Biotribology最新文献

Despite the clinical success of hip joint replacement, the risk of revision, particularly in younger and more active patients, still remains a concern. To identify conditions of high wear, fatigue and potential failure modes, there is need to be able to replicate a range of in vivo conditions with pre-clinical testing methods in order to predict the range of clinical wear. In particular, edge loading of metal-on-polyethylene hip replacements has the potential to have impact on both surface wear and fatigue failure. The mode of edge loading explored in this study involves separation of the centres of the femoral head and acetabular cup during a portion of the gait cycle. Such edge loading can occur due to variations in translational and/or rotational positioning of the hip replacement. In this study, the influence of translational positioning along the medial-lateral axis (medial-lateral translational mismatch) combined with rotational positioning of the acetabular cup about the anterior-posterior axis (cup inclination angle) on the occurrence and severity of edge loading, and wear and plastic deformation, was investigated for size 36 mm metal-on-polyethylene total hip replacements on a ProSim EM13 electromechanical hip joint simulator. A two phase approach was used; a short term study where the mechanics of the hip bearing were assessed under a wide range of input conditions (45° and 65° cup inclination angle and 1, 2, 3, 4 mm medial-lateral translational mismatch); followed by wear simulation for a lower number of conditions.

Larger medial-lateral translational mismatch conditions led to increased levels of dynamic separation between the femoral head and acetabular cup with the largest dynamic separation (2.4 ± 0.2 mm, mean ± 95% confidence limits) measured under 4 mm translational mismatch with the 65° cup inclination angle conditions. The load at the rim at 0.5 mm of separation was also highest at this condition, as was the mean wear rate (23.0 ± 2.4 mm³ / million cycles).

Dynamic separation, load at the rim and wear was consistently greater with the steeper cup inclination angle of 65° compared to 45° for all translational mismatch conditions. Translational mismatch conditions of 3 mm and 4 mm resulted in dynamic separation displacements >0.5 mm. At a 45° cup inclination angle under standard concentric conditions (zero translational mismatch) minimal wear and plastic deformation occurred at the rim of the cup, however at a 65° cup inclination edge contact at the rim was identified.

Variations in rotational (cup inclination angle) and translational (medial-lateral) positioning influenced the magnitude of dynamic separation, severity of edge loading, and wear of metal – on - moderately cross-linked polyethylene hip replacements, demonstrating the importance of surgical component positioning.

This study aimed to develop a method to generate nano/microplastics (NPs/MPs), whose morphology and constituents are clarified for various biological tests. NPs/MPs were generated using a pin-on-disc machine, where a pin made of polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polyethylene terephthalate (PET) was pressed onto a quartz glass disc. Relative motion between the pin and disc was then applied in a saline solution. An ultraviolet lamp (UV-B) was used to irradiate the frictional surfaces through a quartz glass disc to investigate the degradation of the plastic materials. A microtextured glass surface was used to induce fatigue failure of plastic materials and adjust the crack propagation of plastic materials. UV degradation was confirmed for all the plastic materials and UV irradiation increased the equivalent circle diameter (D) of PE, PVC, and PET but decreased the equivalent circle diameter (D) of PP. However, it was thought that UV irradiation did not affect the aspect ratio (R) and complexity (C) of all plastic materials. The physical degradation mechanism of using the microtextured glass surface may increase the generation of NPs/MPs, and the surface profile of microtextured glass may adjust the crack propagation of plastic material surfaces. Notably, almost all the NPs/MPs generated were fragment-shaped. The NPs/MPs were compared to the particles found in the environment or generated by milling, cutting or chemical degradation in vitro. It was concluded that the fragment-shaped NPs/MPs were similar to the particles found in the environment or generated by milling in vitro, through visual inspection, aspect ratios, and complexity. As the presence of NPs/MPs in the human body can pose a serious health risk, a microchamber device capable of both quantitative and time-dependent assessments of inflammatory cytokine (TNF-α) secretion from human monocyte-derived macrophages (HMDMs) was proposed. The microchamber was constructed with a height of 200 μm and a diameter of 15 mm. This configuration enabled the NPs/MPs to pass near the HMDM, which is important in the phagocytosis of NPs/MPs and contributes to quantitative assessment. Although approximately the same morphological aspects of NPs/MPs were administered, the secretion of TNF-α differed depending on the plastic material.

