Robotic technology has diversified to include a variety of tasks, from serving pizza to exploring alien terrains, swimming, and even performing surgery. Yet, a compelling question arises: can robots walk on water?
The newly developed Rhagobot, inspired by Rhagovelia water striders, presents a fascinating leap in robotic design. These small robots mimic the unique abilities of semiaquatic insects commonly referred to as ripple bugs, enabling them to glide across fast-moving streams through advanced adaptations.
Unlike other water strider species, Rhagovelia possess fan-like structures on their middle legs that automatically adjust to the movement of water beneath them. This adaptation allows them to move effortlessly over the surface, and biologist Victor Ortega-Jimenez from the University of California, Berkeley, has studied how these tiny insects execute rapid movements, effectively “flying” over liquid surfaces.
“The fan of Rhagovelia serves as an inspiring model for designing self-morphing artificial propellers, offering valuable insights into both their biological structure and function,” Ortega-Jimenez stated in a study published in the journal Science. He emphasizes that these designs have not yet been explored within the realm of semi-aquatic robotics.
Innovative Morphology
Ortega-Jimenez dedicated five years to uncover the mechanics behind how these insects navigate their environment. Initially believed to be controlled by muscle power, the leg fans of Rhagovelia were found to adjust to surface tension and elastic forces without active muscle engagement. They open and close at a remarkable speed—ten times faster than the blink of an eye—expanding immediately upon contact with water and reshaping according to water flow.
Covering a large surface area relative to their size allows Rhagovelia fans to produce significant propulsion. These structures serve a dual purpose: they are strong enough to maintain their shape when extended yet flexible enough to fold away when not in water, preventing any hindrance to the insect’s movement. Their hydrophobic legs help repel water, aiding in buoyancy and efficiency.
Utilizing a scanning electron microscope, Ortega-Jimenez and his team closely analyzed the leg fans. Understanding their precise structure was essential for developing a similar robotic design inspired by ripple bugs. Initial experiments with cylindrical fan designs led to the discovery that true Rhagovelia fans consist of numerous flat barbs with fine barbules, a detail that had not been documented before.
