A US research team is developing a so-called soft robot that looks like a long spiral noodle. It moves by rolling and can even cross a maze autonomously. However, the Spirelli-shaped device needs certain temperatures for this.
A soft robot can roll autonomously over sunlit car roofs and hot sand. Because the spiral noodle-shaped device draws its drive energy from the hot underground. By reversing its own twisting direction, the liquid crystal soft robot can change the rolling direction and thus find its way out of a mini labyrinth.
Scientists around Jie Yin from North Carolina State University in Raleigh (US state of North Carolina) describe their invention in the “Proceedings” of the US National Academy of Sciences (“PNAS”). “These soft robots demonstrate a concept called physical intelligence,” Yin is quoted as saying in a statement from his university. “This means that structural design and smart materials make it possible to navigate in different situations.”
In the manufacture of the “Spirelli” robot, a nine centimeter long liquid crystal ribbon is stretched and twisted and then hardened with ultraviolet light. It is important that there is a straight line in the center of the spiral around which the outer areas are rotated. From a surface temperature of 55 degrees Celsius, the soft robot begins to roll off very slowly. At 80 degrees, the roll speed is about 1.5 millimeters per second, at 180 degrees 3.8 millimeters per second. High temperatures in the sun reach a stationary car, a road or sand.
The robot can react to obstacles in two ways: if it senses contact near one of its two ends, it turns around the object. If, on the other hand, the soft robot hits the obstacle more in the middle, it partially unwinds and then turns over: The twisting direction changes and with it the direction in which the robot rolls. The robot can find its way out of a mini labyrinth through multiple changes of direction, which never run in the exact opposite direction but at different angles.
The soft robot overcomes sand dunes with an incline of 15 degrees without slipping. Even if sand is thrown on him, he can spin out of it and keep rolling. Locomotion also works on fine pebbles. The soft robot can even do simple jobs: the device, which weighs just 0.36 grams, can roll an aluminum tube that is almost as heavy in front of it on a smooth surface. It can also round up scattered particles.
“The temperature required to power self-propelled locomotion on a hot surface is high for practical applications,” the researchers concede. To overcome this limitation, the crosslinking agents in the material could be changed or their concentration adjusted. This could lower the temperature at which the soft robot rolls. In addition, the device could be designed slightly asymmetrically to change direction at a larger angle when flipping over, allowing faster escape from an entrapment between two parallel walls.
