Scientists from Sichuan University have developed tiny fish-shaped robots that are designed to ‘swim’ around picking up microplastics, removing them from source, and thereby helping to address the polluting effect from the worst excesses of human existence. The bots represent a further advance with soft robotics.
As Digital Journal has described, microplastics are formed by weathering and physicochemical or biological degradation processes from macroscopic plastic products, such as the tonnes of plastic waste in the oceans. Microplastics are found nearly everywhere on Earth and can be harmful to animals if they’re ingested.
Clearing microplastics is challenging, especially when they settle into nooks and crannies at the bottom of waterways. To address this, light-activated robotic fish have been developed. These bots move (or ‘swim’) around quickly, collecting and removing microplastics from the environment.
The robots are small, flexible and self-propelled devices and they have been designed to reach these pollutants and clean them up. Since traditional materials used for soft robots – hydrogels and elastomers – can be damaged easily in aquatic environments, an alternative material has been sourced. This material is inspired by nacre, which is strong and flexible, and is found on the inside surface of clam shells. Using this concept, the researchers developed their own synthetic equivalent.
For this, the Chinese scientists linked β-cyclodextrin molecules to sulfonated graphene, to develop composite nanosheets. Following this, the solutions of the nanosheets were incorporated with different concentrations into polyurethane latex mixtures.
By using a layer-by-layer assembly method, it was possible to create an ordered concentration gradient of the nanocomposites through the material. This provided the template for the tiny fish robot.
The robot is only 15 millimetres long and it moves by rapidly turning a near-infrared light laser on and off, enabling a speed of move 2.67 body lengths per second (equivalent to the velocity achieved by active phytoplankton moving in water).
Trials have demonstrated how the bot can repeatedly adsorb nearby polystyrene microplastics and transport them elsewhere.
The research appears in the journal Nano Letter, with the paper titled “Robust, Healable, Self-Locomotive Integrated Robots Enabled by Noncovalent Assembled Gradient Nanostructure.”
