Switchable Underwater Bubble Wettability on Laser-Induced Titanium Multiscale Micro-/Nanostructures by Vertically...

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• Controlling surface wettability is crucial for various applications.
• Developing methods for tunable surface properties, especially underwater bubble behavior, remains a challenge.

Purpose of the Study:

• To create novel multiscale TiO2 square micropillar arrays on titanium sheets.
• To investigate the switchable underwater bubble wettability of these structures.
• To explore the underlying mechanisms and potential applications in bubble manipulation.

Main Methods:

• Fabrication of multiscale TiO2 micropillar arrays using vertically crossed scanning of a femtosecond laser.
• Inducing superaerophobicity and superaerophilicity through controlled laser ablation, shock compression, and debris self-deposition.
• Switching bubble wettability via thermal treatment (heating in a dark environment) and ultraviolet (UV) irradiation in alcohol.

Main Results:

• Achieved superaerophobicity with a small sliding angle and superaerophilicity with a bubble contact angle (BCA) of ~4° after heating.
• Demonstrated reversible switching between superaerophilicity (BCA ~4°) and superaerophobicity (BCA 156°) within 1.5 hours.
• Confirmed excellent reproducibility and stability over five switching cycles and demonstrated tunable wettability with varying laser scanning spacing.

Conclusions:

• The novel laser-induced multiscale TiO2 structures exhibit switchable underwater bubble wettability.
• The reversible switching mechanism is attributed to the chemical conversion between Ti-OH and Ti-O.
• This work provides a time-saving, stable, and reproducible method for bubble manipulation and gas collection, with potential for patterned bubble generation.