|This Inch Worm walking robot is actuated by nitinol wire. Nitinol is an alloy that can 'remember' a given shape or in this case length. The Inch Worm is powered by 2 AA batteries, and when the button is pressed and a current flows though the nitinol wire, it becomes hot and this causes it to shorten, as it goes to its 'remembered' length. As the nitinol shortens, it causes the two robot legs to move apart. Then, when the current stops, the nitinol wire cools, and - aided by the spring - goes back to its former (longer) length. This causes the robot legs to move together.On the underside of the robot's feet are little bristles, and provided the robot is placed on a non-slippery surface, it can be made to walk forwards by switching the current on and off.The Inch Worm is supplied completely assembled. You will need to supply 2 AA batteries. The Inch Worm is about 40 mm high.