As the COVID-19 Pandemic Persists: 3D Printing with Antimicrobial Polymers

“Additive manufacturing (i.e., 3D Printing) is uniquely well positioned to support the shortage of critical medical devices.”

COVID-19 may have barely been registering on your radar just a few short months ago; however, now somehow everything seems applicable to dealing with life during a pandemic—and the additive manufacturing industry is no exception, evidenced by the recently published work of Jorge M. Zuniga and Aaron Cortes, ‘The role of additive manufacturing and antimicrobial polymers in the COVID-19 pandemic.’

The University of Nebraska at Omaha researchers are concerned with a health risk that has already made significant history as one of the most deadly contagious illnesses to strike, worldwide. As the need for medical supplies and a list of devices that can be critical to the outcome of patients continues to increase in the face of shortages, the authors focus on FDA concerns that indeed there may be a serious impact to the medical product supply chain.

While concerns may remain regarding the use of proper materials in some cases, 3D printing has already been brought to the forefront in the production of items like open-source ventilators, parts like ventilator adaptors and manifolds, reusable metal filters for masks, and more. Materials science has continued to be an enormous quotient in the progressive march forward of 3D printing and additive manufacturing, but as the COVID-19 crisis has brought much in the world to a halt, the use of materials in relation to 3D printing is an area that must be explored—and quickly so.

Theoretical mechanisms for the enhanced antimicrobial behavior of additive manufacturing polymers. (a) Copper nanoparticles on a polymer structure present a stronger antimicrobial effect than microparticles or metal surfaces. Antimicrobial polymers facilitate the process of attaching the microorganism on the polymer surface triggering the diffusion of water through the polymer matrix. Water with dissolved oxygen reaches the surface of embedded metal nanoparticles allowing dissolution or corrosion processes releasing metal ions; metal ions reach the composite surface damaging the bacteria membrane. Afterward, metal ions can diffuse into the interior of the microorganism. (b) The antimicrobial mechanisms of nanoparticles of copper consist in producing cell membrane damage via copper ions that damage polyunsaturated fatty acid compromising the structure of the cell membrane and producing leakage of mobile cellular solutes resulting in cell death. The redox cycling between Cu2+ and Cu1+ can catalyze the production of highly reactive hydroxyl radicals, which can subsequently damage cell membrane lipids, proteins, DNA, RNA, and other biomolecules. Once copper and associated hydroxyl radicals are inside of the cell, it produces DNA denaturalization damaging helical structures. Copper also damages and alters proteins acting as a protein inactivator via RNA, useful to deactivate a wide range of viruses.

“Advancements in additive manufacturing techniques and development of antimicrobial polymers, offer the possibility of printing and customizing a wide range of medical devices. The critical limitation for the use of polymeric materials to additively manufacture critical medical devices is the material contamination by bacteria and viruses,” explain Zuniga and Cortes.

“Several international efforts, such as the Open Source COVID19 Medical Supplies Group (International) and Hack the Pandemic (Copper3D Inc) have made significant progress using additive manufacturing to develop critical medical devices.”

As studies for the use of different and safe and effective materials continue, copper has been explored as a viable source, along with copper nanocomposites for adding antimicrobial properties. PLA is the polymer most often looked toward for compatibility and effectiveness with additives. Made from plant by-products, it may also be important for ‘significantly assisting’ in the flow of the medical product supply chain—currently experiencing disruptions which have made many headlines regarding the lack of gear for medical professionals and necessary devices such as ventilators for patients.

Previous studies have shown that copper may even be more effective than stainless steel, fending off the virus in terms of viability, as well as offering ‘predicted decay and half-life reduction.’ Data showed that after exposure to copper, ‘the median half-life reduction for the COVID-19 virus occurred at 0.774 hours (C.I. = 0.427–1.19) and no viable COVID-19 virus was measured after 4 hours.’

Stainless steel showed a median half-life reduction at 5.63 hours (C.I. = 4.59–6.86) with viable virus detected up to 72 hours, while polypropylene showed a low median half-life reduction at 6.81 (C.I. = 5.62–8.17) hours with viable virus also detected up to 72 hours.

“The development of an affective antimicrobial polymer for additive manufacturing seems increasingly critical due to the extensive use of polymers in the prototyping of critical medical devices,” stated the authors.

Issues with sterilizing 3D printed parts are an ongoing concern, causing a challenge in further development of medical devices. With the introduction of antimicrobial thermoplastics, copper nanoparticles are integrated into material matrices—offering more effect than microparticles or metal surfaces. The need for such polymers is expected to be enormous, with AM processes offering the serious potential for satisfying a supply chain that may be in decline relying on traditional methods of manufacturing.

Devices like ventilators, as well as peripheral attachments and parts, can be customized for use, with innovative designs offering greater efficiency, as well as eliminating issues like air leakage.

“During critical situations when doctors need to take life-or-death decisions due to the lack of ventilator, the use of additive manufacturing would provide a feasible alternative for sharing the use of a single ventilator,” stated the authors.

Examples of open source critical medical devices.

As one ventilator could actually be transformed into a multi-patient device in times of extreme need, previous research indicated challenges in designing connectors efficiently:

“The main limitations of using a customized connector assembled with several connective pieces is the inability of reducing the size of the connector to minimize dead space volume,” stated the authors. Furthermore, repurposing connectors from other medical devices, can result in air leakage and infectious complications from sharing one ventilator.”

“The use of antimicrobial polymers can facilitate the prototyping and clinical testing of these connectors with the objective of accelerating the production of the final product using conventional manufacturing methods, such as injection molding. The final production of these connectors could effectively expand the use of a single machine to ventilate four simulated adults experiencing respiratory failure due to COVID-19.”

Reusable face masks could also be 3D printed, eliminating waste in comparison to the use of disposable masks, along with offering the benefits of an antimicrobial surface for less transmission of germs to healthcare workers and patients too.

The manufacturing process of antimicrobial critical medical devices using an antimicrobial polymer. The process starts with corn fermentation (corn to
Lactic Acid), condensation (Lactide) and polymerization (Polylactic acid; PLA). The addition of copper nanocomposite additive to pellets at different concentrations allows the development of a multipurpose antimicrobial filament. The recyclable characteristics of this filament facilitate the production of new antimicrobial medical devices in austere environments.

“The use of more sophisticated additive manufacturing methods and materials, such as Selective Laser Sintering and Polyamide 12 powdered thermoplastic polymers embedded with copper nanoparticles composite would significantly improve the durability facilitating the implementation of antimicrobial medical devices in clinical settings,” concluded the study with an expert opinion.

“It is feasible that within a 5-year period, additive manufacturing and the use of antimicrobial polymers will play a crucial role in the development of on-demand and implementation of antimicrobial critical medical devices in clinical settings.”