Date of Award

4-2016

Degree Name

Doctor of Philosophy

Department

Chemical and Paper Engineering

First Advisor

Dr. Alexandra Pekarovicova

Second Advisor

Dr. Paul Dan Fleming

Third Advisor

Dr. Pavel Ikonomov

Keywords

3D printing, bone structure, Fused Deposition Modeling (FDM), selective laser sintering, stereolithography, polyjet technology

Abstract

Three-dimensional (3D) printing is an advanced rapid technology that can be used to make human bone substitutes with exact shape and designed structures, based on models created from actual individual bone medical Digital Imaging and Communications in Medicine (DICOM) images. Biocompatible polymers have been selected for 3D printing of human bone structures. The thermoplastics were 3D printed with Fused Deposition Modeling (FDM) are Acrylate Butadiene Styrene (ABS), Polylactic Acid (PLA) and ULTEM 9085 (a polyetherimide). The polyamide PA 2200 was 3D printed using Selective Laser Sintering (SLS). Digital ABS (a crosslinked acrylic polymer) was 3D printed using PolyJet Technology. These 3D printing technologies allow precision manufacturing of bone structures for replacement of the missing/broken parts created from actual Magnetic Resonance Imaging (MRI) or Computed Tomography (CT) scan DICOM images. Differential Scanning Calorimetry (DSC) was used to acquire the thermal analysis profiles of these polymers. The thermal analysis results indicate that ABS and ULTEM9085 are amorphous, PLA is partially crystalline, and PA2200 is completely crystalline. To use these materials as a bone replacement, thorough mechanical property testing was performed to evaluate if the 3D printed bone replacement structures can sustain the same loads that human bones experience.

Furthermore, it is important to create bone structures that can accurately mimic the real human bone structures with a solid outer shell that represents the cortical (compact) bone and porous internal volume that represents the trabecular (spongy) bone. Designing of the proper trabecular bone is one of the most critical steps, because its structure helps support the entire bone, while at the same time keeps the weight low. Due to the low resolution of the DICOM images, the trabecular bone structure cannot be obtained directly from CT and MRI scans.

Therefore, CAD software SolidWorks was used to design special 3D honeycomb structures (hexagonal, triangular, and square). The honeycomb structures are widely used in industry and aerospace applications, because they provide high strength, while reducing the weight, cost, and density.

3D printed samples were designed and produced to test the structure properties with different geometric shapes. Structure property tests, such as: tensile strength test, compressive strength test, and bending test were investigated. We found that the mechanical properties of the designed thermoplastic structures either exceed or fall within the range of the mechanical properties of the human trabecular bones. Therefore, they can be successfully applied for bone structure replacements.

Access Setting

Dissertation-Open Access

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