Scientists Create Lightweight Robots Inspired by Spiders’ Joints

Scientists at the Max Planck Institute for Intelligent Systems in Germany and at the University of Colorado Boulder in the United States have developed new lightweight robots by using the principles of spiders’ joints.

The research titled “Spider-inspired electrohydraulic actuators for fast, soft-actuated joints” was published in Advanced Science. 

Spiders often serve as inspiration in the field of robotics, especially since they move their limbs through hydraulic actuation mechanisms when hunting for prey, which scientists try to implement in robots.

By using these principles, the team of scientists was able to drive articulated robots without any bulky components and connectors, which help avoid them being weighed down and increase portability and speed. 

Because of the lightweight simple structures used in its construction, the robot can jump 10 times its height.

SES Joints

The scientists relied on Spider-inspired Electrohydraulic Soft-actuated joints, or SES joints, to achieve high performance in the robots. The joints can be configured in various ways, even outside an arachno-bot.

The research paper details a bidirectional joint, a multi-segmented artificial limb, and a three-fingered gripper, which can be used to grip and pick up objects. All of the different creations have similar traits. They are lightweight, simple, and exhibit high performance, meaning they are useful for robotic systems that require rapid movement and interact with different environments. 

The SES joints were based on the HASEL technology previously invented by the team to build artificial muscle. The SES joints mimic an exoskeleton mechanism that has both rigid and softer elements, similar to the way a spider extends its legs through hydraulic forces.

Developing the Spider-Inspired Robots

The scientists first created a flexible pouch made of thin plastic films, which were filled with a liquid dielectric. Electrodes were then placed on each side of the pouch, and the pockets served as actuators, with the hydraulic power generated through electrostatic forces. 

The pouch is connected to a rotary joint, and when a high voltage is applied between the electrodes, the liquid dielectric shifts inside the pouch and the joint flexes. SES joints can rotate up to 70 degrees, which leads to high torques, and they can revert back to the starting position very easily. 

Christoph Keplinger is Director of the Robotic Materials Department at the Max Planck Institute for Intelligence Systems. 

“The SES joints are very simple and light, as there are no peripheral components which weigh down the robot,” says Keplinger. “Many applications for soft robots require versatile actuators. These spider-inspired joints allow for high functionality and consume only little power, they are easy and cheap to make—the plastics we are using are for food packaging—and their production is easily scalable. These are all qualities that are critical for the design of robots, which can move in many different ways and manipulate a variety of objects without breaking them.”

The scientists demonstrated the versatility of the SES joints through the application of a three-fingered gripper. If the gripper relied on a muscle-like structure, it would have been obstructed when trying to grab an object. But with the SES joints as the hinges, much less space is required. 

Nicholas Kellaris is first author of the paper.

“The research stands out because we can use a wide variety of materials, even the plastic used to make chips bags to create the pouches,” Kellaris says. “That way we can implement SES in a wide variety of geometries with specifically tuned actuation characteristics.” 

Phillip Rothemund is second author of the publication.

“The ultimate goal of our research was not to make a spider robot,” Rothemund adds. “We wanted to develop a state-of-the-art, active joint that you can put in any type of robot.”