The Faculty of Science, Masaryk University against COVID-19: production of nanofiber filters for voluntary sewn masks

21 Apr 2020 Petr Vašina, Jiří Sopoušek, Vojtěch Kundrát, David Pavliňák, Jakub Kelar, Zuzana Jayasundera

The idea of ​​producing nanofiber filters for masks sewn by volunteers during the coronavirus crisis came from the Institute of Chemistry (IC). The original idea belongs to Vojtěch Kundrát MSc., a doctoral student of material chemistry with long experience as a volunteer, with the support of Prof. Jiří Sopoušek, an academic employee of the IC with research activity in the area of ​​nanomaterials. They then approached David Pavliňák MSc. and Jakub Kelar MSc. from the Institute of Physical Electronics (IPE) and the Director of the Institute, Prof. Petra Vašina. Both institutes were involved in material support for the volunteer movement, who were seeking to address the current lack of protective equipment during the coronavirus crisis.

Both Faculty of Science workplaces contribute to the production of filters made of nanofibrous material prepared by the method of electrostatic spinning electrospinning). These filters can be inserted into voluntary sewn masks and significantly increase their efficiency.

How was the initiative started? Vojtěch Kundrát from the IC states: “During the first week of quarantine it was clear that the lack of hygienic material would lead to a serious epidemic in our territory. This is why the sijemerousky.cz initiative was established with the cooperation of many interested groups (including students of the MU and the IC, Faculty of Science MU). As part of our initiative, we obtained, free of charge, 21 rolls of nonwoven fabric suitable for filter preparation from PFNonwovens Czech s.r.o. It soon became clear that we would be unable to process the entire material efficiently on a hastily remodelled machine, so we approached the IPE” concludes Kundrát.

Isn’t this too big a job for academic workplaces? Prof. Jiří Sopoušek from the Laboratory of Nanoparticle Synthesis at the IC said: “Yes, it has been a difficult task. However, if the idea is there, and there are enthusiastic and dedicated volunteers, it is necessary to support and implement such beneficial activity, even under difficult conditions. This is especially true if you have the necessary equipment and knowledge of how to achieve your goals. A number of other academic institutions have been able to do this in the fight against the new type of coronavirus”.

Nanotechnology for production of filters for sewn masks

Coincidentally, Nanospider® technological equipment had been located at the Faculty of Science before the coronavirus crisis, with the IC having a Nanospider unit (Fig.1a) and the IPE having a similar device with an additive winding device, allowing greater production (Fig. 1b).

Electrospinning technologies use common starting materials, such as organic polymers, biopolymers, ceramic precursors or carbon fibres. These are used to produce polymer solutions, from which ultrathin fibres are spun in a strong electrostatic field. While there are a number of technological variants available, the use of direct voltage for spinning polymer solutions predominates. The resulting fibres can be produced using either spinning needles or from a free surface. Free-spinning of the material from a free surface was first developed at the Technical University of Liberec and successfully commercialized by Elmarco s.r.o. The main difference between free spinning and traditional systems based on electrostatic spinning from a needle is its higher productivity. Thanks to the attached external rewinder, the IPE are able to spin base material (fine nonwoven fabric) of up to 50 cm width in continuous mode. The length of the base roll depends on the manufacturer but is usually around 800 m. This base material acts as a carrier for the nanofibers themselves and forms part of the final nanofiber filter.

Fig.1a. Laboratory-based spinning equipment, with spinning needles and winding technology, at the Institute of Chemistry. On the right of the photo can be seen 17 km reels of non-woven base material obtained as a gift from PFNonwovens Czech s.r.o. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.
Fig. 1b. High-capacity free-flow nanofiber spinning equipment at Faculty of Science’s Institute of Physical Electronics. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.

