Browse our active research projects:
Tribological Characteristics of Nanofibrous Electrospun Materials
Electrospinning and melt-electrospin writing represent two complimentary technologies for the production of stochastic or aligned porous fibrous materials that mimic the natural collagenous extracellular matrix of soft tissues. Natural soft tissues such as cartilage, by nature of their fibre-reinforced hydrated structure, exhibit excellent frictional properties through the mechanism of biphasic self-pressurisation and slow fluid expression under load. We propose a similar function of multi-scale electrospun scaffolds. Objectives include the characterisation of the tribological properties of such materials, the design of fibre-reinforced gel scaffolds using fibre-reinforced poro-viscoelastic simulation models and the characterisation of scaffold fibre architecture and integrity through the use of contrast-enhanced microCT, confocal and scanning electron microscopy.
Elucidation of Friction-Induced Failure Mechanisms in Fibrous Collagenous Tissues
Cartilage fibrillation, the development of local fissures and defects at the tissue surface, is a hallmark of “wear and tear” osteoarthritis. Although a key early morphological indicator of cartilage degeneration, the initiation of fibrillation has generally been only loosely associated with non-specific mechanical factors e.g. Von Mises stress predictions in computational simulations. The objectives of this research are to experimentally characterise the initiation and growth of fissures in surface zone cartilage tissue samples and electrospun synthetic analogues, identify the articulating conditions that specifically lead to the development of surface fissuring and implement the first computational model of mechanically induced fibrillation in fibrous collagenous tissues.
Design of a Self-Lubricating Prosthesis
Natural articulating joints are self-lubricating by virtue of the intrinsic poroelasticity of cartilage tissue and the self-pressurisation of interstitial fluid under load, where fluid pressure supports up to 95% of the applied load. Advances in additive manufacturing (AM) provide an avenue for the production of complex structures incorporating internal porosity with communicating pore spaces, variable feature dimensions and a hierarchical topology which may replicate the features necessary for this self-lubrication. Objectives for this study will be to develop specific mechanical features that would provide self-pressurisation, develop a joint-scale model of a representative bearing surface and determine the response of the joint-scale models in terms of the overall evolution of a fluid film over time.
Development of 3D-printable, self-lubricated and multifunctional UHMWPE/PEEK nano-composites with improved wear resistance for total joint replacement
The objectives of this study are to develop and optimise modern manufacturing method, e.g., rapid prototyping, for newly developed high performance novel nanocomposites with superior self-lubricity and wear resistance. The first objective will be the development of novel self-lubricating and multifunctional materials using rapid prototyping. The second objective is the scale up of the material production to produce acetabular cup components. The third objective is to develop a fundamental understanding of the wear mechanisms for the new self-lubricating composites using advanced techniques.
Biocompatibility responses to newly developed carbon based PEEK/UHMWPE-nanocomposites
One very important aspect of the successful biomaterial development is the biocompatibility and biological responses of, in our cases, composites. Objectives include using pin-on-plate wear simulators to assess the wear mechanism and produce wear particles from experimentally made novel nano-composites and commercial materials, The use of high resolution cold field SEM to analyse isolated particle morphology, and investigate the inflammatory potential of the composite materials, toxicity, and ability to cause oxidative stress and DNA damage compared to control materials.
Bioprinting of cartilage and bone
Bio-printing of tailor-made cartilage implants containing patient-specific cells has the potential to greatly improve reconstructive surgery. To develop these therapeutic interventions the project will use 3D bio-printing to create cartilage and bone constructs, evaluate cell viability, matrix stability and remodelling over time and, finally, use scaled up 3D-printed cartilage and bone models within advanced models.
Development of 3D-printable, degradable, magnesium-based alloys
Magnesium-based alloys have recently been utilised clinically. In this project the aim is to further improve the functioning of these alloys by exploring the incorporation of other bioactive elements, as well as the use of specific additive manufacturing techniques. Objectives include the development of magnesium-based powder suitable for 3D-printing and bone reconstructive applications, demonstrate printability of the material and Objective 3 evaluate the mechanical and degradative properties for applications as a bone reconstructive material.
