Regulating Growth of Strontium Carbonate in Self-Assembled Chiral Chitin Matrices with Robust Mechanical Properties

Abstract

The exoskeleton of arthropods exhibits a Bouligand structure, composed of a chitin matrix and calcium carbonate crystals, which confer exceptional mechanical properties. While many studies focus on the relationship between structure and performance, few investigate the mineral growth process within the Bouligand matrix. Here, chiral chitin films are prepared through evaporation-induced self-assembly of chitin nanowhiskers, and subsequently incubated in SrCO₃ mineralizing solution. Initially, precursors deposit on the film surface and transform into mineralized points, which then radially expand outward along the surface and propagate inward until coalescing into a continuous mineral layer. The growth rate of these mineralized points is significantly enhanced by increasing the reaction temperature; at 60 °C, the growth rate is 13 times faster (650.4 μm²/min) compared to that at 25 °C (49.7 μm²/min). Finally, SrCO₃/chitin composite bulks are fabricated by stacking and hot-pressing multiple mineralized chitin films, adhered using sodium alginate (SA) solution through spin coating. The resulting SrCO₃/chitin@SA composites exhibit a bending strength of 64.2 MPa, representing a 27% increase over pure chitin bulk and a 105% increase over pure SrCO₃ bulk. Our work provides a strategy for low-temperature fabrication of high-performance artificial composites.