Flexible antibacterial Zr-Cu-N thin films resistant to cracking

Abstract

This study investigates how the Cu concentration in Zr-Cu-N films affects the films' antibacterial capacity and mechanical properties. Zr-Cu-N films were prepared by reactive magnetron sputtering from composed Zr/Cu targets using a dual magnetron in an Ar + N2 mixture. The antibacterial capacity of Zr-Cu-N films was tested on Escherichia coli (E. coli) bacteria. The mechanical properties of Zr-Cu-N films were determined from the load vs. displacement curves measured using a Fisherscope H 100 microhardness tester. The antibacterial capacity was modulated by the amount of Cu added to the Zr-Cu-N film. The mechanical properties were varied based on the energy Ei delivered to the growing film by bombarding ions. It was found that it is possible to form Zr-Cu-N films with Cu concentrations ≥10 at. % that simultaneously exhibit (1) 100% killing efficiency Ek for E. coli bacteria on their surfaces, and (2) (1) high hardness H of about 25 GPa, (2) high ratio H/E* ≥ 0.1, (3) high elastic recovery We ≥ 60% and (4) compressive macrostress (σ < 0). The Zr-Cu-N films with these parameters are flexible/antibacterial films that exhibit enhanced resistance to cracking. This enhanced resistance was tested by (1) bending the Mo and Ti strip coated by sputtered Zr-Cu-N films (bending test) and (2) loading the surface of the Zr-Cu-N sputtered on a Si substrate by a diamond indenter at high loads up to 1 N (indentation test). Physical, mechanical, and antibacterial properties of Zr-Cu-N films are described in detail. In summary, it can be concluded that Zr-Cu-N is a promising new material for creating flexible antibacterial coatings on contact surfaces.