Self-Propelled Robo-Fish Can Grab Microplastics Out of the Ocean

Engineers at the Polymer Research Institute of Sichuan University have devised a tiny robo-fish that can flap around a body of water, grabbing microplastics as it goes. The 13mm robot uses a light laser system in its tail to propel itself at approximately 30mm a second. If the robot experiences damage during a swim, it can repair itself and continue the job without outside intervention.

The team took inspiration from ocean-dwelling creatures for the project. They designed a material that mimics nacre (known colloquially as mother-of-pearl) by layering sheets of molecules to match nacre’s chemical gradient. The durable material allowed the engineers to fashion a robo-fish that could twist, stretch, “tow” up to 5 kg, and regenerate up to 89 percent when snagged or cut.

The makeup of the robot’s material is essential to its ability to pick up microplastics as well. Microplastics contain dyes and metals which stick to the artificial nacre via electrostatic and chemical bonds. This means there’s no manual “catching” to be done—the robo-fish simply swims around and passively grabs hold of any microplastics in its path.

Right now the robo-fish only works on the water’s surface; the engineers are working on creating a version of the robot that will be able to dive and swim fully submerged. But until then, the surface-skimming robot is an exciting proof-of-concept, both in the realm of soft robot engineering and microplastic pollution mitigation. Most soft robots are made from hydrogels or silicone, which are “inherently mechanically inferior and easily damaged and difficult to integrate functions,” according to the research published Wednesday in Nano Letters. The engineers’ imitation nacre makes for a robust robot without sacrificing the flexibility typical of more traditional materials.

The team admits robo-fish are a band-aid solution to a larger microplastics problem. Tiny swimming robots are unlikely to keep up with the rate at which we produce microplastics (which are often the result of larger plastic items breaking down). Still, if implemented in the “real world,” these little swimmers might help alleviate the effects of pollution while longer-term strategies are tested. Canada, for example, recently banned the production of certain single-use plastics. On a smaller scale, the US Interior Department is phasing out the use of some plastics on national park lands and facilities.

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