Bio-Inspired Topologically Constrained, Interlocking-like Cellulose Architectures via Sacrificial Oligomer Templating

Overcoming the inherent strength-toughness trade-off remains a persistent challenge for bioinspired structural materials. Here we develop a high-performance topologically interlocking-like cellulose (TICell) via sacrificial oligomer templating followed by post-cross-linking. Calcium phosphate oligomeric clusters (CPOs) are introduced as transient inorganic templates to confine space within a regenerated cellulose network. Subsequent citric-acid treatment removes the templates while simultaneously covalently cross-linking cellulose, effectively "locking in" a topologically constrained architecture after demineralization. Multiscale characterization shows that the cellulose crystalline framework is largely retained, yet the nanoscale organization reorganizes qualitatively into a continuous, percolated network composed of puzzle-like interlocking modules. This interlocked topology reshapes damage evolution: catastrophic crack run-away is suppressed and energy is dissipated progressively through crack deflection and stepwise advance. As a result, TICell exhibits a strength of 226 MPa and a fracture toughness of 7.0 kJ m^-2, representing several-fold improvements over biological materials and conventional polymers. These findings suggest a sustainable route to damage-tolerant, biobased structural materials in which mechanical performance is governed primarily by topology, rather than by crystallinity or composition alone.