Scientists have engineered a tiny robotic fish programmed to remove microplastics from seas and oceans by swimming around and adsorbing them onto its soft, flexible, self-healing body.
Microplastics are the billions of tiny plastic particles that are fragmented from the larger plastic items we use every day, like water bottles, car tires and synthetic t-shirts. They are one of the biggest environmental problems of the 21st century because once released into the environment through the degradation of larger plastics, they are very difficult to get rid of, ending up in drinking water, products and food, harming the environment, animals and human health.
“It is of great importance to develop a robot that accurately collects and samples harmful 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 of the study. Her team’s novel invention is described in a research paper in the journal Nano Letters. “To the best of our knowledge, this is the first example of such soft robots.”
Researchers at Sichuan University have come up with an innovative solution to tracking down these pollutants in water pollution: developing a tiny, self-propelled robotic fish that can swim around, cling to free-floating microplastics, and repair itself if it is cut or damaged during its expedition .
The robo-fish is just 13mm long and thanks to a light laser system in its tail, it swims and flaps at almost 30mm per second, similar to the speed at which plankton propel themselves in moving water.
The researchers created the robot from materials inspired by elements that thrive in the sea: mother-of-pearl, also known as mother-of-pearl, which is the inner lining of seashells. The team created a nacre-like material by layering different microscopic layers of molecules according to nacre’s specific chemical gradient.
This turned them into a robo-fish that is stretchy, flexible to twist and even pull up to 5kg of weight, according to the study. Most importantly, the bionic fish can adsorb nearby free-floating microplastic pieces because the organic dyes, antibiotics and heavy metals in the microplastic form strong chemical bonds and electrostatic interactions with the fish’s materials. This makes them stick to its surface, allowing the fish to collect microplastics and remove them from the water. “After the robot collects the microplastics in the water, the researchers can further analyze the composition and physiological toxicity of the microplastics,” Wang said.
In addition, the newly created material appears to have regenerative abilities as well, said Wang, who specializes in developing self-healing materials. This allows the robotic fish to heal itself at 89% of its ability and continue to adsorb even in the event of damage or a cut – which can often happen when hunting pollutants in rough waters.
This is just a proof of concept, Wang notes, and much more research is needed — particularly on how this might be deployed in the real world. For example, the soft robot currently only works on water surfaces, so Wang’s team will soon be working on more functionally complex robo-fish that can go deeper under water. Still, this bionic design could provide a launch pad for other similar projects, Wang said. “I think nanotechnology holds promise for trace adsorption, contaminant collection and detection, improving intervention efficiency while reducing operational costs.”
In fact, nanotechnology will be one of the key players in the fight against microplastics, according to Philip Demokritou, the director of the Nanoscience and Advanced Materials Research Center at Rutgers University, who was not involved in this study.
Demokritou’s lab is also focused on using nanotechnology to remove microplastics from the planet — but instead of cleaning it, they’re working to replace it. This week he announced in Nature Food magazine the invention of a new plant-based spray coating that can serve as an eco-friendly alternative to plastic food packaging. Their case study showed that this starch-based fiber spray can repel pathogens and protect against shipping damage as well, if not better than current plastic packaging.
“The motto of the chemical industry for the last 40 to 50 years has been: let’s make chemicals, let’s make materials, get them out, and then 20 or 30 years later clean up the mess,” Demokritou said. “This is not a sustainable model. So can we synthesize safer design materials? As part of the circular economy, can we take materials from food waste and turn them into useful materials that we can use to address this problem?”
This is low-hanging fruit for the field of nanotechnology, Demokritou said, and as materials research gets better, so does the multi-pronged approach to replacing plastic in our daily lives and filtering its microplastic residues from the environment.
“But there is a big difference between an invention and an innovation,” said Demokritou. “Invention is something no one has thought about. Right? But innovation is something that will change people’s lives because it makes it to commercialization and can be scaled up.”