Binder jetting company ExOne revealed today that it has been working in collaboration with the University of Pittsburgh to develop reusable metal filters for respirators. The 3D printed filters, which are now undergoing initial testing, could help to protect against the COVID-19 virus and other contaminants in a sustainable way.
The metal filters were designed to fit into a plastic respirator cartridge developed by a team from the University of Pittsburgh’s Swanson School of Engineering, and are made using ExOne’s binder jetting technology. The additive manufacturing technology enables the production of metal parts with specific porosity levels which can filter out contaminants while still allowing for airflow.
This finely tuned porosity is thanks to the nature of ExOne’s binder jetting process: after the initial process of selectively depositing a liquid binder onto thin layers of powdered metal until a part is built, the the object is finished in a sintering furnace. For most industrial applications, parts are sintered until a full density is achieved, however in the case of the filters, the sintering process can be adjusted so that the part maintains a certain degree of porosity.
“The advantage of binder jet 3D printing over other additive manufacturing methods for this filter application is the ability to utilize the porosity of the printed part and then fine tune it during the high temperature densification or sintering process to achieve optimum filtering and airflow performance,” explained Markus Chmielus, Associate Professor of Mechanical Engineering and Materials Science at the Swanson School.
“Our team has been working urgently to expedite this promising and reusable solution for medical personnel on the frontlines of fighting the COVID-19 pandemic,” added John Hartner, ExOne CEO. “Our customers routinely print porous metal filters for a variety of purposes, and we are confident that we’ll have a solution soon that can enable medical personnel to sterilize metal filters for repeated reuse, eliminating waste. Once approved, we can print these filters in a variety of sizes for respirators, ventilators, anesthesia masks or other equipment.”
Presently, the partners are testing a series of 3D printed filters made using ExOne technology, which feature a range of porosity levels. The initial tests consist of using CT scanners to analyze the microstructure and porosity of the filters, while a team at simulation firm ANSYS will conduct computer simulations to analyze and optimize the performance of the filters. Ultimately, the goal is to come up with a reusable metal filter that meets the standards of an N95 respirator.
In terms of materials, the partners are testing both copper and 316L stainless steel. Copper is particularly interesting in that it is known to have antibacterial properties. There has also been evidence that the COVID-19 virus dies faster on copper surfaces than on others. Relevantly, Australian company SPEE3D announced last week it had developed a process for 3D printing anti-microbrial copper onto metal surfaces to kill up to 96% of SARS-CoV-2 in just two hours on any metal or plastic surface.
Watch this space for further updates on the continued development of the 3D printed reusable respirator filter.