watch tiny leaping robots mimic springtail's escape response

jumping robots replicate the mechanics of springtail movement

Engineers at Georgia Tech created a tiny robot that mimics the springtail’s jumping action with the ability to self-right in mid-flight. Springtails are tiny leaping water creatures that can take off, spin, and reorient themselves in midair. Measuring 1/16”, they can impressively jump more than ten times their height, with their precise jumping saving them from predators. During the pandemic, Víctor Ortega-Jiménez was observing and examining the operation of the tiny hexapods, who lived in creeks near his home. Taken by their action to avoid the predator, with accurate control of their jump, self-right in midair, and land on their feet, the team sought to recreate the mechanics of springtails, introducing penny-sized jumping robots.

For the first time, researchers discovered the mechanics of springtail movement using a combination of computational and robophysical modeling, as well as fluid dynamics experiments. They uncovered how springtails have the ability to jump on the water’s surface and land perfectly in the same spot. ‘These extraordinary organisms with unique morphology live at a very precarious place: the water surface,’ said ChBE Assistant Professor Saad Bhamla. ‘So, when they jump from and land back on water, we must understand the effects of both hydrodynamics and aerodynamics. How they land perfectly on their feet almost every time on the surface of water was the puzzle we set to solve in this paper.’

all images by Georgia Tech Research

controlling their jumps like expert acrobats

The secret to the springtails’ success derives from their posture and unique appendages for jumping and adhesion. When they take off, they adjust the angle of their leaping organ, named the furcula, and then while in the air, their body forms a U-shape posture. This creates aerodynamic torque, which effectively self-rights them 20 milliseconds into the jump, the fastest of any wingless organism. When they touch down, they land on a collophore, an appendage particular to the springtail that holds water. The collophore takes shape as a tube-like structure that holds a water droplet and can stick to surfaces.

This appendage is crucial for the springtail to slide on the water’s surface and land on its feet without bouncing. With high-speed imaging and a hydrodynamic oscillator force mathematical model, the researchers calculated how the springtail makes use of its collophore for stable landings. ‘Nobody has ever shown experimentally what the collophore is really for, and we’re showing that it’s for their survival,’ Ortega-Jiménez said. ‘They need this for stability, controlling their takeoff but more importantly how to perfectly land like an acrobat.’

skillful skydiving of wingless springtails

In a computer simulation, the team proved that by controlling the angle of their body and speed, springtails glide on the surface of the water with their collophore. ‘Springtails could not have become the most abundant non-insect hexapod without being able to control their gymnast-like escape response. In addition to being fascinating to watch, this new understanding of the biomechanics of how springtails control their jump, spin in midair, and land safely on water could lead to advances in fields from robotics to aerodynamics,’ said Kathryn Dickson, a program director at the National Science Foundation

After simulations and observations, the researchers created small robots with drag flappers to replicate their results in a physical environment, in collaboration with Professor Je-sung Koh’s team at Ajou University in South Korea.

‘It has been a major challenge for jumping robots, specifically at small scales, to control their orientation in the air for landing and jumping,’ Koh said. ‘The finding in this research could inspire insect-scale jumping robots that are able to land safely and expand the capability of robots in new terrains, such as the open-water surfaces in our planet’s lakes and oceans.’ The robot reaches a 75% success rate, which is impressive compared to the springtail’s 85%.

With this discovery, the researchers open a new path of what smaller animals are capable of doing. ‘There is a belief that because they are tiny, they don’t have as much control as big animals do. So, we are opening some possibilities of control at this small scale that could give insights into the origins of flight in organisms,’ Ortega-Jiménez said.