title: Nanoengineered Superhydrophobic Surfaces of Aluminum with Extremely Low Bacterial Adhesivity.
abstract: Bacterial adhesion and biofilm formation on surfaces are troublesome in many industrial processes. Here, nanoporous and nanopillared aluminum surfaces were engineered by anodizing and postetching processes and made hydrophilic (using the inherent oxide layer) or hydrophobic (applying a Teflon coating) with the aim of discouraging bacterial adhesion. Adhesion of Staphylococcus aureus ATCC 12600 (Gram-positive, spherically shaped) and Escherichia coli K-12 (Gram-negative, rod-shaped) was evaluated to the nanoengineered surfaces under both static and flow conditions (fluid shear rate of 37 s-1). Compared to a nonstructured electropolished flat surface, the nanostructured surfaces significantly reduced the number of adhering colony forming units (CFUs) for both species, as measured using agar plating. For the hydrophilic surfaces, this was attributed to a decreased contact area, reducing bacterial adhesion forces on nanoporous and nanopillared surfaces to 4 and 2 nN, respectively, from 8 nN on flat surfaces. Reductions in the numbers of adhering CFUs were more marked on hydrophobic surfaces under flow, amounting to more than 99.9% and 99.4% for S. aureus and E. coli on nanopillared surfaces, respectively. Scanning electron microscopy revealed a few bacteria found on the hydrophobic nanopillared surfaces adhered predominantly to defective or damaged areas, whereas the intact area preserving the original nanopillared morphology was virtually devoid of adhering bacteria. The greater decrease in bacterial adhesion to hydrophobic nanopillared surfaces than to hydrophilic or nanoporous ones is attributed to effective air entrapment in the three-dimensional pillar morphology, rendering them superhydrophobic and slippery, in addition to providing a minimized contact area for bacteria to adhere to.
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.|University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering (FB40), Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Ferdi
authors.initials: F
authors.lastname: Hizal
authors.affiliation: Food Technology Program, School of Agro-Industry, Mae Fah Luang University , 333 Moo1, Thasud, Muang, Chiang Rai 57100, Thailand.
authors.forename: Natthakan
authors.initials: N
authors.lastname: Rungraeng
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Junghoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Human Nutrition, Food and Animal Sciences, University of Hawaii at Manoa , 1955 East West Road, Agricultural Science Building 216, Honolulu, Hawaii 96822, United States.
authors.forename: Soojin
authors.initials: S
authors.lastname: Jun
authors.affiliation: University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering (FB40), Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.affiliation: University of Groningen and University Medical Center Groningen , Department of Biomedical Engineering (FB40), Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Henny C
authors.identifier: http://orcid.org/0000-0003-0760-8900
authors.initials: HC
authors.lastname: van der Mei
authors.affiliation: Department of Mechanical Engineering, Stevens Institute of Technology , Castle Point on Hudson, Hoboken, New Jersey 07030, United States.
authors.forename: Chang-Hwan
authors.identifier: http://orcid.org/0000-0003-2715-7393
authors.initials: CH
authors.lastname: Choi
mesh_terms: D000535:Aluminum; D001422:Bacterial Adhesion; D004926:Escherichia coli; D048168:Escherichia coli K12; D057927:Hydrophobic and Hydrophilic Interactions; D013211:Staphylococcus aureus; D013499:Surface Properties
chemical_list: D000535:Aluminum
keywords: adhesion; aluminum; anodizing; bacteria; nanostructures; superhydrophobic