I do hope if you plan to take this out into public you plan on changing the black blade to a fake blade instead... This version seems a little dangerous for just an arwork, I do like it though. I'm also curious about the mechanisms you use, and how/if you can extend or retract the blade with just hand movements.
You extend the blade by pulling it out with a string and retract it by flexing your thumb which removes the lock. It only requires one hand to extend or retract. Retracting is automatic and extending is powered by the wearer.