Bubble Nucleation on Nano- to Micro-size Cavities and Posts: An Experimental Validation of Classical Theory

TL;DR

This study experimentally validates classical heterogeneous bubble nucleation theory on nano- to micro-scale cavities and posts, confirming that nucleation temperatures align with predictions and that posts have negligible effect.

Contribution

The paper provides experimental evidence supporting classical nucleation theory at nanoscale features, resolving previous contradictions from recent data.

Findings

Nucleation temperatures match Young-Laplace predictions.

Nano-sized posts do not significantly influence bubble nucleation.

Data confirms classical theory applicability at nanoscale.

Abstract

Recently-reported data suggest that bubble nucleation on surfaces with nano-sized features (cavities and posts) may occur close to the thermodynamic saturation temperature. However, according to the traditional theory of heterogeneous bubble nucleation, such low nucleation temperatures are possible only for surfaces with micro-scale cavities. Motivated by this apparent contradiction, we have used infrared thermometry to measure the nucleation temperature of water on custom-fabricated nano- to micro-scale cavities (from 90 nm to 4.5 um in diameter) and posts (from 60 nm to 5 um in diameter), machined on ultra-smooth and clean silicon wafers using electron beam lithography. Our cavity data are in agreement with the predictions of the Young-Laplace equation, thus re-affirming the correctness of the classic view of heterogeneous bubble nucleation, at least for the water-silicon system investigated here. The data also suggest that individual posts of any size have an insignificant effect on bubble nucleation, as expected from theory. Keywords: Bubble nucleation, superheat, artificial cavities and posts, nanosize, Young-Laplace