Membrane Vibration Research Articles

Molecular Vibration and Physicochemical Performance of Proton-Conducting Solid Polymer Electrolyte Membrane based on CMC/PVA/CH3COONH4

This work studied examined the influence of ammonium acetate (CH3COONH4) on CMC/PVA-based solid polymer electrolyte (SPE) membranes, focusing on molecular vibration, proton conductivity, and physicochemical properties. SPE membranes were prepared via the casting solution method with varying CH3COONH4 concentrations to determine the optimal proton conductivity. Various characterizations, including FTIR, EIS, XRD, and TGA, were performed. The optimal membrane condition was achieved with 10 wt-% CH3COONH4 in the CMC/PVA (80/20) blend, yielding proton conductivity of 3.93×10⁻⁴ S/cm and favorable mechanical, thermal, and crystallinity properties, making it suitable for proton-conducting polymer applications. Keywords: ammonium acetate, carboxymethyl cellulose, ionic conductivity, poly(vinyl alcohol), proton battery, solid electrolyte membrane

Corti fluid is a medium for outer hair cell force transmission.

The mammalian cochlea amplifies sounds selectively to improve frequency resolution. However, vibrations around the outer hair cells (OHCs) are amplified non-selectively. The mechanism of the selective or non-selective amplification is unknown. This study demonstrates that active force transmission through the extracellular fluid in the organ of Corti (Corti fluid) can explain how the cochlea achieves selective sound amplification despite the non-frequency-selective action of OHCs. Computational model simulations and experiments with excised cochleae from young gerbils of both sexes were exploited. OHC motility resulted in characteristic off-axis motion of the joint between the OHC and Deiters cell (ODJ). Incorporating the Corti fluid dynamics was critical to account for the ODJ motion due to OHC motility. The incorporation of pressure transmission through the Corti fluid resulted in three distinct frequency tuning patterns depending on sites in the organ of Corti. In the basilar membrane, the responses were amplified near the best-responding frequency (BF). In the ODJ region, the responses were amplified non-selectively. In the reticular lamina, the responses were amplified near the BF but suppressed in lower frequencies. The suppressive effect of OHCs was further examined by observing the changes in tuning curves due to local inhibition of OHC motility. The frequency response of the reticular lamina resembled neural tuning, such as the hypersensitivity of tuning-curve tails after hair cell damage. Our results demonstrate how active OHCs exploit the elastic frame and viscous fluid in the organ of Corti to amplify and suppress cochlear vibrations for better frequency selectivity.Significance Statement Active outer hair cells have been considered to selectively amplify the basilar membrane vibrations near the sound's tonotopic location. However, recent observations from different labs showed that outer hair cells' action is non-selective-it spreads over the broad span of traveling waves. These observations challenge the existing theory pegged to basilar-membrane mechanics. The motion at the joint between the outer hair cell and the Deiters (ODJ) cell holds the key to account for the non-selective action of outer hair cells. We show that the characteristic motions at the ODJ are explained coherently when Corti fluid acts as the medium for outer hair cell force transmission. Our results demonstrate how non-selective outer hair cell action produces selective neural responses.

Sound insulation analysis of sound insulation materials laminated with membrane vibration type acoustic metamaterial

In recent years, research on various acoustic metamaterials has progressed. We fabricated PP into a honeycomb structure and pasted films on the top and bottom to create an acoustic metamaterial that has a sound-absorbing effect due to membrane vibration. Furthermore, a small hole was made in the center of the film part to add sound absorption effect through Helmholtz resonance. Considering its application to automobile trim, felt and rubber layers were added and laminated on a steel plate. This structure was modeled using the finite element method and the transmission loss was calculated. We will report on comparisons with measurement results and calculation results for various lamination patterns.

Current Loads on a Horizontal Floating Flexible Membrane in a 3D Channel

A 3D analytical model is formulated based on linearised small-amplitude wave theory to analyse the behaviour of a horizontal, flexible membrane subject to wave–current interaction. The membrane is connected to spring moorings for stability. Green’s function approach is used to obtain the dispersion relation and is utilised in the solution by applying the velocity decomposition method. On the other hand, a brief description of the experiment is presented. The accuracy level of the analytical results is checked by comparing the results of reflection and the transmission coefficients against experimental data sets. Several numerical results on the displacements of the membrane and the vertical forces are studied thoroughly to examine the impact of current loads, spring stiffness, membrane tension, modes of oscillations, and water depths. It is observed that as the value of the current speed (CS) rises, the deflection also increases, whereas it declines in deeper water. On the other hand, the spring stiffness has minimal effect on the vibrations of the flexible membrane. When vertical force is considered, higher oscillation modes increase the vertical loads on the membrane, and for a mid-range wavelength, the vertical wave loads on the membrane grow as the CS increases. Further, the influence of the phase and group velocities are presented. The influences of CS and comparisons between them in terms of water depth are presented and analysed. This analysis will inform the design of membrane-based wave energy converters and breakwaters by clarifying how current loads affect the dynamics of floating membranes at various water depths.

