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Previous studies have revealed the potential of powder mixed electrical discharge machining (PMEDM) with regards to concurrently machining part geometry and coating an antibacterial layer on medical devices.This study is aimed at further demonstrating this potential. In order to do so, the PMEDM process was varied by adding different concentrations of silver nano-particles into the dielectric fluid and used to machine Ti-6Al-4V. Afterwards, the resulting machined and coated surfaces were characterized with regards to surface integrity, the coating layer's thickness, microhardness and chemical elements as well as antibacterial property.Material removal rate, tool wear and pulse signals were also analysed in order to give an insight on process feasibility. From both qualitative and quantitative results, it could be established that the surfaces machined and coated by PMEDM method have demonstrated a significant reduction of not only the amount of S. aureus bacteria, but also the number of bacterial clusters on the coating layer's surface. Moreover, the coating layer's silver content, which depends on the powder concentration suspended in the dielectric fluid, plays a vital role in the antibacterial property. As compared to surfaces without silver, surfaces containing approximately 3.78% silver content showed a significant decrease in both bacterial numbers and clusters, whereas a further increase in silver content did not result in a considerable bacterial number and cluster reduction. Regarding the machining performance, as compared to EDM without powder, machining time is remarkably decreased by using the PMEDM method.

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In this study, the efficiency of integration between Taguchi and TOPSIS in multi-response optimization of powder mixed electrical discharge machining (PMEDM) process was evaluated. The input parameters, such as workpiece and tool electrode material, polarity, pulse on time (ton), pulse off time (toff), Current (I) and powder concentration have been selected to optimize two responses; namely surface roughness (Ra) and surface hardness (HV). The results show that titanium powder mixed dielectric fluid improves multi-response optimization efficiency in PMEDM. In addition, machining conditions, such as tool electrode material, powder concentration, pulse on time, polarity, current density, A×G and B×G interactions play a very important role on S/N ratio of C* whereby powder concentration has the strongest influence. TOPSIS-Taguchi is a potential method for multi-response optimization in PMEDM. However, the optimal results using ANOVA analysis show that there is a necessity to have more studies in TOPSIS-Taguchi to improve the integration efficiency between two methods for optimizing multiple responses in PMEDM.