Single-Step Nanoporation of Water-Immersed Polystyrene Film by Gaseous Nanobubbles

Nanoporation of planar polystyrene (PS) film by gaseous nanobubbles is described. Ambient gas (air) surface nanobubbles are used to create rounded nanopinholes in supported ultrathin PS films immersed in water. Nanoporation proceeds under biocompatible conditions-in deionized water at room temperature (20 °C) in the absence of any high-energy-demanding processes, in a single step triggered by short (5 s) moderate pressure drop (Δp ≈ -10 kPa) applied on an aqueous phase. Atomic force microscopy (AFM) analysis shows a relatively narrow dimensional distribution, with the prevailing nanopinhole radius of 10 nm and uniform spread with an appearance density of ∼600/μm². The nanoporation mechanism is discussed. "Nanobubble/tip-assisted" nanoindentation phenomenon is observed based on the compounded interaction of the surface nanobubble with the AFM tip upon prolonged in situ nanobubble scanning.