While a physicist at Mercury Labs was building the first tachyonic prototype, a man in yellow attempted to steal the device but was prevented from doing so by the physicist who locked the door to the prototype's chamber. Believing that the device would serve as an effective lure for the man in yellow, Barry Allen procured it from Dr. Tina McGee and brought it to S.T.A.R. Labs where Cisco Ramon, Caitlin Snow and Eobard Thawne (as Harrison Wells) had built a trap for the man in yellow. Despite these precautions, the man in yellow managed to steal the device. Eobard later put it on the chest of his suit.
After traveling back in time and obtaining information on increasing his speed without the aid of the dangerous Velocity 9 drug, Barry went to ask Eobard for advice on how to get faster, which Eobard's answered that the key to getting faster was tachyon enhancement and gave Barry a flash drive containing the instructions to build a tachyon prototype. Later, Barry and his friends created their own tachyon device to enhance the Speed Force in Barry's system. While testing out the device, Barry accidentally traveled to an alternate Earth. With the aid of Supergirl and his tachyon device, Barry made it back home. At Barry's request, Harry Wells miniaturized the device to fit behind the emblem on his suit. With Harry's enhancements from using the tachyon device, Barry was able to successfully outpace Zoom.
But, after Zoom captured Wally West and was given Barry's original Speed Force, Barry lost all of his speed gained after he used the prototype, though after he encountered the Speed Force itself, Barry has become far faster than he had been before.
Barry's tachyon device was presumably damaged or destroyed in the second particle accelerator explosion, unless it wasn't attached to his suit when they recreated the accident that originally made him a speedster. However, if the device was indeed attached to his suit (which was destroyed) during the explosion, it's possible that when he received a new suit from the Speed Force identical to the one he had before, the Speed Force may have also generated a new tachyon device along with the rest of the suit.
- Eobard Thawne/Reverse-Flash (formerly)
- Firestorm (modified as a Quantum splicer)
- Barry Allen/The Flash (formerly)
- Tachyons, according to Eobard Thawne, are superluminal particles
- According to Eobard, if one properly harnesses tachyon particles, they can use them to move faster than light and be "invincible".