Nanoscale Patterning of Surface Nanobubbles

TL;DR

This study demonstrates that focused ion beam (FIB) milling can precisely control the spatial nucleation of surface nanobubbles on hydrophobic surfaces, combining experimental and simulation approaches to advance nanobubble-based patterning techniques.

Contribution

The paper introduces the first use of FIB milling for nanoscale control of surface nanobubbles, exploring chemical and topographical effects on their formation and properties.

Findings

FIB milling achieves 75 nm precision in nanobubble nucleation.

Chemical heterogeneity via FIB patterning directs nanobubble positioning.

FIB-induced amorphization influences nanobubble morphology and contact angle.

Abstract

Surface nanobubbles forming on hydrophobic surfaces in water present an exciting opportunity as potential agents of top-down, bottom-up nanopatterning. The formation and characteristics of surface nanobubbles are strongly influenced by the physical and chemical properties of the substrate. In this study, focused ion beam (FIB) milling is used for the first time to spatially control the nucleation of surface nanobubbles with 75 nm precision. The spontaneous formation of nanobubbles on alternating lines of a self-assembled monolayer (octadecyl trichlorosilane) patterned by FIB is detected by atomic force microscopy. The effect of chemical vs. topographical surface heterogeneity on the formation of nanobubbles is investigated by comparing samples with OTS coating applied pre- vs. post-FIB patterning. The results confirm that nanoscale FIB-based patterning can effectively control surface nanobubble position by means of chemical heterogeneity. The effect of FIB milling on nanobubble morphology and properties, including contact angle and gas oversaturation, is also reported. Molecular dynamics simulations provide further insight into the effects of FIB amorphization on surface nanobubble formation. Combined, experimental and simulation investigations offer insights to guide future nanobubble-based patterning using FIB milling.