Vacuum cleaners have a primary filter (usually a porous bag or a vortex chamber for bagless vacuum cleaners) for trapping dead skin, hair, food scraps etc. Vacuum cleaners also have filters to remove the small dust particles. Problem with filters is they eventually get clogged (they should be replaced
after 50 hours of use (which should last about 1 year)). But when was the last time you replaced your vacuum cleaner filter?
I reckon it might be possible to replace the standard mesh filter with a water scrubber. This makes replacing the filtering medium much cheaper/easier and gives the additional satisfied feeling that one gets from *seeing* the nasty dust you have removed from your living environment (by the water discolouration).
The vacuum cleaner exhaust is driven through a device that thoroughly mixes the exhaust with water. As the dirty air is mixed with the gas, the dust in the air attaches to the water (since water has interesting properties of being a polar, a good solvent and has high surface tension, and thus giving it its well known cleaning properties).
The air that has mixed with the water is thus cleaned and expelled from the vacuum cleaner.
The mixer device could bubble the exhaust through the water (Im not sure how effective this would be since it would only capture dust on the gas/water bubble interface. Obviously smaller bubbles would be better).
Alternatively the mixer could be a motorized sloshing chamber.
Alternatively it could be a vibrating structure (e.g. coarse mesh) that encourages mixing of air/water.
The chamber would need to be cleverly designed with baffles etc. so that water would not leak when the vacuum cleaner is tipped on its side.