What is wrong with totally replacing the inlet of a piston engine with a surgical mask?As surgical masks get rid of about 80% of air impurities and dusts.
Air impurities are no issue for an ICE, only dust and other bigger particle matter are. The material of a surgical mask has little flow capacity, so a bigger filter is needed than normal, without good reason. You could use them for an ICE, but as is mentioned before, their flow capacity is way too low. You'd need to glue lots of them together, and fold them into a saw pattern to efficiently package them into a filter box. Then they could properly function as an airfilter.
But it won't weigh less, so it won't contribute in your search to lower the weight of your engine. If you don't live in a dusty area, rather remove the entire filter if it's really important for the engine to weigh less. The engine will wear faster though.
How about the volume of air going through it? For a human with assuming 10 breaths a minute and 2 litres per breath that is 40 litres a minute...
An engine will use that is seconds so the life of that filter is going to be very short.
Most racing engines don't have air filters as the servicing and rebuilds are so much more frequent, but for a family car then longevity is a higher priority.
There are 2 ways to increase the airflow through a filter: bigger holes and more surface area.
Bigger holes is usually not possible because that would defeat the purpose of the filter. The face mask doesn't seal all that well to the face resulting in a few large holes at the side where air can escape and enter unfiltered.
More surface area ban be achieved by pleating the filter using a mesh to support it. You can buy ready made performance filters made for high airflow for not all that much money (a quick google found several for < $70) and that will be a better deal than trying to make your own.