Design and characterization of 3D structures for biomedical applications

Abstract

The present thesis features three main targets, the fulfillment of whichmay contribute towards promoting the already gained knowledge in the field ofscaffold structures fabricated via 3D printing.The first target was the material property and structure integrityinvestigation in FDM 3D printing method using a non-destructive techniquepresented in Chapters 3 and 4. In brief, residual strains developed duringsolidification upon the completion of the 3D printing process were measured.This was made feasible by using FBG optical sensors which were embeddedinside 3D printed rectangular solid specimens. The experiments wereconducted in two different printers that both use the same material to allowcomparability of results The second target was the design and fabricationof scaffold structures via 3D printing (Chapter 5). Crucial parameters likeporosity percentage and pore size were taken under consideration. CADsoftware was used in order to come up with three different scaffold designs.Two of the proposed scaffold designs were based on designs alreadypresented in the literature that were, however, solely investigated for theirfluidic characteristics. In our case all scaffold designs were investigated from amechanical behavior characteristics point of view. The third scaffold designwas conceived in an attempt to come up with simpler geometries that exhibitbetter fluidic characteristics. The scaffold designs were forwarded to the 3Dprinter that fabricated the final scaffold specimens. Results from chapter 4were considered when planning the 3D printing.The third target was the scaffold structures’ mechanical testing in orderto come up with the design that would exhibit the finest mechanical behavior(Chapter 6). All scaffold specimens were subjected to compressive testing inorder to experimentally obtain their structural moduli and maximumcompressive strength. Two more scaffold specimen batches with differentporosities were fabricated in order to investigate the contribution of porositypercentage to the structures’ mechanical behavior. FEM studies were alsoconducted in order to predict experimental mechanical testing results (Chapter7). FEM studies were also utilized in investigating the mechanical response ofthe aforementioned scaffold structures assuming they were made out of thebiomaterial hydroxyapatite (HA). In addition, the shear mechanical behavior ofthe three scaffold designs was also investigated by employing FEM studies.The last chapters present in detail all issues, results and experimentaldetails. In the beginning of each chapter a small-scale introduction is given inan attempt to familiarize the reader with each process used alongside withconcluding paragraphs that serve as links to the next chapters. Allexperiments were performed at the Laboratory of Advanced ManufacturingTechniques & Testing of the Department of Industrial Management &Technology of University of Piraeus except from a part of the compressivetesting experiments that were conducted at the Laboratory for Testing andMaterials, Department of Mechanics at the School of Applied Mathematicaland Physical Science of National Technical University of Athens.