| Nanochannels are ubiquitous in biological membranes, where they serve as filters for ions of interest. The working mechanisms of ion channels and selectivity for certain molecules remain an open question. Inspired by nature to understand the gating mechanism of the mass transport through confined geometries, aims of this thesis are to study the fundamentals of transport properties of nanopipette-based nanofluidic devices and to explore potential applications of nanopipettes in biotechnology. In particular, the current-voltage response of a nanopore, especially an asymmetric nanopore, can be employed to evaluate changes in surface charge, and thus serve to transduce analyte binding. Ionic rectification is useful to describe changes in surface charge when the dimensions of the nanochannels are comparable to the Debye length. These results are significant to develop a better understanding of possible mechanisms for signal transduction in nanopores. Recognition elements, bound to the nanopipette surface, are shown to affect signal transduction through irreversible changes in the current-voltage response. Study of substrate surface charge on the ion-current rectification ratio of a nanopipette and the application of these experimental findings to detect localized surface charges is investigated. Qualitative mathematical descriptions of mass transport through confined nanopipette geometries are performed to further study the mechanism of the ion transport. Modeling the effects of surface charge, concentration and geometry on the ion distribution at confined nanopipette geometry are discussed in later portions of this dissertation to provide the fundamental understanding of ion-transport phenomena in confined geometries. Moreover, progress in recent studies that make use of nanopipettes for a delivery tool and a detection device will be discussed in the future work. |
