NANOTEXTURED TITANIUM SURFACES FOR IMPLANTS: MANUFACTURING AND PACKAGING ASPECTS

It has been shown that nanotexturing the surface of otherwise smooth titanium orthopedic materials increases osteoblast proliferation in vitro, and the bone-implant contact area and pullout force in vivo. However, this prior work has not focused on the requirements for scale-up to industrial processes. This dissertation reports on titanium surface modifications by electrochemical anodization using a benign NH4F electrolyte, and a hybrid electrolyte also containing AgF, rather than hazardous hydrofluoric acid used elsewhere. Nanotube fabrication of Ti6Al4V foils, rods, thermal plasma sprayed commercial implants, and laser and e-beam melted powder materials was demonstrated. It was found that the nanotextured morphology depends on electrolyte composition, and dimensional variation depends on anodization conditions using different NH4F and ethylene glycol electrolytes. The fluorine concentration was found to be the most influential factor affecting formation of porous nanostructures. Recognizing the importance of packaged implant storage, the wetting behavior of nanotube surfaces was investigated. It was found that increased surface hydrophobicity due to aging in air can be restored by annealing, and the release of residual fluorine from the surface was measured. The kinetics of the amorphous to crystalline anatase transformation of nanotubes was quantified with isochronal and isothermal experiments by X-ray diffraction and transmission electron microscopy. The anatase phase transformation of TiO2 nanotubes was achieved in as little as 5 minutes at 350C, in contrast to reports of higher temperature and for hours. The fluorine consumed by the formation of the nanotubes during anodization was analyzed and sources of fluorine consumption were identified. Fluorine from the electrolyte is removed and retained in the nanotubes and by the metal removed to form the nanotubes. A metric describing the fluorine removed from the electrolyte per anodized area was developed to help quality control in manufacturing scale-up. A single-step anodization with controlled nanosilver deposition within and among the nanotubes, using a new hybrid electrolyte of NH4F and AgF was demonstrated. Successful fabrication of potentially antibacterial nanotubes on foils, rods and thermal plasma sprayed surfaces was demonstrated and nanosilver concentration was quantified. These new understandings led to improved manufacturing and storage technologies needed for regulatory approvals of nanotextured titanium surfaces for better orthopedic implants

Machine Learning Based Fluid-Transportation Monitoring and Controlling

The discipline of fluid mechanics is developing quickly, propelled by previously unheard-of data volumes from experiments, field measurements, and expansive simulations at various spatiotemporal scales. The field of machine learning (ML) provides a plethora of methods for gleaning insights from data that can be used to inform our understanding of the fluid dynamics at play. As an added bonus, ML algorithms can be used to automate duties associated with flow control and optimization, while also enhancing domain expertise. This article provides a review of the background, current state, and potential future applications of ML in fluid mechanics. We provide an introduction to the most fundamental ML approaches and describe their applications to the study, modelling, optimization, and management of fluid flows. From the standpoint of scientific inquiry, which treats data as an integral aspect of modelling, experiments, and simulations, the benefits and drawbacks of these approaches are discussed. Since ML provides a robust information-processing framework, it can supplement and potentially revolutionize conventional approaches to fluid mechanics study and industrial applications. &nbsp

Rapid heat treatment for anatase conversion of titania nanotube orthopedic surfaces

© 2017 IOP Publishing Ltd. The amorphous to anatase transformation of anodized nanotubular titania surfaces has been studied by x-ray diffraction and transmission electron microscopy (TEM). A more rapid heat treatment for conversion of amorphous to crystalline anatase favorable for orthopedic implant applications was demonstrated. Nanotube titania surfaces were fabricated by electrochemical anodization of Ti6Al4V in an electrolyte containing 0.2 wt% NH4F, 60% ethylene glycol and 40% deionized water. The resulting surfaces were systematically heat treated in air with isochronal and isothermal experiments to study the temperature and time dependent transformation respectively. Energy dispersive spectroscopy shows that the anatase phase transformation of TiO2 in the as-anodized amorphous nanotube layer can be achieved in as little as 5 min at 350 C in contrast to reports of higher temperature and much longer time. Crystallinity analysis at different temperatures and times yield transformation rate coefficients and activation energy for crystalline anatase coalescence. TEM confirms the (101) TiO2 presence within the nanotubes. These results confirm that for applications where amorphous titania nanotube surfaces are converted to crystalline anatase, a 5 min production flow-through heating process could be used instead of a 3 h batch process, reducing time, cost, and complexity

