Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Electrical Engineering

Major Professor

Jie Wu

Committee Members

Shigetoshi Eda, Gong Gu, Nicole McFarlane


Capacitive bioaffinity detection using microelectrodes is considered as a promising label-free method for point-of-care diagnosis, though with challenges in sensitivity, specificity and the time “from sample to result.” This work presents an alternating current (AC)-electrokinetic based capacitive affinity sensing method that is capable of realizing rapid in-situ detection of specific biomolecular interactions such as probe-analyte binding. The capacitive biosensor presented here employs elevated AC potentials at a fixed frequency for impedimetric interrogation of the microelectrodes. Such an AC signal is capable of inducing dielectrophoresis (DEP) and AC electrothermal (ACET) effects, so as to realize in-situ enrichment of macro and even small molecules at microelectrodes and hence accelerated detection. Experimental study of the DEP/ACET-enhanced capacitive sensing method was conducted, and the results corroborate our hypothesis.

This capacitive sensing method has been shown to work with various types and sizes of biomolecules (such as antibodies, virus and small molecules) to differentiate disease-positive samples from negative samples within or less than two minutes, while conventional assay would require multiple processing steps and take hours to complete. The results showed high accuracy and sensitivity. Overall, this capacitive affinity biosensor may form a basis for the development of a feasible point-of-care diagnostic platform for the detection of infectious diseases in the future.

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