A research group from Ibaraki University Graduate School, Asahikawa Medical University, and Osaka University Graduate School used direct measurements and image analysis to clarify the leg strength of water striders as they move across the water surface.It is hoped that the development of ultra-compact robots that can move on the water surface by applying the water-repellent function of the water strider's legs is expected.
Water striders move smoothly on the water surface.Progress is being made in the development of highly water-repellent functional industrial products that imitate the surface microscopic features, as well as ultra-compact robots that move on water surfaces, and in the elucidation of the evolutionary mechanism for acquiring water-repellent functionality.Conventional methods for measuring the force with which water striders hit the water surface with their legs, using image analysis and propulsion, were inaccurate due to calculation errors and failure to take into account energy loss during movement.There have also been reports of deriving leg force from the propulsive force of the entire body, but the force of a single leg was not directly measured, which could lead to inaccuracy.
Therefore, the research group built a system that can directly measure the leg strength of a water strider's individual legs.The probe for connecting the sensor, which requires a highly water-repellent function, was cut out of a water strider's leg and used, so it no longer gets caught on the water surface.Indirect measurements were also performed to derive leg force from acceleration using a high-speed camera and image analysis.
As a result, the leg force at the center of the middle leg (between the femur and tibia) is approximately 2.17 millinewtons, and when calculated from the principle of moments, the leg force at the tip of the water strider's leg (polypodium + anterior ligament) is 0.96 millinewtons. Ta.On the other hand, image analysis revealed that the leg force of the middle leg of the water strider was approximately 0.49 millinewtons, suggesting that image analysis may be underestimated due to energy loss.
In the future, the research group will incorporate the measured values into the water strider water repellency model proposed by the research group, attempt to develop a detailed water repellency theory, and aim to contribute to the development of high-performance applied products.
