Soft Robotics Octopus Arms Bring Flexibility to Robotic Movement

August 25, 2016 by Mark Hughes

Cephalopods have no rigid structures in their bodies and can adjust their bodies to fit the size and shape to the environment. A robot with similar properties would have an advantage in search and rescue environments if it could squeeze through openings other robots could not.

Nature often provides inspiration for designers. Researchers at the OCTOPUS Integrating Project have created a robot octopus that is able to move through water, grab objects, and walk along the floor of a pool.

European scientists and engineers with the OCTOPUS Integrating Project have drawn on nature for inspiration in their latest robot—an octopus that can swim, walk, and grab objects with soft robotic arms. The arms are filled with fluids and lack the rigid support structures that most actuators depend on.  

Octopi and squid have no bones or exoskeletons to support their appendages, yet they are able to twist, turn, flex, and curl every part of their arms to walk, swim, and grab objects. Better understanding how these fascinating sea creatures work will provide engineers with a brand new set of materials they can use to move and manipulate the world around us. Perhaps these tools will be used to explore other distant worlds as well.

This video from IEEE Spectrum explains some of the prototype models in the OCTOPUS program:

Robotic Ingenuity

Soft robotics is a relatively new field that you can explore to some degree in your home workshop by taking advantage of the tools and resources made available here. There you can learn to make your own manipulators, bending-actuators, and artificial muscles.

In this demo from Soft Robotics Inc., a soft robotics "hand" manipulates small-scale items with precision:

The Octopus Project research is taking place at many institutes and universities throughout Europe and the Middle East and is coordinated by the BioRobotics Institute of the Sant'Anna School of Advanced Studies in Italy. Researchers are investigating how cephalopods are able to sense and move through their environments so they can develop robots that can act in a similar fashion. 

Currently, the scientists have a robot that can swim through water, walk along the sea floor, and insert itself in small gaps on command.

Different labs have different research interests, with some labs focused on making artificial muscles and other labs interested in making robots that can interact with humans.


Image courtesy of Alex Koch.


The octopus was selected for study because of their dexterity of movement and adaptability to their surroundings using a combination of central and peripheral nervous systems.

Additionally, scientists enjoyed the design challenge of controlling eight separate complex control arms to produce a wide variety of movements.

Design Difficulties

Every joint on a robot that allows it to bend or to pivot is called a degree of freedom. Each degree of freedom increases the range of motion of the robot. Popular industrial robots typically have just six degrees of freedom.

This video from RobotWorx shows the separate elements of a basic 6-axis robot:

Each degree of freedom allows increased maneuverability, but each degree of freedom also increases the complexity of the control systems. Industrial robots have control arms that are made to exact and unchanging specifications.

Robotic tentacles, however, can shrink and stretch at any point along their length. A soft robotic octopus arm has almost unlimited degrees of freedom and the ability to change the rigidity of each segment of its length.


A prototype soft robotic tentacle wrapping around a wrist. Image courtesy of the SSSA Biorobotics Institute.


Scientists at the Octopus Project will have to investigate novel control systems if they hope to have their octopus crawl out of its design pool and into waters near you anytime soon.

They might do this by implementing sensors throughout the arms to allow the arms to have basic autonomous control of each segment, similar to at actual octopus. Or they might find that science leads them along a novel path to a new control architecture not yet implemented in any robotic systems—that's the beauty of exploration.

Design Implications

The research taking place in soft-robotics can lead to devices that can grab and lift a fallen patient without risk of them being bruised by the rigid support arm in most similar devices on the market today. Or perhaps NASA will send robots to explore a distant comet and grab on to its unpredictable surface with soft claws that expand from and retract into the rigid underbelly of a return rocket. Maybe the result of the research is something that no-one has yet imagined.

That's the beauty of science—you never know where the quest for understanding might lead.