Orthogonal Nano-Engineering (ONE): Modulating Nanotopography and Surface Chemistry of Aluminum Oxide for Superior Antifouling and Enhanced Chemical Stability

Abstract

Decoupling certain material surface properties can be key to attaining critical property-activity relationships that underpin their antifouling performance. Here, we employed Orthogonal Nano-Engineering (ONE) to decouple the influences of nanotopography and surface chemistry on surface antifouling. Nanotopography and surface chemistry were systematically varied with a two-step process. Controlled nanotopography was obtained by electrochemical anodization of aluminum, which generated anodic aluminum oxide (AAO) surfaces with cylindrical nanopores (diameters: 15 nm, 25 nm, 100 nm). To modify surface chemistry while preserving nanotopography, an ultrathin (~5 nm) yet stable zwitterionic coating of poly(divinylbenzene-4-vinylpyridyl sulfobetaine) was deposited on these surfaces using initiated chemical vapor deposition (iCVD). Antifouling performance was assessed by quantifying 48-h biomass formed by Gram positive and negative bacteria. The ONE surfaces demonstrated enhanced antifouling performance, with small-pore nanotopography and zwitterionic chemistry each lowered biomass accumulation by tested species, with potential additive effects. The most effective chemistry-topography combination (ZW-AAO15) enabled an overall reduction of 91% for Escherichia coli, 76% for Staphylococcus epidermidis, 69% for Listeria monocytogenes, and 67% for Staphylococcus aureus, relative to the uncoated nanosmooth control. Additionally, the composite ZW coating exhibited encouraging anticorrosion properties under both static and turbulent cleaning conditions, vital to antifouling applications in healthcare and food industries.