Here is a design challenge:
Design an effective mask made from commonly and abundantly available materials. Should meet the specifications of N95 (or whatever keeps coronavirus out). Involves studying what is needed, some of the science behind it, etc.
Found some examples using activated carbon. Whether we follow the following method or not, it gives a clue as to how one could proceed.
This challenge is particularly hard from what I gathered so far. An n95 mask blocks at least 95 percent of 0.3 micron particles. Most single virus particles are between 0.02 - 0.25 microns. Corona virus specifically has mean size of 0.11 microns. So even with a mask one needs to be lucky to not contract an infection. 
Size is one of the factors to consider. Other than that, the material used in the filter is another factor. Charcoal or activated carbon are known to adsorb microbes and other chemicals.
What about static charge? Do we know if RNA viruses have a natural charge. The filter we design may also consider this as well.
Is the single virus particle size relevant here? Maybe viruses are transported only in droplets or only in clusters? I suppose the research has been done with other coronaviruses. Do these other viruses also have the same size when taken as single virus particle?
Activated carbon is probably not that easy to obtain. Here is a description of how to make it: How to Make Activated Charcoal (with Pictures) - wikiHow. The process is somewhat involved and not easy to implement in most Indian urban contexts.
Perhaps we don’t need activated charcoal, A filter of the right size may be sufficient. Is 2-ply or 3-ply toilet tissue paper sufficient as a filter? If you use multiple layers?
0.02–0.25 microns is general size range of all virus. Coronaviruses have a size range of 0.08-0.15 microns. Probably they can only survive in aerosols and apparently they survive longer on plastic and steel surfaces than on cardboard or copper. https://www.nejm.org/doi/10.1056/NEJMc2004973
Static charge will cause viri and other particles to stick. Even if they are neutral one can have one layer of one charge followed by a 2nd layer of another charge. This will electrostatically precipitate particles including viri. The problem is that the layers will clog quickly with dust.