Biotribology最新文献

Additive manufacturing (AM) holds significant potential in transforming medical applications, with a particular focus on polyetheretherketone (PEEK) and its derivatives, collectively known as poly-aryl-ether-ketone (PAEK) materials. Advances in AM precision have paved the way for the successful 3D printing of high-performance thermoplastics like PEEK, offering new prospects in load-bearing medical applications. This systematic review comprehensively assesses recent scientific literature concerning the tribo-mechanical properties and bioactivity of additively manufactured PAEK materials, with a specific emphasis on PEEK, for load-bearing medical uses. Despite substantial research into AM of metallic biomaterials, knowledge gaps persist regarding AM processing parameters, structure-property relationships, biological behaviours, and implantation suitability of PAEKs. This review bridges these gaps by analysing existing literature on the tribo-mechanical properties and bioactivity of additively manufactured PAEK materials, providing valuable insights into their performance in load-bearing medical applications. Key aspects explored include printing conditions, strength limitations, and outcomes of in-vitro and in-vivo evaluations. Through this systematic review, we consolidate current knowledge, delivering essential information for researchers, clinicians, and manufacturers involved in advancing additively manufactured PAEK materials for load-bearing medical applications.

Based on a proven concept of using nanoparticles to lubricate an articulating interface, we developed a set of formulations to demonstrate the feasibility of using polymeric nanoparticles as physical intervention for early stage osteoarthritis (OA). The biocompatible polymeric nanoparticles (NPs), namely polymethylmethacrylate (PMMA), polycaprolactone (PCL), and polylactic acid (PLA) were accompanied with hyaluronic acid (HA) and surface actives, of which the lubrication effect was examined between a steel ball and a silicone elastomer substrate to replicate the bone-cartilage contact. All three types of polymer nanoparticles were found to reduce the overall Coefficient of Friction (CoF), with PLA NPs being the most effective - providing a reduction up to 24.3%, which suggests that soft (low Young's modulus) nanoparticles are the most efficient frictional additives. Based on the data acquired, it is likely that surface deposited NPs could smooth the solid substrates, hyaluronic acid ensures bulk viscosity, and the surfactant enhances formulation stability. We suggest that surface adsorbed nanoparticles are beneficial in providing interfacial lubrication, which offers insight on the development of early stage intervention strategies for OA.

During archaeological fieldwork wedge-shaped quartz stones that show clearly visible "glossy patches" composed of high quartz have been found. It is generally accepted that these tools have been used to cleave or punch wood and bone materials. For the transformation from quartz to high-quartz to occur, the temperature should exceed 574 °C. The hypothesis tested in this manuscript is that the phase change in the stone tool results from frictional heating during the cleaving action. Dry sliding friction measurements were carried out on a reciprocating tribometer using four types of stone, representing the punch tool, and pine, oak and bovine bone, representing the work piece. Measured coefficients of friction were approximately 0.1 on oak, 0.2 on pine and up to 0.35 on bovine bone, with some minor fluctuations for the different types of stone. These coefficients of friction were inserted into a computational model describing the flash temperatures in a moving contact, from which it was shown that the hypothesis might hold in the case of lydite-bone contact. This means that the glossy patches on the stone tools may have been caused by frictional heating during the cleaving of bone.

In recent years tribology tests have been used to measure friction properties of oral consumables such as semi-solid foods and medicines. The tests aim to simulate thin-film mastication conditions and are intended to correlate with mouth feel or food texture properties. In this paper a new approach is proposed to better simulate shear conditions, fluid supply and friction data capture associated with mastication and swallowing. Two primary changes are suggested: these are the reduction of the inlet influence on lubricant film properties and the ability to measure transient and time-dependent friction. The new test was used to measure friction for a range of oral medicines including a viscous solution (cough syrup) and particulate suspensions (paediatric, calcium carbonate) in combination with an artificial saliva (mucin solution), The tongue-palate was replicated by a PCX glass lens loaded and reciprocating against a textured silicone surface. A short stroke length, comparable to the Hertzian diameter of the contact, was used so the contact operated in a partially replenished lubrication condition. This ensured the film in the contact region has the same composition as the bulk fluid. Friction was measured continuously during reciprocation for up to 5 cycles (comparable to mastication time) and data was sampled at 100 Hz to capture transient friction. Tests were run with and without a mucin layer present. The results showed that tests performed after 20 min adsorption of an artificial saliva solution reduced the friction coefficient from μ = 1 to μ = 0.2–0.3. Tests with the paracetamol suspensions, which contain hard particles, recorded transient friction spikes which were not recorded for the softer calcium carbonate suspensions. Key conclusions for the design of pertinent simulation tests are that the film properties in the oral cavity are not determined by the inlet as for classical lubrication. The (bulk) oral sample is captured in the tongue-palate contact and not continually replenished. When sheared it will exhibit time (transient, longer-term) and speed dependent friction responses which contribute to sensory and texture perception.

Metal wear and corrosion debris remain a limiting factor for long-term durability of total hip replacement (THR). Common wear particle production techniques for research differ from the actual tribocorrosion processes at the implant site, potentially causing loss of valuable information. The aim of this study was to investigate reactions to freshly generated and time-stabilized particles and ions released from CoCrMo-alloy using a bio-tribometer, which mimics conditions of the periprosthetic environment.