The tradition of nanofiber production at the Faculty of Science’s Institute of Physics

The IPE has been actively engaged in the production of nanofibers, and especially their subsequent modification, since 2013. At that time, close cooperation with Elmarco s.r.o. resulted in a joint project involving the installation of Nanospider technology (free spinning equipment) at the IPE. The original laboratory concept was supplemented by an external rewinder and converted to a pilot plant unit, which allowed for the simulation of nanofibrous material production processes. For many years, the IPE, and especially the CEPLANT centre, has been engaged in verification of technologies using plasma generated at atmospheric pressure. CEPLANT experts have focused on increasing the adhesion of nanofibers to substrates, changing the pore size, chemical and physical functionalization of the material and replacing the lamination step. They have also focused on spinning biomaterials suitable for applications in regenerative medicine. Recently, they have been engaged in the preparation of ceramic nanofibers. The IPE focuses primarily on the production of nanofibers themselves, and especially on their modification and enhancement of their practical

Laboratory of Nanoparticle Synthesis at the Institute of Chemistry, Faculty of Science, Masaryk University

Members of this group are engaged in the theoretical and experimental study of metal and metal alloy nanoparticles. Their theoretical studies deal with the prediction of nanoalloy phase diagrams, and especially their verification, while their experimental work focuses on the synthesis and characterization of nanoparticles.

Protection of intellectual property

The IC, in cooperation with the State Institute of Nuclear Chemical and Biological Protection and Elmarco s.r.o., tested the most suitable recipe and layer thickness for the nanofiber membrane (Fig. 2). The optimal shape of the pocket into which the filter is inserted was also tested. The results were shared with colleagues from the IC, who made recipe changes related to their equipment: “In the same way, we supplied the necessary spinning polymer and the aforementioned base material from the IC to the IPE. As part of the volunteer initiative, Both the IC and the sijemerousky.cz volunteer group approached an industrial partner supplying laminating and cutting technology (Fig. 3). Lamination, which is necessary for fixing the nanofibers to the base non-woven material, was then tested in parallel with the production of masks at the IC” concludes Vojtěch Kundrát.

 

Fig. 2. Detail of a nanofiber filter layer (electron microscope image). Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.
Fig. 3. The external supplier’s laminating machine, which bonds the nanofiber layer and the underlying non-woven fabric firmly together. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.
Fig. 4. Volunteers at the Divadlo Husa na provázku (and other unlisted sites) sew masks. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.

The shape of the mask and insert filter matters

The product itself is not usable on its own but serves as an insert filter (Fig. 6) for cotton masks, preferably of the type currently sewn by sijemerousky.cz (Figs. 4 and 5).

The shape used (Fig. 5) achieves a filtration efficiency of about 80 to 90%, based on the number of particles on the outer side and inner side of a mask fitted with a nanofiber insert (Fig. 6). However, a truly efficient mask relies not only on the material’s properties but also on the mask fitting tightly to the face. With a well-fitting mask, efficiency levels can achieve 100%, while a mask that does not seal properly will ultimately be as effective as a cotton handkerchief. Under normal use, the riskiest part of the mask is always the fitting around the nose. While the filter insert is designed to be disposable, it can be soaked in 70% ethanol enhanced with 3% hydrogen peroxide and reused after drying.

Fig. 5. A simple pocket-shaped mask provided with a reinforcing wire for the nose contact area. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.
Fig. 6. The final filter insert design giving increased efficiency. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.

Efficiency of the nanofiber filters

And what about the efficiency of the nanofilters themselves? According to experts from the IPE, the reported efficiency of nanofiber filters is a controversial issue. Although it is possible to produce a filter that would have almost 100% efficiency, the question is whether one would then be able to breathe through it. Filtration efficiency, and the associated degree of protection, depends on many factors. Among these we can include the design of the mask itself and, especially, its proper fit on the face. As stated by Dr. Pavliňák “Our prerequisite was the production of a mask that would be slightly more efficient than conventional commercial masks for healthcare. It would therefore provide good protection in everyday environments, such as when shopping or traveling on public transport. Obviously, it cannot be compared to a full-face mask variant equipped with a professional screw-on filter. When moving in highly infectious environments, I would recommend it only as a last resort” concludes Pavliňák.