The Potential Changes and Stereocilia Movements during the Cochlear Sound Perception Process

Sound vibrations generate electrical signals called cochlear potentials, which can reflect cochlear stereocilia movement and outer hair cells (OHC) mechanical activity. However, because the cochlear structure is delicate and complex, it is difficult for existing measurement techniques to pinpoint the origin of potentials. This limitation in measurement capability makes it difficult to fully understand the contribution of stereocilia and transduction channels to cochlear potentials. In view of this, firstly, this article obtains the stereocilia movement generated by basilar membrane (BM) vibration based on the positional relationship between the various structures of the organ Corti. Secondly, Kirchhoff’s law is used to establish an electric field model of the cochlear cavity, and the stereocilia movement is embedded in the electric field by combining the gated spring model. Finally, a force-electric coupling mathematical model of the cochlea is established. The results indicated that the resistance variation between different cavities in the cochlea leads to a sharp tuning curve. As the displacement of the BM increased, the longitudinal potential along the cochlea continued to move toward the base. The decrease in stereocilia stiffness reduced the deflection angle, thereby reducing the transduction current and lymphatic potential.

Wake interference effects on flow-induced vibration of flexible membrane wings

This work investigates the effect of wake interference on the nonlinear coupled dynamics and aerodynamic performance of flexible membrane wings at a moderate Reynolds number. A high-fidelity computational aeroelastic framework is employed to simulate the flow-induced vibration of flexible membrane wings in response to unsteady vortex wake flows produced by an upstream stationary circular cylinder. The coupled dynamics of the downstream membrane are investigated at different gap ratios, aeroelastic numbers, and offset distances. The variations in flow features, membrane responses, and frequency characteristics are analyzed to understand the wake interference effect on membrane aeroelasticity. The results indicate that the aerodynamic performance and flight stability of the downstream membrane are degraded under the wake interference effect. Four distinct flow regimes are classified for the cylinder–membrane configuration, namely (i) single body flow, (ii) co-shedding I, (iii) co-shedding II, and (iv) detached vortex-dominated vibration, respectively. The mode transition is found to build new frequency synchronization between the flexible membrane and its own surrounding flows, or the wake flows of the cylinder, to adjust the aerodynamic performance and membrane vibration. This study sheds new light on membrane aeroelasticity in response to wake flows and enhances understanding of the fluid–membrane coupling mechanism. These findings can facilitate the development of next-generation bio-inspired drones that have high flight efficiency and robust flight stability in gusty flows.

Generation of quasi-traveling waves in a finite rectangular membrane with two internal viscoelastic line supports

In this work we study the forced vibration of a finite rectangular membrane driven by arbitrarily distributed boundary motion on two adjacent edges and internally coupled with multiple viscoelastic line supports, as an extension of the analysis of coexisting vibrations and waves in one-dimensional elastic strings and ducts. Using the static solution for the membrane displacement in the absence of interior supports, the response of the nonclassically damped system is obtained through a normal-mode expansion. A traveling-wave index based on complex orthogonal decomposition is utilized to identify and optimize the traveling waves in the rectangular membrane. A vibration localization condition in a semi-infinite membrane is analytically derived, from which the complex boundary excitations and constraints in a finite membrane are specified to effectively realize pure traveling waves and confine the vibration to a restricted area. Then the membrane is edge-driven by a simpler time-periodic, spatially sinusoidal excitation for practical realization, with the line-support parameters optimized using the traveling-wave index function and a derivative-free optimization routine with lower-bound constraints. Analytical results show that quasi-traveling waves are produced for ranges of line-support parameters (location, stiffness and damping) following optimization using the traveling-wave index. The developed wave patterns are examined with a power-flow analysis and numerically verified through finite element analysis. Wave localization is demonstrated to be valid in a finite membrane with specific boundary conditions and multiple viscoelastic line supports. The proposed method shows the predictive ability of the orthogonally stiffened membrane configuration as the basic unit cell for the design of periodic structures with directional wave propagation as well as vibration localization dynamics.

