integrated Circuit Design
BIOM 581B5 – Electrochemical Sensors
ECE 536 – RF Integrated Circuit Design
ECE 580A4 – Analog/Digital Interface Circuits
ECE 623 – Electric Power Quality
GRAD 550 – STEM Communication
MATH 535 – Foundation of Applied Mathematics
STAA 552 – Generalized Regression Models