Electromechanical Interaction Research Articles

Flexoelectronics of a centrosymmetric semiconductor cylindrical nanoshell

Cylindrical shell-type semiconductors are essential for sensing and energy harvesting when integrated into surfaces of certain equipment, such as spacecraft, marine devices, and portable electronics, where mechanical forces play a significant impact on charge transport. Traditionally, such functionalities are only manifested in piezoelectric or pyroelectric crystals that possess non-centrosymmetry. Here, we theoretically investigate electronic behaviors driven by strain gradient-induced flexoelectric polarization in a centrosymmetric semiconductor cylindrical nanoshell, expanding the flexoelectronics in shell structures. The governing equations and accompanying boundary conditions are formulated simultaneously using the principle of virtual work and the fundamental lemma of the calculus of variation. Electromechanical interactions through static bending and forced vibration analyses of the newly developed model are systematically investigated. Under localized force excitation, the distribution of mobile charges is manipulated by tuning loading magnitudes and areas. The effects of doping levels on electric potentials and mobile charges are explored to show the interaction mechanism between flexoelectric and semiconducting properties. Moreover, the natural frequencies and modes of all mechanical displacements, electric potentials, and carrier concentration perturbations within the shell are identified. This paper provides a new approach for designing shell-shaped sensors and energy harvesters specifically for centrosymmetric semiconductors.

Remote sensing of a levitated superconductor with a flux-tunable microwave cavity

We present a cavity-electromechanical system comprising a superconducting quantum interference device which is embedded in a microwave resonator and coupled via a pickup loop to a 6-μg magnetically levitated superconducting sphere. The motion of the sphere in the magnetic trap induces a frequency shift in the SQUID-cavity system. We use microwave spectroscopy to characterize the system, and we demonstrate that the electromechanical interaction is tunable. The measured displacement sensitivity of 10−7m/Hz defines a path towards ground-state cooling of levitated particles with Planck-scale masses at millikelvin environment temperatures. Published by the American Physical Society 2024

Identification of electro-mechanical interactions in wind turbines

Abstract. Large direct-drive wind turbines with a multi-megawatt power rating face design challenges, especially concerning tower top mass, due to scaling laws for high-torque generators. This work proposes to extend the design space by moving towards a more system-oriented approach, considering electro-mechanical interactions. This requires an extension of the state-of-the-art wind turbine models with additional degrees of freedom. To limit the computational effort of such models, a profound understanding of possible interaction mechanisms is required. This work aims to identify interactions of an additional degree of freedom in the radial direction of the generator with the wind turbine structure, the aerodynamics, and the wind turbine controller. Therefore, a Simpack model of the IEA 15 MW RWT is implemented and coupled to a quasi-static analytical generator model for electromagnetic forces. The analytical model, sourced from literature, is code-to-code validated against a finite element model of the generator in COMSOL Multiphysics. Electro-mechanical simulation results do not show interactions with the aerodynamics or the controller. However, interactions with the wind turbine structure occur. It is shown that the modelling approach can affect the system's natural frequencies, which can potentially impact the overall system design choices.

Ibrutinib, a Bruton's tyrosine kinase inhibitor, regulates ventricular electromechanical activities and enhances arrhythmogenesis

BackgroundIbrutinib, a Bruton's tyrosine kinase inhibitor used in cancer therapy, exerts ventricular proarrhythmic effects; however, the underlying mechanisms remain unclear. Excitation-contraction coupling (E-C) disorders are pivotal for the genesis of ventricular arrhythmias (VAs), which arise mainly from the right ventricular outflow tract (RVOT). In this study, we aimed to comprehensively investigate whether ibrutinib regulates the electromechanical activities of the RVOT, leading to enhanced arrhythmogenesis, and explore the underlying mechanisms. MethodsWe utilized conventional microelectrodes to synchronously record electrical and mechanical responses in rabbit RVOT tissue preparations before and after treatment with ibrutinib (10, 50, and 100 nM) and investigated their electromechanical interactions and arrhythmogenesis during programmed electrical stimulation. The fluorometric ratio technique was used to measure intracellular calcium concentration in isolated RVOT myocytes. ResultsIbrutinib (10–100 nM) shortened the action potential duration. Ibrutinib at 100 nM significantly increased pacing-induced ventricular tachycardia (VT) (from 0% to 62.5%, n = 8, p = 0.025). Comparisons between pacing-induced VT and non-VT episodes demonstrated that VT episodes had a greater increase in contractility than that of non-VT episodes (402.1 ± 41.4% vs. 232.4 ± 29.2%, p = 0.003). The pretreatment of ranolazine (10 μM, a late sodium current blocker) prevented the occurrence of ibrutinib-induced VAs. Ibrutinib (100 nM) increased late sodium current, reduced intracellular calcium transients, and enhanced calcium leakage in RVOT myocytes. ConclusionIbrutinib increased the risk of VAs in the RVOT due to dysregulated electromechanical responses, which can be attenuated by ranolazine or apamin.

