Directional droplet transfer on micropillar-textured superhydrophobic surfaces fabricated using a ps laser

Abstract

Directional droplet transfer is essential for water collection, microfluidic and remote material transfer. Laser-enabled 2.5-dimensional fabrication of micropillars on shape-memory-polymers transfers the surface wettability from hydrophilicity to superhydrophobicity in a simple, fast, and large-scale manner. The surface wettability exhibits a tight relationship with the topographic features of the surface microstructures. By adjusting the height, diameter, bending angle of the micropillars as well as superhydrophobic chemical treatment, the contact angles of water droplets on the micropillar-textured surfaces exceed 160° and exhibit finely-tunable sliding angles from 5.4 ± 1.9° to 71.8 ± 5.9°. A water droplet on a surface textured with bended micropillar shows anisotropic sliding behavior depending on the sliding direction and the micropillar bending angle. By properly design and assembly of straight and bended micropillars, speedy sliding tracks are constructed and directional droplet transfer is demonstrated, suggesting great potential in the fields of lossless material transportation, biomedical testing and microfluidic devices.