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Additive Manufacturing of Porous Titanium for Orthopedic Applications
Additive Manufacturing of Porous Titanium for Orthopedic Applications
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20260202104842
- ISBN
- 9798291584798
- DDC
- 620.11
- 서명/저자
- Additive Manufacturing of Porous Titanium for Orthopedic Applications
- 발행사항
- [Sl] : Northwestern University, 2025
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2025
- 형태사항
- 156 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 87-03, Section: B.
- 주기사항
- Advisor: Dunand, David C.
- 학위논문주기
- Thesis (Ph.D.)--Northwestern University, 2025.
- 초록/해제
- 요약Porous Ti addresses the longstanding orthopedic challenges of aseptic loosening and stress shielding by reducing the stiffness of the Ti and enabling additional locations for bone anchoring. This dissertation investigates the mechanical properties and microstructure of porous titanium with the combination of additive manufacturing and spaceholders, unlike previous work which focused on manufacturing titanium exclusively through powder metallurgy or spaceholders. I am to verify that the spaceholder approach may be used with additive manufacturing effectively to create complex geometries with microporosity tailorable with the spaceholder. I investigate the (i) processing, (ii) microstructure after spaceholder removal, and (iii) mechanical characteristics of the porous scaffolds.To begin, I manufacture hierarchically porous, low stiffness, ductile Ti scaffolds via direct-ink write (DIW) extrusion and sintering of inks containing Ti and NaCl particles. Scaffold macrochannels were filled with a subtherapeutic dose of recombinant bone morphogenetic protein-2 (rhBMP-2) alone or co-delivered within a bioactive supramolecular polymer slurry (SPS) composed of peptide amphiphile nanofibrils and collagen, creating four treatment conditions (Ti struts: microporous vs. fully dense; BMP-2 alone or with SPS). The BMP-2-loaded scaffolds were implanted bilaterally across the L4 and L5 transverse processes in a rat posterolateral lumbar fusion model. In-vivo bone growth in these scaffolds is evaluated with synchrotron X-ray computed microtomography (μCT) to study the effects of strut microporosity and added biological signaling agents on the bone formation response. Optical and scanning electron microscopy confirms the ~100μm space-holder micropore size, high-curvature morphology, and pore fenestrations within the struts. Uniaxial compression testing shows that the microporous strut scaffolds have low stiffness and high ductility. A significant promotion in bone formation was observed for groups utilizing the SPS, while no significant differences were found for the scaffolds with the incorporation of micropores.Subsequently, filaments - alone or stacked into scaffolds - are additively manufactured via direct-ink writing (DIW) from titanium powders and steel spaceholder fibers. After titanium sintering, the steel fibers are chemically dissolved, generating meso-channels with ~200 μm diameter and 10-20 aspect ratios. The macro- and meso-level porosity in these scaffolds is desirable for reduced stiffness and high osseointegration for orthopedic implants. First, the millimeter-wide macro-channels between the printed struts of the scaffold allow for nutrient transport and vasculature/bone growth; second, dissolution of the steel spaceholders creates a network of meso-channels within the struts of the scaffold that can promote cell movement and anchoring. Synchrotron microtomography (μCT), performed at the green-body, sintered, and dissolved stages on the same specimen, reveals the evolution of porosity during these processing steps. Optical and scanning electron microscopy, before and after steel chemical dissolution, confirms the meso-channel size, orientation, and fenestrations within the struts. Finite element modelling, informed by hardness and energy dispersive spectroscopy, predicts the mechanical properties of a representative lattice junction under various compositions and meso-channel orientations, including with infiltrated bone.Finally, I use CaCl2 powder integrated in titanium for two purposes, (i) as a chemically inert pore-former (spaceholder) during laser powder-bed fusion (L-PBF) additive manufacturing and (ii) as an anticipated osteogenic enhancer in the resulting Ti-CaCl2 composite. During L-PBF of powder blends, both Ti and CaCl2 are melted, creating elongated CaCl2 inclusions in Ti upon solidification, enabled by the immiscibility of the two liquid phases and, after solidification, the two solid phases. After subsequent CaCl2 dissolution in water, interconnected porosity is formed in the metallic matrix, either in bulk specimens or within struts of microlattices. As laser energy density decreases more CaCl2 is trapped in Ti, creating less elongated, more homogenous porosity from smaller meltpools during manufacturing. Micro-computed tomography shows that most porosity is attributable to the CaCl2 spaceholder after its removal, but additional porosity is also generated from the L-PBF process via vaporization of the CaCl2. Uniaxial compression testing illustrates that lower overall porosity produces higher elastic modulus and yield strength specimens.Future work includes L-PBF-processed osteogenic spaceholders combined with bioactive polymers to enable the development of increasingly more biocompatible scaffolds. Another proposed direction is coaxial spaceholder-based DIW that would produce a higher degree of porosity continuity in scaffolds than is currently available, boosting the extent of osseointegration for such an additively-manufactured implant material. Finally, a new field of semi-permanent implants is proposed in the field of additively manufactured aluminum alloys, which uses controlled gallium intergranular corrosion.
- 일반주제명
- Materials science
- 일반주제명
- Industrial engineering
- 일반주제명
- Polymer chemistry
- 키워드
- Osseointegration
- 키워드
- Titanium
- 기타저자
- Northwestern University Materials Science and Engineering
- 기본자료저록
- Dissertations Abstracts International. 87-03B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
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■00520260202104842
■006m o d
■007cr#unu||||||||
■020 ▼a9798291584798
■035 ▼a(MiAaPQ)AAI32173102
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a620.11
■1001 ▼aPatrick Misiaszek, John.▼0(orcid)0000-0002-5478-9292
■24510▼aAdditive Manufacturing of Porous Titanium for Orthopedic Applications
■260 ▼a[Sl]▼bNorthwestern University▼c2025
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2025
■300 ▼a156 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 87-03, Section: B.