The lack of limbs on snakes enables its ventral scales to be in almost constant contact with the substrate. Their skin is presumably adapted to generate high and low friction to slither. This frictional characteristics in snakes were hypothesized to be contributed by the be tooth-shaped or denticle-like microstructures found on the snake ventral scales. The frictional properties of the microstructures found on snake ventral scales was studied and its feasibility as an inspiration for surface modifications was observed. This study was carried out to analyze the frictional anisotropy exhibit by the snake ventral scale microstructures and also how it changes the frictional properties of the PDMS surface when the microstructures are replicated on to it. The PDMS embedded-elastomeric stamping method was used in this experiment to replicate the snake ventral scales onto the PDMS. Based on the data collected the microstructures on the snake ventral scales does exhibit frictional anisotropy. The PDMS with replicated snakeskin microstructures displays higher COF compared to PDMS with smooth surface. When sliding on most types of surfaces, the COF of real snakeskin and replicated snakeskin is higher if the surface is semi wet. Whereas for smooth PDMS the COF is lower when the surfaces are semi wet. Generally, from both experiments, when the replicated snakeskin is sliding on the surface in the lateral direction, it is observed that the COF is the lowest followed by the caudal then the rostral direction.

The purpose of this research is to evaluate the lubrication properties of a synthetic synovial fluid in combination with biocompatible polyurethanes, versus materials commonly used in biomedical implants. This combination is found in endurance testing of meniscal implants made from polyurethane.

Two different polyurethanes were used for friction measurements, applying a synthetic lubricant, containing a Ringer's solution, hyaluronic acid and bovine serum albumin. The results were compared with friction measurements, using a polyurethane sphere against bovine cartilage, lubricated with bovine synovial fluid. The influence of the lubricants was tested by comparing water, synthetic- and bovine synovial fluids with the various material combinations, found in existing knee implants. From the measurements it was shown that the friction pairs including metal surfaces did not show the common Stribeck behaviour, with respect to transitions from the boundary regime to full film lubrication, and friction remained relatively constant over the whole velocity range. Friction pairs including the polymer counter surfaces and the water lubricated contacts, showed the expected transitions from boundary to mixed lubrication. From this it was concluded that protein adsorption mainly defined the frictional behaviour when using metal surfaces, leading to a coefficient of friction (COF)≈0.2 using synthetic synovial fluid, and COF≈0.15 when using bovine synovial fluid. PEEK samples showed higher values in the boundary lubrication region, which decreased to values of COF≈0.1 at higher velocities. Polyethylene samples showed higher friction results, which was attributed to the surface roughness. From the observed friction results and wear tracks it was concluded that a synthetic synovial lubricant performs very well with all material combinations, when more attention is paid to the polyethylene surface finish.

While biomimetic adhesive solutions have succeeded to be used in various engineering applications such as climbing robotic, handling systems facilities and mobile sensor platforms, their adaptation to biomedical engineering, such as patches for external use, is still in its early stage due to critical issues that must be resolved before wide usage. In this study, we show that the integration of different biomimetic adhesive micro-texture of different shapes. As observed in nature, increases their adhesive efficiency on uneven surfaces under diverse environmental conditions. The integrated samples lead to uniform and stable peeling strength, which enables long-term adhesive ability. Our work sheds light on the synergetic effect of various combinations and their effectiveness in achieving optimized adhesion that could be suitable for biomedical applications.

The formation of mucin layers on dental materials are intrinsic to maintaining a healthy oral cavity. Of interest to this study is the absorption-property-lubrication ability of surface bound mucin layers on to hard dental surface akin to those observed in oral salivary pellicles. QCM-D experiments examined the growth of these mucin layer overtime. Pseudo First Order, Pseudo Second Order and Elovich kinetic adsorption models were applied to gain a greater insight into the adsorption process. As lubrication on teeth is an important property of oral lubrication, a micro-tribometer was used to assess the lubricity of surfaces over a range of normal loads. Mucin layers grew with an initial rapid phase followed by a second slower adsorption phase which followed Pseudo First Order or Elovich adsorption kinetics on hydroxyapatite and gold surfaces respectively. Enhanced lubrication was seen when hydroxyapatite and mucin were used demonstrating the chemical nature of the underlying surfaces is important in establishing effective mucin films. The formation of mucin layers was attributed to the surface composition driving the adsorption process and subsequent viscoelastic properties of these layers. Hydroxyapatite was important in promoting enhanced mucin lubricity and that mucin boundary lubrication was related to the viscosity and shear modulus of mucin layers.

