Liquid Nitrogen Bug Spray

This Idea requires an in-home air-separation and liquefaction system. Kind of expensive, but perhaps manageable on a small-enough scale.

What that device does is first separate nitrogen out of ordinary air (there are things already available in the prescription market that separate oxygen out of the air, and that means nitrogen could be separated, instead). Then the separated nitrogen is liquified, and fed into a Dewar Flask (designed to hold liquid gas with a low rate of heat transfer and boiling). There of course should be an arrangement to capture boiled-off nitrogen and to re-liquefy it.

The Dewar Flask is removeable from the unit. The cap for the Flask has a liquid-feed-in valve, an evaporation pressure-release valve, and also one other thing, a pump-action aerosol mist-sprayer.

One neat thing about a Dewar Flask is that even though it holds liquid nitrogen, you can hold the Flask in your bare hand. The Flask is double-walled, with a vacuum in between the walls. Your classic glass "Thermos" brand bottle was actually a Dewar Flask surrounded by a steel protective shell (which didn't often protect it enough, alas).

OK, so you see a bug you want to kill -- so grab the Flask and squirt! The nitrogen spray hits the air and immediately starts to warm up, on its way to the bug. Meanwhile, while IT warms up, a significant volume of air surrounding the spray is being cooled; it is giving its heat up to warm the nitrogen, of course.

A very cold blast of air surrounds the bug! Bugs are cold-blooded animals, so this makes it start to move kind of slowly. (Just the other day I saw a fly buzz into my refrigerator, so I closed the door. A little while later the bug was stiff with cold; it would have warmed up again and flown away if I had let it.)

So, for a bug sprayed with liquid nitrogen, the same thing will happen, and rather faster because the gas is MUCH colder than the insides of a refrigerator. Now you can more easily swat it with a flyswatter, or even step on it, before it gets away. Then all you have to do is trash the corpse and put the Dewar Flask back into the liquefaction unit.