Mimosa

Mimosa (オジギソウ) are microscopic bits of reflective alloy.

Background
They are little bits of reflective alloy which give specific responses to specific frequencies. They have no circuitry or power. By using various frequencies, they can be controlled much like controlling a radio controlled car with a TV remote. Normally, they are placed on microorganisms in the air and spread around like that.

Battle Royale Arc
The Professor used Mimosa to attack SCHOOL while SCHOOL was hiding out in a refrigerated warehouse for meat in District 4 of Academy City. With them he cut out a door-shaped portion of the thick wall of the warehouse and kills SCHOOL's driver before the Pincet Glove in Kakine Teitoku's possession detects the Mimosa. The Mimosa disintegrated the skin, fat, muscles, and brain of the driver leaving only his bones and cloths which fell to the ground. After a short conversation he attacks Kakine Teitoku with them. He controls them from a program on his computer terminal. He did this from a location just outside the warehouse. Despite the Professor's confidence that the Mimosa would easily kill Kakine, the Level 5 was able to fend them off and created a large explosion which blew them far enough away for that the Professor could not control them anymore.

Volume 16
Mimosa are used by Academy City to attack Acqua of the Back.