Design and Fabrication of Superhydrophobic Porous Structures via 3D Printing and Phase Separation for Oil–Water Separation

Overview & Synopsis

Superhydrophobic materials, inspired by natural surfaces such as lotus leaves and water striders, have shown exceptional potential in oil–water separation due to their selective wettability. However, conventional fabrication methods—such as electrospinning, sol–gel processing, and templating—often involve complex steps and limited scalability. This thesis explores the development of bioinspired superhydrophobic membranes and three-dimensional (3D) porous structures for efficient oil–water separation using 3D printing techniques, particularly fused filament fabrication (FFF). First, a comprehensive review is conducted to trace the origins of hydrophobicity in natural structures, such as lotus leaves, desert beetles, and rose petals. These surfaces feature hierarchical micro/nanostructures and low-surface-energy coatings, which inspired the development of synthetic materials with self-cleaning, antifouling, and water-repellent properties. Building upon this foundation, recent studies were reviewed that examine both 2D and 3D hydrophobic surfaces fabricated via 3D printing, highlighting the benefits and limitations of each. Next, this work presents a simplified method for fabricating 2D porous membranes using fused filament fabrication (FFF) 3D printing combined with a surface spray-coating of silica nanoparticles. By adjusting slicing parameters such as infill density, pore sizes were precisely controlled without the need for CAD modeling. The resulting membranes exhibited a water contact angle of up to 154.6°, high separation efficiency (above 90%), and excellent oil flux performance (up to 81.89 mL·cm⁻²·min⁻¹) for various organic solvents. Finally, a novel 3D cubic porous architecture was developed using optimized FFF printing parameters to achieve pore heights as small as 186.7 μm. Surface modification with nano-silica produced a superhydrophobic coating with a contact angle of 158.2°. The printed structure showed strong mechanical durability and long-term performance in continuous suction-driven separation, maintaining an 87.2% efficiency for over 24 hours. This marks the first report of directly printing 3D porous structures with uniform pores for this purpose. Overall, this thesis offers a customizable and cost-effective strategy for fabricating superhydrophobic materials for oil–water separation.