I was introduced to robotics and shape-memory alloys when I bought the book Stiquito for Beginners: An Introduction to Robotics and made the small hexapod robot that comes with the book as a kit. The clever little two-legged inchworm robot shown here is powered by the same Muscle Wire, also known as Nitinol. Nitinol is nickle/titanium allow that will return to a pre-defined shape when brought to specific temperatures. Heat from an electrical current causes it to contract, making this little inchworm take tiny steps. Though the Stiquito was fun to make, this robot looks like an even better introduction because the design is simple, robust, and moves along a bit better.
From the Inchworm Robot description:
Each BioMetal Fiber Walking Robot Inchworm has one strand of BioMetal Fiber. When current is applied, the fiber heats up and contracts. This pulls the Inchworm's feet apart. When the current is stopped, the fiber cools and expands. Add a little grippy fabric on the bottom of each foot and the spring to return it to its original position, and you can easily see how the little inchworm can walk along most non-slick surfaces.
Here is where you can get your own BioMetal Fiber Walking Robot Inchworm. Here are some items for those interested in Stiquito robots. The basic Stiquito (as shown on the book cover, right) is controlled manually like the Inchworm. You have to push the button to provide the electrical current that causes the muscle wire to contract. The newer Stiquito book uses a microcontroller to provide the current automatically for a more autonomous robot.