Robostrider

http://web.mit.edu/chosetec/www/robo/robostrider.html
The study of live water striders led us to attempt the construction of a mechanical water strider "Robostrider". The challenge was to build a device capable of self propulsion light enough to be supported by surface tension. At the scale where surface tension is important, the weight of a handmade water strider increases with complexity; therefore it was important to develop a very simple driving mechanism.