Today, motors and servos are used on a majority of robots that we use for various purposes, as well as on the robots in development stage. Artificial Muscles is one alternative way in robotics for providing force to moving structure of a robot. A German company called Festo, designed a robot arm based entirely on artificial muscles which seems to move as elaborately as a human arm. The arm consists of 30 muscles and its design mimicks the actual human arm as far as the bone structure. Artificial muscles move when compressed air is filled into the flexible fibres of the muscle. See video below:
You can also find more information about the muscle by the actual video posted in youtube.