Inflatables

Here's a nice idea. An inflatable robot arm.

It looks as if there are three sections which are independently inflatable: the lower section, the upper section and the gripper. Obviously there is going to be a limit on how much mass this arm can lift, but if it's good enough to lift a bottle then it can probably handle a lot of other small objects.  It would also be quite cheap to produce, and safe to use around people.

A possible variant would be to make it hydraulic, or hydraulically reinforced. That would be heavier (the robot would need to carry a reservoir of liquid), but since water is relatively incompressible it would also be stronger.

Whether the arm would be able to retract back into the body is another issue, but if there was a cable inside this could be used to reel in a deflated arm.