Three-Dimensionally Ordered Array of Air Bubbles in a Polymer Film

TLDR

The study reports forming a three‑dimensionally ordered array of monodisperse air bubbles in a polymer film via a thermocapillary‑convection templating mechanism. By casting a dilute coil‑like polymer solution on a glass slide under moist air flow, evaporative cooling generates breath figures that, through thermocapillary convection, produce multilayers of hexagonally packed droplets that are frozen as spherical air bubbles in the solid film. The bubble dimensions are tunable by airflow velocity, and when the pore size matches visible‑light wavelengths, the material functions as a photonic band‑gap or optical stop‑band.

Abstract

We report the formation of a three-dimensionally ordered array of air bubbles of monodisperse pore size in a polymer film through a templating mechanism based on thermocapillary convection. Dilute solutions of a simple, coil-like polymer in a volatile solvent are cast on a glass slide in the presence of moist air flowing across the surface. Evaporative cooling and the generation of an ordered array of breath figures leads to the formation of multilayers of hexagonally packed water droplets that are preserved in the final, solid polymer film as spherical air bubbles. The dimensions of these bubbles can be controlled simply by changing the velocity of the airflow across the surface. When these three-dimensionally ordered macroporous materials have pore dimensions comparable to the wavelength of visible light, they are of interest as photonic band gaps and optical stop-bands.