Flexible antibacterial Al–Cu–N films

• The three-functional antibacterial/protective/flexible Al–Cu–N film was sputtered.
• The hard Al–Cu–N films are highly elastic and resistant to cracking.
• The Al–Cu–N films kill E. Coli bacteria in the daylight as well as in the dark.
• The conditions necessary to form three-functional Al–Cu–N films are found.

The paper reports on the effect of Cu content in the Al–Cu–N film on its antibacterial activity and mechanical properties. The Al–Cu–N films were prepared by reactive magnetron sputtering from composed Al/Cu targets using a dual magnetron. The antibacterial activity of Al–Cu–N films was tested on the killing of Escherichia coli bacteria. Mechanical properties of Al–Cu–N films were determined from the load vs. displacement curves measured by a Fischerscope H 100 microhardness tester. Mechanical properties were controlled by (i) the Cu content in the film and (ii) the energy Ei delivered to growing film by bombarding ions and fast neutrals. Correlations between the energy Ei, the content of Cu in the Al–Cu–N film and its mechanical and antibacterial properties were investigated in detail. It was found that (1) Al–Cu–N films with Cu content ranging from ~ 2 to ~ 12 at.% exhibit (i) high hardness H ranging from ~ 15 to ~ 23 GPa, (ii) high ratio H/E⁎ ≥ 0.1, (iii) high elastic recovery We ≥ 60%, (iv) compressive macrostress (σ < 0) and (v) enhanced resistance to cracking and (2) the Al–Cu–N films with ≥ 7 at.% Cu exhibit 100% efficiency of killing Ek of E. coli bacteria on their surface both in the daylight and in the dark. It means that the Al–Cu–N films sputtered under ion bombardment are three-functional antibacterial/flexible/protective films. Both the mechanical and antibacterial properties of sputtered Al–Cu–N films are described in detail.