Stronger when wet: Water-resistant chitinous objects via zero-waste coordination with metal ions

Abstract

Plastics have become integral to our society due to their durability and water stability, which is achieved through strong intermolecular interactions. However, these properties also make them persistent disruptors of ecological cycles, in contrast with biological structures, which work with their environments to achieve both excellent mechanical properties and ecological integration. This study takes inspiration from the arthropod cuticle to adapt Earth's second most abundant organic molecule for use in water. The process involves the vitrification of chitosan with small traces of nickel to create a dynamic network of intermolecular bonds using environmental water, resulting in a material that increases its strength to values well above commodity plastics when wet. The approach preserves the molecule's original chemistry and therefore its seamless integration into Earth's metabolism while avoiding the use of the strong organic solvents typically associated with biomolecules. The method demonstrates the potential for a paradigm shift in manufacturing, with zero waste production of both consumables and large objects that could meet the global demand for plastic.