Prof Yilong HAN, PHYS/HKUST (Chairperson)
Prof Levent YOBAS, ECE/HKUST (Thesis Supervisor)
Prof Dieter TRAU, Department of Biomedical Engineering, National University of Singapore (External Examiner)
Prof Andrew W O POON, ECE/HKUST
Prof Zhiyong FAN, ECE/HKUST
Prof Shuhuai YAO, MAE/HKUST
The past decades have witnessed the remarkable development of nanofluidics and its widespread applications in chemical and biomedical research. Nanochannels, which typically feature at least one critical dimension below 100 nm, exhibit new physical properties that differ markedly from those of microchannels. These include physical confinement of macromolecules (e.g. DNA) and unique ionic transport mechanisms in such extremely restricted fluidic constructions. The utilization of these interesting effects has led to numerous innovative nanofluidic systems such as nanofluidic diodes and transistors that offer great potential in detecting and manipulating biomolecules.
This thesis aims to develop integrated, robust, and cost-effective nanoelectrofluidic systems that can be used in practical biomolecular analysis. In particular, the very first account of integrated nanofluidic diode-based biosensor is presented, which features a tapered 70-nm nanoslit array that can be functionalized to selectively detect a human cardiac-injury biomarker with a sensitivity level that is about >3 orders of magnitude higher than those associated with discrete nanofluidic diodes. Next, a highly effective integrated nanofluidic transistor is developed, which is based on a 50-nm-diameter in-plane alumina capillary that is surrounded by a gate electrode along the entire length. The capacity of the nanofluidic transistor to actively regulate protein transport and DNA translocation is also demonstrated. Notably, the fabrication of both the devices presented herein does not required advanced lithographic techniques and thus is highly cost-effective. A novel label-free method of quantifying nucleic acids in polymerase chain reaction leveraging on nanofluidic diodes and a convenient approach to fabricate self-enclosed nanocapillaries relying on only coarse lithography (>1 μm) are also described.