The BBC has a story summarizing the latest developments in polymer micromuscles in Sweden. Edwin Jager is working on the project to develop useful microrobots from the muscles that can operate inside the human body. Unlike previous attempts at making nano-scale robots, these can operate in water, blood, urine, and other bodily fluids. They seem to be the nearest to a practical application yet for robots of this size. There are videos on the web site showing the robots doing actual work like lifting and placing objects.