This starfish robot can transform and heal itself like a real starfish

2022/01/04

Natural camouflage is one of nature's most interesting features. Materials scientists have now developed a material that mimics the camouflage abilities of marine mollusks. They created a starfish-shaped soft robot that deforms, moves and changes color in response to heat and pressure. Severed tentacles can be welded together and the material can be completely recycled, they write in the journal Angewandte Chemie.

Octopus, jellyfish and starfish are capable of natural camouflage, that is, they can quickly change their color or shape to match the background. A research team led by Quan Li of Southeast University in China has now created a soft material that can mimic this characteristic. As a base material, they chose a liquid crystal elastomer that changes phase at different temperatures. When heated, the oriented liquid crystal molecules of the elastomer lose order, causing parts of the material to shrink.

The researchers exploited this shrinkage effect to enable the soft robot to "crawl." To do this, they molded the polymer material into the shape of a starfish and added an infrared-sensitive dye to the base of one of the tentacles. This modified site contracts when heated by the photothermal effect created by near-infrared radiation, and expands when cooled. With only one arm being stimulated by light, the starfish robot moved slowly across the surface, propelled like caterpillars by contracting-expanding tentacles.

The starfish soft robot can change its color. The researchers integrated a cross-linking agent -- molecular dyes that link polymer chains -- into the material. However, the dynamic covalent cross-linking system used here is made to break easily. During the process of heating and pressurizing, its molecular parts separated, and the previously yellowish dye molecules turned red, similar to the natural camouflage effect of sea stars.

Finally, the starfish robot also demonstrated the qualities of self-healing and even recycling. When the researchers severed a tentacle, it healed seamlessly after the part was heated again. The same thing happened when the whole robot was cut into pieces. Molding it into a starfish shape again, the researchers regained a new, soft robot with its properties intact.

According to the authors, the key to this multi-adaptive capability is the integration of a cross-linked dye molecule, a tetraarylsuccinonitrile, which can perform several functions simultaneously. It acts as a light-absorbing chromophore and provides a dynamic covalent bond for the elastic network. The authors propose the use of this biomimetic soft material with thermal and mechanochromic properties (changing color due to heat and pressure) for biomimetic robots, sensors, and artificial camouflage.

Key words:

Starfish,Material,Molecule

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