Harbopagh0132

The fracture resistance and the relevant toughening mechanisms are directly related to the highly-hierarchical crossed-lamellar structures on different length scales. This article is aimed to review the different arranged modes of crossed-lamellar structures existing in nature, with special attention to their impact on the mechanical behavior and salient toughening mechanisms over several length scales, for seeking the design guidelines for the fabrication of bio-inspired advanced engineering materials that are adaptive to different loading conditions.Baleen is a resilient and keratinised filter-feeding structure attached to the maxilla of mysticete whales. It is strong and tough, yet a pliant and resilient material, that withstands extreme pressures in the oral cavity during feeding. We investigated the structure, water content, wettability and mechanical properties of baleen of the Southern right (SRW) and Pygmy right whales (PRW), to understand the effects of hydration on the physical and mechanical properties of baleen. Sixty 25 × 15mm baleen subsamples were prepared from one individual of SRW and PRW. Half were hydrated in circulated natural seawater for 21 days and half were dry. Water content analysis showed that SRW baleen was 21.2% water weight and PRW was 26.1%. Wettability testing indicated that surfaces of both hydrated and dried SRW and PRW baleen were hydrophilic, with hydrated samples of both species having lower contact angle values. For the SRW, the average contact angle of hydrated baleen was 40° ± 13.2 and 73° ± 6 for dried samples. Hydrated PRW baleen had an average contact angle of 44° ± 15.3, which was lower than in dried samples (74° ± 2.9). Three-point bending mechanical tests showed that the average maximum flexural stress of dried SRW (134.1 ± 34.3 MPa) and PRW samples (117.8 ± 22.3 MPa) were significantly higher than those of hydrated SRW (25.7 ± 6.3 MPa) and PRW (19.7 ± 4.8 MPa) baleen. Scanning electron microscope images showed the stratification of the outer cortical layer, with cross-linked keratin fibres observed within and between baleen keratin sheets. Hydrated baleen, as in its natural and functional behaviour, has greater flexibility and strength, attributes necessary for the complex filter feeding mechanism characteristic of whales. Hydration must be considered when addressing the physical and mechanical properties of baleen, especially when using dried museum specimens.To develop an orthopedic material for bone substitution, the substitute material must mimic living tissue from an anatomical and physiological point of view. The high wear and impact resistance besides the low friction coefficient, make ultra-high molecular weight polyethylene (UHMWPE) a suitable material to be used in orthopedic applications. However, UHMWPE is a bioinert material, not providing a proper interaction with the bone tissue surrounding to the implant. One way to mitigate this issue is improving UHMWPE bioactivity. This can be done by adding bioactive fillers in the polymeric matrix. In this work, UHMWPE composites were prepared by twin-screw extrusion. The fillers used were carbonated hydroxyapatite (CHA) and hybrids formed by precipitating CHA in collagens (hydrolyzed and type II). The results show that the fillers used caused a slight reduction in UHMWPE crystallinity degree, while both crystallization and melting temperatures remained almost unchanged. Dynamic-mechanical thermal analysis indicated a weak adhesion between filler and polymeric matrix, which is good from the biological point of view since the bioactive filler surface will be available to apatite deposition. The obtained materials exhibited good mechanical properties and in vitro bioactivity assay showed that all of the prepared materials are bioactive.Panoramic shape and deformation measurements of human skin in vivo may provide important information for biomechanical analysis, exercise guidance and medical diagnosis. This work proposes the application of an advanced mirror-assisted multi-view digital image correlation (DIC) method for dynamic measurements of 360-deg shape and deformation of human body parts in vivo. The main advantage of this method consists in its capabilities to perform full-panoramic non-contact measurements with a single pair of synchronized cameras and two planar mirrors thus representing a lean yet effective alternative to conventional multi-camera DIC systems in 'surrounding' configuration. We demonstrate the capabilities of this method by measuring the full-panoramic shape of a plastic human head, the deformation of a woman face and the principal strain distribution over the full-360-deg surface of a forearm during fist clenching. The applications of this method can be the most disparate but, given the possibility to determine the full-field strains and derived information (e.g. skin tension lines), we envisage a great potential for the study of skin biomechanics in vivo.We report on the mechanical properties regarding self-cured acrylic polymethyl methacrylate (PMMA) reinforced with hexagonal boron nitride (h-BN) and stabilized zirconia (8Y ZrO2) nanopowders. The nanocomposites were prepared by using both manual and ultrasonic mixing techniques. The fabricated specimens were subjected to micro indentation, bending strength, and modulus of elasticity measurements. A fully complete polymerization process under liquid monomer was provided by ultrasonic mixing as evidenced by Fourier transform infrared (FTIR) measurement. Independently of the nanopowder used, the hardness, bending strength, and modulus of elasticity of the formed nanocomposites highly increase in values with the increase of the filler concentrations. Higher bending strengths and modulus of elasticity of the nanocomposite were recorded when using h-BN nanopowder fillers whereas hardness increases when using 8Y ZrO2 