THP-1 macrophages were challenged with freshly produced or time-stabilized wear debris. Wear generation took place in a custom-built bio-tribometer inside a CO₂ incubator operating with a reciprocating rotation of an Al₂O₃ ball against a CoCrMo disc. Two different electrochemical conditions with increasingly forced corrosion rates were tested: +0.45 V (passive domain) and +0.67 V (transition to transpassive domain). Cell viability, proinflammatory cytokines, electrochemical measurements and ICP-MS metal ion content analyses were performed.

Cobalt/ chromium concentrations were 6.6/ 1.6 ppm in the passive domain and almost doubled to 11.4/ 3.0 ppm in the passive-transpassive domain. Under those electrochemical conditions, freshly produced and time-stabilized CoCrMo wear decreased cell viability to the same extent. Secretion of proinflammatory cytokines were not significantly different for freshly produced and time-stabilized debris.

This study suggests that freshly generated and time-stabilized metal particles/ions cause similar toxicity and inflammatory reactions in macrophages, indicating that standard practices for generating wear debris are valid methods to evaluate wear particle disease. Other cell types, materials, and corrosion potentials need to be studied in the future to solidify the conclusion.

Pyrolytic carbon (PyC) is a common material used in mechanical heart valves. This investigation studies the effects of surface finish on the the sliding wear between two PyC surfaces. The primary application being, the prediction of wear at articulating surfaces within bileaflet mechanical heart valves. An experimental apparatus is designed which allows a cylinder to rotate on a flat plate at a constant frequency and load. The cylinder is harder (greater modulus of elasticity) than the flat surface. Two surface finishes of a single (hard) cylinder and two flat surfaces of different hardnesses (single surface finish) are investigated, for a total of four cases. These four cases are studied at four sliding distances. The exerimental data is used to develop theoretical load and stress-dependent models for sliding abrasive wear. For the boron alloyed PyC material used in this investigation, the load-dependent wear model is most applicable for unpolished cylinders and the stress-dependent model is most applicable for polished cylinders. These two models are used to make theoretical predictions of pivot wear in a bileaflet mechanical valve of the same material. The predictions from the stress-dependent wear model was found to be quite accurate with actual wear measurements. The methods developed in this paper are generalized and applied to other valve designs and materials.

A custom-built tribometer was employed to investigate the impact of the roughness of deformable tongue mimicking surfaces (TMS) on friction mechanisms occurring under the effect of lubrication with Newtonian solutions of glycerol. TMSs with modulated roughness (range of asperity heights Ra: 20–140 μm) were manufactured from gels of polyvinyl alcohol (PVA). Newtonian aqueous solutions of glycerol covering a wide range of viscosity (1–1400 mPa.s) were used as simple food models spread on the TMSs. The tribological behavior of the system was studied during shear back and forth movements. The ratio between tangential and normal forces was analyzed both in terms of average values and of fluctuations, over specific time periods set at the end of motion and rest steps. The average values of friction level were reported to increase when (i) the roughness of the TMSs increased and when (ii) the viscosity of glycerol solutions decreased. These trends could be consistent with mixed lubrication. The fluctuations of friction level during motion steps were for their part generally of higher amplitude as the roughness of the surface increased, with main frequencies ranging from 10 to 20 Hz. The study demonstrates the importance (i) of the biological relevance of tongue properties (contact areas, rigidity, and asperity heights) and (ii) of the thorough analysis of tangential to normal force ratio to better understand the complex mechanisms of friction occurring in the mouth during food consumption.

Polyethylene wear has been a concern for the longevity of total knee replacements (TKR). A characteristic wear feature often observed on the articular surfaces of retrieved polyethylene tibial inserts is a striated pattern of hills and troughs. This pattern is of interest because its surface area has been found to correlate with increased tibial insert wear. We therefore addressed the following two research questions: (1) What is the prevalence of the striated pattern on a contemporary tibial insert design made from conventional ultra-high-molecular-weight polyethylene (UHMWPE)? (2) Are the peaks and troughs of the striated pattern connected with differences in crystallinity developed during the wear process? The prevalence and area coverage of the striated patterns were determined on a set of 81 retrieved tibial inserts of a cruciate-retaining TKR design. The striated areas were mapped using an optical coordinate measuring machine. Differences in crystallinity between troughs and hills were determined on a representative tibial insert using Raman spectroscopy. The striated pattern was observed on 61 out of 81 (75%) of the retrieved tibial inserts, covering an average of 32% of the total articular area. In the representative insert that was evaluated, the hills exhibited higher crystallinity (68%) than the troughs (54%) (p = 0.001). Conversely, the troughs exhibited higher amorphous phase content (22%) than the hills (19%) (p = 0.04). In conclusion, this pattern of hills and troughs is another example of microstructural changes in UHMWPE stemming from tribological stresses.

Digital Image Correlation (DIC) systems have been used to measure surface displacement fields by tracking a pattern applied to a surface. Offering many benefits in comparison to conventional strain-measurement devices, the use of DIC has been reported in the study of tissue biomechanics and performance of joints underneath. In this study, a new method was developed to apply a quality speckle pattern on the skin of knees. Temporary tattoo paper provided a safe, easy, and quick way for pattern application to the skin without hindering its natural behavior. A pattern was developed for analyzing the knee during a squatting motion in which the field of view, system set up, and curvature of the knee were contributing factors to the development. This research is designed to prove the feasibility of using tattoo papers as patent indicators for DIC measurement. The software was able to map the entire region of the knee and measure the displacement of each area independent of other parts, thus making it easy to identify twisting and bending of the joint. Experimental results indicated that it is an effective method to accurately analyze the motion of the knee without the need of sophisticated equipment. This methodology can be used to understand how strain affects the knee during action and thus will be useful for various sports-related activities such as training and injury management.