Decoupling mechanical and morphometric properties in meta-biomaterials

Abstract

Meta-biomaterials are engineered biomaterials with unprecedented properties derived from their designed microscale structure, positioning them as promising candidates for developing medical devices (e.g., meta-implants). A significant challenge in developing meta-biomaterials lies in effectively decoupling their intrinsically intertwined mechanical properties (e.g., elastic and shear moduli, Poisson’s ratio) and morphometric properties (e.g., porosity, connectivity, surface area). To address this challenge, we introduced non-stochastic unit cells featuring cubic and isotropic properties with three orthotropic planes of symmetry. We explicitly derived the geometrical relationships necessary to explore our design spaces, and calculated the morphometric properties (e.g., pore sizes). We employed a numerical homogenization method based on a 3D voxelization approach to model the unit cells of the meta-biomaterials within our design space, representing the empty and solid phases in a binary format. Through an extensive number of simulations (i.e., 43,000) and a multi-objective optimization technique, we successfully isolated the Poisson’s ratio while maintaining other mechanical properties (i.e., effective elastic and shear moduli, and anisotropy level), morphological properties (i.e., relative mass density, pore size, tortuosity, surface/volume ratio and connectivity) and mass transport parameters (i.e., permeability) as constant as possible, with an average deviation below 9%. The resulting meta-biomaterials were additively manufactured using PolyJet 3D printing and two-photon polymerization techniques, respectively at the macro- and microscales. Mechanical testing was conducted on these fabricated meta-biomaterials to validate the predictions of our computational models. The established computational model and fabricated meta-biomaterials provide promising avenues for advancing tissue engineering and facilitating studies in cell mechanobiology, enabling precise exploration of the isolated effects of mechanical and morphometric properties.