• Additive manufacturing of anti-SARS-CoV-2 copper-tungsten-silver alloy

      Robinson, John; Arjunan, Arun; Baroutaji, Ahmad; Martí, Miguel; Tuñón Molina, Alberto; Serrano-Aroca, Ángel; Pollard, Andrew (Emerald, 2021-08-23)
      Purpose The COVID-19 pandemic emphasises the need for antiviral materials that can reduce airborne and surface-based virus transmission. This study aims to propose the use of additive manufacturing (AM) and surrogate modelling for the rapid development and deployment of novel copper-tungsten-silver (Cu-W-Ag) microporous architecture that shows strong antiviral behaviour against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Design/methodology/approach The research combines selective laser melting (SLM), in-situ alloying and surrogate modelling to conceive the antiviral Cu-W-Ag architecture. The approach is shown to be suitable for redistributed manufacturing by representing the pore morphology through a surrogate model that parametrically manipulates the SLM process parameters: hatch distance (h_d), scan speed (S_s) and laser power (L_p). The method drastically simplifies the three-dimensional (3D) printing of microporous materials by requiring only global geometrical dimensions solving current bottlenecks associated with high computed aided design data transfer required for the AM of porous materials. Findings The surrogate model developed in this study achieved an optimum parametric combination that resulted in microporous Cu-W-Ag with average pore sizes of 80 µm. Subsequent antiviral evaluation of the optimum architecture showed 100% viral inactivation within 5 h against a biosafe enveloped ribonucleic acid viral model of SARS-CoV-2. Research limitations/implications The Cu-W-Ag architecture is suitable for redistributed manufacturing and can help reduce surface contamination of SARS-CoV-2. Nevertheless, further optimisation may improve the virus inactivation time. Practical implications The study was extended to demonstrate an open-source 3D printed Cu-W-Ag antiviral mask filter prototype. Social implications The evolving nature of the COVID-19 pandemic brings new and unpredictable challenges where redistributed manufacturing of 3D printed antiviral materials can achieve rapid solutions. Originality/value The papers present for the first time a methodology to digitally conceive and print-on-demand a novel Cu-W-Ag alloy that shows high antiviral behaviour against SARS-CoV-2.
    • Mechanisms of selective laser sintering and heat transfer in Ti powder

      Tolochko, Nikolay K.; Arshinov, Maxim K.; Gusarov, Andrey V.; Titov, Victor I.; Laoui, Tahar; Froyen, Ludo (Emerald Publishing Group Ltd., 2003)
      Coupled metallographic examination and heat transfer numerical simulation are applied to reveal the laser sintering mechanisms of Ti powder of 63-315?µm particle diameter. A Nd:YAG laser beam with a diameter of 2.7-5.3?mm and a power of 10-100?W is focused on a bed of loose Ti powder for 10?s in vacuum. The numerical simulation indicates that a nearly hemispherical temperature front propagates from the laser spot. In the region of a-Ti just behind the front, heat transfer is governed by thermal radiation. The balling effect, formation of melt droplets, is not observed because the temperature increases gradually and the melt appears inside initially sintered powder which resists the surface tension of the melt. (Emerald Publishing Group Limited)