Inactivation of bacteria under visible light and in the dark by Cu films. Advantages of Cu-HIPIMS-sputtered films

Abstract

Introduction The Cu polyester thin-sputtered layers on textile fabrics show an acceptable bacterial inactivation kinetics using sputtering methods. Materials and methods Direct current magnetron sputtering (DCMS) for 40 s of Cu on cotton inactivated Escherichia coli within 30 min under visible light and within 120 min in the dark. For a longer DCMS time of 180 s, the Cu content was 0.294% w/w, but the bacterial inactivation kinetics under light was observed within 30 min, as was the case for the 40-s sputtered sample. Results and discussion This observation suggests that Cu ionic species play a key role in the E. coli inactivation and these species were further identified by X-ray photoelectron spectroscopy (XPS). The 40-s sputtered samples present the highest amount of Cu sites held in exposed positions interacting on the cotton with E. coli. Cu DC magnetron sputtering leads to thin metallic semi-transparent gray-brown Cu coating composed by Cu nanoparticulate in the nanometer range as found by electron microscopy (EM). Cu cotton fabrics were also functionalized by bipolar asymmetric DCMSP. ConclusionSputtering by DCMS and DCMSP for longer times lead to darker and more compact Cu films as detected by diffuse reflectance spectroscopy and EM. Cu is deposited on the polyester in the form of Cu 2 O and CuO as quantified by XPS. The redox interfacial reactions during bacterial inactivation involve changes in the Cu oxidation states and in the oxidation intermediates and were followed by XPS. High-power impulse magnetron sputtering (HIPIMS)-sputtered films show a low rugosity indicating that the texture of the Cu nanoparticulate films were smooth. The values of R q and R a were similar before and after the E. coli inactivation providing evidence for the stability of the HIPIMSdeposited Cu films. The Cu loading percentage required in the Cu films sputtered by HIPIMS to inactivate E. coli was about three times lower compared to DCMS films. This indicates a substantial Cu metal savings within the preparation of antibacterial films.

Antibacterial and Biocompatible Titanium-Copper Oxide Coating May Be a Potential Strategy to Reduce Periprosthetic Infection: An In Vitro Study

“…In this regard, we chose titanium copper oxide coating because while copper ions are eluting, titanium oxide theoretically provided corrosion resistance to the substrate [3]. However, there are many other coatings containing copper that could have similar or potentially even better performance (eg, titanium-copper, copper-nickel, titaniumcoper-nitride, titanium-silver-copper) [5,6,18,22,41,44]. Also, we chose HiPIMS, a physical vapor deposition method, for coating because it enables deposition of dense, firm, and thin films.…”

Recent Progress in Magnetron Sputtering Technology Used on Fabrics

“…The nano Cu film fabrics coated by magnetron sputtering had favorable antibacterial property against Escherichia coli . Under the same sputtering conditions, bacteriostatic rates against Escherichia coli of the nano Cu film deposited by high-power pulse sputtering was more than three times higher than that deposited through direct current magnetron sputtering [ 37 ]. Scholz et al [ 38 ] sputtered Cu and Ag on fabrics, respectively.…”

“…However, the adhesion between coatings and fabrics was discrepant due to sputtering processes and substrates different. For example, high-power impulse magnetron sputtering proceeded with a higher density of electrons/metalion pairs and at higher energies compared to direct current magnetron sputtering (DCMS) and direct current pulsed magnetron sputtering (DCMSP), thereby improved the adhesion between coatings and substrates [ 37 ]. For this kind of fabric substrate, the different surface chemical property, surface morphology and porosity size of the fiber materials can also cause differences in adhesion between coatings and substrates, besides the fabric structure differences such as knitted fabrics, woven fabrics and nonwoven fabrics, etc.…”

A Review of Last Developments in Thin Films Parameters of Direct Current Sputtering for Optical and Biomedical Applications

“…For example, the antibacterial ability of nano-thickness Cu film manufactured by DC sputtering was investigated to be higher more than 3 times [4]. Thickness can affect coating properties such as shielding against electromagnetic, ultraviolet (UV) resistance, electrical conductivity, antibacterial ability, and so on [5,6]. Kylián et al (2014) illustrates an example of the deposition of nano-thickness of Cu thin film coatings on polymer substrate [3].…”

“…Zakharova et al (2012) investigated the effect of Cu coating nanothickness on transparency ability for the visible light, it shows that there are transparency and reflection enhancement of about 60% and 84%, respectively [8]. There are many factors in the nano-film coating procedure in DC sputtering that can affect the thickness and coating related properties which including optical and optic-electric properties [3,5,7]. These parameters may belong into materials characteristics that used in the coating process, such as type and compositions of target and substrate materials.…”