TORONTO -- A physicist has found a new way to create N95 filtering respirators, using an unusual tool -- a cotton candy machine.
Mahesh M. Bandi, a physicist and associate professor at the Okinawa Institute of Science and Technology Graduate University in Japan, described the innovative process in a research paper published last month in Proceedings of the Royal Society A.
Face masks have become a regular part of everyday life across most of the world. But while surgical masks and cloth face masks can provide some protection and help prevent people from spreading COVID-19 to others, they’re not as effective as the higher grade N95 masks.
These masks have an electrocharged filtration layer that provides a higher level of filtration than other models by trapping and holding oppositely charged particles of all sizes. However, it’s not easy to make these filter layers, as they generally require “industrially sophisticated processes,” according to the paper.
What if it was possible to spin together common materials to create a comparatively effective filter? This was Bandi’s goal -- to make electrocharged polymer-based fabric using more easily found resources and tools.
To create plastic or electrocharged fabrics, polymer fibres are bound together in a “porous mesh,” the paper stated. Bandi theorized that one could use a cotton candy machine to spin molten polymer into fibres using the “centrifugal force generated from fast spinning.” Much like the wispy netting of cotton candy itself, the polymer would form into a mesh that could then be cut into filters.
Photos from the trial runs show plastic fibres pressed to the walls of the cotton candy machine bowl, like particularly thick sugar.
In his test of the theory, Bandi used commonly available materials only, focusing on polypropylene and polystyrene — plastics that can be found in items such as margarine containers, yogurt pots, plastic bottle caps, disposable coffee cups and plastic cutlery, among others.
“When using discarded PP and PS containers, they were crushed into powder using a commonly available blender,” the study explained.
The plastic was heated up to greater than 280 C in the process to make the optimal polymer mesh. After they had been spun in the modified cotton candy machine, Bandi increased the charge on the mesh by simply placing the polymer fabric one centimetre away from a household ionizing air purifier for ten minutes.
Bandi then tested the filters with face masks. First, the filter was added to the inside of commercially available surgical masks — but the lack of a tight facial fit decreased the effectiveness even though filtration was shown to be boosted in tests.
The best method was to 3D print a tighter fitting mask, available for download through an open-source design called the Montana mask, and insert four layers of the filtration mesh spun in the cotton candy machine. According to the research, this mask performed as well as standard N95 respirator masks in filtering out particles.
The paper outlines the process of setting up the cotton candy machine in high detail, seemingly so others can give it a whirl as well, including suggestions such as modifying a soda or beer can by cutting it in half to use the bottom half as a “readymade emitter” in the cotton candy machine.
The conclusions specified that the research was published for proof of concept, and that more research is planned into other types of plastic that could be used.
“Decentralized local manufacture of face masks with high filtration efficiency from commonly available materials and simple designs could potentially alleviate global supply chain disruptions,” the study stated. “It is hoped that this effort will help communities with face mask protection during such pandemics.”
