Superaerophobic polymer objects prototyped via liquid crystal display (LCD)-based 3D printing: one-step post-surface-treatment and application in underwater bubble manipulation

Underwater superaerophobic surface is of great significance for controllable manipulation of gas bubbles in scientific research and practical applications. However, the fabrication of arbitrary-shaped superaerophobic solid surfaces through a simple and low-cost approach is still hard. Herein, superaerophobic 3D objects were manufactured via liquid crystal display (LCD)-based 3D printing (vat photopolymerisation-based additive manufacturing) combined with one-step post-surface-treatment in sodium hydroxide (NaOH) solution. The influences of NaOH concentration, reaction temperature and time on the wettability of the polymer surface were systematically investigated. After a suitable alkali-treatment, the object surface obtained a bubble contact angle of 159° with extremely low bubble adhesion, featuring the underwater superaerophobicity. Morphology and composition characterisation demonstrated that a hydrophilic gel layer was produced on the printed sheet after the alkali-treatment, which is explained as the main mechanism of the superwetting transition from aerophobicity to superaerophobicity. Interestingly, spontaneously formed surface microgrids (size in <i>xy</i> direction: ∼50 μm) during 3D printing accelerated the alkali-treatment. Further, a superaerophobic 3D tweezer was designed, fabricated, and successfully applied in a toxic nitric oxide (NO) bubble reaction underwater for gas purity detection. The one-step post-surface-treatment method is also suitable for other commercial photosensitive resins and digital-light-processing (DLP) 3D printing.