Piezoceramic membrane with built-in ultrasound for reactive oxygen species generation and synergistic vibration anti-fouling

Piezoceramic membranes have emerged as a prominent solution for membrane fouling control. However, the prevalent use of toxic lead and limitations of vibration-based anti-fouling mechanism impede their wider adoption in water treatment. This study introduces a Mn/BaTiO3 piezoceramic membrane, demonstrating a promising in-situ anti-fouling efficacy and mechanism insights. When applied to an Alternating Current at a resonant frequency of 20 V, 265 kHz, the membrane achieves optimal vibration, effectively mitigating various foulants such as high-concentration oil (2500 ppm, including real industrial oil wastewater), bacteria and different charged inorganic colloidal particles, showing advantages over other reported piezoceramic membranes. Importantly, our findings suggest that the built-in ultrasonic vibration of piezoceramic membranes can generate reactive oxygen species. This offers profound insights into the distinct anti-fouling processes for organic and inorganic wastewater, supplementing and unifying the traditional singular vibrational anti-fouling mechanism of piezoceramic membranes, and potentially propelling the development of piezoelectric catalytic membranes.

Near-field optomechanical transduction enhanced by Raman gain.

Raman-gain-enhanced near-field optomechanical transduction between a movable optical cavity and SiN-membrane resonator is demonstrated. The Raman gain compensates for the intrinsic loss of the cavity and amplifies the optomechanical transduction, through which the membrane vibration is sensed using a high-Q whispering-gallery-mode optical cavity evanescently. The optical Q of the cavity resonance is improved with respect to the optical pump power, which results in an increase in the optomechanically transduced vibration signals of the mechanical resonator. Our near-field optomechanical coupling approach with optical gain realizes highly sensitive displacement measurement in nano- and micro-mechanical resonators consisting of arbitrary materials and structures.

Vibration of microphone membrane: Effects of thermal stress

The aim of this work is to improve theoretical and experimental tools for modelling and characterising the global behaviour of measurement microphones in a large range of environmental conditions. In most of measurement microphones, the sensitive part is a vibrating membrane stretched and clamped on the body of the microphone. If the sensor is operated at ambient temperatures that significantly differ from atmospheric one, thermal expansion of the microphone membrane and body causes strain and stress variations in the membrane, which lead to altered vibrational behaviour when it is submitted to an acoustic wave. An analytical approach is developed here to express the thermal stress related to the fact that thermal expansions of the microphone membrane and body are different. These effects are then taken into account in a classical modelling procedure for describing the vibration of a microphone membrane in vacuo. An experiment, that relies on the electrostatic actuator technique, has been performed in a fine vacuum to characterise the first resonance mode of a commercial microphone membrane in low temperatures range, from atmospheric to cryogenic. The experimental results highlight the significant effects of the thermal stress induced by the differences between thermal expansion properties of the materials constituting the microphone. These results are consistent with the membrane vibration predicted by the analytical modelling proposed. Thus, even small differences between the thermal expansion properties of the microphone membrane and body have to be taken into account in a modelling procedure to get reliable predictions of the membrane vibration at various ambient temperatures.

Programmable photoacoustic manipulation of microparticles in liquid

Particle manipulation through the transfer of light or sound momentum has emerged as a powerful technique with immense potential in various fields, including cell biology, microparticle assembly, and lab-on-chip technology. Here, we present a novel method called Programmable Photoacoustic Manipulation (PPAM) of microparticles in liquid, which enables rapid and precise arrangement and controllable transport of numerous silica particles in water. Our approach leverages the modulation of pulsed laser using digital micromirror devices (DMD) to generate localized Lamb waves in a stainless steel membrane and acoustic waves in water. The particles undergo a mechanical force of about several µN due to membrane vibrations and an acoustic radiation force of about tens of nN from the surrounding water. Consequently, this approach surpasses the efficiency of optical tweezers by effectively countering the viscous drag imposed by water and can be used to move thousands of particles on the membrane. The high power of the pulsed laser and the programmability of the DMD enhance the flexibility in particle manipulation. By integrating the benefits of optical and acoustic manipulation, this technique holds great promise for advancing large-scale manipulation, cell assembly, and drug delivery.

Questions for proponents of Bekesy’s theory

The theory of hearing called Bekesy’s traveling wave theory, announced in 1928 by a young engineer from Budapest, Georg Bekesy (1899-1972), was revised and supplemented many times. In 1961 it was awarded the Nobel Prize. It still contains several ambiguities that require analysis. The most important points requiring clarification include: 1. Sound wave resonance in the cochlear fluids with the transverse wave of the basilar membrane. 2. Own vibrations of the basilar membrane. 3. Frequency resolution associated with the basilar membrane. 4. Transmission of information through the cochlear fluid. 5. Tip-link mechanism. 6. Amplification of quiet sounds by OHC contraction 7. The pathway of auditory information conducted to the receptor.

