Antimicrobial and Aging Properties of Ag-, Ag/Cu-, and Ag Cluster-Doped Amorphous Carbon Coatings Produced by Magnetron Sputtering for Space Applications

Abstract

Inside a spacecraft, the temperature and humidity, suitable for the human crew onboard, also creates an ideal breeding environment for the proliferation of bacteria and fungi; this can present a hazard to human health and create issues for the safe running of equipment. To address this issue, wear-resistant antimicrobial thin films prepared by magnetron sputtering were developed, with the aim to coat key internal components within spacecrafts. Silver and copper are among the most studied active bactericidal materials, thus this work investigated the antibacterial properties of amorphous carbon coatings, doped with either silver, silver and copper, or with silver clusters. The longevity of these antimicrobial coatings, which is heavily influenced by metal diffusion within the coating, was also investigated. With a conventional approach, amorphous carbon coatings were prepared by cosputtering, to generate coatings that contained a range of silver and copper concentrations. In addition, coatings containing silver clusters were prepared using a separate cluster source to better control the metal particle size distribution in the amorphous carbon matrix. The particle size distributions were characterized by grazing-incidence small-angle X-ray scattering (GISAXS). Antibacterial tests were performed under both terrestrial gravity and microgravity conditions, to simulate the condition in space. Results show that although silver-doped coatings possess extremely high levels of antimicrobial activity, silver cluster-doped coatings are equally effective, while being more long-lived, despite containing a lower absolute silver concentration.

Amorphous Carbon Films for Electronic Applications

“…The hardness and elastic modulus of MAC were experimentally reported to be proportional to the fraction of sp 3 orbitals, and it was proved by MD simulation (Figures 5c). [15,86] Since metalloid or metal doping (Si, [58,63] B 4 C, [54] Ag, [87,88] Cu, [87] Ti [59,60] ) in the a-C thin film significantly increased the hardness, the depth of indentation after the friction scratch test was much less in the Ti (9.75%)-doped a-C thin film. However, surface cracks and wear scars were prominent because the enhanced hardness lost the plasticity of the pristine a-C thin film.…”

Antiviral and Antibacterial Efficacy of Nanocomposite Amorphous Carbon Films with Copper Nanoparticles

“…Recent studies on Ag and Cu NPs have shown that there is a strong influence of metal particle size, shape, surface charge, and other factors on the release of metal ions that are critical to bactericidal and virucidal properties. Smaller metal NPs oxidize more easily, releasing more metal ions which in turn increases the bactericidal effect [5]. Cu is less expensive than Ag, but it is also a very practical choice because it possesses not only bactericidal but also virucidal properties at the same time and can serve as a multifunctional protecting coating [7,8].…”

“…Among the various approaches explored, the utilization of novel materials with inherent antibacterial properties has shown great promise. It has been shown that silver, copper, and their compounds are among the most popular materials used for different antimicrobial and biomedicine applications 5, 6 because of their high bactericidal performance 7 . It should be noted that Cu has been recognized by the United States Environmental Protection Agency (EPA) as the first metallic antimicrobial agent in 2008 but with ongoing waterborne hospital-acquired infections and antibiotic resistance, research on Cu as an antimicrobial agent is booming again 8 .…”

Improving antibacterial ability of Ti-Cu thin films with co-sputtering method

“…Recently, various approaches such as spray deposition, spin-coating, sol–gel, acid etching, anodic oxidation, physical vapor deposition (PVD), and electrodeposition have been employed to modify antibacterial surfaces, and alter their surface properties, and topology 55 . Among these methods, magnetron sputtering has been shown in several studies to be a suitable and feasible way to modify antibacterial coatings 56 – 58 . This method offers an excellent opportunity to produce homogeneous, smooth, and dense coatings with a rapid deposition rate, thereby increasing the coating-substrate adherence 59 , 60 .…”