nanopowder. Results showed that with respect to the unloaded specimens made by manual mixing, ultrasonic mixing of PMMA with a 5 wt% h-BN increased the flexural strength (FS) and the modulus of elasticity or Young's modulus (YM) values to about 550% and 240%, respectively. However, a similar concentration of 8Y ZrO2 increased the Vickers Hardness numbers (VH) to about 400%. This may suggest that PMMA loaded with a combination of h-BN and 8Y ZrO2 nanopowders may lead to nanocomposites with outstanding mechanical performance.Many experimental techniques have been reported to provide knowledge of the mechanical behavior of cells from biomechanical viewpoints, however, it is unclear how the intercellular structural differences influence macroscopic and microscopic mechanical properties of cells. The aim of our study is to clarify the comprehensive mechanical properties and cell-substrate adhesion strength of cells, and the correlation with intracellular structure in different cell types. We developed an originally designed micro tensile tester, and performed a single cell tensile test to estimate whole cell tensile stiffness and adhesion strength of normal vascular smooth muscle cells (VSMCs) and cervical cancer HeLa cells one half side of the specimen cell was lifted up by a glass microneedle, then stretched until the cell detached from the substrate, while force was simultaneously measured. The tensile stiffness and adhesion strength were 49 ± 10 nN/% and 870 ± 430 nN, respectively, in VSMCs (mean ± SD, n = 8), and 19 ± 17 nN/% and 320 ± 160 nN, respectively, in HeLa cells (n = 9). The difference was more definite in the surface elastic modulus map obtained by atomic force microscopy, indicating that the internal tension of the actin cytoskeleton was significantly higher in VSMCs than in HeLa cells. Structural analysis with confocal microscopy revealed that VSMCs had a significant alignment of F-actin cytoskeleton with mature focal adhesion, contrary to the randomly oriented F-actin with smaller focal adhesion of HeLa cells, indicating that structural arrangement of the actin cytoskeleton and their mechanical tension generated the differences in cell mechanical properties and adhesion forces. The finding strongly suggests that the mechanical and structural differences in each cell type are deeply involved with their physiological functions.This article demonstrates our efforts in developing and evaluating all-ceramic, biodegradable composites of calcium phosphate cements (CPCs) reinforced with silver (Ag)-doped magnesium phosphate (MgP) crystals. Two primary goals of this study were to 1) enhance CPC's poor mechanical properties with micro-platelet reinforcement, and 2) impart antibacterial functionalities in composites with the aim to inhibit surgical site infections (SSI). The work embodies three novel features. First, as opposed to well-known reinforcements with whisker or fiber-like morphology, we explored micro-platelets for the first time as the strengthening phase in the CPC matrix. Second, in contrast to conventional polymeric or calcium phosphate (CaP) fibrous reinforcements, newberyite (NB, MgHPO4.3H2O) micro-platelets belonging to the less explored yet promising MgP family, were evaluated as reinforcements for the first time. Third, NB micro-platelets were doped with Ag+ ions (AgNB, Ag content 2 wt%) for enhancing antibacterial functionalities. Results indicated that 1 wt% of AgNB micro-platelet incorporation in the CPC matrix enhanced the compressive and flexural strengths by 200% and 140% respectively as compared to the un-reinforced ones. Besides, antibacterial assays revealed effective bactericidal functionalities (>99% bacteria kill) of the AgNB reinforced CPCs against Escherichia coli. Finally, cytocompatibility studies confirmed favorable pre-osteoblast cell proliferation and differentiation in vitro. Hence, this effort was successful in developing a self-setting and injectable AgNB reinforced CPC composition with favorable mechanical and antibacterial properties.Explant analysis can provide key insights to understanding failures of artificial joints and thus how they might be improved for the ultimate benefit of patients. There are no previous reports of explant analysis of an artificial wrist joint. see more In this study, an explanted metal-on-polymer Maestro wrist was analysed both in macro and nanoscales to estimate its biotribological performance. The articulation was formed between a cobalt chromium carpal head and an ultrahigh molecular weight polyethylene bearing. The surface roughness values of its articulating surfaces and the backside of the articulation were measured. On average, the articulating surface roughness values were calculated as 0.06 ± 0.02 μm and 1.29 ± 0.63 μm for the cobalt chromium carpal head and ultrahigh molecular weight polyethylene bearing, respectively. Both surfaces had negative skewness, indicating a preponderance of valleys. On the articulating surface of the carpal head, light scratches were observed, and no impingement was observed throughout the component. The polymeric surface had a polished appearance. It had unidirectional scratches at the centre of the articulation, pits of different sizes on its articulating surface, and matt white subsurface regions. The backside of the UHMWPE bearing and the convex surface of the radial body that it was sitting on, were found to have average surface roughness values of 4.23 ± 0.69 μm and 5.57 ± 1.05 μm, respectively. The difference in the means was not significant (p > 0.05). Taking the articulating surface roughness values, the lubrication regime that the explanted Maestro wrist operated under in vivo was estimated for varying physiological conditions, i.e. varying loads, entraining velocities and lubricant viscosities. In every case considered, the explant was found to operate under boundary lubrication.