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A BA (bionic ampulla) was designed and fabricated using an SMPF (Symmetric electrodes Metal core PVDF Fiber) sensor, which could imitate the sensory hair cells to sense the deformation of the cupula of the BA. Based on the BA, a bionic semicircular canal with membrane semicircular canal (MBSC) and a bionic semicircular canal without membrane semicircular canal (NBSC) were designed and fabricated. The biomechanical models of the MBSC and NBSC were established. The biomechanical models were verified through the perception experiments of the MBSC and the NBSC. The results showed that the SMPF could sense the deformation of the cupula. The MBSC and NBSC could sense the angular velocity and accelerations. What's more, it was speculated that in a human body, the endolymph probably had a function of liquid mass while the membranous semicircular canal and the cupula had a function similar to a spring in the human semicircular canal.

To study the sensing process of the human semicircular canals (HSCs) during head rotation, which is difficult to directly measure due to physiological reasons. A 1-BSC (one-dimensional bionic semicircular canal) and 3-BSC were prepared with soft SMPFs (symmetric electrode metal core polyvinylidene difluoride fibers), which could sense deformations similar to human sensory cells. Based on these models, experiments were carried out to study the principle of the HSCs. Deformations of the bionic ampulla (BA) depended on the angular acceleration. Gravity had a strong influence on the deformation of the BA in the vertical plane. When the 3-BSC was subjected to angular acceleration around one of its centerlines, the three BAs all deformed. The deformation of the BAs was linearly related to the angular acceleration. The deformation of the BA in the main semicircular canal was exactly three times that of the other two BAs.

Background: The relationship between utricle diseases and structural lesions is not very clear in the clinic due to the complexity and delicacy of the utricle structure. Therefore, it is necessary to study the perception mechanism of the utricle. Methods: Imitating the sensory cells in the macula of the utricle, a symmetrical metal core PVDF fiber (SMPF) was designed as a bionic hair sensor to fabricate a bionic macula (BM), a bionic macula with sand (BMS) and a bionic utricle (BU). Then experiments were carried out on them. Results: This indicated the SMPF sensor can sense its bending deformation, which was similar to the sensory cell. The amplitude of the output charges of the SMPF in BMS and BU were significantly improved. The SMPF, whose electrode boundary was perpendicular to the impact direction, exhibited the largest output charges. Conclusion: The presence of otoliths and endolymph can improve the sensing ability of the utricle. The human brain can judge the direction of head linear accelerations based on the location of the sensory cell in the macula that produces the largest nerve signals. This provides a possibility of studying utricle abnormal functions in vitro in the future.

Prediction accuracy is a key problem in estimating the fatigue resistance of engineering structures. Here, we consider mechanical structures with fasteners that are simultaneously subjected to a combination of shear and tension (or compression) loads. The currently used detail fatigue rating method is modified and an extended detail fatigue rating method is proposed to improve the estimation results. This is achieved by considering the effect of the load, stress concentration, and fatigue failure criterion on the fatigue capacity. An experimental assessment is also made of many specimens with different structures. A comparison of the estimation results obtained using the extended detail fatigue rating method and the experimental results shows that the new method gives results that are acceptable in engineering practice.

A type of persistent direction-changing positional nystagmus with a null point during head position deflection is known as light cupula syndrome (LCS) in the clinic. To date, the pathogenesis and biomechanical response of human semicircular canals with light cupula syndrome (LCS) (HSCs–LCS) are still unclear. In this study, based on the anatomical structure and size of the one-dimensional human semicircular canal (HSC) and imitating the pathological changes of the endolymph in HSC with LCS, a visual bionic semicircular canal (BSC) with LCS was fabricated using three-dimensional printing technology, hydrogel modification, and target tracking technology. Through theoretical derivation, mathematical models of the HSC–LCS perception process were established. By conducting in vitro experiments on the bionic model, the biomechanical response process of HSC–LCS was studied, and the mathematical models were validated. The results of pulse acceleration stimulation showed that the pathological changes in the density and viscosity of the endolymph could reduce the deformation of the cupula of the BSC–LCS and increase the time constant. The results of the sinusoidal acceleration stimulation showed that the amplitude–frequency gain of the BSC–LCS decreased and the phase difference increased. The BSC-LCS can be used as a tool for pathological research of the HSC–LCS. The results of this study can provide a theoretical basis for clinical diagnosis. [ABSTRACT FROM AUTHOR]

Academia often uses the "circular geometry hypothesis" to explain the sensing principle of the human semicircular canal (SCC) system for angular acceleration, which is widely accepted as an important angular acceleration sensor in the human balance system. On the basis of this hypothesis and the anatomical structure of human SCCs, a series of physical SCC models with different geometries at 4x magnification were prepared via three-dimensional printing and modification of hydrogels. Theoretical models of the SCC perception mechanism were established. Then, impulse angular acceleration, sinusoidal rotation, and sinusoidal linear stimulation were applied to the models, and their responses were visually observed and analyzed in detail. As a result, the circular SCC model had a larger system gain and a smaller phase difference for angular acceleration stimulation but a smaller system gain and a larger phase difference for linear acceleration stimulation. These results verified that the circular semicircular canal was more sensitive to angular acceleration. Our bionic model is hoped to be used for demonstrating the human SCC working process, facilitating researchers in better understanding of the working mechanism of the human SCC, or as a manual model for medical staff to simulate the diagnosis and treatment of human SCC. [ABSTRACT FROM AUTHOR]

