Could a tiny robotic fish be the answer to the planet’s microplastics crisis?


SICHUAN, China — A robotic fish that swims by sucking microplastics from the waters has been created by scientists in China. The little machine “wiggles” its body and “flaps” its fins just like the real thing.

The robot fish measures only half an inch from nose to tail. Quickly turning on and off a near-infrared light laser at the tail propels it forward. It was inspired by mother of pearl and could help save the planet.

In experiments, the robot moved almost three body lengths per second – a record for soft sea robots. It reached the same speed as the active phytoplankton. Untethered device repeatedly adsorbed nearby polystyrene microplastics and transported them elsewhere.

Incredibly, the device can also “repair” itself after being cut, while retaining its ability to pick up debris. Its durability and speed make it ideal for monitoring microplastics and other pollutants in harsh aquatic environments.

“The proof-of-concept robot has been shown to emphasize its maximum swimming speed of 2.67 body lengths per second, the speed of which is comparable to that of plankton, representing the outperformance of most artificial soft robots,” the authors write in their article. “In addition, the robot can stably absorb pollutants and regain its sturdiness and functionality even when damaged.”

Microplastics are found almost everywhere on Earth and can be harmful to animals if ingested. They are notoriously difficult to remove from the environment, especially once settled in the nooks and crannies at the bottom of rivers, streams, lakes or oceans.

Could this light-activated robotic fish be the key to healthier waters?

Traditional materials used for soft robots are hydrogels and elastomers, which are easily damaged in water. But mother of pearl, also known as nacre, is strong and flexible. It is found inside clam shells. It is made up of layers that have a microscopic gradient – one side with lots of calcium carbonate composites and the other with silk protein filler.

Scientists have developed a similar structure to make a durable, bendable material for their fish. They first made nanosheets from a cocktail of chemicals, including graphene, the strongest material on Earth. Solutions were incorporated at different concentrations into polyurethane latex mixtures.

A layer-by-layer assembly method formed an ordered concentration gradient, just like mother-of-pearl. The Chinese team trained the robot out of the new material.

“This study breaks the mutual exclusivity of functional execution and rapid locomotion,” the authors write. “We anticipate that our nanostructural design will provide an efficient extended path to other embedded robots requiring multi-functional integration.”

The robot is described in the Journal of the American Chemical Society Nano-letters.

South West News Service writer Mark Waghorn contributed to this report.

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