Researchers from the Center for Extreme Materials Research at the Korea Institute of Science and Technology (KIST) have created a floating drone outfitted with hydrophilic tooth structures that leverages surface tension to skim microplastics from bodies of water.

The success of the design is due to a hydrophilic ratchet structure wherein a water bridge forms between the teeth thanks to its affinity for water. This subsequently maximizes the surface tension of the water so that the microplastics adhere to the teeth.

Skimming mechanism of hydrophilic teeth for MP (MP, microplastic) balls. The neighboring concave meniscus induces the Cheerios effect, causing the MP ball The schematic shows the skimming process of the MP ball with periodic deformation of the water meniscus. Source: Korea Institute of Science and Technology

According to the team, this allows for the removal of microplastics ranging in size from 1 micrometer (μm) to 4 millimeters, thus addressing the challenges current filtering technologies encounter in terms of size and shape variability.

During trials of the technology, the team reportedly achieved more than 80% recovery efficiency of microplastics — including expanded polystyrene, polypropylene and polyethylene, among others.

Specifically, the hydrophilic ratchet structure design of the floating drone can be used to remove microplastics from large bodies of water, including oceans, lakes and rivers. Further, the drone moves autonomously and purifies water quality much like a household robot vacuum cleaner.

"This technology can be applied not only to floating drones, but also to stationary systems such as water treatment filters in aquaculture farms. It can also be expanded into a home water treatment filter device that individuals can use in their daily lives."

An article detailing the technology, “Capillary Skimming of Floating Microplastics via a Water‐Bridged Ratchet,” appears in the journal Advanced Science.