Direct ink writing of bioactive PCL/laponite bone Implants: Engineering the interplay of design, process, structure, and function

Direct ink writing (DIW) is a room-temperature extrusion-based 3D printing technique that enables the fabrication of dense, customizable implants from viscous inks with precise spatial control. In this study, we present an engineering design framework for DIW-printed PCL/Laponite composites by tuning ink formulations and printing orientations to systematically investigate and control the complex interplay between shape fidelity, mechanical performance, and cellular response. Our findings show that printing at 0° orientation enhances filament-aligned surface topographies, which guide osteoblast attachment and significantly promote cell proliferation and mineralization. In contrast to previous studies using fused deposition modeling (FDM), we observe that printing at 90° orientation (perpendicular to the tensile load direction) results in higher mechanical performance due to improved filament bonding. Increasing Laponite loading (up to 30 ​%) improves shape retention by increasing ink viscosity, raises Young's modulus by up to 110 ​%, and enhances surface bioactivity by introducing hydrophilic and bioactive cues. This study provides a tunable strategy for engineering bioactive and surface-active implants for the clinical need for non-load-bearing orthopaedic applications where structural integrity, surface-mediated osteointegration, and customized geometry are clinically essential. • Ink tuning : Incorporation of Laponite enhanced viscosity, crystallinity, and mechanical stiffness, while simultaneously increasing osteoconductivity. • Reframing print orientation : Contrary to conventional FDM trends, 90° orientation (perpendicular to tensile load) enhanced tensile strength due to better filament bonding, while 0° preserved topographical features that guided osteoblast alignment and boosted mineralization. • New insights into post-printing deformation : Typically seen as undesirable, we show that post-printing deformation can improve interfacial bonding and mechanical performance. • 3D characterization and translational relevance : We employed comprehensive micro-CT imaging and SEM to evaluate structural fidelity linking it to cell responses.