A team of engineers from Harvard University and Seoul National University (SNU) has worked out how to build robotic insects that can jump on water. Many small creatures leverage water’s surface tension to move themselves around. One of the most complex ways of doing this is jumping on water, which is achieved by water striders that both skim over the water’s surface and generate enough upward thrust with their legs to launch themselves off the water.
The team observed the natural mechanics of the water strider to see how it launches itself off the water’s surface, and accordingly built a unique robotic insect that mimics the strider’s natural locomotion. The study’s co-senior author Kyu Jin Cho from SNU observed that the “water’s surface needs to be pressed at the right speed for an adequate amount of time, up to a certain depth, in order to achieve jumping”.
The team had to go through numerous robotic prototypes as it strove to comprehend the full mechanics of the water strider. Study co-author, Robert Wood of Harvard, gave one example, “If you apply as much force as possible on water, the limbs will break through the surface and you won’t get anywhere.” The international collaboration to achieve the new understandings involved biologists and robots. The resulting data includes biological insight into the natural mechanics of water striders, as well as the generation of a new form of robotic locomotion. The team watched the ways in which striders performed numerous extreme types of locomotion – from jumping on water to floating to flying – with great ease despite their lacking complex cognition. Extensive videos of their movement were captured in order to analyze the mechanics that allow them to skim on and jump off water’s surface.
“Pop-up” manufacturing was used to create the body of the robotic insect. Folded composite structures were built which self-assemble, similar to the foldable sections that “pop-up” in 3D books. The layering and folding process allows the microrobots to be rapidly fabricated. The team also ensured that the robotic insect could exert up to 16 times its own body weight on the water’s surface without breaking through without complex controls in place. Robert Wood explained, “the resulting robotic insects can achieve the same momentum and height that could be generated during a rapid jump on firm ground – but instead can do so on water”.
Kyu Jin Cho described the water striders’ natural “physical intelligence” as being something “we can learn from” in order “to build robots that are similarly capable of performing extreme maneuvers without highly-complex controls or artificial intelligence”.