Researchers Develop Octopus-Inspired Soft Robotic Arm

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Beihang University have developed a soft robotic arm based on an octopus. It can grip, move, and manipulate a range of different objects with its flexible and tapered design. The robot arm consists of suction cups that help it have a firmer grasp when gripping objects of various shapes, sizes, and textures. 

The new development is another example of robotics that are based on nature. In an octopus, two-thirds of the neurons are located in its arms, basically making each one independent. The arms of an octopus are capable of untying knots, opening childproof bottles, and wrapping around prey of various shapes and sizes. One of the most impressive aspects of the arms is the suckers, which can form strong seals on rough surfaces underwater. 

August Domel is a recent Ph.D. graduate of Harvard and co-first author of the paper. 

“Most previous research on octopus-inspired robots focused either on mimicking the suction or the movement of the arm, but not both,” said Domel. “Our research is the first to quantify the tapering angles of the arms and the combined functions of bending and suction, which allows for a single small gripper to be used for a wide range of objects that would otherwise require the use of multiple grippers.”

The research was published in Soft Robotics. 

The first step taken by the researchers was to study the tapered angle of real octopus arms. They then figured out which design would be best for a soft robot to bend and grab objects. The team studied the layout and structure of the suckers and found a way to incorporate them into the new design. 

Zhexin Xie is co-first author and a Ph.D. student at Beihang University. He is the co-inventor of the Festo Tentacle Gripper. It is the first fully-integrated implementation of its kind in a commercial prototype.

“We mimicked the general structure and distribution of these suckers for our soft actuators,” said Xie. “Although our design is much simpler than its biological counterpart, these vacuum-based biomimetic suckers can attach to almost any object.”

The soft robotic arm is controlled by the researchers with two valves. One valve is used to apply pressure for bending the arm, and the other is for a vacuum that engages the suckers. The researchers can change the pressure and vacuum in order to get the arm to attach to an object, wrap around it, and release it. 

The device was successfully tested by the researchers on various different objects, including thin plastic sheets, coffee mugs, test tubes, eggs, and live crabs. Because of the tapering design, the soft robotic arm was able to operate within confined spaces in order to retrieve objects.

Katia Bertoldi is co-senior author of the study and the William and Ami Kuan Danoff Professor of Applied Mechanics and SEAS. 

“The results from our study not only provide new insights into the creation of next-generation soft robotic actuators for gripping a wide range of morphologically diverse objects, but also contribute to our understanding of the functional significance of arm taper angle variability across octopus species,” said Bertoldi.