Not the person you asked but you'd probably be better served by looking at ways to stick with directed energy but find ways to converge it at that point so that the energy density +/- a few feet from the target is safe. Like a lower power version of this https://youtu.be/WAI7Lu4UFi4?t=825 basically long distance frying of ants with a magnifying glass.
Sand grains suffer from a large surface area relative to their mass, so their speed would drop off very quickly. I have one of those bug-a-salt guns and they kinda suck at anything more than 10 feet (also bugs seem to be pretty resilient to that kind of damage). Obviously you could make one that is more precise but I feel like there would be a lot of new variables to deal with.
Some kind of beam steering ultrasonic setup might work as well (although probably expensive) If you can get 10-15 transducers to pop off a precisely timed 5W burst of say 60kHz sound such that they constructively interfere at the critter, you might be able to get them to disassemble in air without any moving parts on your rig.
That seems like a winning strategy: an array of ultrasonic transducers could both detect and range the bug, and then you just play back a loud impulse spike with the same phase delays as you heard. No moving parts, no misses, no calculations. If the spike is short enough, you physically can't damage anybody's ears.
Maybe you only deafen them, so they die of old age without mating.
I once priced out an array of half-inch-sized ultrasonic transducers. Seems like they were astonishingly cheap... like under $.50 each? Plus $.50 microcontrollers and a drive transistor for the spike. Maybe an FPGA running parallel convolutions?
Sand grains suffer from a large surface area relative to their mass, so their speed would drop off very quickly. I have one of those bug-a-salt guns and they kinda suck at anything more than 10 feet (also bugs seem to be pretty resilient to that kind of damage). Obviously you could make one that is more precise but I feel like there would be a lot of new variables to deal with.
Some kind of beam steering ultrasonic setup might work as well (although probably expensive) If you can get 10-15 transducers to pop off a precisely timed 5W burst of say 60kHz sound such that they constructively interfere at the critter, you might be able to get them to disassemble in air without any moving parts on your rig.