An African elephant called Kelly has helped elucidate a physical mystery: How an elephant trunk can carry heavy logs and delicately handle fragile objects.
Jianing Wu at Georgia Institute of Technology in Atlanta and his colleagues offered Kelly food items in four different sizes – powdered bran, cubed bran, cubed swede, and largest of all, cubed celery.
“We wanted to know how she would grab different-sized foods,” says Wu.
They offered the food on a table that measured Kelly’s downward force she generated when gripping and took detailed measurements of her trunk maneuvers to figure out how she varied the shape of her trunk and the forces it applied to grab each target.
Kelly’s mystery, it turns out, was her ability to create a kink at any point along her 2-meter-long trunk that would provide just the right squeezing pressure to grip each size of the food item.
The kink divided her trunk into two sections, one that supported the weight of the trunk and another pointing vertically downwards for a dexterous grasp.
Force fine-tuning
Wu and his colleagues found that Kelly could reduce the amount of downward force by making the vertical part of her trunk shorter – and create more force by making the vertical section longer.
In other words, Kelly had the ability to fine-tune how much force to apply by altering the position of the “kink” in her trunk.
Counterintuitively, as objects became smaller, Kelly needed more force to pick them up. The most challenging part was getting the whole-wheat bran powder to compact into a solid first before she could pick it up.”
“In order to pick up the smaller particles, she sweeps, scoops, and squeezes the food,” says Wu, who presented his team’s results at the annual meeting of the Society for Integrative and Comparative Biology in New Orleans last week.
The insights the team is armed with make it easy to build a small prototype gripper, which will bear the same principles. “If we know how an elephant manipulates its trunk to control such a huge range of objects, we may be inspired to develop universal robotic grippers in the future,” Maddi says.
It will not be easy because existing artificial muscle technology would struggle to match the complexity of the muscular movements within the trunk. But Professor Wu thinks that the science behind it could lead to sturdy robotic gripping devices that people use in industry, and perhaps, in delicate rescue operations.
