Fused filament fabrication of polycaprolactone bioscaffolds: Influence of fabrication parameters and thermal environment on geometric fidelity and mechanical properties

Abstract

Polycaprolactone (PCL) is frequently used in the fabrication of porous scaffold architectures for tissue engineering applications. PCL's biocompatibility, bio-resorption profile and thermoplasticity make it an exceptionally versatile polymer for the fabrication of 3D printed lattice bioscaffold architectures. However, despite its ubiquitous use, optimal parameters for printing PCL lattice bioscaffolds have not been fully elucidated. In this study, fused filament fabrication (FFF) and a custom temperature-regulated enclosure were used to fabricate cubic PCL lattice porous solids. It was hypothesised that the cooling rate of the extruded scaffold material plays a key role in ensuring geometrical fidelity. Samples were fabricated at 3 different layer heights 0.12, 0.13 and 0.14 mm within two temperature regulated envelopes at 17.5 ± 1.5 °C for sample group ET17.5 °C and 27.5 ± 1.5 °C for sample group ET27.5 °C.Scaffold architectures fabricated within the 17.5 ± 1.5 °C envelope at the respective layer heights presented consistently less geometric deviation from the original CAD model than those scaffolds fabricated within a 27.5 ± 1.5 °C envelope. Echoed in the mechanical performance evaluation, the ET17.5 °C group performed with greater consistency and less deviation in Young's modulus and ultimate compressive strength. Samples from ET17.5 °C were also found to possess lower levels of crystallinity compared to ET27.5 °C which correlates with the extended cooling cycle within a 27.5 ± 1.5 °C envelope. Optical profilometry also revealed less undulation in the surface topography of polymer struts from ET17.5 °C when compared to ET27.5 °C. These results could assist tissue engineers in further optimising FFF of PCL bioscaffolds by reducing geometric variability between the design and fabrication of bioscaffold architectures; reducing the potential for inconsistent mechanical performance and improving yield rates as this technology transitions from prototyping to mass manufacturing environments.