Inspenet, January 31, 2023
An international team of engineers, with support from the National Natural Science Foundation of China, was inspired by sea cucumbers to design miniature robots that quickly and reversibly switch between liquid and solid states on command. These robots, which can conduct electricity, use magnetic induction to heat up and change state, even escaping from behind bars.
“Giving robots the ability to switch between liquid and solid states gives them more functionality,” said Chengfeng Pan, an engineer at the University of China in Hong Kong who led the study. The hard character of traditional robots entails problems of excessive rigidity, and in the same way their flexible counterparts err on the side of being too soft and their movements are difficult to control.
To solve this difficulty, the researchers took inspiration from the sea cucumber, which can reversibly alter the stiffness of its tissue to improve its carrying capacity and prevent physical damage from the environment. In this way, Pan’s team created the new material called “magnetoactive solid-liquid phase transition machine”, by incorporating magnetic particles into gallium, a metal with a very low melting point (29.8 °C). .
“The magnetic particles here have two functions,” says lead author and mechanical engineer Carmel Majidi of Carnegie Mellon University, USA. “One is that they make the material respond to an alternating magnetic field, so it can, through induction, heat the material and cause the phase change. But magnetic particles also give robots mobility and also the ability to move in response to the magnetic field,” Majidi explained.
Another relevant feature of the new material is that it has an extremely fluid liquid phase compared to other phase-change materials, whose “liquid” states are considerably more viscous.
Engineers conducted mobility and strength tests of the material in a variety of contexts. With the help of a magnetic field, the robots jumped over moats, scaled walls, and even split in half to cooperatively move other objects before coming back together. In the best ‘Terminator 2’ movie style, they made a ‘Humanoid Lego’ robot liquefy and slip through a grate. The robot was then reshaped to its original form. The study was published in Matter.
Photo : Screenshot Qingyuan Wang et al.
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