A Plastic Alternative Made From Shrimp Shells Gets Stronger When Wet

Most things fall apart in water. Paper, cardboard, and many eco-friendly alternatives to plastic turn soft and useless the moment they get soaked. Researchers have now created a biodegradable material that does the opposite: submerge it, and it grows nearly 50% stronger.

That single property could matter enormously. Every year, the world generates roughly 400 million tons of persistent plastic waste, much of it designed specifically to resist water. Bottles, cups, food containers, and packaging dominate because few biodegradable materials have matched conventional plastics in wet conditions. Research published in Nature Communications suggests that a molecule already being produced by nature in enormous quantities may help close that gap.

The material is made from chitosan, derived from shrimp shells, combined with trace amounts of nickel. Chitosan comes from chitin, a structural molecule found in crustacean shells and insect exoskeletons, with an estimated renewable biosynthesis rate of about 100 billion tons per year globally. Most of it currently goes to waste, discarded as a byproduct of shrimp and crab processing, or used in low-value applications like water filtration. Despite that abundance, chitosan-based materials have long been held back by one stubborn flaw: they weaken and dissolve in water. The team, based at the Singapore University of Technology and Design and the Institute for Bioengineering of Catalonia in Barcelona, appears to have solved that problem using an approach borrowed from nature itself.

How a Shrimp Shell Material Becomes Stronger Than Common Plastics

The inspiration came from a sandworm. Researchers knew that when zinc is removed from the fangs of a worm called Nereis virens, the fangs lose their structural strength when submerged. That observation led the team to ask whether trace metals might help chitosan actually use water, rather than be weakened by it.

To test the idea, they dissolved chitosan flakes, sourced from shrimp-processing factory byproducts in India, in a weak acetic acid solution, roughly one-fifth the concentration of regular table vinegar. Nickel chloride dissolved in water was then mixed in, poured into molds, and dried. The result was a series of thin, green-tinted films at varying nickel concentrations.

In dry conditions, the films matched the strength of common plastics like polypropylene or polystyrene. Once submerged, they reached the range of engineering plastics such as polycarbonate and PETG, the kind used in water bottles and structural components. The researchers described this behavior as “never achieved artificially.”

To understand why, picture the chitosan chains as a loosely woven net. When nickel and water move into the gaps between those chains, they act like cinches, pulling everything tighter rather than loosening it. Most materials work in reverse, their internal structure loosening when water gets in. This one locks down.

A Biodegradable Plastic Alternative Built to Survive Water

When a freshly made film is first submerged, about 87% of the nickel washes out. Only a small fraction of what was originally added actually drives the strengthening effect. That released nickel is not discarded. The researchers built a zero-waste production cycle in which the wash water from one batch feeds directly into the next. As the paper noted, “the nickel content of a discarded AAA battery (2.2 g) would be sufficient to manufacture more than a dozen typical drinking cups (4.7 g each) using nickel-doped chitosan.”

The team molded the material into cups and containers and confirmed it holds water without leaking for at least a week. A film more than three square meters in area was produced without processing problems, suggesting the approach is not confined to laboratory scales. In a standard soil burial test, the material reached its half-life in about four months. Most conventional plastics take centuries under the same conditions.

Both chitosan and nickel have existing FDA-approved medical uses individually, though the combined material would require further safety evaluation before any medical applications move forward.

No new synthetic polymer chemistry was required here. Shrimp shells and a trace of a common metal, combined with a process inspired by how crabs build their exoskeletons, produced something rare in synthetic materials: a substance that performs better in water than in dry air. The researchers believe medical applications and waterproof coatings for other biodegradable materials are realistic next steps, with more complex shaping and large-scale manufacturing still to be worked out. For now, what exists is a proof of concept built from seafood scraps and a battery’s worth of nickel, and the early results are hard to ignore.

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Disclaimer: The information in this article is based on peer-reviewed research and is intended for general informational purposes. It does not constitute medical, environmental, or product safety advice. The material described is in early-stage development and has not been approved for consumer use.

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