Fabrication of three-dimensional micropatterned hydrophobic surfaces by fused filament fabrication printing technology

In recent years, the interest in structured hydrophobic surfaces has considerably grown, finding applications in many industrial fields, including aerospace, automotive, and biomedical. Three-dimensional (3D) printing technology is a simple, rapid, and economic process to fabricate structured surfaces based on neat polymers and composite materials, allowing working with a wide variety of plastic materials. The manufactured surfaces show a roughness depending on the printing design and the printing resolution: this characteristic is ideal to achieve superhydrophobic properties. Furthermore, patterned surface structures can be printed by fused filament fabrication (FFF), so increasing the hydrophobic character of the samples; indeed, micro- and nanosurface structures are required to make a hydrophobic surface. In this study, 3D micropatterned textures of pillars were printed by FFF using polylactide (PLA) and polypropylene (PP) as polymer filaments and PLA/carbon nanotubes (PLA/CNTs) and PP/carbon fibers (PP/CF) as composite filaments. Morphologies of printed specimens were analyzed by optical microscopy and scanning electron microscopy. Good correspondence was found between pillar dimensions and edge-edge pillars distance of computer aided design (CAD) and composites 3D-printed samples. Their wettability was evaluated by static contact angle (CA) measurements. Results clearly show a significant increase of water CA values up to 50% in all micropatterned samples with respect to flat surfaces. This improvement was achieved by surface microstructuring without the use of nanoparticles and/or chemical treatment.