Biosurface and Biotribology最新文献

A layer of micro-sized periodontal membrane can buffer most chewing forces to protect the interface between the natural tooth root and alveolar bone. Artificial dental implants usually direct contact onto the alveolar bone without a buffer layer, which increases the risk of surface damage. The main purpose of this work was the bionic design of a flexible layer of nanowire scaffold on a titanium implant surface according to the function of the periodontal membrane. Millions of nanowires were woven into a superhydrophilic layer of porous scaffold. The evolution of mechanical properties displayed that the biomimetic nanowire scaffold could absorb a maximum of about 1.59 KJ energy per square centimeter by low-speed impact. The minimum tensile strength of one nanowire was 2 GPa. A biomimetic flexible periodontal membrane connection functioning between the natural tooth root and alveolar bone has great potential value for developing advanced artificial dental implants for dental restorations.

Conventional polyethylene is not used much in total hip arthroplasty (THA); it has been supplanted by oxidation-resistant cross-linked polyethylene (≥50 kGy irradiation). However, studies persist that de-emphasize or ignore cross-linked polyethylene. A selective literature review is used briefly to present the early use of conventional polyethylene and its implication in wear particle-induced osteolysis leading to premature revision surgeries. The current situation is established based on Australian registry data and other studies that advocate the use of cross-linked polyethylene in preference to conventional polyethylene. Although some studies suggest caution in using cross-linked polyethylene, overall it is strongly supported. In the author’s opinion, cross-linked polyethylene is the new reference standard bearing material in THA.

The biochemical reaction during the formation of lubricant film the in case of a cobalt-chromium ball on an ultrahigh-molecular weight polyethylene cup was studied. Three types of model synovial fluids and hyaluronic acid (HA) at physiologic concentrations were used in the experiment. The coefficient of friction was measured using a pendulum hip simulator, and Raman spectroscopy was used to perceive chemical reactions between the synovial fluid and implant material. Raman spectra evidenced that the three model fluids and HA chemisorbed onto the cobalt-chromium surface. An α-helix structure of the model fluid components was detected on the surface of the prosthesis.

Many studies have been performed to analyse the lubrication of artificial joints since the pioneer work by the late Professor Duncan Dowson. However, the viscoelastic deformation of one of the most widely used bearing materials, ultra-high-molecular-weight polyethylene (UHMWPE), has only been considered recently. The described study attempted to investigate the effect of UHMWPE viscoelasticity on the elastohydrodynamic lubrication of such a soft artificial hip replacement under squeeze-film motion. A transient viscoelastic squeeze-film lubrication model of a typical hip implant was developed and solved to obtain the film thickness and pressure distributions. A boundary film thickness was adopted to consider the direct and indirect lubricant contact conditions. The results showed that the viscoelasticity had marked effects on the squeeze-film lubrication performance of UHMWPE artificial hip joints. The minimum film thickness in the viscoelastic model was smaller than that of the elastic model, causing an earlier direct contact. However, the film thickness within the central contact region in the viscoelastic model was greater than that of the elastic model due to the restricted flow of the lubricant, therefore enhancing the lubricating effect and particularly with a short relaxation time and mechanical loss factor.

Because of their good performance, including biocompatibility and mechanical properties, polyurethanes (PUs) are widely used in medical devices. However, undesired compatibility troubles, including thrombus, inflammation, and hyperplasia, still limit the applications of PUs. In this study, copper-mediated polyurethane (PU-Cu) materials with enzyme-like catalysis were prepared. The PU-Cu materials effectively catalysed the nitric oxide (NO) released from endogenous NO donors because of the glutathione peroxidase (GPx)-like function of copper ion. The PU-Cu materials were respectively evaluated via platelet adhesion and endothelial cell (EC), smooth muscle cell (SMC), and macrophage (MA) cultures. Scanning electron microscopy results showed that PU-Cu materials significantly inhibited platelet adhesion and activation. Meanwhile, PU-Cu materials not only promote the proliferation of EC but also inhibit SMC growth. Moreover, MA culture results intuitively stated the anti-inflammatory ability of PU-Cu. In addition, experimental samples were implanted into the subcutaneous tissue of Sprague Dawley rats. The anti-inflammatory function of PU-Cu was further confirmed by haematoxylin-eosin staining results. With regard to their excellent biological performance, PU-Cu materials are proposed for biocompatibility improvement of blood-contacting materials, which should in turn provide new ideas for advanced medical devices.

Articular cartilage has a unique collagen fibre network structure that exhibits both anisotropy and depth dependency. Collagen fibre orientation in a cross-section parallel to the articular cartilage surface may affect the lubrication properties of articular cartilage. The effect of collagen fibre orientation on the frictional properties of articular cartilage was examined through finite element analysis of the friction. Specifically, a three-dimensional fibre-reinforced poroelastic biphasic model was used to determine the influence of collagen fibril orientation on the frictional properties of articular cartilage. The simulations reveal that collagen fibre orientation has a significant influence on the deformation behaviour of articular cartilage in front of and behind the contact area. The coefficient of dynamic friction was lower in the direction parallel to the collagen fibre orientation than in the direction perpendicular to the collagen fibre orientation, regardless of the indenter speed.

In this study, the adhesion-detachment behaviour of a gecko-inspired adhesive pad was investigated to understand the on/off switching mechanisms of adhesion in gecko feet. A macroscopic spatula model was fabricated using silicone rubber, and adhesion tests combining lateral sliding and vertical debonding were conducted. It was observed that the contact state and the adhesion force of the pad vary considerably with the direction of lateral sliding prior to debonding, and that the pad achieves adhesion during debonding even when it loses contact due to excess lateral sliding. These results explain the mechanisms behind the on/off switching and stable adhesion of gecko feet, and suggest the possibility of developing new-generation adhesives capable of switchable adhesion.

The lubrication ability of a contact lens is one of its most essential properties because high friction on an eyelid causes discomfort during blinking. Friction measurements allow assessment of lubrication ability. So far, several apparatuses have been developed to measure contact lens friction. However, thus far, ocular physiological conditions including sliding speed and area have been imperfectly realised. Herein, a pendulum-type friction tester was developed for the assessment of contact lenses under physiological conditions. A high sliding speed of 90 mm/s was achieved thanks to the short oscillation period of the small pendulum. Physiologically, the sliding surface on a contact lens was realised at the fulcrum of the pendulum. The coefficient of friction for the interaction between a contact lens and plastic hemisphere was directly calculated from the decay in potential energy during the free libration of the pendulum. Friction coefficient of a commercially available contact lens in saline solution, 0.1% and 0.3% HA solutions were 0.036, 0.039 and 0.050, respectively. These results were reliable because they ranged within the low levels reported by previous studies. It was shown that the present pendulum machine represents a major advancement in the realisation of physiologically realistic contact lens friction measurement.

Professor Duncan Dowson was a pioneer in the field of tribology and simulator design. His work sparked many branches of research across orthopaedics. The first knee simulator described by Dowson was intended to measure the wear performance of early total knee replacements (TKRs). The industry has since advanced to achieve simulator designs with significant improvements including multi-station, multi-axis, multi-control, and multi-environmental capabilities. These simulators are used to test and compare not only wear, but also the kinematic/kinetic behaviour of TKRs and many other TKR design interactions prior to implantation. This has led to changes to the design of TKRs ranging from improvements to the tibial insert to the femoral component; all, in some way, thanks to Professor Duncan Dowson's inquisitive nature. This article provides a selective review to show the interdependencies of research and development endeavours starting with the evolution of knee simulators, the many advances in TKRs and finally the interconnection with cadaveric motion simulators.