■500 ▼aAdvisor: Dunand, David C.
■5021 ▼aThesis (Ph.D.)--Northwestern University, 2025.
■520 ▼aPorous Ti addresses the longstanding orthopedic challenges of aseptic loosening and stress shielding by reducing the stiffness of the Ti and enabling additional locations for bone anchoring. This dissertation investigates the mechanical properties and microstructure of porous titanium with the combination of additive manufacturing and spaceholders, unlike previous work which focused on manufacturing titanium exclusively through powder metallurgy or spaceholders. I am to verify that the spaceholder approach may be used with additive manufacturing effectively to create complex geometries with microporosity tailorable with the spaceholder. I investigate the (i) processing, (ii) microstructure after spaceholder removal, and (iii) mechanical characteristics of the porous scaffolds.To begin, I manufacture hierarchically porous, low stiffness, ductile Ti scaffolds via direct-ink write (DIW) extrusion and sintering of inks containing Ti and NaCl particles. Scaffold macrochannels were filled with a subtherapeutic dose of recombinant bone morphogenetic protein-2 (rhBMP-2) alone or co-delivered within a bioactive supramolecular polymer slurry (SPS) composed of peptide amphiphile nanofibrils and collagen, creating four treatment conditions (Ti struts: microporous vs. fully dense; BMP-2 alone or with SPS). The BMP-2-loaded scaffolds were implanted bilaterally across the L4 and L5 transverse processes in a rat posterolateral lumbar fusion model. In-vivo bone growth in these scaffolds is evaluated with synchrotron X-ray computed microtomography (μCT) to study the effects of strut microporosity and added biological signaling agents on the bone formation response. Optical and scanning electron microscopy confirms the ~100μm space-holder micropore size, high-curvature morphology, and pore fenestrations within the struts. Uniaxial compression testing shows that the microporous strut scaffolds have low stiffness and high ductility. A significant promotion in bone formation was observed for groups utilizing the SPS, while no significant differences were found for the scaffolds with the incorporation of micropores.Subsequently, filaments - alone or stacked into scaffolds - are additively manufactured via direct-ink writing (DIW) from titanium powders and steel spaceholder fibers. After titanium sintering, the steel fibers are chemically dissolved, generating meso-channels with ~200 μm diameter and 10-20 aspect ratios. The macro- and meso-level porosity in these scaffolds is desirable for reduced stiffness and high osseointegration for orthopedic implants. First, the millimeter-wide macro-channels between the printed struts of the scaffold allow for nutrient transport and vasculature/bone growth; second, dissolution of the steel spaceholders creates a network of meso-channels within the struts of the scaffold that can promote cell movement and anchoring. Synchrotron microtomography (μCT), performed at the green-body, sintered, and dissolved stages on the same specimen, reveals the evolution of porosity during these processing steps. Optical and scanning electron microscopy, before and after steel chemical dissolution, confirms the meso-channel size, orientation, and fenestrations within the struts. Finite element modelling, informed by hardness and energy dispersive spectroscopy, predicts the mechanical properties of a representative lattice junction under various compositions and meso-channel orientations, including with infiltrated bone.Finally, I use CaCl2 powder integrated in titanium for two purposes, (i) as a chemically inert pore-former (spaceholder) during laser powder-bed fusion (L-PBF) additive manufacturing and (ii) as an anticipated osteogenic enhancer in the resulting Ti-CaCl2 composite. During L-PBF of powder blends, both Ti and CaCl2 are melted, creating elongated CaCl2 inclusions in Ti upon solidification, enabled by the immiscibility of the two liquid phases and, after solidification, the two solid phases. After subsequent CaCl2 dissolution in water, interconnected porosity is formed in the metallic matrix, either in bulk specimens or within struts of microlattices. As laser energy density decreases more CaCl2 is trapped in Ti, creating less elongated, more homogenous porosity from smaller meltpools during manufacturing. Micro-computed tomography shows that most porosity is attributable to the CaCl2 spaceholder after its removal, but additional porosity is also generated from the L-PBF process via vaporization of the CaCl2. Uniaxial compression testing illustrates that lower overall porosity produces higher elastic modulus and yield strength specimens.Future work includes L-PBF-processed osteogenic spaceholders combined with bioactive polymers to enable the development of increasingly more biocompatible scaffolds. Another proposed direction is coaxial spaceholder-based DIW that would produce a higher degree of porosity continuity in scaffolds than is currently available, boosting the extent of osseointegration for such an additively-manufactured implant material. Finally, a new field of semi-permanent implants is proposed in the field of additively manufactured aluminum alloys, which uses controlled gallium intergranular corrosion.
■590 ▼aSchool code: 0163.
■650 4▼aMaterials science
■650 4▼aIndustrial engineering
■650 4▼aPolymer chemistry
■653 ▼aAdditive manufacturing
■653 ▼aBioactive polymers
■653 ▼aDirect-ink extrusion
■653 ▼aOsseointegration
■653 ▼aTitanium
■690 ▼a0794
■690 ▼a0546
■690 ▼a0495
■71020▼aNorthwestern University▼bMaterials Science and Engineering.
■7730 ▼tDissertations Abstracts International▼g87-03B.
■790 ▼a0163
■791 ▼aPh.D.
■792 ▼a2025
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17359153▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