Conductive and Enhanced Mechanical Strength of Mo2Ti2C3 MXene-Based Hydrogel Promotes Neurogenesis and Bone Regeneration in Bone Defect Repair.

Bone defects are common with increasing high-energy fractures, tumor bone invasion, and implantation revision surgery. Bone is an electroactive tissue that has electromechanical interaction with collogen, osteoblasts, and osteoclasts. Hydrogel provides morphological plasticity and extracellular matrix (ECM) 3D structures for cell survival, and is widely used as a bone engineering material. However, the hydrogels have poor mechanical intensity and lack of cell adhesion, slow gelation time, and limited conductivity. MXenes are novel nanomaterials with hydrophilic groups that sense cell electrophysiology and improve hydrogel electric conductivity. Herein, gelatin had multiple active groups (NH2, OH, and COOH) and an accelerated gelation time. Acrylamide has Schiff base bonds to cross-link with gelatin and absorb metal ions. Deacetylated chitosan improved cell adhesion and active groups to connect MXene and acrylamide. We constructed Mo2Ti2C3 MXene hydrogel with improved elastic modulus and viscosity, chemical cross-linking structure, electric conductivity, and good compatibility. Mo2Ti2C3 MXene hydrogel exhibits outstanding osteogenesis in vitro. Mo2Ti2C3 MXene hydrogel promotes osteogenesis via alkaline phosphatase (ALP) and alizarin red S (ARS) staining, improving osteogenic marker genes and protein expressions in vitro. Mo2Ti2C3 MXene hydrogel aids new bone formation in the in vivo calvarial bone defect model via micro-CT and histology. Mo2Ti2C3 MXene hydrogel facilitates neurogenesis factors nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression, and aids newly born neuron marker Tuj-1 and sensory neuron marker serotonin (5-HT) and osteogenesis pathway proteins, runt-related transcription factor 2 (Runx2), osteocalcin (OCN), SMAD family member 4 (SMAD4), and bone morphogenetic protein-2 (BMP2) in the bone defect repair process. Mo2Ti2C3 MXene hydrogel promotes osteogenesis and neurogenesis, which extends its biomedical application in bone defect reconstruction.

Observation of dislocation-controlled domain nucleation and domain-wall pinning in single-crystal BaTiO3

Electro-mechanical interactions between topological defects and domain walls play a key role in the macroscopic response of bulk and thin-film ferroelectrics. The applications of ferroelectrics are derived from their inherent ability to nucleate new domains and to move the domain walls that separate adjacent domains. Here, we report dislocation-mediated domain nucleation in single-crystal BaTiO3, achieved by dislocations generated via high-temperature uniaxial compression on a notched sample. We also present a direct observation of domain-wall pinning of 90° ferroelastic domain walls by dislocations using in situ transmission electron microscopy. Dense and well-aligned “forest” dislocations, featuring {100}⟨100⟩ slip systems oriented in the out-of-plane [001] direction, exclusively nucleate in-plane domain variants. We reveal that the 90° domain walls are strongly pinned by imprinted dislocations due to the presence of their associated stress fields. Our findings may advance our understanding of the control of defects in ferroelectrics and propose a strategy applicable to both emerging nanoelectronic and bulk applications.

Simultaneous assessment of mechanical and electrical function in Langendorff-perfused ex-vivo mouse hearts.

