Unleashing asymmetrical "brainless" robots can autonomously navigate through complex mazes

Researchers have created a soft robot that can navigate simple mazes without human or computer guidance. Its asymmetric shape allows it to complete turns independently and prevent it from getting trapped. Now, they have built on this work to create a "brainless" soft robot that can navigate more complex and dynamic environments.

"In our earlier work, we showed that our soft robot was able to reverse direction in a very simple obstacle," said Jie Yin, co-corresponding author of the paper and an associate professor in the Department of Mechanical and Aerospace Engineering at NC State. "However, it cannot turn unless it encounters an obstacle. In practice, this means that the robot sometimes gets stuck, bumping back and forth between parallel obstacles."

"Later, we developed a new type of soft robot that can turn on its own, allowing it to navigate twisting mazes and even around moving obstacles. And all this is done using physical intelligence, rather than being guided by a computer."

Physical intelligence is when the behavior of dynamic objects, such as soft robots, is governed by their structural design and materials, rather than being guided by computers or human intervention.

Researchers have created a soft robot that can navigate simple mazes without human or computer guidance. Half of the robot is shaped like a twisted ribbon that runs in a straight line, and the other half is shaped like a more tightly twisted ribbon that also rotates around itself like a spiral staircase. This asymmetric design means one end of the robot exerts more force on the ground than the other. Source: North Carolina State University, Yin Jie

Materials and motion mechanisms

Like earlier versions, the new soft robot is made from ribbon-shaped liquid crystal elastomer. When the robot is placed on a surface with a temperature of at least 55 degrees Celsius (131 degrees Fahrenheit), which is warmer than the surrounding air, the parts of the soft straps that contact the surface shrink, while the parts exposed to the air do not. This creates a rolling motion; the warmer the surface, the faster the robot rolls.

However, where the previous version of the soft robot had a symmetrical design, the new robot has two distinct halves. One half is shaped like a twisted band that extends in a straight line; the other half is shaped like a more tightly twisted band that also spirals around itself like a spiral staircase.

This asymmetric design means one end of the robot exerts more force on the ground than the other. Think of a plastic cup with a wider lip than the base. If you roll it across a table, instead of rolling in a straight line, it will create an arc across the table. This is because of its asymmetrical shape.

Overcome design limitations

"The idea behind our new robot is pretty simple: Because of its asymmetric design, it can turn without touching objects," said Yao Zhao, the paper's first author and a postdoctoral researcher at North Carolina State University. "So while it can still change direction when it comes into contact with objects - allowing it to navigate a maze - it doesn't get stuck between parallel objects. Instead, its ability to move in an arc allows it to essentially twist its body and gain freedom."

The researchers demonstrated the ability of an asymmetric soft robot design to navigate more complex mazes, including those with moving walls, and to move through spaces narrower than its body dimensions. The researchers tested the new robot design on metal surfaces and sand. For a video of the asymmetric robot at work, click here: