Pathological Study of Light Cupula Syndrome on a Visual Bionic Semicircular Canal.

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.

Design of an In Vitro Semicircular Canal Model and Its Use for the Study of Canalithiasis.

Canalithiasis is a common vestibular system disorder, which may lead to a specific form of vertigo known as BPPV or top-shelf vertigo. In this paper, based on the actual geometric parameters of the human semicircular canal, we designed a four-fold in vitro one-dimensional semicircular canal model using technologies such as three-dimensional printing, image processing, and target tracking. We investigated the essential characteristics of the semicircular canal, such as the time constant of the cupula and the relationship between the number, density, and size of the canalith and the cupular deformation during canalith settlement. The results showed a linear relationship between the number and size of the canalith and the amount of cupular deformation. We also found that when the number of canaliths reached a particular scale, the interaction between the canaliths exerted an additional disturbance on the cupular deformation ("Z" twist). In addition, we explored the latency time of the cupula during canalith settlement. Finally, we verified that the canaliths had little effect on the frequency characteristics of the semicircular canal by a sinusoidal swing experiment. All the results validate the reliability of our 4-fold in vitro one-dimensional semicircular canal model.

A low-frequency acceleration sensor inspired by saccule in human vestibule.

A human vestibular system is a group of devices in the inner ear that govern the balancing movement of the head, in which the saccule is responsible for sensing gravity accelerations. Imitating the sensing principle and structure of the Sensory Hair (SH) cell in the saccule, a Bionic Sensory Hair (BSH) was developed, and 9 BSH arrays were arranged in the bionic macular at the bottom of the spherical shell to prepare a Bionic Saccule (BS). Based on the piezoelectric equation, the electromechanical theoretical models of the BSH cantilever and BS were deduced. They were subjected to impact oscillations using an exciter, and their output charges were analyzed to check their sensing ability. The results showed that BSH could sense its bending deflection, and the BS could sense its position change in the sagittal plane and in space. They exhibited a sensitivity of 1.6104 Pc s2/m and a fast response and similar sensing principles and low resonance frequency to those of the human saccule. The BS is expected to be used in the field of robotics and clinical disease diagnosis as a part of the artificial vestibular system in the future.

Study the biomechanical performance of the membranous semicircular canal based on bionic models.

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.

Development of Bionic Semicircular Canals and the Sensation of Angular Acceleration.

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.

Outcomes of the bionic semicircular canals support the "density hypothesis" and "circular hypothesis".

To date, there are three main hypotheses explaining why the human semicircular canals (HSCCs) cannot sense linear accelerations. To further study this issue, we designed a bionic ampulla (BA) instrumented with a symmetrical metal core polyvinylidene fluoride fiber as a bionic sensor, which imitates the structure and function of the human ampulla. The BA was confirmed to have a good sensing ability in experiments with a straight tube. Additionally, we designed a bionic semicircular canal model, a blocking model, and a square model. We compared the perception performance of these three models to test the "density hypothesis," the "closed loop hypothesis," and the "circular hypothesis." The outcomes of these experiments verified the "density hypothesis" and "circular hypothesis," but did not support the "closed loop hypothesis," shedding light on why the HSCC is sensitive to angular acceleration, but not to linear acceleration.

Study on the Perception Mechanism of Utricles Based on Bionic Models.

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.

Design and fabrication of an E-whisker using a PVDF ring.

Mammalian whiskers can perceive obstacles and airflows. In this study, an electronic whisker (E-whisker) sensor was designed and fabricated by setting a PVDF ring with symmetrical electrodes on the root of a fiber beam. Vibration displacements with different waveforms were applied at the free end of the E-whisker beam to study the relationship between the vibration displacements and the output signals. The E-whisker protrusion sensing ability was investigated by driving it to sweep through the surface of a base platform. A static E-whisker beam and a swinging E-whisker were then separately placed in a wind tunnel to detect the airflow perception of the sensor. The experimental results suggested that the E-whisker could sense the frequencies and amplitudes of displacements at its free end, the height and width of a platform or the heights of other irregular protrusions; the static E-whisker could sense the magnitude or direction of an impact airflow, while the swinging E-whisker could sense the magnitude of a constant airflow. Thus, this kind of E-whisker could perceive the environment and airflow through touch sensation and could be used as a physical model to study the principles and abilities of animal whiskers to perceive obstacles and airflows.