Ultraslippery/hydrophilic patterned surfaces for efficient fog harvest

The rapid and controllable sliding of droplets on anisotropic slippery liquid infused porous surfaces (SLIPS) has promising application prospects in the fields of energy, lab-on-a-chip, etc. In this work, the fabrication of hydrophilic patterned SLIPS on copper substrates that can achieve efficient droplet transport and fog harvest was reported. A single superhydrophilic stripe and array of superhydrophilic stripes were fabricated on SLIPS background, respectively. Contact angles, sliding angles and contact angle hysteresis of the surfaces were investigated and analyzed. Results showed that hydrophilic patterned SLIPS with superhydrophilic stripe array had remarkable anisotropy in contact angle hysteresis in the parallel and perpendicular directions due to the large energy barrier induced by liquid surface tension in the direction perpendicular to the stripes, which can be used to transport droplets rapidly and precisely. In addition, the fog harvest performance, as a typical example of droplet transport, was significantly improved on hydrophilic patterned SLIPS due to high nucleation density on the hydrophilic SLIPS, high condensate mobility, efficient condensate transferring from SLIPS to superhydrophilic stripes and liquid shedding along the stripes for departing.