In tribosystems that include contact with a flexible body, friction-induced vibration may be present. Dimensionless analysis coupled with numerical manipulation was employed to model the discontinuity between the static and kinetic behaviour of the friction. The present paper discusses the nature of stick-slip between a human fingertip and standard printing paper, intending to describe the theoretical stability conditions of movement. The amplitude of the stick-slip phenomenon is analised as a function of the human skin's rheological and tribological properties, the system's rigidity, and the sliding contact velocity.

Preclinical wear testing of joint implants has primarily focussed on the wear properties of Ultra-High Molecular Weight Polyethylene (UHMWPE) articulating on wrought/cast metals. Advancements in additive manufacturing (AM) technologies, such as laser-based powder bed fusion (LPBF), have led to the increasing use of this manufacturing method in metal articulating joint components. There is, however, still uncertainty regarding the wear properties of UHMWPE against AM metals. This study employed LPBF Co-Cr-Mo and Ti-6Al-4V pins in articulation against UHMWPE to assess the wear of the latter. A multidirectional pin-on-plate wear testing machine was used to simulate in vivo knee joint conditions over 5 × 10⁶ cycles. Wear testing was conductedwith ASTM F732 as guideline. The LPBF Ti-6Al-4V pins underwent a thermal oxidation heat treatment to improve the material's wear properties. The state of the thermal oxide layer was investigated after wear testing by sectioning the pins and measuring the thickness of the oxide layer. Wear testing showed that UHMWPE against Co-Cr-Mo had better wear properties compared to UHMWPE on Ti-6Al-4V. The wear properties of UHMWPE against Co-Cr-Mo and UHMWPE on Ti-6Al-4V were within ASTM F732 requirements and comparable to those reported in the literature. The thermal oxide layer on the LPBF Ti-6Al-4V pins showed signs of delamination after 5 × 10⁶ cycles. A small oxygen diffusion zone of 1–2 μm was argued to be the reason for the delamination.

A lot of work has been done to enhance the mechanical properties of natural fiber composites to increase their strength and applicability. This research aims to investigate the utilization of natural fibers for below-knee prosthesis socket manufacture using the vacuum bagging technique experimentally, theoretically, and numerically. Lamination groups of different layering arrangements were evaluated by tensile tests. The finite element methodology (FEM) was utilized by noting the dispersion of safety factors, equivalent Von-Mises stress, and total deformation, while the theoretical part estimated Poisson's ratio, volume fraction, failure index, and theoretical safety factor. The study found that the number and type of fibers affected mechanical properties, in addition, that combining natural and artificial reinforcements permits the creation of high-performance bio-composites. FEM results coincided with both the theoretical and experimental results, with lamination 9 having the highest modulus of elasticity (5.6 GPa) and tensile strength (423 MPa). This work uncovered the properties of the proposed hybrid fiber-reinforced composites that haven't been exasperated up to the present and showed that sockets can be assembled from sustainable, low-risk materials without sacrificing the composite materials' strength. The study found that bio-composites with better performance could be created by combining synthetic with natural reinforcements.

Products of densification continue to gain importance in the daily activities due to certain advantages such as reduced cost of logistics, better handling and improved performance with regard to their respective purposes. The durability is a measure of defining the quality of these products thus determining the extent of research and development required to enhance these products. Various methods of determining durability such as the impact tests, tumbling, pneumatics, and high speed dural mechanism have reportedly been utilized. There is sparsity literature on the development of high-speed locally made systems for determining durability of agglomerates. The durability testing apparatus is a locally fabricated device designed as a hybrid of the tumbler and the dural to evaluate agglomerates in a bid to determine their resistance to damages when in dynamic state. The design of this apparatus was carried out putting into consideration various components and fabricated to be used for a wide range of agglomerates. It was evaluated using starch bonded kenaf pellets which was found to have a durability of 98.15–99.72% for trial periods of 60 s per run. The durability testing drum was able to effectively determine the durability of kenaf starch bonded pellets.