摘要: The focus of this review is to outline the remarkable ability of the gecko to climb surfaces vertically, at tremendous speed (over 1 m/s) using van der Waals forces (one of nature’s amazing “sticking and unsticking” directional dry adhesion design) as well as contact splitting mechanism. Further, the elasticity of the hairs conforming to the topology of the surface and hence contributing to an increased adhesion force is discussed, apart from the applications of gecko feet bio-inspired solutions. Such applications are in areas as diverse as, and not restricted to, climbing vertically and horizontally on glass surfaces; fitting televisions and computers on the walls; in robots for the inspection and maintenance of installations in space stations and self-cleaning surfaces. By this review, we hope to inspire and motivate the current generation of engineers to study, mimic and abstract the fundamental hierarchical structures as well as the incredible dry adhesion principles (as closely as is possible) objects of nature. This approach will help in improving upon the existing methods to produce gecko feet-like materials with dry adhesion as well as self-cleaning properties. Such refinement strategies can also include the development of hybrid structures utilizing a combination of designs found in other organisms in Mother Nature (for e.g., the mushroom-shaped structure found in the beetle). This requires improvements in the fundamental hierarchical arrangement of the gecko feet-like hairs and their inter-facial interactions with model substrata. Also, the mechanical deformations of the different gecko feet-like materials as well as how sliding velocity impacted adhesional and frictional phenomena should be studied and better understood. This will enable the engineer to develop better gecko feet-like adhesives.
摘要: With the development of science and technology, the development of underwater vehicles with many advantages such as low energy consumption, low noise, high propulsion efficiency and high mobility, and the exploration is the direction of science and technology, and also becomes a hot research field. This paper introduces the status of researches of three different motion modes of the underwater nature objects and analyzed the propulsion mechanisms of different bionic underwater systems and of the existing problems in the development of the bionic underwater propulsion mechanism. This analysis of the use the new materials, existing decisions in bionics and intelligent control technology can be used in the development and design of the bionic thrusters for underwater robots.
摘要: A Knee-Ankle-Foot orthosis (KAFO) is used as a supportive device by individuals with lower limb disability. A type of KAFO that allows knee flexion-extension is prescribed for people who need knee stability in the transverse and frontal planes. In such an orthosis, mimicking the human knee motion is vital to avoid relative motion (called pistoning) between the limb and the orthosis. A four-bar mechanism, owing to its polycentric nature, simplicity and ease of fabrication can provide a customizable, biomimetic solution. This paper presents an improved and robust optimization approach to synthesize a four-bar mechanism to closely mimic the anatomical knee motion. The reference human knee centrode is obtained from literature. A genetic algorithm is used for optimal synthesis of the fourbar mechanism. Results show that the average error between the reference centrode and the centrode of the synthesized four-bar mechanism is very small (0.2 mm). Thus, the synthesized crossed four-bar linkage can reproduce better anthropomorphic characteristics of the knee joint. The methodology can be used for the design of customized orthotic knee joints for KAFOs and knee braces.
摘要: Knee malalignment is considered one of the key biomechanical factors that influence the progression of knee osteoarthritis. In this context, a three-dimensional Finite Element model of the knee joint is developed and used to investigate the effect of the frontal plane femoro-tibial angle as well as the body weight load on the stress distribution in the knee cartilage and menisci. Therefore, the knee joint model is obtained through CAD software. Bones, articular cartilage and menisci are considered linear, elastic and isotropic materials. Ligaments were modelled using connectors. Consequently, contact pressures and equivalent stress (von-Mises) are calculated in Abaqus software. This model was validated using experimental and numerical results obtained by other authors. Results of this work demonstrated that; compressive stress and contact pressure on the medial compartment of the knee joint were found to be larger compared to those in the lateral compartment when the femoro-tibial angle and the body weight load increased from 0° to 12° varus and 500 N to 1250 N, respectively, suggesting that these two parameters might be risk factors for developing medial compartment knee osteoarthritis.
摘要: There are a few years, it has become the use of artificial discs and effectively to compensate for damaged discs in humans due to the eccentric load applied on the spine. As we know very well that the success of a disc implantation depends strongly on the initial stability of the implant and the integration of the bone tissue of the vertebrae with these discs in the long term. Due to the optimal distribution of mechanical stresses in the surrounding bone. It is for this reason that the search for reasonable solutions to compensate the damaged disk and reduce the stresses in the cortical bone and spongy has become a very important research axis. Several alternatives have been studied, including implant design, prosthesis geometry, prosthetic components and biomaterials used. In this regard, we have proposed two new models for some innovative artificial disks by some of the biomechanics researchers and we have installed these discs between the two vertebrae L5 and S1 of the spine, to ensure spinal stability and avoid slipping, we installed a posterior attachment system (6 screws plus 2 rods) at the pedicular levels of the lumbar vertebra (S1-L5, L5-L4).It is for this technique that we have used finite elements in three dimensions and using the software ANSYS to know the extent of the realization of these discs under the influence of the load applied to them. The numerical results show that these disks played a very important role in the absorption of the stresses and to minimize, On the other hand, the lumbar inter-somatic cage (Model II) filled with cancellous bone is too great a role in reducing the stress compared to another synthetic (Model I) disc. In general, the new model of the inter-somatic cage filled with cancellous bone and reinforced by a posterior fixation system has given a lower level of stress in the cortical bone and the spongy bone of the lumbar vertebra (L5) compared to the healthy disk (D1).
