This past week we've been spending some time thinking on how we would do the mechanical design. It's a little harder than you would think. To release the CO2 canister we need to twist it. So far we've figured out that the Arduino can control a motor (DC or step) and that there has to be a way to twist the CO2 canister through a motor. Here is a picture of what we came up with after some discussion. It looks pretty simple and we're already thinking of improving it.