(18g) Bioinspired Biodegradable Superhydrophobic Membrane for Oil-Water Separation Using 3D Printing Technology

In nature, many species show great adaptability by exploiting surface properties derived from unique surface topographical features, such as superwettability. There are countless living things that exhibit wettability; in contrast, the lotus leaf, an ancient but popular plant, exhibits superhydrophobicity, low water adhesion and self-cleaning properties. Inspired by the lotus leaf, materials with superhydrophobicity-superoleophilicity have been proposed as promising candidates for oil-water separation by selectively repelling water from their surface against oil. Many forms of such materials have been fabricated to date, including metal meshes, membranes, aerogels, sponges and textiles, with high selectivity, high flux and low energy consumption. As in nature, superhydrophobicity is typically achieved by either roughening the surface of low surface-energy materials or by modifying the rough surface with low surface-energy compounds. Poly(lactic acid) (PLA) is a biocompatible and biodegradable synthetic polyester and is one of the few synthetic polymers approved by the Food and Drug Administration (FDA) for a variety of human clinical and ecological applications. PLA is a typical hydrophilic polymer comprising ester groups in its skeleton and terminal hydroxyl and carboxyl groups, both of which exhibit water affinity. Hence, it is challenging to construct a superhydrophobic surface out of pure PLA substrate.

Here, we report a superhydrophobic PLA porous membrane with a lotus-inspired surface structure for gravity-driven oil-water separation through 3D printing and facile two-step post-treatments. The membrane surface show a hierarchical roughness. Specifically, the micro-scale feature of the superhydrophobic PLA membrane was fabricated via 3D printing and chemical etching, leading to an ultra-high water adhesion (380 μN). The nanoscale features were achieved by further decoration of PS nanospheres. The hierarchical structure provided a large surface roughness and led to low water adhesion (21.8 μN). Furthermore, 3D printing technology provides an efficient, precise and customized route to fabricate membranes with specific shape and pore sizes. By tailoring the membrane pore sizes and wettability, the PLA membrane exhibited an excellent oil-water separation efficiency of over 99% while retaining a high flux of 60 kL m^-2 h^-1. The relatively low cost, excellent chemical tolerance and mechanical durability demonstrate its promising application in sophisticated and practical situations, such as the recovery of oil spills in waste water.