Scientists have designed a tiny, light-activated fish robot that can remove microplastics from seas and oceans as it swims.

Microplastics are found nearly everywhere on Earth and can be harmful to animals if they are ingested, but it is hard to remove such tiny particles from the environment, especially once they settle into nooks and crannies at the bottom of waterways.

The bionic fish can adsorb free-floating bits of microplastics because the organic dyes, antibiotics, and heavy metals in the microplastics have strong chemical bonds and electrostatic interactions with the materials used to make the robot - causing the microplastics to cling on to the surface of the fish as it 'swims.'

“It is of great significance to develop a robot to accurately collect and sample detrimental microplastic pollutants from the aquatic environment,” said Yuyan Wang, a researcher at the Polymer Research Institute of Sichuan University and one of the lead authors on the study.

Her team’s novel invention is described in a research paper in the journal Nano Letters which says, “To the best of our knowledge, this is the first example of such soft robots.”

The robo-fish is 13mm long, and thanks to a light laser system in its tail, swims and flaps around at almost 30mm a second - comparable to the speed at which plankton drift around in moving water. The traditional materials used for soft robots are hydrogels and elastomers, however they can be damaged easily in aquatic environments, so researchers created the robot from materials inspired by nature.

The answer was found in mother-of-pearl, also known as nacre, which is the interior covering of clam shells and a material of extraordinary strength - similar to spider's silk or a mollusk's limpet teeth. The team created a material similar to nacre by layering various microscopic sheets of molecules according to nacre’s specific chemical gradient. This nacre-inspired material makes the robo-fish stretchy, flexible, and able to pull up to 5kg in weight.

The newly created material also has regenerative abilities. Incredibly, the researchers found the robot fish can heal itself to 89% of its ability and continue adsorbing even after being damaged.

The researchers are careful to note that this is just a proof of concept and more research is needed into how this could be deployed in the real world. For example, the soft robot currently only works on the surface of water, so the research team are due to start work on a robo-fish that can go deeper under the water.

Still, this bionic design offers an exciting glimpse at the future of nanotechnology and how it could be used to tackle pollution.

“I think nanotechnology holds great promise for trace adsorption, collection, and detection of pollutants, improving intervention efficiency while reducing operating costs,” added Wang.