Coupled Dynamics of Steady Jet Flow Control for Flexible Membrane Wings

We present a steady jet-flow-based flow control of flexible membrane wings for the adaptive and efficient motion of bat-inspired drones in complex flight environments. A body-fitted variational computational aeroelastic framework is adopted for the modeling of fluid–structure interactions. High-momentum jet flows are injected from the leading edge and transported to the wake flows to alter the aerodynamic performance and the membrane vibration. The coupled dynamic effect of active jet flow control on membrane performance is systematically explored. While the results indicate that the current active flow control strategy performs well at low angles of attack, its effectiveness degrades at high angles of attack with large flow separation. To understand the coupling mechanism, the variations of the vortex patterns are examined by the proper orthogonal decomposition modes, and the fluid transport process is studied by the Lagrangian coherent structures. Two scaling relations that quantitatively connect the membrane deformation with the aerodynamic loads presented in our previous work are verified even when active jet flow control is applied. A unifying feedback loop that reveals the fluid–membrane coupling mechanism is proposed. These findings can facilitate the development of next-generation bio-inspired drones that incorporate smart sensing and intelligent control.

Nonlinear vibrations of fractional viscoelastic PET membranes subjected to tangential follower force

Nonlinear forced vibrations of simply supported viscoelastic Polyethylene Terephthalate (PET) membranes subjected to a harmonic excitation and tangential follower force are investigated in this paper. The consideration of vibration systems under follower force requires special attention to the modeling of non-conservative force and its influence on nonlinear analysis. Herein, a fractional Kelvin-Voigt Hamilton-based framework accounting for the viscoelastic PET membrane is developed. Based on the Hamilton principle for the non-conservative system, the mathematical modeling of viscoelastic PET membrane taking into account non-conservative force and geometric nonlinearity is formulated, and the derived equations are discretized via the Galerkin schemes. A technique of multiple scales is employed to numerically acquire the frequency–response curves with different system configurations. Numerical investigations are conducted to analyze the effects of tangential follower force, viscous coefficient, as well as fractional order on the dynamic stability of the considered structure. Further ramifications of the present study point to the paramount importance of tangential follower force and an accurate viscoelasticity model on the dynamic behaviors of the viscoelastic structures.

Multi-factors effects analysis of nonlinear vibration of FG-GNPRC membrane using machine learning

Functionally graded graphene nanoplatelet reinforced composite (FG-GNPRC) have exhibited significant potential for the development of high-performance and multifunctional structures. In this paper, we present a machine learning (ML) assisted uncertainty analysis of nonlinear vibration of FG-GNPRC membranes under the influence of multi-factor coupling. Effective medium theory (EMT), Mori-Tanaka (MT) model and rule of mixture are utilized to evaluate the effective material properties of the composite membrane. Governing equations are derived via an energy method with the frameworks of the hyperelastic membrane theory, Neo-Hookean constitutive model and the couple dielectric theory. Randomly generated inputs after data pre-processing are fed into governing equations, which are solved by numerical methods for outputs. Three ML models, including artificial neural network (ANN), support vector regression (SVR) and AutoGluon-Tabular (AGT), are adopted to capture the complex relationship between the systematic inputs (i.e., structural dimensions, attributes of GNPs and pores, external electric field, etc.), frequency ratio and dimensionless amplitude of FG-GNPRC membranes. The results demonstrate that all three ML models demonstrate exceptional computational efficiency, and AGT presents higher prediction accuracy compared to the other two models. Based on the Shapley additive explanations (SHAP) approach, the effects of uncertainties of system parameters and multi-factor coupling on the nonlinear vibration of the FG-GNPRC membrane are analyzed. It is found that the uncertainty of structural parameters has the greatest impact on the nonlinear vibration of FG-GNPRC membranes, particularly when the membrane is subjected to a voltage of 10 V and smaller stretching ratio.

Characterizing the primary resonator in the cochlea

The cochlear traveling waves are explained by a bank of independent resonators coupled longitudinally by lymphatic fluids. Many cochlear models require at least two resonators to account for observed responses. To investigate the resonators in the cochlea, we used high-resolution optical coherence tomography to measure 2-D vibration patterns of the organ of Corti in acutely excised cochleae from young Mongolian gerbils. The excised tissues were acoustically stimulated. The transverse and radial vibrations of the basilar membrane (BM) and the tectorial membrane (TM) were obtained over their radial span. The BM vibrated from the primary to a higher mode transversely as the stimulating frequency increased. The higher-order mode appeared near the best frequency (BF) of the measured location. Meanwhile, the TM showed no sign of a mode transition up to 1 octave above the BF in radial or transverse vibrating patterns. Within the physiological frequency range, the BM exhibits the characteristic behavior of a resonator. In contrast, the TM does not. Our results suggest that the TM as the second resonator is not the universal mechanism across the entire cochlea.

