Computer modelling and simulation of a novel printing head for complex tissue engineering constructs

Gokhan Ates,G Mansour,P Kyratsis,D Tzetzis

doi:10.1051/matecconf/202031801045

Abstract

In tissue engineering, three-dimensional functional scaffolds with tailored biological properties are needed to be able to mimic the hierarchical structure of biological tissues. Recent developments in additive biomanufacturing allow to extrude multiple materials enabling the fabrication of more sophisticated tissue constructs. These multi-material biomanufacturing systems comprise multiple printing heads through which individual materials are sequentially printed. Nevertheless, as more printing heads are added the fabrication process significantly decreases, since it requires mechanical switching among the physically separated printheads to enable printing multiple materials. In addition, this approach is not able to create biomimetic tissue constructs with property gradients. To address these limitations, this paper presents a novel static mixing extrusion printing head to enable the fabrication of multi-material, functionally graded structures using a single nozzle. Computational fluid dynamics (CFD) was used to numerically analyze the influence of Reynolds number on the flow pattern of biomaterials and mixing efficiency considering different miscible materials.

Highlights

Natural tissues are complex structures composed of a hierarchical multi-functional and multi-material extracellular matrix and cells
Velocity boundary condition was employed for mixer inlets and the velocities are fixed for each fluids corresponding to the Reynolds number ranging from 10 to 2000
The influence of Reynolds number on the mass fraction distribution of both the gelatin and alginate was evaluated by plotting mass fraction contours at successive cross-sectional planes across the mixing zone

Summary

Introduction

Natural tissues are complex structures composed of a hierarchical multi-functional and multi-material extracellular matrix and cells. Biomanufacturing, the combined use of additive manufacturing (3D Printing), biocompatible and biodegradable materials, cells and biomolecular signals (growth factors), emerged as a suitable approach to create tissue constructs [1]. In the case of a cell-laden approach, additive manufacturing is used to print bioinks (hydrogels containing cells and growth factors) allowing the fabrication of soft tissues [2]. A wide range of printing heads (e.g. screw, pressure, or pneumatic-assisted) are being used allowing to process a wide range of materials but limited to the fabrication of single-material scaffolds or cell-laden constructs. Co-axial printing heads have been developed enabling the fabrication of core-shell or hollow fibres None of these systems are able to create functionally graded structures enabling the fabrication of structures based on a specific number of materials but with gradients of properties in a tailored way. CFD analysis was used to evaluated critical parameters such as mixing index, pressure drop and velocity

Static mixer printing head and simulation conditions

Governing equations

Boundary conditions

Mixing index

Results and Discussion

Conclusion