Unless you want to use magic or a magical force, you need to be careful about what technologies you want to include in your universe. Forcefields, Antigrav, Shields and similar creations are difficult to explain without magic. Transporters don't require magic, but the level of technology required is near magic.
Robots are dangerous to use in a story.
They are too difficult to kill. Remotely controlled robots are possible and slightly safer. Computer chips will eventually become intelligent enough to give us a fully automated security robot. However, guards are cheaper than an advanced robot. Bionics are difficult.