Characterisation and antibacterial investigation of a novel coating consisting of mushroom microstructures and HFCVD graphite

The resistance of bacteria toward antibacterial drugs is a rising problem. This threat is a major concern for space stations, where antibacterial surfaces would be ideal for materials which also need to be corrosion-resistant, hard and durable. Accordingly, the purpose of this work is to investigate novel coatings that have superhydrophobic mushroom microstructures. The microstructures are made of nickel deposited on a substrate which is composed of a gold layer on top of the silicon. The microstructures were fabricated with UV-light assisted nanoimprint lithography. These superhydrophobic microstructures have a well-defined alignment and shape which does not have any detrimental effect on the plastic deformation of the substrate. Similar structures were coated with carbon by hot-filament chemical vapour deposition (HFCVD) for a duration varying from 30 min to 120 min. Raman spectroscopy shows that the coating is composed of graphite, due to nickel-induced graphitisation during the deposition process. The antibacterial evaluation shows the bare nickel microstructures offer no antibacterial properties despite their superhydrophobic behaviour. On the other hand, the graphitic coated microstructures demonstrate significant antibacterial properties. Especially, 30 min HFCVD coated samples was antibacterial against E. coli and S. aureus with Gram-dependence and dependent on the coating deposition duration.