Unravelling the Morphology-Function Relationships of Catshark Denticle Base Through Bio-Inspired 3D Printing and Mechanical Testing

Shark dermal denticles have been extensively investigated with respect to their morphology, elemental composition, and mechanical properties. Among these features, the denticle crown is recognized as the principal structure driving functional adaptations, such as drag reduction, anti-fouling, bioluminescence, and protection. However, research on the denticle base has generally been overlooked its morphology and the way it embeds within the skin remain insufficiently explored. In this study, we extracted the base of the longfin catshark (Apristurus herklotsi) from a 3D-reconstructed model to investigate the mechanical behavior of its root, which is characterized by asymmetrical branching. Symmetrical bases were also generated by assembling components from the original model to provide a comparative framework, thereby enabling verification of whether the natural asymmetry represents an optimized structural trait. For further investigation, denticle arrays based on the longfin catshark model were constructed with varying penetration levels, enabling observation of distinct mechanical behavior. Our samples were fabricated by a multi-material 3D printer, followed by pull-out tests on single denticle bases and compression tests on denticle arrays. This study deepens our understanding of the underexplored morphology–function relationships in shark denticle roots, offering insights that could exploit new micro-scale anchoring systems for biological tissues or underwater gripping devices.