Laser Direct Writing of Tree-Shaped Hierarchical Cones on a Superhydrophobic Film for High-Efficiency Water Collection

Abstract

Directional water collection has stimulated a great deal of interest because of its potential applications in the field of microfluidics, liquid transportation, fog harvesting, and so forth. There have been some bio or bioinspired structures for directional water collection, from one-dimensional spider silk to two-dimensional star-like patterns to three-dimensional Nepenthes alata. Here we present a simple way for the accurate design and highly controllable driving of tiny droplets: by laser direct writing of hierarchical patterns with modified wettability and desired geometry on a superhydrophobic film, the patterned film can precisely and directionally drive tiny water droplets and dramatically improve the efficiency of water collection with a factor of ∼36 compared with the original superhydrophobic film. Such a patterned film might be an ideal platform for water collection from humid air and for planar microfluidics without tunnels.

Fog collection on a superhydrophobic/hydrophilic composite spine surface

“…During this process, the gradient of the Laplace pressure between two sides induced the droplets on the spines to continuously move towards the base of the spines. This type of conical shape generated a Laplace pressure difference between the two opposite sides of the droplet: [23][24][25] DP ¼ À…”

Molecular Dynamics Study on the Wetting Transition of a Hierarchical Groove

“…Superhydrophobic surfaces have extremely wide applications including anti‐icing, anti‐frosting, biological materials, and water collection . A typical superhydrophobic surface exhibits a water contact angle (CA) above 150°, a sliding angle (SA), and a contact angle hysteresis (CAH) below 10° …”

Beetle-like droplet-jumping superamphiphobic coatings for enhancing fog collection of sheet arrays

“…However, currently reported biomimetic materials oen prepared by reactive ion etching, 14,32 electrochemistry, 33,34 photocatalysis, 35,36 photolithography 37 and other high cost means. [38][39][40] And, these technologies are relatively expensive and are not conducive to mass production of materials. Furthermore, researchers mainly focus on superhydrophobic/superoleophobic property, 41 droplets transportation, [42][43][44][45][46] oil/water separation [47][48][49] and self-cleaning 50,51 for the materials surface, and how to realize both rapid nucleation and droplet removal remains an important challenge.…”