The Anti-Matter Machine is a device created by Dr. Ivo Robotnik that can make various objects invisible.
Dr. Robotnik once hatched plan to lure Sonic the Hedgehog into a trap by spreading a rumor that he had build an Anti-Matter Machine that he could use to gain the upper-hand against his enemies. Sure enough, Sonic and Sally Acorn went to Robotropolis to investigate the rumor. After finding the machine, Sonic went into it's chamber to blow it up with a homemade bomb. But Robotnik sprung his trap by sealing the room shut and then told Sonic that although the rumor was true, he failed to get the machine to work, so he decided to use it as bait instead. As Sonic is surrounded by SWATbots, he decides to detonate the bomb and escape the room before it explodes. But he trips on a wire and fails to get out on time, making the other Freedom Fighters believe he was killed in the blast. However, Sonic survived and eventually found out that the effects from the machine had made him temporarily invisible. (StH: #20)