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In tissue engineering, three-dimensional (3D) functional constructs (cellular or acellular) with tailored biological properties are needed to be able to mimic the hierarchical structure of biological tissues. Recent developments in extrusion based additive manufacturing considerably improved the ability to fabricate sophisticated tissue constructs by allowing to extrude multiple materials through different printing heads. This paper investigates the flow behavior of two miscible biomaterials inside an extrusion chamber incorporated with a Kenics static mixer (KSM). A computational fluid dynamics (CFD) model for isothermal non-Newtonian fluid flow was developed to numerically analyze the flow behavior of the fluids. The power-law model was used to characterize the shear-thinning behavior of the studied biomaterials. The mixing performance of designed chamber was also investigated by varying the inlet angles and velocities as well as the effect of the number of mixing units, pseudoplastic behavior of fluids, and pressure drop throughout the fluid domain. The results indicated that the inlet angle did not have a significant impact on the mixing quality and the proposed mixing channel showed good mixing performance regardless of the inlet velocities. The mixing index increases by increasing the power-law index and the shear-thinning behavior decreases the pressure drop value compared to Newtonian fluids., Journal of Additive Manufacturing Technologies, Vol. 1 No. 3 (2021): J AM Tech

Complex and hierarchically functionalised scaffolds composed of micro and nanoscale structures is a key goal in tissue engineering. The combination of 3D printing and electrospinning enables the fabrication of these multi-scale structures. This study presents a polycaprolactone 3D printed and electrospun scaffold with multiple mesh layers and fibre densities. The results show successful fabrication of a dual-scale scaffold with the 3D printed scaffold acting as a gap collector with the printed microfibres as the electrodes and the pores a series of insulating gaps resulting in aligned nanofibres. The electrospun fibres are highly aligned perpendicular to the direction of the printed fibre and form aligned meshes within the pores of the scaffold. Mechanical testing showed no significant difference between the number of mesh layers whilst the hydrophobicity of the scaffold increased with increasing fibre density. Biological results indicate that increasing the number of mesh layers improves cell proliferation, migration and adhesion. The aligned nanofibres within the microscale pores allowed enhanced cell bridging and cell alignment which was not observed in the 3D printed only scaffold. These results demonstrate a facile method of incorporating low-density and aligned fibres within a 3D printed scaffold and is a promising development in multi-scale hierarchical scaffolds where alignment of cells can be desirable.