Tunable Wetting Patterns on Superhydrophilic/Superhydrophobic Hybrid Surfaces for Enhanced Dew-Harvesting Efficacy

Dew collection is a promising strategy to address the water scarcity problem in arid regions. Inspired by the natural species, engineering superhydrophilic/superhydrophobic hybrid (SSH) surfaces has received much attention for water harvesting in recent years. However, it is still challenging to design a surface that is capable of fast condensate droplet capture and directional droplet transport, both of which are essential for efficient dew harvesting at low subcooling conditions. Herein, a convenient, straightforward method to fabricate SSH surfaces with superhydrophilic (SHPi) triangular patterns on the superhydrophobic (SHPo) substrates by using a laser ablation approach is presented. The triangle spacing is optimized to delicately control condensate droplet nucleation and directional water transport. It is found that water collection performance on the SSH surfaces exhibits remarkable dependence on the triangle spacing. The SSH surface with a triangle spacing of 1.5 mm enables fast condensate droplet nucleation, directional transport, and efficient departure, yielding an approximate to 54% or approximate to 21% enhancement of water collection rate compared to the uniform SHPo or SHPi surfaces. This study of exploiting multiple coupling effects of the surface features to enhance dew collection efficiency can provide important insights for developing high-performance water-harvesting systems via dew.