PRINCETON, N.J. — Scientists have taken a cue from nature’s fuzziest insects, creating a caterpillar-like robot that can bend and twist when navigating mazes. This new technology owes its flexibility to the art of origami, which influenced the design of this innovative soft robot.
Soft robots are challenging models to move around because adding steering equipment makes them more rigid and reduces their flexibility. Incorporating the ancient practice of paper-folding helped overcome these design issues because the steering system is built directly into the robot’s body rather than an external device.
The robot is made of cylindrical segments that can work independently or join other segments to form a longer unit. These combinations allow the robot to move and steer. Additionally, the new system makes the robot flexible enough to crawl forward, crawl backward, pick up items, and make themselves longer.
Writing in the the team notes that the ability to become longer or split into smaller parts allows the robot to work by itself or as a swarm of mini caterpillars.
“Each segment can be an individual unit, and they can communicate with each other and assemble on command,” says Tuo Zhao, a postdoctoral researcher at Princeton University, in a media release.
Magnets also help to connect the segments together again. An origami form called the Kresling pattern created the robot’s cylindrical segments. Each Kresling pattern lets the segment twist into a flattened disk and expand back into a cylinder.
This twisting, expanding motion allows the caterpillar robot to crawl and change direction. Partially folding a section of the cylinder also allows a lateral bend in a robot segment. Combining the small bends together gives the robot the freedom to change direction as it moves ahead.
“This is a very promising technology with potential translation to robots that can grow, heal, and adapt on demand,” says Glaucio Paulino, a professor in the Department of Civil and Environmental Engineering at Princeton University and the Princeton Materials Institute.
Although the authors fixed one major issue with soft robots, another arose. While the soft robot could now bend and fold, a mechanism was needed to control when to activate these movements when in motion. North Carolina State University researchers helped overcome this dilemma by adding thin strips of liquid crystal elastomer and polyimide along the creases of the Kresling pattern.
These two materials shrink or expand when heated. A thin stretchable heater of silver nanowire network was installed along each fold. Silver nanowire is known as a useful building block for stretchable electronic devices.
An electrical current on the nanowire heater helped heat the control strips, and the two materials’ expansion created a fold in the strip. By calibrating the current, researchers could control the folding and bending to steer the robot. While the robot can move around, it is not fast. The next steps in this project are to figure out ways to increase its speed without sacrificing its flexibility.