Piezoelectric excitation and acoustic detection of thin film polymer membrane vibrations.

A simple method of measuring the vibrational response of a thin film membrane was developed. Piezoelectric excitation and acoustic detection (using a microphone) allowed the vibrational spectra of thin membranes to be measured in the kHz range. Vibrational frequencies were used to determine Young's modulus in thin (µm) solvent tensioned films of polydimethylsiloxane and to measure tension in ultrathin polystyrene films. Simulations of membrane motion generated vibrational spectra that agreed with the results of experiments for different membrane shapes.

Crossflow-induced membrane vibration and its effects on fouling and scaling in direct contact membrane distillation

Membrane distillation (MD) is driven by vapor pressures rather than hydraulic pressures. Consequently, certain regions of the membrane may be in an unrestrained state, which potentially lead to membrane vibrations due to the turbulence caused by crossflow. However, this crossflow-induced membrane vibration has been largely overlooked in the previous studies. Here, we made the first attempt to investigate the crossflow-induced membrane vibration through the observation using optical coherence tomography (OCT), and explore the effect of this vibration on membrane fouling and scaling. The experimental results revealed that the vibration exhibited a self-excited vibration mode, with amplitudes reaching tens of micrometers. Moreover, the amplitude could be readily adjusted through changing crossflow velocity, transmembrane pressure, and the mesh size of spacer. For humic acid (HA) fouling, the membrane vibration could effectively reduce the thickness of HA cake layer, thereby stabilizing the specific flux at a constant level of 0.85, in contrast to the continuous decline of the flux under non-vibration condition. For gypsum scaling, the membrane vibration allowed the MD under low crossflow velocity (5 cm/s) to achieve comparable scaling occurrence concentration and scaling layer thickness as those under high crossflow velocity (10 cm/s). Our findings emphasized the potential of crossflow-induced membrane vibration as an effective strategy to mitigate membrane fouling and scaling in MD and other non-pressure driven membrane systems.

Effectiveness of active middle ear implant placement methods in pathological conditions: basilar membrane vibration simulation.

Active middle ear implants (AMEI) amplify mechanical vibrations in the middle ear and transmit them to the cochlea. The AMEI includes a floating mass transducer (FMT) that can be placed using two different surgical approaches: "oval window (OW) vibroplasty" and "round window (RW) vibroplasty." The OW and RW are windows located on the cochlea. Normally, sound stimulus is transmitted from the middle ear to cochlea via the OW. RW vibroplasty has been suggested as an alternative method due to the difficulty of applying OW vibroplasty in patients with ossicle dysfunction. Several reports compare the advantages of each approach through pre and postoperative hearing tests. However, quantitatively assessing the treatment effect is challenging due to individual differences in pathologies. This study investigates the vibration transmission efficiency of each surgical approach using a finite-element model of the human cochlea. Vibration of the basilar membrane (BM) of the cochlea is simulated by applying the stimulus through the OW or RW. Pathological conditions, such as impaired stapes mobility, are simulated by increasing the stiffness of the stapedial annular ligament. RW closure due to chronic middle ear diseases is a common clinical occurrence and is simulated by increasing the stiffness of the RW membrane in the model. The results show that the vibration amplitude of the BM is larger when the stimulus is applied to the RW compared to the OW, except for cases of RW membrane ossification. The difference in these amplitudes is particularly significant when stapedial mobility is limited. These results suggest that RW vibroplasty would be advantageous, especially in cases of accompanying stapedial mobility impairment. Additionally, it is suggested that transitioning to OW vibroplasty could still ensure a sufficient level of vibratory transmission efficiency when placing the FMT on the RW membrane is difficult due to anatomical problems in the tympanic cavity or confirmed severe pathological conditions around the RW.

Questions for Proponents of Bekesy's Theory

The theory of hearing called Bekesy’s traveling wave theory, announced in 1928 by a young engineer from Budapest, Georg Bekesy (1899-1972), was revised and supplemented many times. In 1961 it was awarded the Nobel Prize. It still contains several ambiguities that require analysis. The most important points requiring clarification include • Sound wave resonance in the cochlear fluids with the transverse wave of the basilar membrane. • Own vibrations of the basilar membrane. • Frequency resolution associated with the basilar membrane. • Transmission of information through the cochlear fluid. • Tip-link mechanism. • Amplification of quiet sounds by OHC contraction • The pathway of auditory information conducted to the receptor.