Wetting Behavior and Chemistry of Titanium Nanotubular Orthopedic Surfaces: Effect of Aging and Thermal Annealing

© 2017, Springer International Publishing Switzerland. In the present work, we investigate wetting behavior and chemical composition of anodized titanium nanotubular surfaces for orthopedic implant research. The wetting behavior of the nanotubes by alternating UV irradiation and dark storage is reported. This study suggests that hydrophobicity due to aging in air can be restored by annealing, and release of residual fluorine was observed as a function of annealing time, which is important considering side effects of fluorosis. Fabrication of nanotubes on thermal plasma-sprayed implants and super-hydrophilic behavior of these nanotubular surfaces needed for enhanced bioactivity are demonstrated

Facile Synthesis of Nanosilver-Incorporated Titanium Nanotube for Antibacterial Surfaces

© 2017, Springer International Publishing AG. The battle against postoperative infection in orthopedic surgery calls for the development of surfaces with antibacterial activity on the implant side of the bacterial biofilm. Incorporation of nanosilver into titanium nanotube surfaces offers a potential solution. This study presents a novel single-step anodization approach to incorporating nanosilver particles within and among anodized titanium nanotubes on implant surfaces using a new hybrid electrolyte. The amount of nanosilver deposited on the titanium nanotubes was analyzed by varying the silver concentration in the hybrid electrolyte. Successful fabrication of titanium nanotubes by anodization of foils, rods and thermal plasma-sprayed surfaces of Ti6Al4V, and simultaneous nanosilver deposition was quantified by field emission scanning electron microscopy, transmission electron microscopy and X-ray energy-dispersive spectroscopy. Upon post-anodization heat treatment, the amorphous to anatase conversion of these structures was confirmed using X-ray diffraction analysis. This study presents a simple single-step fabrication of antibacterial titanium nanotube surfaces allowing controlled nanosilver deposition needed to avoid unintended cytotoxicity

Enhancing Osseointegration of Orthopaedic Implants with Titania Nanotube Surfaces

Category: Basic Sciences/Biologics Introduction/Purpose: Solid biologic fixation at the bone-implant interface provides long-term stability of orthopaedic implants. Historically, coatings and surface treatments on implant surfaces have been used to promote osseointegration of orthopaedic implants. The purpose of this research study is to evaluate two morphologies of titania nanotube (TiNT) surfaces via in vitro experiments as well as an in vivo model of femoral intramedullary fixation, in order to assess the influence of TiNT structure on de novo bone formation and bone-implant stability. Methods: TiNT structures were grown from Ti-6Al-4 V materials via an established electrochemical anodization process. Samples were either sonicated then annealed (Aligned TiNT) or annealed without prior sonication (Trabecular TiNT), to produce different morphologies. As-received titanium alloy was the control. Marrow-derived stem cells were isolated from long bones of Sprague Dawley rats and cultured on samples. Alkaline phosphatase (ALP) and osteocalcin (OC) expression by stem cells were assessed via ELISA. Cells were lysed and subjected to quantitative polymerase chain reaction (qPCR) to assess Col1a1, osteonectin, and IGF- 1 expression. An in vivo study evaluated bone formation at 4- and 12-week endpoints. Eight female Sprague Dawley rats per group per endpoint received bilateral Ti-6Al-4 V K-wires as femoral implants. Left femur received control, while right femur received Aligned/Trabecular TiNT K-wire. Bone formation was assessed via microCT, backscatter electron imaging (BEI), and non- decalcified histologic analyses. Results: Aligned and Trabecular TiNT groups demonstrated higher ALP activity than control at 2 and 3 weeks. The in vivo study demonstrated increased bone volume fractions (BV/TV) and total bone volume (TBV) for TiNT surfaces (microCT). The ratio of both BV/TV and TBV in the distal VOI were nearly equivalent for both TiNT surfaces, indicating similar bone formation between both TiNT surfaces and control. In the midshaft VOI, the ratios between TiNT surfaces and control were 1.5 or greater, indicating increased bone formation. At 12 weeks, the bone-implant contact fraction ratio (BEI) showed Aligned TiNT and Trabecular TiNT were 1.3 and 1.4 times greater than control, respectively. Histologic analysis showed both TiNT surfaces had 1.5 times the bone-implant contact as control. Conclusion: In vitro studies demonstrated improved support for osteogenic functions of cultured marrow-derived stem cells on TiNT surfaces compared to controls. μCT, BEI, and histologic analyses associated with the in vivo study demonstrated increased bone formation in the TiNT femora, at specific timepoints and VOIs