One-Step Spontaneous Formation of Dual Wrinkling on Uniform-Sized Microparticles Induced by Surface

Abstract

This study demonstrates the wrinkle formation on biodegradable polymer-blend microparticles prepared from an emulsion-solvent evaporation method and investigates the formed patterns. A labyrinthine pattern is obtained for uniform-sized microparticles, owing to the considerable size reduction during solvent evaporation. Changing the radius of the organic droplets dispersed in the aqueous solution switches the wrinkle pattern from labyrinth to bi-phase. For the first time, the dual wrinkling structure is prepared; both labyrinthine texture and hexagonal dimple structures are spontaneously formed on the same microparticle surface. The former pattern is due to the surface instability from blends of hydrophobic polymer and amphiphilic block copolymer, while the latter is due to a mechanism similar that of the breath figure formed with organic phase change materials during solidification of microparticles. The general applicability of this approach is demonstrated on other pairs of polymer blends.