EU-funded researchers have developed a soft robot that moves like an elephant’s trunk. Precise enough to pick fresh fruit, yet powerful enough to lift a patient.
Lucia Beckai, a soft robotics expert at the Italian Institute of Technology in Genoa, came up with the idea while watching a documentary about elephants. She marveled at the trunk’s versatility, being able to delicately remove a single leaf from a tree and then move a huge log.
That versatility was lacking in today’s robots. But what if researchers could emulate the anatomy and function of an elephant’s trunk? This could revolutionize the way robots handle objects, from helping around the house to searching for survivors in rubble.
“Elephant trunks are really fascinating because they’re so dexterous and delicate,” Beckai says. “It’s a large, boneless sensory organ, but it’s extremely versatile. Today, its performance is unparalleled in robotics.”
This observation became the seed for PROBOSCIS, a five-year EU-funded research initiative that brings together biologists, engineers and materials scientists to decipher how elephant trunks work.
The goal was to go beyond today’s specialized grippers and create a more versatile robotic hand. This is a robotic hand that can gently grasp grapes, firmly lift heavy objects, and adapt to a wide range of shapes and textures without major hardware changes.
Stem: one continuous structure
Currently, most robots have a rigid arm with motorized joints and a gripper at the end, making them separate elements with clear limitations. These robots, unlike elephant trunks, cannot perform what Beckai calls “whole-body manipulation,” or wrapping their entire arm around an object in a continuous, fluid manner.
The torso is what biologists call a muscular hydrostat, similar to an octopus’ tentacles or a human tongue. It has over 100,000 individual muscles, and although it has no skeleton, it can stretch, contract, bend, and twist in all directions simultaneously, with no distinction between arms and grippers. This is one continuous structure.
The trunk is also very durable and can carry around 300 kg of luggage. African elephants also have two small finger-like projections on their tips for more delicate tasks.
Simple movements, complex results
To better understand how the core works, Professor Michel Milinkovic, an evolutionary biologist at the University of Geneva, led a team that turned to filmmaking techniques.
Bands of reflective marker spots, similar to those used in blockbuster movies, tracked precise trunk movements as elephants manipulated objects of different shapes, sizes and textures in a South African reserve. The footage was captured with high-speed cameras and captures an incredibly efficient system.
“What we noticed is that they put together small sequences of actions,” Milinković said. “Short some sections, stretch some sections, bend some sections, and combine them to accomplish a task.”
Milinković found one movement particularly outstanding. When the elephants reached behind their heads to get a treat from their handlers, they didn’t just curl their trunks back.
Instead, the top part stuck out and became temporarily stiff, creating two “pseudo-joints” that functioned like shoulders and elbows, while the bottom part swung backwards to grab the treat.
“This was absolutely amazing because no one had seen this before. They do it so fast,” Milinkovic said. It showed that the trunk can form different parts separated by joints.
The research team also conducted anatomical studies of a male African elephant and a male Asian elephant taken from animal carcasses at the zoo.
3d muscles
To apply Milinković’s findings to robotics, Beckai’s team focused on the tip of the trunk. They used 3D printing to integrate sensing and artificial muscles, or actuators, into one seamless body. These pneumatic balloon-like structures expand and contract by being inflated and deflated with air. By changing its size and shape, researchers can program specific movements into the system.
To create a soft, trunk-like robot, the researchers combined pneumatic actuators with a mesh-like lattice structure that can deform in multiple directions.
The device is printed in one continuous process from the same soft resin, including optical sensors that provide feedback about touch and bending of the torso tip.
Beckai said a single material is key. “This is very important because it removes the material and mechanical interfaces between the various components, allowing continuity of movement in combination with sensory feedback.”
The prototype can be stretched, compressed, and bent, and can also perform movements such as pinching, scooping, and reaching. This design represents a step toward a truly versatile gripper that can handle everything from soft, delicate objects to heavy, irregularly shaped objects with a single, adaptable system.
Although the research project will end in April 2025 and the soft robotic arm remains a laboratory demonstrator for now, the research team says they have already overcome most of the design issues holding back today’s robotic arms.
gentle control
One of the key insights gained from elephants was about control. Although the torso contains thousands of muscles, elephants do not control all of them.
Instead, their brains control what Milinković’s team discovered is the synergy of a small number of muscles, or how muscles work together in concert to perform a movement, Beckai explained. The physical structure of the trunk takes care of the rest.
This showed researchers how to make functional soft robots viable outside the laboratory, and how to design future systems around synergies rather than individual actuators.
Beccai hopes this will reduce complexity and energy demands, making the device battery-powered and making it easier to deploy. She envisions a wide range of practical applications, from picking soft fruit, a big challenge in robotics today, to household chores like sorting laundry and handling fragile tableware.
Such robots have potential in environmental applications, from handling debris and sorting waste to operating in fragile ecosystems without damaging surrounding plants, soil, or marine life. In search and rescue, their soft arms could help them dig through debris and use their sense of touch to find people.
But Beckai is most interested in assistive robotics. “My dream is to build a medical system that can lift and help disabled and elderly people, for example, and at the same time hand them a fork or fresh fruit,” Beckai said.
A single robot powerful enough to assist with transfers but gentle enough to handle everyday items could help people live more independently. Unlike traditional machines, it doesn’t have to feel intimidating due to its softness.
For Becky, improving her grip wasn’t the only goal. It was a robot that was strong when needed, gentle when it mattered, and felt natural to be around.
This article was originally published in Horizon, EU Research and Innovation Magazine.
The research for this article was funded by the EU’s Horizon program.
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