Here's a robot video that I found interesting:
MIT researchers at the David H. Koch Institute for Integrative Cancer Research have developed a new material that changes its shape after absorbing water vapor.
This material is made from an interlocking network of two different polymers. One forms a hard but flexible matrix that provides structural support while the other is a soft gel that swells when it absorbs water. Together these polymers create a material that converts water vapor to energy without the use of an external energy source.
When the 20-micrometer-thick film is exposed to moisture the bottom layer absorbs the evaporated water, forcing the film to curl away from the surface. Once the bottom of the film is exposed to the air, it quickly releases the moisture causing it to somersault forward and start to curl up once more. Researchers were surprised to discover not only does it need a very small amount of vapor, but it also demonstrated a large amount of strength. Using only water vapor as an energy source, the film can lift a load of silver wires 10 times its own weight.
Harnessing this continuous motion could drive artificial robotic muscles or generate enough electricity to power small electronics.
Read more: http://web.mit.edu/newsoffice/2013/new-material-harvests-energy-from-water-vapor-0110.html