3D Printed Cobalt-Chromium-Molybdenum Porous Superalloy with Superior Antiviral Activity.

COVID-19 pandemic and associated supply-chain disruptions emphasise the requirement for antimicrobial materials for on-demand manufacturing. Besides aerosol transmission, SARS-CoV-2 is also propagated through contact with virus-contaminated surfaces. As such, the development of effective biofunctional materials that can inactivate SARS-CoV-2 is critical for pandemic preparedness. Such materials will enable the rational development of antiviral devices with prolonged serviceability, reducing the environmental burden of disposable alternatives. This research reveals the novel use of Laser Powder Bed Fusion (LPBF) to 3D print porous Cobalt-Chromium-Molybdenum (Co-Cr-Mo) superalloy with potent antiviral activity (100% viral inactivation in 30 min). The porous material was rationally conceived using a multi-objective surrogate model featuring track thickness (tt) and pore diameter (ϕd) as responses. The regression analysis found the most significant parameters for Co-Cr-Mo track formation to be the interaction effects of scanning rate (Vs) and laser power (Pl) in the order PlVs>Vs>Pl. Contrastively, the pore diameter was found to be primarily driven by the hatch spacing (Sh). The study is the first to demonstrate the superior antiviral properties of 3D printed Co-Cr-Mo superalloy against an enveloped virus used as biosafe viral model of SARS-CoV-2. The material significantly outperforms the viral inactivation time of other broadly used antiviral metals such as copper and silver, as the material's viral inactivation time was from 5 h to 30 min. As such, the study goes beyond the current state-of-the-art in antiviral alloys to provide extra protection to combat the SARS-CoV-2 viral spread. The evolving nature of the COVID-19 pandemic brings new and unpredictable challenges where on-demand 3D printing of antiviral materials can achieve rapid solutions while reducing the environmental impact of disposable devices.

Fused Deposition Modelling: Current Status, Methodology, Applications and Future Prospects

Fused deposition modelling (FDM) is an advanced 3D printing technique for the manufacture of plastic materials. The ease of use, prototyping accuracy and low cost makes it a widely used additive manufacturing technique. FDM creates 3D structures through the layer-by-layer melt-extrusion of a plastic filament. The production of a printed structure involves the generation of a digital design of the model by 3D design software and its execution by the printer until the complete model is reproduced. This review presents the current status of FDM, how to handle and operate FDM printers, industry standards of printing, the types of filaments that can be used, the post-processing treatments, advantages, and limitations as well as an overview of the increasing application fields of FDM technology. The application areas of FDM are endless, including biomedicine, construction, automotive, aerospace, acoustics, textiles, and occupational therapy amongst others. Even during the current Coronavirus disease (COVID-19) pandemic, FDM has helped to fabricate face masks, ventilators and respiratory systems, respiratory valves, and nasopharyngeal swabs for COVID-19 diagnosis. FDM 3D and 4D printing can produce polymeric and composite structures of various designs, and compositions in a range of materials according to the desired application. The review concludes by discussing the future prospects for FDM.

3D printed auxetic nasopharyngeal swabs for COVID-19 sample collection.

The COVID-19 pandemic has resulted in worldwide shortages of nasopharyngeal swabs required for sample collection. While the shortages are becoming acute due to supply chain disruptions, the demand for testing has increased both as a prerequisite to lifting restrictions and in preparation for the second wave. One of the potential solutions to this crisis is the development of 3D printed nasopharyngeal swabs that behave like traditional swabs. However, the opportunity to digitally conceive and fabricate swabs allows for design improvements that can potentially reduce patient pain and discomfort. The study reports the progress that has been made on the development of auxetic nasopharyngeal swabs that can shrink under axial resistance. This allows the swab to navigate through the nasal cavity with significantly less stress on the surrounding tissues. This is achieved through systematically conceived negative Poisson's ratio (-υ) structures in a biocompatible material. Finite element (FE) and surrogate modelling techniques were employed to identify the most optimal swab shape that allows for the highest negative strain (-εlat) under safe stress (σvon). The influence and interaction effects of the geometrical parameters on the swab's performance were also characterised. The research demonstrates a new viewpoint for the development of functional nasopharyngeal swabs that can be 3D printed to reduce patient discomfort. The methodology can be further exploited to address various challenges in biomedical devices and redistributed manufacturing.