Biosurface and Biotribology最新文献

In general, tooth wear is difficult to be noticed until it leads to toothache in vivo. Developing a dynamic dental wear monitoring system to predict tooth wear in daily life is a necessity. The translation between complex surface wear morphology and corresponding digital signal source is a technical limitation to develop this kind of monitoring system. Microwear texture analysis has been widely employed in predicting diet by a palaeontologist. The main question is whether the microwear texture analysis has potential development space to develop a sensor for monitoring tooth wear. According to obtained results, the microwear texture analysis had enough sensitivity to display the surface morphology variations for different chewing foods and various angles. The corresponding sensitive digital signal of tooth microwear surface morphology makes it possible to develop a dental microwear sensor.

Understanding material-protein interactions is the basis for regulating material-blood interactions, which is a common topic of interest for medical material developers. In recent years, researchers have conducted extensive studies on (1) the structural characteristics of the plasma protein adsorption layer on the material surface, including the evolution of the protein adsorption layer and its typical binary structure. (2) Influence factors of the protein adsorption layer formation include protein factors (e.g., isoelectric point, structural stability), material factors (e.g., wettability, surface charge, morphology, size), and environmental factors. (3) Effects of some common plasma proteins in the protein adsorption layer on material-blood interactions. Here, we review the important research results in this field, hoping to provide a reference for future development of advanced blood contact materials.

Slippage is a common phenomenon between laparoscopic graspers and tissues during minimally invasive surgery, which may lead to inefficient surgical operations, prolonged operation time, and increased patient suffering. The stability factors related to the friction behaviour between laparoscopic graspers and the large intestine, including bio-surface liquids, pulling angle, and surface profile of graspers, were studied. The friction behaviour at the large intestine–grasper interface was tested using a UMT-II tribometer under the conditions of clamping force of 1–4 N, sliding displacement of 15 mm, and sliding velocity of 2 mm/s to simulate the grasping and pulling operations of soft tissue. The results showed that the bio-surface liquid (serum) of the large intestine significantly decreased the friction coefficient, thus reducing the grasping efficiency. A pulling angle of 15° could generate the peak frictional force and enhance the grasping stability. The frictional force increased with the ratio of the profile surface area of the grasper. These results demonstrate that the grasping stability can be improved by changing either the bio-surface liquid condition or the pulling angle. In addition, a grasper with a larger profile surface area can also prevent slippage due to its significant influence on the pressure distribution and actual contact area for tissue retention.

In this study, the effects of in vivo (head flexion-extension, lateral bending, and axial rotation) and in vitro (ISO 18192-1) working conditions on the wear of ultrahigh molecular weight polyethylene (UHWMPE)-based cervical disc prosthesis were studied via numerical simulation. A finite-element-based wear prediction framework was built by using a sliding distance and contact area dependent Archard wear law. Moreover, a pre-developed cervical spine multi-body dynamics model was incorporated to obtain the in vivo conditions. Contact mechanic analysis stated that in vitro conditions normally led to a higher contact stress and a longer sliding distance, with oval or crossing-path-typed sliding track. In contrast, in vivo conditions led to a curvilinear-typed sliding track. In general, the predicted in vivo wear rate was one order of magnitude smaller than that of in vitro. According to the yearly occurrence of head movement, the estimated total in vivo wear rate was 0.595 mg/annual. While, the wear rate given by the ISO standard test condition was 3.32 mg/annual. There is a significant impact of loading and kinematic condition on the wear of UHMWPE prosthesis. The work conducted in the present study provided a feasible way for quantitatively assessing the wear of joint prosthesis.

The performance of CoCrMo alloy in orthopaedic implants may be unfavourably affected by hyaluronic acid (HA) in synovial fluid. In this study, the authors aimed to understand the interactions between HA and CoCrMo using dedicated electrochemical experiments and surface analyses. A sequence of electrochemical measurements (open-circuit potential, linear polarization resistance, potentiodynamic and potentiostatic polarizations) was run on LC-CoCrMo (ASTM F1537) in Dulbecco's phosphate-buffered saline (DPBS) solution with and without HA and in DPBS mixed with newborn calf serum (NCS) and HA, partially under simultaneous recording of surface pH using custom-made microelectrodes. Samples were analysed by optical and electron microscopy. HA had no significant impact on the corrosion potential of CoCrMo alloy (E_CORR = −173 ± 8, −211 ± 16, and −254 ± 30 mV_Ag/AgCl, in DPBS, DPBS + HA, and DPBS + NCS + HA, respectively). Average current density values at the transpassive domain were double in DPBS compared to DPBS + HA and DPBS + NCS + HA. At potentials above +0.6 V_Ag/AgCl, surface pH values decreased from 7.5 to 6.5 in DPBS and from 7.5 to below 4 in DPBS + HA. In conclusion, the presence of HA did not compromise the corrosion resistance of CoCrMo alloy at free potential, but it enhanced acidic conditions at the near surface under anodic-applied potential in the transpassive domain.