Crickets and many other orthopteran insects can detect an impinging airflow using mechanosensory hairs located on their cerci. Inspired by these filiform mechanosensory hairs, a new symmetrical electrodes metal-core piezoelectric fiber (SMPF) was designed and fabricated as a building block for future airflow sensors. This novel type of airflow sensor was produced utilizing the extrusion method and high-temperature sintering. A metal core was basically located at the center of the fiber and surrounded by a hollow cylinder of ceramic material. Two thin metal films were spray-coated symmetrically on the surface of the fiber on opposite sides. After successful polarization, the two surface metal layers could be used as sensor electrodes. This way, a cantilevered SMPF was able to detect the strength and direction of an impinging airflow. A theoretical model of the SMPF airflow sensor was established and validated by the experimental results. The results further showed that the electric charge generated on the electrodes of a cantilevered SMPF grows exponentially with the airflow strength, and that it is proportional to the cosine of the airflow direction. [ABSTRACT FROM AUTHOR]

The metal core piezoelectric fiber (MPF) is one of the new type piezoelectric devices for sensors and actuators. To investigate the dynamic characteristics of a cantilever MPF, the dynamic admittance matrix is established. It can describe the response of a cantilever MPF subjected to driving parameters, a harmonically varying axial force F at the tip and a harmonically varying voltage V on the electrodes. The responses parameters of a cantilever MPF, including a dynamic tip elongation δ and a dynamic electric charge Q, can be obtained using the vibration theory and the average distributed electrical charge method. The response parameters are related to the driving parameters by a 2 × 2 matrix. The dynamic models for measuring piezoelectric parameters of a MPF are given in order to illustrate the applications of the previous dynamic admittance matrix. The piezoelectric parameters, the elastic coefficient s_{11}^E , the piezoelectric coefficient d_{31} and the dielectric constant ℇ _{33}^T of MPF were measured experimentally. [ABSTRACT FROM AUTHOR]

The half coated metal core piezoelectric fiber (HMPF) is one of the new type piezoelectric devices for sensors and actuators. The constitutive equations of cantilevered HMPFs under various mechanical and electrical loading conditions are derived. The equations can describe the behavior of HMPF subjected to an external voltage V on the electrodes, a bending moment M at the free end of the beam, a lateral force F at the tip of the beam and a uniformly distributed load p on the whole length. The internal energy density of the beam is expressed in mechanical strain and electrical field. The internal energy is calculated by integrating the energy density over the whole volume of the beam. The voltage V, bending moment M, lateral force F, and distributed load p are generalized force acting on the fiber and their corresponding generalized displacement are the charge Q on the electrodes, the tip angle α, the tip deflection δ, the areal displacement A of the fiber. The constitutive equations give the dependence of the generalized displacements upon generalized forces. The equations are given in the direct form, with external parameters (M, V), (F, V), and (p, V) as independent variables and also in a linear combination with (M, F, p, V) as variables. The constitutive equations derived in this paper can be used for further analysis of HMPF sensors and actuators. Two experiments, in which a HMPF was used as a sensor or an actuator, were performed to verify the constitutive equations. The experimental results are compared with the numerical results. [ABSTRACT FROM AUTHOR]

To track prey or avoid predators, many arthropods can detect variations in airflow and pressure gradients using an array of very thin and sensitive filiform hairs. In this study, metal core piezoelectric poly(vinylidene fluoride) (PVDF) fibers were prepared to mimic such hair sensors. The flexibility of the fibers was very good, which was helpful for overcoming the typical brittleness of piezoelectric ceramic fibers. At the same time, the diameter of the fibers was very small (down to 50 μm in diameter). In order to mimic the insects’ hairs to the maximum extent, which was expected to greatly improve the sensitivity of such PVDF fiber-based sensors, a feasible process to prepare and extract electrodes on the surface of the fibers had to be developed. Compared with stainless steel filament-core fibers, the molybdenum filament-core PVDF fibers were easy to stretch. The molybdenum filament was then covered by a cylindrical PVDF layer with a diameter of 400 μm. One half of the longitudinal surface of the fibers was spray-coated with a conductive silver adhesive. The metal core was then used as one electrode, and the conductive silver adhesive was used as the other electrode. After polarization, a single metal-core PVDF fiber could be used as an airflow sensor. The surface structure and the sections of the PVDF fiber were analyzed by scanning electron microscopy. The results of the mechanical stretching tests showed that the metal core greatly enhanced the mechanical properties of the PVDF fibers. X-ray diffraction revealed that the greater the stretching ratio, the higher the α-to-β-phase conversion rate during the preparation of the PVDF fibers. A single metal-core PVDF fiber was used as a bionic airflow sensor, and a mechanical model of this sensor was derived. The airflow sensing capability of the PVDF fiber was experimentally confirmed in a miniature wind tunnel. The results showed that a cantilevered metal-core PVDF fiber is capable of detecting the range and direction of the surrounding airflow variations. The experimental results also verified the theoretical model. [ABSTRACT FROM AUTHOR]