Anti-microbial plastic parts fabricated by high-speed sintering

 This study utilizes Mg(OH)2 nanocrystals (a non-leaching biocide) to develop plastic articles with anti-microbial activity. The standard method for manufacturing plastic nanocomposites involves melt compounding Mg(OH)2 nanocrystals into a polymer melt, followed by injection molding; however, this approach did not produce a part with anti-microbial activity because there were no Mg(OH)2 nanocrystals on the surface of the parts. Anti-microbial polyamide 12 (PA 12) parts could be produced using a specific 3D printing method called high-speed sintering (HSS). The HSS-printed parts were subsequently dip-coated with an anti-microbial suspension of Mg(OH)2 nanoplatelets (NPs). The Mg(OH)2 NPs embedded on the surface of the HSS-printed part exhibited a log10 4 reduction (effective killing) of the bacterium Escherichia coli K-12 MG1655 (E. coli). The Mg(OH)2 NPs adhered well to the HSS-printed parts and could be used repeatedly with no loss of anti-microbial activity. In contrast, the dip-coated injection-molded PA 12 part was ineffective because the Mg(OH)2 NPs did not adhere to it. The surface of the HSS-printed part naturally allows the binding of the Mg(OH)2 nanocrystals. The anti-microbial activity of Mg(OH)2 NPs depends on direct contact between them and the microbe, which is feasible with the dip-coated HSS-printed part but not with the injection-molded nanocomposite. The work illustrates some of the unique possibilities arising from 3D printing.