Researchers from the University of Portsmouth, University of Greenwich, and City St. George’s University of London have successfully 3D printed nacre-inspired composites using a multi-material inkjet-based 3D printing process that integrates hard and soft polymers with precise architectural control. Published in Scientific Reports in February 2025, the study investigates how material interface quality and print orientation affect mechanical performance in bioinspired composites modeled after nacre, or mother-of-pearl.
The team used a generative design workflow to replicate nacre’s characteristic brick-and-mortar architecture, alternating hexagonal platelets of stiff polymer with a compliant soft phase. By varying platelet aspect ratios and print orientation, they demonstrated how interfaces parallel or perpendicular to the build plane influence fracture mechanisms such as pull-out, crack deflection, and brittle fracture. These results provide new insight into how printed interface geometry can replicate toughening mechanisms observed in biological composites.
Multi-material biomimicry by design
Using Grasshopper and Rhino, the researchers created parametric models of nacre-like composites with platelet aspect ratios from 2 to 9. These models were printed using a ProJet 5500X 3D inkjet 3D printer, depositing hard white (VisiJet CR-WT) and soft black (VisiJet CE-BK) photopolymers in a single build. The composites were printed in both in-plane (XY) and out-of-plane (XZ) orientations, enabling the team to evaluate how interfacial orientation relative to the print direction affects mechanical behavior
Each sample included a 300 μm soft interlayer, with platelet dimensions controlled to produce reinforcement volume fractions ranging from ~53% to 65%. All builds used a 13 μm layer thickness and high-resolution print settings (750 × 750 × 2000 DPI), ensuring dimensional accuracy.
Interface direction governs mechanical behavior
Tensile testing showed that out-of-plane printed composites exhibited higher stiffness and strength across reinforcement volume fractions than in-plane counterparts. The improvement is attributed to stronger interfacial bonding in the vertical (XZ) direction, where soft and hard phases are deposited together during each layer’s formation. This enhanced shear stress transfer supports brittle failure through the platelets rather than delamination.
By contrast, in-plane printed composites exhibited platelet pull-out and crack deflection, consistent with nacre-like energy-dissipation mechanisms. However, their impact strength was generally lower, except for samples with small platelet sizes, suggesting weaker interfaces due to layer-by-layer bonding being confined to the horizontal (XY) plane.
In situ X-ray computed tomography (XCT) was used to visualize internal damage. XCT confirmed that out-of-plane composites restricted crack opening, while in-plane samples showed more severe delamination and crack propagation under mechanical load.
Implications for tough, functional bioinspired materials
This study shows that printing orientation alone can shift nacre-inspired composites between ductile and brittle mechanical behavior. The findings reinforce the role of interface directionality in controlling mechanical performance, an aspect often overlooked in prior nacre-mimetic additive manufacturing studies.
The approach also validates generative design workflows combined with multi-material 3D printing as a viable method to replicate nacre-like architectures with customizable mechanical properties. The authors note that future designs could explore more complex interfacial motifs, such as mineral bridges or dovetail joints, to further enhance mechanical response.
With potential applications in impact-resistant systems, protective structures, and functionally graded components, this research demonstrates a scalable method for translating biological composite strategies into digitally manufactured engineering materials.
Programmable architectures mimic natural toughness in additive manufacturing
The work follows a growing body of research into how biological principles can inform mechanical design in additive manufacturing. Recent studies have shown that introducing controlled disorder into metamaterial lattices can enhance impact resistance, while under-extrusion in FDM has been explored as a way to emulate joint flexibility in bioinspired robotics. Other approaches, such as ultra-stiff lattice structures for safety and construction, highlight the importance of microstructural control in tuning energy absorption and failure behavior.
By integrating generative design, multi-material printing, and a nacre-like architecture, the present study extends these efforts, offering a digitally programmable route to hierarchical, toughened composites inspired by natural armor systems.
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Featured image shows the evolution of the cracks over a hybrid nacre structure. Image via Curto et al., Scientific Reports
