On a morning in Wako, a small city just outside Tokyo, Takuzo Aida held up a thin piece of clear plastic. It looked like the kind that wraps sandwiches or cushions electronics. But when he dropped it into a container of salt water and gave it a gentle stir, something extraordinary happened: it began to dissolve. Within hours, it was gone—leaving nothing behind. Not even a microscopic crumb.

“We have created a new family of plastics that are strong, stable, recyclable, can serve multiple functions, and importantly, do not generate microplastics,” said Aida, a chemist at Japan’s RIKEN Center for Emergent Matter Science.

“Children cannot choose the planet they will live on. It is our duty as scientists to ensure that we leave them with the best possible environment,” he told Reuters.

Plastic 2.0

The team, which included researchers from the University of Tokyo and RIKEN, has developed a plastic with seemingly contradictory properties: strong and flexible, yet soluble in seawater. It can wrap a tomato, hold a load, resist heat—until it touches the ocean. Then, it vanishes.

Made by combining two small molecules—ionic monomers—the plastic gains its strength from salt bridges, electrostatic bonds that hold the material together. But these bonds have a hidden weakness: saltwater. When exposed to seawater, the very bridges that give the plastic strength are disrupted, breaking the material down into harmless components.

This is the product of more than a decade of work. In a study published in Science, Aida’s team first described how to create plastics from what they call supramolecular assemblies. These are materials built with small, reversible interactions. A bold move. “The reversible nature of the bonds in supramolecular plastics has been thought to make them weak and unstable,” Aida explained. “Our new materials are just the opposite.”

They proved it. Their final product, dubbed alkyl SP2, is tough, moldable above 120°C, and can be made into everything from rigid shells to soft films. And unlike most biodegradable plastics, which often survive in the sea and degrade into harmful microplastics, this one disappears completely.

“In about two to three hours, depending on its thickness, it dissolves completely in seawater,” Aida said.

In soil, where salt is also present, the material breaks down more slowly—taking just over 200 hours for a five-centimeter sample. That’s about ten days. Once broken down, the components, including guanidinium ions and sodium hexametaphosphate (a common food additive), can be digested by natural soil bacteria, essentially recycling the plastic into nutrients.

An Answer to a Growing Crisis

The United Nations Environment Programme estimates that plastic pollution could triple by 2040, adding between 23 to 37 million metric tons of waste into oceans each year. And despite years of efforts, less than 9% of plastic is successfully recycled.

Part of the problem lies in the very chemistry of modern plastics. Durable by design, they often persist for decades. Even plastics labeled as “biodegradable” can resist degradation in natural environments, especially the sea. That’s where microplastics—bits smaller than a grain of rice—come into play, infiltrating marine food chains, soil systems, and even human bodies.

Existing materials like polylactic acid (PLA) need industrial composting to break down. When they end up in oceans or landfills, they can stick around, fragmenting into microplastics. Aida’s plastic breaks that pattern. When submerged in water with salinity levels similar to the ocean, it dissolves fully, leaving no microplastic residue behind.

This wasn’t easy to achieve. In their initial experiments, Aida’s group struggled with brittleness. The breakthrough came when they realized that removing excess salt during the manufacturing process, a step they call “desalting,” stabilized the salt bridges and created a strong, flexible film. Later, reintroducing salt reverses this stability, causing the plastic to fall apart.

What’s more, the plastic doesn’t release carbon dioxide during degradation and is non-toxic and non-flammable. After dissolution, over 90% of its components can be recovered and reused, making it potentially recyclable and circular in use.

What Comes Next?

Although the plastic is not yet available commercially, Aida says the project has already sparked interest from the industries, especially in Japan’s packaging sector.

“In Japan, almost all packaging is made of plastic, and if we can really manage to reduce that, we can expect less environmental damage,” Aida told the BBC.

For now, the focus is on refining the product—finding optimal coating methods to make it last just long enough for practical use, but still vanish at the right moment. The researchers are also working on custom variations: tougher plastics for 3D printing, more flexible ones for packaging, and even medical applications.

And unlike fossil fuel-based plastics, the raw materials for this invention are both abundant and safe. In soil, their breakdown even contributes nutrients like phosphorus and nitrogen, acting much like a slow-release fertilizer.

The road ahead still includes hurdles. Large-scale production, regulatory approval, and cost-effectiveness will all play a role in determining whether this plastic becomes a niche innovation or a widespread replacement. But the researchers believe the urgency of the plastic crisis could help speed things up.

After all, time is running out. Every minute, the equivalent of a garbage truck’s worth of plastic enters the ocean.