Development of 3D-printed gradient alloys for joint implant component
Additive manufacturing techniques will be used to develop 3D-printed structures of CoCr, Ti-based or other relevant alloys, adequate for tribological applications through topologically optimized surfaces. The produced materials will be evaluated at least in terms of surface chemistry, roughness, and in 2D wear tests. The project objectives include the prototyping of topologically optimized surfaces for enhanced lubrication and reduced wear additive manufacturing, development of a surface-treated material for improved wear resistance and the use of advanced wear testing using 2D and 3D specimens on joint simulators.
Biological characterization of 3D-printed alloys for reconstructive surgery
This project will focus on the biological characterization of materials used for reconstructive surgery, in close collaboration with other BioTrib researchers. Objectives include utilisation of control materials for advanced method development, evaluation of the biological response using these new methods including information regarding the behaviour of the chosen elements and their resulting ions and the verification of the potential bacteriostatic and antibacterial properties of the materials.
Tribology of 3D Printed Prostheses
The increasing use of Additive Manufacturing (AM) technologies has the potential to revolutionise the design of personalised joints. However, one of the challenges of such technologies is that the resulting printed tribological interface requires significant post-processing. Here final outcomes will include an exploration the potential of tailoring the topographical features resulting from the printing process itself, combine experimental and computational tribological characterisation of the bearing surface to enhance performance and publish a set of design rules for these novel bearing surfaces.
Mechanical and tribo-chemical wear modelling of artificial joint prostheses
Synergistic wear and corrosion are a significant issue in the failure of joint replacement where the deleterious products can arise from a number of interfaces. Synovial fluid plays a key role as lubricant and media of chemical reactions. Challenges in understanding this process depend on the modelling of the mixed lubrication (roughness asperity contact and fluid film lubrication), and coupling of the mechanical and chemical wear. To this end the objectives are the elucidation of the reaction rate of tribo-film growth for a number of environmental factors, the Integration of the tribo-film and mechanical wear models using a mixed lubrication analysis and the utilisation of a mixed lubrication model to solve the heat generation and transfer in the bearing system to provide the temperature field to the chemical wear model.
Boundary Lubrication of Fibrous Scaffolds (Synthetic and Biological)
The cartilage surfaces of natural joints are composed of collagen-fibre reinforced biopolymer gels which enhance lubrication through fluid pressurisation and a complex boundary lubrication arrangement. Objectives of the study are to determine the potential of cell-seeded electrospun fibrous scaffolds to produce lubricin, where mechanical stimulation will be generated in an multi-axis bioreactor, to demonstrate the potential benefit of conjugating synthetic lubricating polymers directly onto the surface of electrospun fibrous scaffolds and to determine of the surface properties of the biopolymer gels using advanced mechanical techniques.
Functional Biotribology of the Surface Engineering 3D Printed Components
A specification for all bearing surfaces employed in total joint replacement regardless of tribological conditions is provided by current ISO standards. Current 3D printing techniques are not sufficiently precise to produce surface finishes of this quality across various scale lengths. This project will seek to undertake a biotribological characterisation of 3D printed prostheses before and following surface treatment. The objectives include the assessment of the metal and polymeric printed specimens under the standard ISO 14242-1 configurations, the specimen assessment under newly developed adverse testing regimes and determination of particle size of the generated debris using the newly developed protocol, CWA 17253-1:2018 or similar.
Towards real-time sensing of corrosion and wear in simulations
The project goal is to develop robust measurement techniques to determine the wear and corrosion processes occurring in real-time during hip simulation. The first objective to is to enhance recent experimental techniques based on electrochemical, acoustic emission and more recently eddy current sensing. Two further objectives will implement new techniques for the in situ analysis of the lubricating fluid and the particulates therein and near continuous wear measurements.
Understanding the nature, origin and degradation of implant debris
The overall project goal is to understand how the tribo-corrosion interfaces established in vivo influence the chemical and mechanical nature of the implant derived debris. To this end the objectives are to investigate the degradation processes of the debris at the nano-scale and its interactions with cellular matter, to assess the biological response to implant derived particulates in simulated inflammation environments and cell cultured conditioned media, and to determine of the debris (particulate and ionic)-biological interface at the nano-scale using advanced electrochemical techniques and spectroscopy.