Extreme Liquid Superheating and Homogeneous Bubble Nucleation in a Solid State Nanopore

Abstract

This thesis explains how extreme superheating and single bubble nucleation can be achieved in an electrolytic solution within a solid state nanopore. A highly focused ionic current, induced to flow through the pore by modest voltage biases, leads to rapid Joule heating of the electrolyte in the nanopore. At sufficiently high current densities, temperatures near the thermodynamic limit of superheat are achieved, ultimately leading to nucleation of a vapor bubble within the nanopore.

A mathematical model for Joule heating of an electrolytic solution within a nanopore is presented. This model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally.

Knowledge of this temperature distribution is used to evaluate related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics. In particular, bubble nucleation is shown to be homogeneous and highly reproducible. These results are consistent with experimental data available from electronic and optical measurements of Joule heating and bubble nucleation in a nanopore.