Bulkhead broke it while he assured Agent Fowler they could adequately judge how much force to use. Its loss later caused problems with Ratchet's analysis of the Dark Energon sample he retrieved from Arcee. As he moved the sample to another part of the lab, some of it dripped on the manipulator arm. 
Unseen by Ratchet, the arm twitched into life, turning into a one-eyed, spider-like creature. The piece of animated equipment attacked Ratchet until Optimus Prime destroyed it, but it did give them a clue as to the true nature of Dark Energon.