Simultaneous realization of superhydrophobicity and multiple droplet bouncing through laser ablation, organic adsorption and fluorination treatment

Abstract

Realizing proactive anti-icing and efficient thermal management on metal surfaces is still an extreme challenge. However, superhydrophobicity and multiple droplet bouncing capability can increase the probability of deicing. Especially, when the surface is dynamic such as the wings of an aircraft, the multiple droplet bouncing can increase the probability of the droplet passively leaving the solid surface by the forces parallel to the surface. Meanwhile, the droplet forming ability can increase the efficiency of condensation heat dissipation through dropwise condensation rather than film mode. When the surface is applied to absorb the kinetic energy of the impacting droplet, more bounce times can also increase energy collection efficiency based on the collection frequency. To imitate the “lotus effect” with a Cassie-Baxter state, the superhydrophobic surface with a unique quaternary “micro column-micro protrusions-nano particle-fluorinated layer” cross-scale structure is fabricated on Ti alloy through sequential laser ablation, organic adsorption and fluorination treatment. Based on a laser scanning space of 50 μm, although the quaternary structures exhibited crosslinked morphology and irregular micro-column array, subsequent 4 h high-temperature organic adsorption and 0.5 h fluorination treatment realize a contact angle of 164.2°, a slide angle of 7.8° and 5 times droplet bounces. The proposed “mechanical spring” effect induced by the gap between the C–C/C–H layer and the fluorinated layer promotes the multiple bouncing.