Antimicrobial coating methods
The invention is directed to efficient methods for depositing highly adherent anti-microbial materials onto a wide range of surfaces. A controlled cathodic arc process is described, which results in enhanced adhesion of silver oxide to polymers and other surfaces, such as surfaces of medical devices. Deposition of anti-microbial materials directly onto the substrates is possible in a cost-effective manner that maintains high anti-microbial activity over several weeks when the coated devices are employed in vivo.
1. A cathodic arc ion plasma deposition method for producing an anti-microbial coating on a substrate, comprising:
positioning a substrate between an anode and a cathode target, said target comprising an ionizable metal selected from silver, copper, hafnium or zirconium;
introducing only oxygen gas into a vacuum chamber pressurized to about 0.1 to about 30 mTorr which houses the cathode target and the substrate;
variably controlling power to the arc to produce a discharge between the anode and the cathode target; and
moving the substrate toward or away from the target during arc discharge to deposit a high density, adherent anti-microbial macroparticulate metal/metal oxide coating comprising a range of macroparticle sizes of about 1 nm to 50 microns wherein macroparticle size increases with coating thickness to provide a coating that exhibits antimicrobial activity at least four days longer than a uniform coating containing few macroparticles produced without movement of the substrate during deposition under the same deposition conditions.
2. The method of claim 1 wherein power to the arc is externally controlled by a single variable power supply or by at least two independently variable power supplies attached in opposed positions to the cathode target.
3. The method of claim 2 wherein power to the arc is adjusted to about 12 to about 60 volts providing between 5 and about 500 amps during deposition of a 100-200 nm coating on the substrate.
4. The method of claim 1 wherein the substrate comprises a metal.
5. The method of claim 4 wherein the substrate is selected from the group consisting of titanium, steel, chromium, zirconium, nickel, alloys and combinations thereof.
6. The method of claim 1 wherein the substrate comprises a polymer or ceramic.
7. The method of claim 6 wherein the polymer is polypropylene, polyurethane, EPTFE, PTFE, polyimide, polyester, PEEK, UHMWPE, nylon or combinations thereof.
8. The method of claim 7 wherein the polymer is PEEK or polyethylene.
9. The cathodic arc ion plasma deposition method of claim 1 further comprising monitoring the ratio of the metal/metal oxide deposited in the coating in relation to the distance of the substrate from the target, wherein increased antimicrobial activity of the coating correlates with a decrease in said metal/metal oxide ratio.
10. The method of claim 9 further comprising increasing deposition time to obtain a coating thickness of about 50 nm to about 5 microns.
11. The method of claim 1 wherein the deposition is conducted at a temperature between about 25° C. and 75° C.