<p>The overarching goal of this research work is to fabricate biocompatible and biodegradable porous bone scaffolds, designed to incorporate autologous human bone marrow mesenchymal stem cells, for the treatment of large osseous fractures. In pursuit of this goal, the objective is to investigate the compressive properties of triply periodic minimal surface (TPMS) bone scaffolds, composed of Polycaprolactone (PCL) and fabricated using pneumatic micro-extrusion (PME) additive manufacturing process. PME is a high-resolution direct-write method, which has been widely utilized for the fabrication of biological tissues, structures, and organs. It has a layer resolution as well as positioning precision of 100 μm and 10 µm, respectively. In addition, the PME process allows for non-contact, multi-material deposition of a wide range of functional bioinks for tissue engineering applications. However, the PME process is inherently complex (highly nonlinear), governed by complex multi-physics phenomena (e.g., phase-change, coalescence, receding-relaxation, and wetting equilibrium). The PME complexity, in addition, stems from the presence of a broad spectrum of process parameters – e.g., photo-polymerization light intensity, material viscosity, flow pressure, material deposition temperature, and solidification rate – as well as material-process interactions. Consequently, investigation of the effects of significant process parameters and their interactions on scaffold functional properties would be inevitable. Although the PME process has been utilized in various applications, a review of literature reveals that the influence of PME process parameters on the mechanical properties of PCL-based TPMS scaffolds has not been rigorously explored. This gap is addressed in this work.</p><p>In the PME process, a high-pressure flow (typically, compressed air) is injected into a barrel (also known as cartridge), which contains a polymer material, leading to pressure-driven material deposition on a surface with the aid of a converging micro-capillary nozzle. In this study, PCL powder was loaded into the cartridge, maintained at 180 °C. To ensure steady-state and uniform material deposition, the loaded PCL was kept in the heated barrel for 15 minutes prior to deposition. Supplied by an oilless, rust-free air compressor, the flow pressure was set to 300 kPa. Laminar molten PCL flow was deposited on a glass surface (uniformly kept at 10 °C) with a print speed of 2 mm/s, using a 200 μm nozzle. Having a porosity of 60%, the following TPMS scaffolds were characterized in this study: (i) Schwarz-Gyroid, (ii) Schwarz-Diamond, (iii) Schwarz-Primitive, (iv) Neovius, and (v) Schoen I-WP. Furthermore, the scaffolds were fabricated using a layer height and line width of 200 μm. Finally, the compressive properties of the fabricated bone scaffolds were measured using a compression testing machine. The results of this study pave the way for optimal fabrication of complex biocompatible scaffolds for the treatment of bone fractures and defects.</p>

Characterization of the Compressive Properties of Triply Periodic Minimal Surface PCL Scaffolds for Bone Tissue Engineering

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.