Boops and mercury.
Found out today that mercury liquid locks are ideal for boops because it doesn't cause any short circuiting since it is a liquid metal. Obviously this issue can be ignored altogether with atmo suits but if for any reason you didn't want to have them in an atmo suit then mercury works. This also works with any other liquid metal tho that's irrelevant because mercury is the only one that is a safe temp at melting point.