For turtle hatchlings struggling to reach the sea, success may depend on having flexible wrists that allow them to move without disturbing too much sand. A similar wrist also helps a robot known as “FlipperBot” move through a test bed, demonstrating how animals and bio-inspired robots can together provide new information on the principles governing locomotion on granular surfaces.

Both the baby turtles and FlipperBot run into trouble under the same conditions: traversing granular media disturbed by previous steps. Information from the robot research helped scientists understand why some of the hatchlings they studied experienced trouble, creating a unique feedback loop from animal to robot – and back to animal.

The scientists – Daniel Goldman and Nicole Mazouchova of the Georgia Institute of Technology – came from separate disciplines: Physics and Biology. Their findings were published this week in the journal Bioinspiration & Biomimetics.

The research could help robot designers better understand locomotion on complex surfaces and lead biologists to a clearer picture of how sea turtles and other animals like mudskippers use their flippers. The research could also help explain how animals evolved limbs – including flippers – for walking on land.

“We wanted to make a systematic study of what makes flippers useful or effective. We’ve learned that the flow of the materials plays a large role in the strategy that can be used by either animals or robots.”

The research began in 2010 with a six-week study of hatchling loggerhead sea turtles emerging at night from nests on Jekyll Island, one of Georgia’s coastal islands.

Mazouchova and Goldman studied data from the 25 hatchlings, and were surprised to learn that they managed to maintain their speed regardless of the surface on which they were running.

“On soft sand, the animals move their limbs in such a way that they don’t create a yielding of the material on which they’re walking,” said Goldman. “That means the material doesn’t flow around the limbs and they don’t slip. The surprising thing to us was that the turtles had comparable performance when they were running on hard ground or soft sand.”

The key to maintaining performance seemed to be the ability of the hatchlings to control their wrists, allowing them to change how they used their flippers under different sand conditions.

Further reading:
Georgia Institute of Technology
Flipper-driven terrestrial locomotion of a sea turtle-inspired robot. Nicole Mazouchova et al 2013 Bioinspir. Biomim. 8 026007