Fabrication of multi-scale and tunable auxetic scaffolds for tissue engineering

Highlights: • Scaffolds with tunable auxetic properties were designed and fabricated using melt electro writing. • Both thick and thin fibers were printed using a same device but with different configurations. • Thick fibers were for auxetic properties while thin fibers were for promoting the cell growth. Melt electro writing (MEW) provides three-dimensional (3D) printing porous scaffolds with well-defined geometrical features of ultrafine fibers in the tissue engineering. Scaffolds with adjustable Poisson's ratio are more suitable in certain biological applications for mimicking the behavior of native tissue mechanics. However, it is still a challenging issue to tune the Poisson's ratio. In order to resolve this problem, a new method is proposed in the present study to design and fabricate tunable auxetic scaffolds through altering the printing configurations in the MEW. Patterns with thick fibers are designed using specific geometries and then these patterns are utilized to tune the Poisson's ratio based on the intended deformation mechanism. Moreover, the electrospun thin fibers are used to fill the unit cell of auxetic lattice structures for promoting the cell growth. Investigating the mechanical characteristics of the fabricated scaffolds demonstrates that the Poisson's ratio of the scaffold can be effectively tuned. Furthermore, cell sense and response to the fabricated scaffolds are studied. Obtained results indicate that the proposed approach can potentially be applied in a wide variety of biomedical applications.