Nonlinear Interfacial Dynamics at Nanoscale

Nanostructure intrinsically possesses large interface area to volume ratios at nanoscale that gives rise to many amazing properties differing from their macroscopic behaviors. This thesis addresses two interfacial phenomena at nanoscale: the Taylor cone of electrospray and stick-slip dynamics of confined liquid. 1.The conducting Taylor cone can activate specified harmonics of Laplace equation near the cone and can generate field maxima at multiple discrete polar angles. These harmonics are verified by nanocolloids electrospray. The nanocolloid ejected along the discrete electric field lines of these mode maxima and observed to deposit a universal spectrum of rings on an intersecting plane. 2.Different size nanocolloid selects different harmonics resulting in the size-dependent separation. A scaling theory that collapses the binary nanocolloid spatial distribution suggests that the nanocolloid-controlled Rayleigh fission cascade asymptotes towards a distinct size-sensitive charge and trajectory due to a balance between axial electrophoresis and Coulombic radial repulsion. 3.A rapid electrospray-nanocolloid based platform for simultaneous docking and detection of DNA/RNA/biomarker is developed. As the hybridization of the target ssDNA or biomarker docking onto a nanocolloid can increase its surface charge and particle size significantly. This causes hybridized or biomarker docked nanocolloids select different harmonics and deposit on a single line or single band different from ones without the molecular target. Furthermore, the In-Situ hybridization or docking is verified in the electrospray-bead based platform. It is a distinguish advantage of this technique which shortens the detection time significantly. 4.A mesoscopic continuum model with local lattice resolution quantitatively reproduces the stick-slip dynamics of a solid mass (cylinder) connected laterally to a stationary restoring spring and separated from a translating substrate by two monolayers of lubricating liquid. Key to the model is that liquid molecules can reversibly condense onto the solid with a corresponding jump in the film viscosity, which is estimated with Kramer's molecular activated transport theory. The transitions between the 'melted' and condensed phases are determined by viscous drag and the viscosity jump stipulates a hysteretic phase transition with respect to the substrate velocity. This hysteresis couples with the restoring spring force to produce stick-slip dynamics and with premature melting due to cylinder inertia to generate two-frequency oscillations.