## 5 Conclusions  
The selective plating method described in the current study allows for uniform and continuous deposition of copper coatings on medical-grade stainless steel 1.4021 and nickel alloy Ni200 substrates without presence of cracks or defects. The use of both acidic and alkaline electrolyte solutions enables formation of single-phase solid-solution copper coatings, indicating a high level of coating integrity.  
One significant advantage of the selective plating technique is that it can refine the surface roughness of the substrates. The copper coatings produced with the acidic or alkaline solution exhibited surface roughness approximately 20% or 40% finer than that of the substrates, respectively. This reduction in surface roughness can have several benefits, including improved aesthetics, enhanced corrosion resistance, and reduced friction in certain applications.  
Importantly, the copper coatings deposited using selective plating demonstrated antibacterial activity. The inhibition zones formed around the coatings indicate their ability to inhibit the growth of bacteria, making them suitable for applications where preventing bacterial contamination is crucial. The use of an alkaline copper solution resulted in slightly larger inhibition zones compared to the acidic solution, suggesting potentially higher antibacterial effectiveness.  
These findings highlight the potential of selective plating as a reliable and effective method for deposition of antibacterial copper coatings on stainless steel and nickel alloy substrates. The ability to achieve uniform and continuous coatings without compromising their surface integrity, coupled with their antibacterial properties, makes this technique promising for various applications, including use of surgical instruments, medical devices, and other healthcare-related equipment. Given the promising results obtained, further studies will be undertaken to investigate the long-term stability, compatibility, and specific mechanisms underlying the antibacterial effectiveness of these coatings. Additionally, the applicability of this technique to a wider range of medical-grade materials and its potential integration with other surface modification methods will be explored to enhance its versatility and suitability for diverse healthcare applications.  
**Author Contributions:** Conceptualization, D.V. and H.S.; formal analysis, D.V., H.S., R.Y. and S.I.; investigation, D.V., R.Y. and T.F.M.; supervision, H.S. and B.G.; validation, H.S., R.Y., S.I. and T.F.M.; visualization, D.V.; writing--original draft, D.V.; and writing--review and editing, D.V., H.S., R.Y., S.I., T.F.M. and B.G. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This work was supported by the Bulgarian National Science Fund within the M-ERA.NET Programme, Project \"New generation copper based coatings of improved antimicrobial resistance to pathogens\", No. KIT-06-DO-02/1.  
**Data Availability Statement:** The datasets analyzed during the current study are available from the corresponding author on reasonable request.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.