Sewage water-repellent PDMS and magnetic silicone composites: lab to commercialization

Abstract

Liquid-repellent surfaces are beneficial for improving corrosion resistance, anti-biofouling, anti-icing, and reducing material sticking in food, beverages, cosmetics, and medical industries. However, limited research data are available on fabricating sewage water-repellent surfaces, which should repel suspended organic/inorganic and biological matter in addition to water. Herein, we unveil the sewage water repellency and superhydrophobicity of magnetic silicone composites and poly(dimethylsiloxane) (PDMS). Hexagonally arranged microconical pillars (Wenzel roughness of 1.2-2.4) were printed via hot embossing and replica molding methodologies. High static contact angles of ~160 degree, low contact angle hystereses of ~5 degree, and low roll-off angles of ~5 degree were achieved. At least 30 textured silicone composites were fabricated by successively hot embossing from a single custom-made and durable commercializable Ni-steel mold. All of them demonstrated excellent replication efficiency and retained superhydrophobicity and sewage water repellency as a function of embossing cycles. Furthermore, sewage water and deionized water droplets bounced off the silicone composite surface for a Weber number of up to 149, revealing a robust Cassie configuration. Furthermore, textured surfaces retained under-sewage water phobicity for up to 24 h, when submerged at 3 cm depth (0.3 kPa gauge pressure), wherein coated and untextured surfaces have failed just within 15 min, i.e., covered by a liquid film or sticky droplets. Also, textured surfaces inhibited the growth of the Escherichia coli bacterium, while a huge biofilm was observed on the untextured region. Briefly, this is the first demonstration of a one-step, upscalable, and facile hot embossing methodology to manufacture sewage water-repellent silicone composite and PDMS surfaces.