Hypersonic soundwave manipulator

The hypersonic soundwave manipulator was a genetic manipulator invented by Professor Richard Lazarus. The machine would turn anyone inside decades younger, but the process contained one side effect: genes that evolution rejected and left dormant would be unlocked, transforming the human into a giant skeletal scorpion-like beast that fed off the lifeforce of living creatures. The Doctor later used it to try to kill Lazarus, but he was just knocked out and reverted to human form. (TV: The Lazarus Experiment)

In the Tenth Doctor's words, this was achieved by:
 * "[using] hypersonic sound waves to destabilise the cell structure, then a metagenic programme to manipulate the coding in the protein strands. Basically, he hacked into his own genes and instructed them to rejuvenate."

, the human alias of the Master, supported Lazarus's research so that he could copy, improve and focus the technology into his laser screwdriver and reverse it to, instead of rejuvenate people, make them older. (TV: The Sound of Drums)

Behind the scenes
The prop for the device was a redesigned version of the descent pod from The Impossible Planet/The Satan Pit.