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Exploiting the unique properties of three‐dimensional (3D) auxetic scaffolds in tissue engineering and regenerative medicine applications provides new impetus to these fields. Herein, the results on the fabrication and characterization of 3D auxetic scaffolds for tissue engineering applications are presented. The scaffolds are based on the well‐known re‐entrant hexagonal geometry (bowtie) and they are fabricated by multiphoton lithography using the organic−inorganic photopolymer SZ2080. In situ scanning electron microscopy–microindentations and nanoindention experiments are employed to characterize the photocurable resin SZ2080 and the scaffolds fabricated with it. Despite SZ2080 being a stiff material with a positive Poisson's ratio, the scaffolds exhibit a negative Poisson's ratio and high elasticity due to their architecture. Next, mouse fibroblasts are used to seed the scaffolds, showing that they can readily penetrate them and proliferate in them, adapting the scaffold shape to suit the cells' requirements. Moreover, the scaffold architecture provides the cells with a predilection to specific directions, an imperative parameter for regenerative medicine in many cell‐based applications. This research paves the way for the utility of 3D auxetic metamaterials as the next‐generation adaptable scaffolds for tissue engineering. [ABSTRACT FROM AUTHOR]

The need for control of the elastic properties of architected materials has been accentuated due to the advances in modelling and characterization. Among the plethora of unconventional mechanical responses, controlled anisotropy and auxeticity have been promulgated as a new avenue in bioengineering applications. This paper aims to delineate the mechanical performance of characteristic auxetic and anisotropic designs fabricated by multiphoton lithography. Through finite element analysis the distinct responses of representative topologies are conveyed. In addition, nanoindentation experiments observed in-situ through scanning electron microscopy enable the validation of the modeling and the observation of the anisotropic or auxetic phenomena. Our results herald how these categories of architected materials can be investigated at the microscale. [ABSTRACT FROM AUTHOR]

The article focuses on use a previously unexplored Bayesian optimization framework, "evolutionary Monte Carlo sampling," tosystematically design the arrangement of defects in an architected microlattice to maximize its strain energy density before undergoing catastrophic failure. Topics include the algorithm searches a design space with billions of 4 × 4 × 5 3D lattices, yet it finds the global optimum with only 250 cost function evaluations.