How effective are products using other nanotechnologies? Products with silver or accelerated copper oxide nanoparticles are also available on the market. According to Prof. Sopoušek: “it is necessary to approach the use of nanoparticles with great caution. One must realize that nanoparticles permeate cell membranes and can elicit unexpected reactions. These can be useful in eliminating viruses and bacteria, for example, but they can also be harmful. As such, health safety tests for such products are very important. In this pandemic situation, therefore, the path we have taken at our workplace is to use a fine sieve of tightly trapped nanofibers that mechanically separate unwanted particles. There is not enough time for the development and use of filter layers with a self-cleaning effect, but we can work on them after the emergency state subsides” concludes prof. Sopoušek.

20,000 filters per week

Nanofiber production takes place at the IPE and IC. Due to the manufacturing process itself, and the current situation around COVID-19, very strict working and hygienic rules were set up at both workplaces, possibly of a conspiratorial nature. The four-member production team at the IPE (D. Pavliňák, O. Galmiz, J. Kelar, R. Přibyl) is able to prepare more than 1.5 km of nanofiber material per week, while the three-member team at IC (V. Kundrát, D. Bolzareva, A. Žagar) can prepare a slightly lower amount. This is followed by further manufacturing steps, including lamination, cutting to final size and final placement. If we count the weekly production and divide this figure by the estimated material size for one mask, the teams can produce up to 20,000 filter inserts per week.

Fig. 7. Ten thousand filter inserts packed in tens ready for distribution. Photo: Archives of the Departments of Chemistry and Physical Electronics, SCI MUNI.

Cooperation of the Faculty of Science MU with other institutions in the fight against COVID-19

IPE is a partner in the MATCA National Competence Centre, a consortium that consists of 16 workplaces from the academic and industrial sphere. The members of MATCA are intensively seeking opportunities for cooperation in the field of combating COVID-19 (e.g. production of respirators or ozone generators for disinfection). As stated by the Director of the IPE, Petr Vašina: “Within these activities, our institute covers research and development in the use of plasma technologies to achieve final products with the best possible practical properties. We have also started cooperating with Brno Technology University (Assoc. Prof. Jan Podroužek, Faculty of Civil Engineering and Ing. David Škaroupka Ph.D., Faculty of Mechanical Engineering) and an industrial partner (Čegan, s.r.o.) in developing and preparing antimicrobial coatings by magnetron sputtering. Such coatings could form a protective layer on objects that are exposed to direct, or accidental, contact with the human hand. Applying a thin protective layer would reduce the risk of contamination and subsequent spread of COVID-19. We are currently testing the application of antimicrobial coatings on protective equipment for physicians and exposed surfaces in healthcare facilities, such as the outside of a face mask adapter made by 3D printing or conventional door handles and switch covers. The aim of this project is to develop surface protection for common products, which will bring added value for their application in extremely exposed areas, such as infectious hospital wards, public areas, etc.” concludes Vašina.

Fig. 8. Antimicrobialsurface treatment using magnetron sputtering prepared by the IPE at the Faculty of Science. Photo: J. Podroužek, Brno Technology University.

Join sijemerousky.cz!

If you have been sewing masks you deserve thanks, especially if you have done so since the onset of the coronavirus crisis. Why not log in at www.sijemerousky.cz and try sewing them now. We have two sewing workshops at 5 Hilleho street and the Industra Gallery. “We still need volunteers, so do please call in. Although the situation seems calmer, the social sector is still inadequately supplied; there are also smaller towns and regional hospitals outside of Brno that also suffer from an acute lack of protective equipment. Together with our team of volunteers (especially Mr and Mrs Nohavica) and their extensive contacts, we presently supply 18 senior citizen homes in the South Moravian Region and a centre for homeless people on Vlhká Street in Brno” concludes Vojtěch Kundrát from the IC.

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