Secret of walking on water uncovered
August 6, 2003 - BBC
The team, based at the Massachusetts Institute of Technology (MIT) in the US, were testing out a theory about how one family of foraging insects performs the same trick. Previous theories put forward to explain how water striders (Gerridae) manage to propel themselves across the surface of ponds and lakes had one major problem. They predicted that young water striders should be too weak to move, while nature shows clearly that they are not.
Surface tension explains why water striders do not sink below the surface as they stand on water. But a careful experimental study was needed to explain how they propel themselves forward. "What we did was to apply some conventional techniques of flow visualization in fluid dynamics," MIT's John Bush told BBC News Online. "You basically sprinkle dye or tiny particles into the water and record what happens with a high-speed camera." Dr Bush and his collaborators, David Hu and Brian Chan, discovered that the secret to the water strider's locomotion is that it rows across the water without penetrating the surface. The rowing motion leaves a telltale vortex behind each foot, clearly visible on camera. The robotic version of the water strider is bigger than its real-life counterpart and its motion less graceful, but it does seem to show that the MIT team has managed to capture the essence of a natural phenomenon.
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