Filters for masks have been developed using the nanofiber technology, which is the process of fabrication of very small fibres, typically having a diameter of less than 1 micron
By: Neelam Jhangiani
Coronavirus cases are mounting with each passing day; and India is now the third most affected country in the world. While scientists across the globe are working hard to find out solutions to beat this lethal disease, our country is also contributing to this scientific pool with almost all Indian Institute of Technology Institutes doing their bit to deal with the current crisis.
As a part of such ongoing efforts, researchers from IIT Madras have developed a nano-coated filter media for healthcare workers treating Covid-19 patients. This nano-coated filter media has been fabricated by a nylon-based polymer coating on cellulose paper. The coating properties are optimised for efficient removal of sub-micron sized dust particles in the air. The nano coating can be positioned according to the need to enhance surface/depth filtration for healthcare workers or public responders.
In fact, this filter has applications not only in healthcare but also has defence applications and in places where air filtration of submicron particles is required.
Dr. K Arul Prakash, Professor, Department of Applied Mechanics, IIT Madras shares more information about the innovation.
What is the technology behind this innovation?
Nanofiber technology is the process of fabrication of very small fibers, typically having a diameter of less than 1 micron. The most common method for manufacturing nanofibers is the electrospinning process. The nanofiber coating can be applied to any nonwoven base material, such as glass, cellulose, or synthetic fibers. This nanofiber coated media offers higher initial filtration efficiency than conventional filters.
Nano particles like nylon 6, nylon 66 and graphene and carbon nanotubes are coated in the conventional filter, so that it can filter fine particles of the size of the order of 1 micron because all the aerosols present and airborne are in the order of 1 micron.
The researchers are in the process of optimising the coating parameters of nanomaterials for bulk manufacturing at an affordable cost and testing the antiviral properties for broader utilisation in various applications. Also, attempts are being made to develop composite nano-coated filter media having more than 1 nanomaterial coating with the possibility of manufacturing multi-layered masks.
Various characteristics of the nano-coated material such as permeability (a measure of flow-through media), coating thickness, and mechanical strength have been measured. The optimised nano-coated filter media has been developed using computer tools and validated with experimental results. An increased filtration efficiency for submicron size dust particles of the order of 0.25 microns with a marginal increase in pressure drop is a notable achievement through this technology. The filtration can be further improved with multilayer nanomaterial coating.
What has been the timeline of the development?
This project was sanctioned two years back and work had started at that time itself, with the procurement of all the equipment like electrospinning, and more. The work has been originally funded by the Defence Research Development Organisation (DRDO) for defence applications. Initially we started the work for developing a filter for armoured vehicles like Arjun tanks, T 75 and more.
However, due to its high potential and the need of the hour, it has been repositioned in healthcare applications where we want to make different combinations of nano particles to deposit on the conventional filter.
A numerical methodology was developed to model fibrous filter media in a 2D random approach. The creation of a representative microstructure of filter media was done with the help of a Matlab code, where the statistical parameters of required fibre size distribution, solidity and other filter media parameters are provided. Similarly, an attempt has been made to model composite (nanofibrous) filter media, where a thin layer of nano coating is provided over microfibrous (base) media to enhance the filtration performance.
How can this filter be applied to the already-existing face masks for healthcare workers?
We are developing the nano filter media of size A4 and that can be suitably made to sandwich between the cloth mask or we can separately use it with the elastic bands in a casing for various age groups.
What are the other possible uses of this filter?
The filter can be used in respirator devices, air purification system in operation theatres, cabin air filters for the comfort and health of air passengers, computer hard disk drive, pneumatic equipment and air filters for armoured vehicle engines.
Have you started the commercial use of the filter?
We are in the process and are exploring partnerships with start-ups and some companies in Hyderabad and New Delhi. We are looking to have a separate unit for the manufacturing of the filters. We can also provide the companies with the coated filter and they can further manufacture the mask. In fact, we may either opt to collaborate with an established filter manufacturing company, or with a start up from IIT Madras for commercial production of the filter.
However, at the moment, the product is not commercialised, as we are awaiting clearance from healthcare professionals.
In that case, when is it supposed to hit the market?
The nano-coated filter is in the process of being field tested in practical applications. Upon validation through field trials, the filter would be recommended for mass manufacturing through industry collaborations.
We have already developed the prototype with the filters and mask, so it depends upon the clearance, cost and antiviral property of the mask. We are exploring all these things and are expecting it to take up to 6 months to reach the market.
What is the cost range we are looking at?
As of now, the Hepa filters used in the N95 masks for healthcare workers are made from nonwoven polypropylene, so we are also working hard to keep the cost at par with the existing solutions. Although the product is a bit more advanced in filtering particles of the order of 1 micron.
