Process‐Driven Microstructure Control in Melt‐Extrusion‐Based 3D Printing for Tailorable Mechanical Properties in a Polycaprolactone Filament

Abstract

3D printing techniques are utilized to produce biomaterial scaffolds with porous architectures that enable cell attachment, biological factors, and appropriate mechanical strength. As the basic building block of a scaffold, the individual filaments should have sufficient mechanical properties, comprising high compressive loading, and fracture resistance to mimic the natural tissue organisation. In this contribution, process–structure–property relationships in melt extruded polycaprolactone filaments are investigated by considering crystalline features, tensile properties, and an array of processing parameters. The tensile properties of the filaments are improved significantly with relatively higher screw rotational speed and relatively lower processing temperature resulting in considerable increase in Young's modulus. The favorable properties are attributed to the increased crystal volume fraction and anisotropy. Thus, this study provides initial pathways for the potential control of mechanical properties of bioscaffolds via engineering crystalline structural features in printed filaments.

The effect of 3D printing on the morphological and mechanical properties of polycaprolactone filament and scaffold

“…The present study examined the effect of printing parameters and process on the morphological and mechanical properties of tissue engineering scaffolds through considering the properties of their constituent filaments. Printing parameters had a significant effect on the filament and scaffold properties, which are in accordance with related studies …”

“…In other words, the time dependency of PCL filament elastic modulus may be due to the change of its crystallinity during the resting time because its crystal structure can be affected by the 3D printing process. In addition, the higher degree of crystallinity of PCL filament was reported to result in a higher elastic modulus, ie, increasing resting time may lead to higher crystallinity in the PCL filament and so its elastic modulus. Our findings are in good agreement with the previous results in which the printing process and parameters like rotational screw speed and temperature had a significant effect on the PCL filament elastic modulus.…”

“…Among different biomaterials, PCL has been used frequently in fabricating tissue engineering scaffolds because of its low melting point 60°C and considerable cell‐biomaterial interaction . However, the 3D printing process could affect the PCL filament molecular structure and so its material behavior . So, the PCL material behavior should be studied during the time of filament cooling and relaxing in the air after printing (resting time) and during the time of the remaining of PCL material in the metal syringe (remaining time) to be printed because thermal gradients may induce instability and degradation to the PCL material.…”

“…Microextrusion‐based FEM models of the scaffold can be made accurately using Computer‐Aided Design (CAD) approach. These CAD models consist of patterned filaments in a layer‐by‐layer fashion in which the morphological and mechanical characteristics of filament play an important role in the overall properties of scaffold . On the other hand, since the printing process and parameters can change the material behavior and morphology of filament, the effect of the printing process on the scaffold behavior can be simulated and estimated using FEM.…”

“…On the other hand, since the printing process and parameters can change the material behavior and morphology of filament, the effect of the printing process on the scaffold behavior can be simulated and estimated using FEM. Each microextruded filament with an approximately circular cross section and a specified diameter can be used to design the 3D filament geometry in CAD models. The filament diameter along with the elastic modulus are two important factors that have been shown to directly affect the scaffold properties, and they are exposed to variation during the 3D printing process.…”