Research On The Mechanism Of Rapid Closure Of The Snapping Shrimp Claw

The ocean contains abundant bioenergy and mineral resources.Along with the decreasing of land resources,people begin to pay more attention to the huge energy storehouse.With the development and utilization of marine resources,people's awareness of marine resources is increasing.As an important deep-sea operation tool for marine operations and scientific investigation,the underwater robot arises at the historic moment and develops vigorously and rapidly.The manipulator device is an important part of a robot in interacting with the external environment,and it is also the most important and indispensable component.Simultaneously,it is one of the most necessary equipment for the development of marine resources to accomplish the difficult and dangerous work instead of human beings in various extreme environments.The dynamic performance and dexterity of the manipulator control directly determine the performance of the entire underwater robot or the submersible operating system.However,there are many deficiencies in the driving mode of underwater manipulator,such as larger volume and mass,slower response speed and lower driving and transmission efficiency.Many creatures have special biological function and motion patterns of high efficiency and exquisite,after ten thousand years of evolution,which provide a natural inspirations for the new bionic drive and transmission technology.Therefore,The objective of this study is to discuss the mechanism of rapid closure of snapping shrimp claw based on the analysis of surface morphorlogy,micro structure,musculoskeletal system,in order to supply new ideas for the development of drive and transmission technology.In the study,measurements of the microstructure,surface morphology,material composition and mechanical properties of the snapping shrimp claw were conducted.It was found that the surface of dactyl and propus consists of cone-shaped micropapillae,rhombic dents and short straight stripes with a hierarchical structure across different scales.CFD simulation and PIV experiments were conducted to verify the possible drag reduction function of the cone-shaped micropapillae morphology and the configuration.The CFD analysis results suggested that the cone-shaped micropapillae units played a role during the rapid closure motion by reducing drag under water.The microstructures of the cross-section of the snapping claw were obtained in the study.It was showed that there are four different layers.The outermost layer is a thin layer with a layer of waxy on its surface.The second layer is made up of smooth layer and fiber lamella structure.And the fiber lamella structure consists of chitin fibers arranged vertically in a lamellar-fashion,which forms a cavity.This structure can not only significantly reduce the overall weight,but also make the shrimp have strong compression performance,and effectively block the heat transfer.The third layer is Bouligand structured endocuticle,it gives the light quality of the shrimp and also can absorb and disperse the kinetic energy and load of the impact.In addition,the staggered stacking structure of the spiral plywood layer can also effectively prevent the crack from continuing to propagate,thereby preventing the overall structure from breaking and improving the crack arrest performance.The inner layer is a layered structure,and the stacking structure greatly increases the stiffness of the claw.The arrangement and thickness of fiber in the four layers are different,and the corresponding functions are different.The elements in the four layers,the dactyl and propus of the claw are the same through the EDS analysis,but their contents are different.We further confirmed the composition of the claw by Fourier transform infrared spectroscopy and XRD experiment.Then the mechanical properties of the claw,including its surface and cross-section,were tested through the Nano-indentation,and the yield strength and elastic index were also calculated.The results showed that the elastic modulus and hardness of different test positions are different,and the differences of mechanical properties indicate the heterogeneity of biomaterials.The mechanical properties of dactyl are better than that of propus.This may be beneficial to the transmission of driving force,and ensures it acts as an active part to complete the rapid closure motion,and also helps the shrimp to provide its attack and defense effectiveness in fighting process.Nano-indentation measurements on the different layers of cross-section of snapping claw showed that both the modulus and hardness decrease progressively from the distal smooth layer of exocuticle to the innermost membranous layer.This modulus and hardness gradients of the exocuticle and endocuticle layer may arise from gradations in different fiber orientations and stack density.Even in the same layer,the hardness and modulus of elasticity also fluctuated greatly.The main reason is that the microstructure is mainly composed of chitin fibers,and the difference in the density of microstructures is caused by fibers due to fiber orientation,stacking way and density.The changes in the mechanical properties of the four layers also have an inevitable relationship with the gradient of calcium content.The differences of mechanical properties are conducive to the absorption and dispersion load of the snapping shrimp when it is impacted,so as to prevent the occurrence of the rupture or to inhibit the expansion of the crack.At the same time,a bionic composite structure with a light weight,high strength,high impact resistance was developed based on the microstructure of the cross-section.In addition,we observed and analyzed the whole process and motion details of the rapid closure motion of the claw through the high-speed motion capture measurement.We obtained the muscle topological structure of the shrimp's claw,and finally got the mechanism of rapid closure motion of the claw,combined with the tissue slice test and the Micro-CT scanning.This thesis comprehensively analyzed the characteristics and functions of the claw of the snapping shrimp with multiple scales,including its material,structure,configuration and so on,through the SEM observation,Nano-indentation mechanical test and CFD simulation.The topological structure of the skeletal muscle system of the shrimp claw was investigated by the tissue section experiment and Micro-CT 3D scanning experiment.In final we proposed of the mechanism and principles of the rapid closure motion of the claw under multi-factors coupling action.Therefore,It provides a new idea for the development and design of bionic manipulator with highly efficient driving and transmission characteristics,and also provides an important biomechanical theory foundation and technological support for developing new fast drive and transmission device.It is of scientific significance and has potential value in engineering application.