The light-activated fish robot designed to collect microplastics

Researchers have invented a light-activated fish robot that “swims” around quickly and removes microplastics from the water

Becoming increasingly difficult to remove from the environment, microplastics are found nearly everywhere on Earth and can be harmful to animals and humans if ingested – so, researchers have created a fish robot to collect microplastics.

Humans have struggled to tackle the microplastic problem, so the fish robot was designed to settle into nooks and crannies at the bottom of waterways that humans can’t reach. The tiny light-activated fish robot “swims” around quickly and collects the unwanted plastics from aquatic environments.

Microplastics have been found in human blood

One solution to remove microplastics from aquatic environments is by using small, flexible and self-propelled robots to reach these pollutants and clean them up, however, the traditional materials used for soft robots are hydrogels and elastomers, and they can be damaged easily in aquatic environments.

Looking at a different material called mother-of-pearl, also known as nacre, which is strong and flexible, Inspired Xinxing Zhang and colleagues, and made them try a similar type of gradient structure to create a durable and bendable material for soft robots, as published in ACS’ Nano Letters.

This natural substance is found on the inside surface of clam shells, and its layers have a microscopic gradient, going from one side with lots of calcium carbonate mineral-polymer composites to the other side with mostly a silk protein filler.

So, the researchers then linked β-cyclodextrin molecules to sulfonated graphene, creating composite nanosheets. Then solutions of the nanosheets were incorporated with different concentrations into polyurethane latex mixtures.

The fish robot can move 2.67 body lengths per second and self-heal

After a layer-by-layer assembly method, there became an ordered concentration gradient of the nanocomposites through the material.

Thus, the team formed a tiny fish robot that was 15 mm (about half an inch) long. Rapidly turning a near-infrared light laser on and off at a fish’s tail caused it to flap, propelling the robot forward – moving up to 2.67 body lengths per second – a speed that’s faster than previously reported for other soft swimming robots and that is about the same speed as active phytoplankton moving in the water.

The researchers showed that the swimming fish robot could repeatedly adsorb nearby polystyrene microplastics and transport them elsewhere, and the material could also heal itself after being cut, still maintaining its ability to adsorb microplastics.

The durability and speed of the fish robot could allow it to be used for monitoring microplastics and other pollutants in harsh aquatic environments.