This robot, developed by Sukho Park and his colleagues at Chonnam National University, Korea, uses the contraction of heart muscle cells for movement:
The robot has three short front legs (400 micrometres long) and three longer back legs (1200 micrometres long), which are all attached to a central rectangular body. As the heart cells contract, the longer rear legs bend inwards. This creates a difference in friction between the front and rear legs, which pushes the robot forward. The scientists measured the robot's average speed at about 100 micrometres per second.Amazing.
Park says these crab-like robots could be used inside the body to clear blocked tubes or arteries. The robots could travel along the length of a blocked vessel, releasing a dissolving agent to clear the blockage as they go.
But the thought of these things crawling around inside me feels a bit like a scene from Aliens.
Reference: Jinseok Kim, et al. Establishment of a fabrication method for a long-term actuated hybrid cell robot. Lab Chip, 2007 DOI: 10.1039/b705367c.