Lace 3D printing for deployable mechanical metamaterials

‘A single thread cannot be spun into a cord, and a single tree cannot create a forest’ – an ancient Chinese proverb highlighting the necessity of collective integration. This proverb captures the essence of fused deposition modeling (FDM) 3D printing, where multiple filaments merge into a solid structure. Diverging from this approach, we introduce lace 3D printing – an FDM-based approach that embodies the concept of ‘a single thread forming a cord, a single tree becoming a forest’. Using a continuous zig-zag filament path with tunable geometry, this approach enables direct and efficient fabrication of millimeter-scale deployable metamaterials that transform from a compact to a mechanically stable cellular state under uniaxial tension. Plastic hinge formation under uniaxial stretching drives structural deployment. We investigate how printing parameters and geometries affect fabrication quality, deployment behaviours, and mechanical responses, and develop a theoretical model to predict nonlinear deformation. Introducing spatial gradients enables programmable morphing, suggesting applications in aerospace engineering and biomedical devices. Finally, the mechanical performance of the deployed metamaterials is evaluated under various loading conditions, including compression, cyclic loading, bending, and impact, highlighting their potential as cellular materials for load-bearing and energy-absorbing applications.