A Microfluidic Platform Based on Nanotube Forests for Anti-Evaporation Applications

Vertically aligned nanotube forests (NTFs) with multiple inner-tube structures are prepared by maskless reactive ion etching via plasma repolymerization. Ascribed to the multiple inner tubes, the solid-liquid contact area is increased, which enhances the capillary and van der Waals forces while in contact with liquid. After fluorination, the NTFs show superhydrophobicity, oleophobicity, and strong liquid adhesion, enabling immobilization of oil or water droplets. Consequently, a microfluidic platform with pinned oil-wrapping-water open droplets is realized. Such a platform mitigates the droplet evaporation issue commonly observed in open-droplet microfluidic systems, thus may have wide applications.