Engineers at Princeton and North Carolina State Universities have developed a soft robot that easily bends and twists arounds mazes — a feat that has previously been challenging due to the likelihood of steering mechanisms to compromise their flexibility by adding rigidity.

To design this soft robot, the researchers used a combination of origami and materials science, while also incorporating the robot’s steering system directly into the design of its body.

Source: Frank Wojciechowski/Princeton University

The robot was created using modular cylinder segments, wherein each segment is capable of independent operation or can be integrated to form an extended unit, thereby collectively enhancing its mobility and steering capabilities. This design reportedly allows the flexible robot to navigate forward and backward, as well as manipulate cargo and assemble into elongated configurations.

The researchers suggest that their design could possibly pave the way for future modular soft robots that grow, repair and develop new functions, due to its capacity to assemble and split apart while in motion, and functioning as either a single robot or a swarm.

Each segment of the robot can operate as an individual unit, communicating with each other and assembling on command, connected by magnets. Likewise, the segments can easily separate.

“We have created a bio-inspired, plug-and-play, soft modular origami robot enabled by electrothermal actuation with highly bendable and adaptable heaters,” the researchers explained.

To assemble their robot, the researchers used cylindrical pieces with an origami shape known as a Kresling pattern on them. This pattern enabled each segment to twist into a flattened disk and then expand back into a cylinder — the repeated motion of which enables the robot to crawl and change direction.

Further, a lateral bend in a robot segment was introduced by partially folding a cylinder section. The addition of such minor bends allows the robot to move forward and subsequently change direction.

To control the bending and folding motions of the robot, a combination of liquid crystal elastomer and polyimide, which exhibit differential expansion when heated, was used. The combination of those materials was incorporated into thin strips along the creases of the Kresling pattern.

The team then added to each fold a thin, stretchable heater created using a silver nanowire network. As an electrical current was applied to the nanowire heater, the control strips were heated, thereby causing differential expansion between the materials and inducing precise folding and bending, thus enabling the controlled driving and steering of the robot.

The team’s work is detailed in the article “Modular multi-degree-of-freedom soft origami robots with reprogrammable electrothermal actuation,” which appears in the journal Proceedings of the National Academy of Science.