Session: 07-04-01: Biomaterials and Tissue: Modelling, Fabrication and Characterization

Paper Number: 192762

Parametric Optimization of Polymer-Based Bone Scaffolds: A Comparative Micro-CT and Volumetric Deviation Analysis 

Healing of critical sized bone defects remains difficult for both clinicians and patients, mostly because autologous bone grafts are available only in limited quantities; consequently, structures providing mechanical support like synthetic scaffolds are needed and widely used in current clinical practice. Gyroid scaffolds, a class of Triply Periodic Minimal Surfaces (TPMS), are premier candidates as a bone scaffold due to their biomimetic porosity and mechanical efficiency. However, a significant reality gap exists between idealized computer-aided design (CAD) models and physical scaffolds fabricated via Fused Deposition Modeling (FDM). In FDM, geometric fidelity is often compromised by the physics of polymer extrusion, where thermal gradients and nozzle flow rate leads to deviations from the intended architecture. This study introduces a robust parametric optimization framework designed to quantify and bridge the discrepancy between nominal geometry and as-built morphology in Polylactic Acid (PLA) gyroid lattices.

Cubic PLA gyroid scaffolds with 15 mm edge having 0.4 volume fraction were fabricated under systematically varied parameter combinations, with layer height, print speed, and flow rate selected as the principal controllable factors due to their direct influence on filament deposition behavior, thermal history, and strut consolidation. To evaluate manufacturing fidelity at high resolution, the physical scaffolds were scanned via micro-computed tomography (micro-CT). The resulting data were segmented, reconstructed into 3D volumes, and imported into COMSOL Multiphysics to perform a comparative structural analysis between the "as-designed" CAD models and "as-manufactured" geometries. The proposed framework evaluates manufacturing quality across four complementary dimensions by quantifying volumetric fidelity to detect material excess or deficits, measuring surface morphology through roughness factors and irregularities, mapping pore connectivity to identify artifacts obstructing internal pathways, and assessing geometric accuracy via global dimensions and strut-level deviations from nominal values.

Statistical analysis (ANOVA) was used to isolate main effects and interaction effects among process parameters across those metrics, while also estimating process uncertainty and repeatability trends. While certain parameters improved volumetric conformity, they simultaneously compromised pore openness and effective surface area. Layer height and flow rate emerged as the primary drivers of volumetric and pore-related deviations, while print speed influenced deposition stability and feature resolution, emphasizing the need for multi-objective optimization rather than single-metric tuning. 

In particular, layer height and flow rate emerge as dominant contributors to volumetric and pore-related deviations, whereas print speed exhibits coupled effects through deposition stability and feature resolution. Beyond reporting correlations, this study provides a reproducible end-to-end workflow for micro-CT processing, registration, and statistical interpretation applicable to additively manufactured lattice systems. By providing evidence-based guidance for parameter selection, this methodology enhances the reproducibility of gyroid scaffolds, ensuring they meet the stringent structural requirements for functional bone tissue regeneration.

Presenting Author: Gullu Kızıltas Sendur Sabancı University

Presenting Author Biography: Gullu Kiziltas Sendur is a Professor of the Mechatronics Program at Sabanci University and an affiliated research faculty member of the Sabanci University Nanotechnology Research and Application Center. She received her Ph.D. degree in Mechanical Engineering from the University of Michigan, Ann Arbor in 2003 and worked as a Post Doctoral researcher at both the ElectroScience Laboratory at the Ohio State University and the University of Michigan until September 2005. She also coordinated with the Ceramic Research Group at the University of Michigan on the advanced fabrication of dielectric composites. Her main theme of research focuses on topology optimization, FEA modeling, design optimization and fabrication of complex engineering systems. Over the years, she developed new material designs based on numerical simulation schemes and advanced fabrication methods for tissue engineering, thermo-mechanical and electromagnetic applications. She has received the Young Scientist Award by the Turkish Academy of Sciences.

Authors:

Mervenaz Sahin TOBB University of Economics and Technology
Miray Yalcin Boğaziçi University
Demirhan Dumanli Sabancı University
Alper Gokalp Sabancı University
Gullu Kızıltas Sendur Sabancı University