Excellent Superhydrophobic Cone-Array Surfaces with Low Contact Time of Droplet Pancake Bouncing Under Various Conditions

Superhydrophobic surfaces with a low liquid–solid contact time have huge application prospects in anti-icing, corrosion-resistant, self-cleaning, etc. Significant attempts have been devoted to reducing the contact time through altering the hydrodynamics of the process through which the droplet contacts the superhydrophobic surface. However, these works are rarely considered to be related to the influence of environmental conditions (e.g., the pH of the droplet, salinity of the droplet, droplet viscosity, and supercooled droplet impact). Here, we report various superhydrophobic cone arrays (SCAs) with low droplet impact contact times under various conditions (pH of the droplet, salinity of the droplet, droplet viscosity, droplet temperature, etc.). We demonstrate that the low contact time of the droplet impacting cone-arrays can be optimized via the critical Weber number, pillar-to-pillar spacing, and pillar height (e.g., 11.1, 350 μm, and 300 μm, respectively). The lowest droplet contact time of ~6 ms, which is reduced by more than 60% compared to conventional bouncing, can be achieved. In addition, directional pancake bouncing behaviors can achieve the largest horizontal displacement (85% of the droplet size, ~3 mm) on a tilted SCA with optimal tilt angles. These findings offer insights into the interface effect for controlling wetting that would extend the practical applications, e.g., liquid repellency, anti-corrosion, anti-icing, heat transfer, etc.