Examination Committee

Prof Andrew POON, ECE/HKUST (Chairperson)
Prof Levent YOBAS, ECE/HKUST (Thesis Supervisor)
Prof Zhiyong FAN, ECE/HKUST

Abstract

In the past decade, advances in nanofluidics have opened up the possibility of rapid and sensitive biomolecule analysis based on unique ionic transport, specifically the rectification of ionic current through a nanochannel as in the rectification of an electronic current through a solid-state diode. A nanofluidic diode shows asymmetric ionic conduction with respect to the polarity of the applied voltage. In a nanofluidic diode biosensor, it is crucial to have accurate control of both the critical dimension and surface properties of the nanochannel. These properties are vital to achieving the most pronounced rectification. This thesis aims to develop an innovative integrated nanofluidic diode biosensor that allows the precise control of the surface properties as well as the critical dimension of the nanofluidic diode, which can eventually be employed for rapid and sensitive label-free sensing of biomolecules.

Sensing of a cardiac troponin biomarker is a powerful tool for early stage diagnosis of acute myocardial infarction, which is essential for the identification and effective treatment of cardiovascular disease. The thesis presents a label-free electrical method for the quantification of the sensing functionality of a troponin biomarker on the different surface interface through a discrete nanopipette for the very first time. The inexpensive nature of this electrical measurement could potentially become helpful in finding a suitable material for biomarker grafting without the need for an expensive optical method. For further scaling and integration, an innovative integrated nanofluidic diode biosensor is presented that features a single nanoslit with a nominal width of 30 nm. The process is simple, and it promises low-cost fabrication with mass producibility and significantly improved sensing capability. The experimental demonstration shows that this biosensor can perform real-time, label-free selective detection of the human cardiac biomarker at clinically relevant concentrations across a range over four orders of magnitude with high sensitivity.