From Nature’s Design to Heritage Preservation: Biomimetic Hydroxyapatite for Consolidating Waterlogged Archaeological Ivories

The Sanxingdui Site's waterlogged ivory tusks, a testament to ancient sacrificial practices and a biogenetic archive of the Chengdu Basin's paleo-environment, face collapse due to centuries of burial-induced degradation. Clay and moisture clogging microcracks weaken their structure, greatly increasing the challenge of effective consolidation. Inspired by bone's natural resilience, we developed a biomimetic, minimally invasive method to preserve these cultural treasures, using Sanxingdui waterlogged and deteriorated ivories as a model. Through detailed analysis, we identified barriers to consolidation and introduced calcium-based solutions─calcium acetate solution for deep, clay-rich fissures and calcium hydroxide nanoparticle suspension for larger cracks, combined with diammonium phosphate─to form a bone-like hydroxyapatite network in situ within cracks and fissures. This strengthens artifacts by 69.7% in hardness and 90.9% in elastic modulus, reduces water loss during dehydration from 31.3 ± 2.6% to 9.6 ± 0.7%, and ensures stability after 180 days of aging (25 ± 3 °C, 85 ± 5% RH). Our integrated approach to material design, synthesis, and evaluation not only sets a standard for conserving waterlogged heritage materials, such as bones, wood, and textiles, but also inspires innovative binding solutions for fields like adhesives and civil engineering. Blending materials science with archeology, this work safeguards humanity's shared history.