摘要: Total hip replacement (THR) that is widely used today is the cemented type, which its application will lead to aseptic loosening. To avoid the occurrence of aseptic loosening, THR coated with hydroxyapatite (HA) is required because HA is osteoconductive which can stimulate the growth of osteoblasts. This study aims to determine the optimum sinter temperature which produce HA coating suitable as implant material. To achieve these objectives, the electrophoretic deposition (EPD) conducted coating method at concentrations of HA 1,0M, voltage of 100V for 30 minutes and then sintered at temperatures are 550°C, 700°C and 900°C respectively detention for 10 minutes. The results showed that the treatment of sintering after the coating process through the EPD method affect the characteristics of the layer thus formed. Sintering process affects the crystallinity of the HA layer. The higher the sintering temperature the higher its crystallinity. The higher the crystallinity the stronger the HA layer attached to the substrate cobalt alloy. Based on this research, the selected sintering temperature was 900 °C for 10 minutes which produced a layer of HA with the best characteristics that meet the standard of implant prosthesis, the crystallinity of 89.4%, thick layer of 70.80 ± 4.18 μm, adhesion strength of 21.87 ± 0.23 MPa, the corrosion rate of 0.025 mpy and 70.3% cell viability.
摘要: There is a need for high performance scaffold in tissue engineering. Keeping this perspective in mind, the present study delineates the preparation and physico-chemical characterization of soluble eggshell protein (SEP) modified silk fibroin (SF)-polyvinyl alcohol (PVA) scaffold and its application in bone tissue engineering. The SF/PVA scaffold were prepared by salt leaching and modified with eggshell protein. Micro-architechture and porosity analysis revealed that all the scaffolds were having desired pore size (230-360 µm), interconnected porous network and 90% porosity. The scaffolds were found with suitable swelling behavior and biodegradability to support cell proliferation till replaces native osseous tissue. In vitro cyto-compatibility and differentiation study showed that SEP(SF-PVA) supports viability , proliferation and differentiation of cord blood derived human mesenchymal stem cell. Further, in vivo study in mice model showed that the scaffolds are non-immunogenic and support tissue growth. In conclusion, SEP modified SF-PVA scaffold could be a better option for tissue engineering.
摘要: In case of burns, scaffolds serve as cover for burns and facilitate cells regeneration. Accordingly, this study seeks procedures to synthesize composite scaffolds for burns utilizing collagen-chitosan-Aloe vera to find the best concentration of Aloe vera as scaffolds application. The synthesis of scaffolds was performed with collagen constituent composition as follow: chitosan (1:1) was dissolved in 0.05M Acetic Acid, then subsequent variations of Aloe vera (AV), namely 0% AV; 0.1% AV; 0.15% AV; 0.2% AV; and 0.25% AV were added into collagen-chitosan solution, and freeze dry method was applied. Sample characterization was done by FTIR, tensile strength test, SEM test, cytotoxicity assay and degradation test. Typical absorption bands of collagen in the FTIR test was obtained at 1645.5 cm-1 (C = O stretch), chitosan at 1540.28 cm-1 (NH stretch) and Aloe vera at 3474.41 cm-1 (NH stretch). Tensile test data showed the highest number of tensile strength from the 0.1% AV sample at 0.017 MPa. The SEM test revealed a pore size of <50 μm. During cytotoxicity assay, the entire sample is not toxic. Degradation test demonstrated that overall sample was not exhausted within two weeks. In conclusion, sample with 0.2% AV was potential as scaffolds for burns skin tissue.
摘要: The prevalence rate of surgical wound infections caused by bacteria is an average of 9% of the 1.4 million patients worldwide. For this reason, a modification of an absorbable surgical suture coated with extract of Jatropha curcas L. leaves to kill and inhibit the growth of microorganisms needs to be made. The forming of multifilament fibers is done by electrospinning method. The test results of the functional groups showed the presence of interaction between PLGA-Collagen with the extract of Jatropha Curcas L. leaves indicated by an absorption band at 2924 cm-1 which showed the vibrations of C-H. The tensile test results showed that all samples were in the range of 19.5-87.1 MPa values which corresponded with the modulus of elasticity of the suture thread in the forehead and elbows. The MTT Assay results showed that the percentage of living cells of all samples was above 50%. The bacterial activity test showed that the inhibition zone were in the range of 5-10 mm. The optimal sample showed the degradation rate of 82.2% on the 60th day of the soaking period. It can be concluded that PLGA-collagen Jatropha curcas L. extracts is safe composite and has potential as antibacterial absorbable surgical sutures.
摘要: The complexity of the multiple interactive reactions of various cells/proteins and biochemical processes during phagocyte transmigration for foreign body responses to subcutaneous biomaterial implants have been studied through developed kinetics-based predictive models which have been numerically analyzed. However, the need for direct relationship between the kinetic-based predictive models parameters and the requirements for continuous insights into the significance of various process parameters affecting the phenomena have led to the quest for developing analytical solutions. Therefore, in this work, differential transform method is used to develop analytical solutions for the prediction of phagocyte transmigration for foreign body responses to subcutaneous biomaterial implants. The approximate analytical solutions are used to study the effect of various model parameters on phagocyte transmigration to foreign body responses in biomaterial implantation. The results of the analytical solutions are agreement with the results of the previous studies.