The purpose of this study is to achieve better understanding of associated mechanisms and to recommend and identify new strategies to develop new rock breaking technology for Tunnel Boring Machines (TBMs). Tunnel Boring Machine tunnelling mainly depends upon the rock breakage caused by cutters moving on a rock surface in a rolling and sliding motion while under the action of thrust force. The rock breaking behaviour is controlled by the mechanical interaction between the cutters and the rock. Due to the high hardness and high abrasiveness of rock, the cutters have to work under very high thrust force and suffer heavy-load-impact and abrasive wear, causing serious wear and low rock breaking efficiency. Rock-boring organisms exist in nature, which achieve drilling and/or tunnelling in rocks through a tribochemical interaction. This phenomenon is called bioerosion and the organisms are natural ‘TBMs’ to some degree. In this study, the interaction between TBM cutters and rock is presented, and current measures to improve cutter wear and rock breaking efficiency and their limitations are reported. Then, the connotation, mechanism and typical cases of bioerosion are presented. Finally, inspired by bioerosion, a new chemically assisted rock breaking technology is proposed for TBMs.

Reliable and reversible adhesion underwater is challenging due to the water molecules and weak layers of contaminants at the contact interface, which requires to deepen the understanding of wet adhesion of biological surfaces. Herein, the co-effect of microstructures and mucus of abalone foot on wet adhesion is investigated from both experimental and theoretical perspectives. The morphologies, adhesion force and coefficient of friction indicate that the mucus in adhesion zone is crucial for successful attachment of abalone based on capillary forces and viscous forces, and the mucus in non-adhesion zone with lower adhesion force and friction coefficient may behave as a lubricant for the locomotion. The theoretical calculation manifests that the microstructures may help abalone to form multiple liquid bridges with the secreted mucus, and significantly increase the wet adhesion force of abalone. These findings will bring profound views into the underlying mechanisms of biological surface adhesion.

The human knee implant is computationally modelled in the mixed lubrication regime to investigate the tribological performance of the implant. This model includes the complex geometry of the implant components, unlike elliptical contact models that approximate this geometry. Film thickness and pressure results are presented for an ISO gait cycle to determine the lubrication regime present within the implant during its operation. It was found that it was possible for the lubrication regime to span between elastohydrodynamic, mixed and boundary lubrication depending on the operating conditions of the implant. It was observed that the tribological conditions present in one condyle were not necessarily representative of the other. Multiple points of contact were found within the same condyle, which cannot be computed by the elliptical contact solvers. This model can be used to balance forces in all directions, instead of only the normal loads, as often done in elliptical contact models. This work is an initial step towards understanding the role of the complex geometry in the tribological characteristics of the human knee implant when operating in physiological conditions.

Surfaces with hydrophilic and antimicrobial properties are very attractive for cardiovascular device-associated applications. The aim of this study was to prepare and coat a hydrophilic polymer containing a functional group capable of forming triazole functionality onto the surface of polyurethane (PU). The modified surfaces were assessed with cell adhesion, bacterial adhesion and bacterial viability. Mouse fibroblast cells (NIH-3T3) and three bacterial species were used for assessment. The results showed that the modified surface not only exhibited a significant reduction in cell adhesion with a 25%–59% decrease to mouse fibroblast but also showed a significant reduction in bacterial attachment with 26%–67%, 24%–61% and 23%–57% decrease to Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, respectively, as compared with original PU. Furthermore, the polymer-modified surface exhibited a significant antibacterial function by inhibiting bacterial growth with reduction of 49%–84%, 44%–79% and 53%–79% to S. aureus, E. coli and P. aeruginosa, respectively, as compared with original PU. These results indicate that covalent polymer attachment enhanced the antibacterial and antifouling properties of the PU surface.

Dental enamel is the most mineralised hard tissue with a complex hierarchically organised anisotropic structure and it protects human teeth from mechanical damage during the dental function. Due to the sample size constraints, the available data for quantitative evaluation of the fracture toughness of human enamel is very limited. Here, on the basis of microstructural characterisation, the fracture toughness of human dental enamel at small scale with respect to orientation was measured using notched microcantilever beams fabricated by focussed ion beam. The fracture toughness of human enamel with perpendicular orientation was measured to be 1.244 ± 0.12 MPa · m^1/2, 80% tougher than that of in-plane parallel orientation (0.698 ± 0.18 MPa · m^1/2). The present results are expected to provide deep insights into cusp fractures and the synthesis of enamel-like restorative materials.