Microplastics are now ubiquitous in water bodies worldwide, posing threats to human and environmental health as they may require hundreds or even thousands of years to decompose. To speed the cleanup process, North Carolina State University developed cleansing microparticles based on chitosan and engineered to self-disperse, hunt for microplastics and return to the surface with their prey for collection.

As detailed in Advanced Functional Materials, soft dendritic chitosan-derived colloids have a hierarchical fibrillar structure that enables adhesive collection of microplastic particles through van der Waals attraction – the interaction between uncharged molecules or atoms. Dispersion of the cleansing agents isOptical microscopy image of soft dendritic colloids capturing microplastics. Source: North Carolina State University effected by combining the colloids into larger supracleansing agents capable of self-propelling on water by surface tension gradients, or the Marangoni effect, driven by small amounts of plant-based oil.

The cleaning agents also contain small particles of magnesium, which makes them bubble up and rise to the surface when reacting with water. The magnesium is coated with an environmentally safe gelatin layer that blocks the magnesium’s reaction with water, thereby delaying their immediate return to the surface and allowing the microcleaners to collect more microplastics as they swirl and descend in water.

During laboratory and field tests, the released particles were demonstrated to maneuver and harvest microplastics for up to 30 minutes. The microplastic-laden microcleansers that float up to the water surface can then be collected by skimming.