Background: Introductory robotics competition for college freshmen; Bot has to open 8 jars (with two balls in each of them) in ten minutes and load the balls into a shooting mechanism.
So, we were doing this project and we hit upon a challenge that the jar is not opening like we originally intended to. So we decided to get a rack-pinion mechanism and use it for unscrewing the lid. However, it is too large and we are unable to fit the bot in the required dimensions
The actual question: Are there any wires or rigid columns/things which can contract ~1 cm when electricity is passed through it? And what would their price range be? Our budget is also in the list of constraints for the bot
Edit: We can include a wire of length <1m or a column of length <30 cm. Also, the wire needs to contract only more than 7mm