Superhydrophilic and Superhydrophobic Surfaces with Reversible Wettability Using Laser Processing.

Laser surface microtexturing has become increasingly popular due to its low cost, scalability, automation, and lack of use of hazardous chemicals. Laser surface microtexturing can be used to control the wettability of various surfaces by varying surface roughness for a wide range of applications. In recent years, the reversible transition between superhydrophobicity and superhydrophilicity has gained significant attention due to a variety of applications, including self-cleaning, corrosion protection, anti-icing, microfluidics, water harvesting, and thermal management. The ability to manipulate liquid behavior facilitates processes like coalescence, rolling, and pinning. However, the current methods of making reversible superhydrophilic-superhydrophobic surfaces have several disadvantages, such as complex fabrication processes, use of high temperatures and chemicals, time-consuming, and high costs. This paper presents a facile, low-cost laser microtexturing method capable of inducing superhydrophilicity with a contact angle (CA) of less than 1°. Additionally, a thin poly-(dimethylsiloxane) (PDMS) coating can render the laser microtextured surface superhydrophobic with a CA of 169°. Furthermore, the thin PDMS layer can be easily removed by laser ablation, thereby restoring the superhydrophilic behavior, and allowing to achieve a reversible transition between superhydrophilicity and superhydrophobicity. As an example, the reversibility is shown for transparent glass surfaces and aluminum. Also, we demonstrate the laser method for the fabrication of selective areas having superhydrophilic and superhydrophobic properties selectively distributed over the surface.