The Langendorff-perfused ex-vivo isolated heart model has been extensively used to study cardiac function for many years. However, electrical and mechanical function are often studied separately-despite growing proof of a complex electro-mechanical interaction in cardiac physiology and pathology. Therefore, we developed an isolated mouse heart perfusion system that allows simultaneous recording of electrical and mechanical function. Isolated mouse hearts were mounted on a Langendorff setup and electrical function was assessed via a pseudo-ECG and an octapolar catheter inserted in the right atrium and ventricle. Mechanical function was simultaneously assessed via a balloon inserted into the left ventricle coupled with pressure determination. Hearts were then submitted to an ischemia-reperfusion protocol. At baseline, heart rate, PR and QT intervals, intra-atrial and intra-ventricular conduction times, as well as ventricular effective refractory period, could be measured as parameters of cardiac electrical function. Left ventricular developed pressure (DP), left ventricular work (DP-heart rate product) and maximal velocities of contraction and relaxation were used to assess cardiac mechanical function. Cardiac arrhythmias were observed with episodes of bigeminy during which DP was significantly increased compared to that of sinus rhythm episodes. In addition, the extrasystole-triggered contraction was only 50% of that of sinus rhythm, recapitulating the "pulse deficit" phenomenon observed in bigeminy patients. After ischemia, the mechanical function significantly decreased and slowly recovered during reperfusion while most of the electrical parameters remained unchanged. Finally, the same electro-mechanical interaction during episodes of bigeminy at baseline was observed during reperfusion. Our modified Langendorff setup allows simultaneous recording of electrical and mechanical function on a beat-to-beat scale and can be used to study electro-mechanical interaction in isolated mouse hearts.

Scale transition and residual fields in modeling of polycrystalline ferroelectrics based on the internal energy potential and a Voigt–Reuss approximation

A multiscale constitutive model, implemented within a semi-analytical computational framework, is presented. Accounting for domain switching in a tetragonal lattice and electromechanical intergranular interactions, it aims to accurately reproduce experimental data available from butterfly and dielectric hysteresis loops. For the sake of validation, these have been collected from various sources providing ranges of values for characteristic quantities. Adopting the fundamental ideas of a previously published model, a different homogenization approach is employed for the transition from grain to polycrystalline domain, providing both residual stress and electric fields. Furthermore, the thermodynamic driving force and constitutive equations on the grain level are based on a different thermodynamical potential. While the modeling approach inherently does not include any tuning parameters, the introduction of one and two, respectively, additional parameters is investigated, although computational results are basically in good agreement with experimental ranges.

Electromechanical interactions between cell membrane and nuclear envelope: Beyond the standard Schwan’s model of biological cells

We investigate little-appreciated features of the hierarchical core–shell (CS) models of the electrical, mechanical, and electromechanical interactions between the cell membrane (CM) and nuclear envelope (NE). We first consider a simple model of an individual cell based on a coupled resistor–capacitor (Schwan model (SM)) network and show that the CM, when exposed to ac electric fields, acts as a low pass filter while the NE acts as a wide and asymmetric bandpass filter. We provide a simplified calculation for characteristic time associated with the capacitive charging of the NE and parameterize its range of behavior. We furthermore observe several new features dealing with mechanical analogs of the SM based on elementary spring–damper combinations. The chief merit of these models is that they can predict creep compliance responses of an individual cell under static stress and their effective retardation time constants. Next, we use an alternative and a more accurate CS physical model solved by finite element simulations for which geometrical cell reshaping under electromechanical stress (electrodeformation (ED)) is included in a continuum approach with spatial resolution. We show that under an electric field excitation, the elongated nucleus scales differently compared to the electrodeformed cell.

Low-voltage dielectric elastomer actuators by electro-mechanical resonance syntonization

Generally, a serious practical limitation of dielectric elastomer (DE)-based capacitors is the need for high voltage supply (in the order of 1 kV) to activate them. High voltages require a power level that is currently challenging due to the limit in the operating range of existing function generators. These high voltages are also dangerous for humans, thereby overshadowing many applications of dielectric elastomers. The purpose of this work is to develop a new simple actuation technique to introduce low-voltage driven DE-based capacitors, in which the electrical resonant frequency is syntonized to the mechanical natural frequency by tuning the circuit inductance. This results in extensive voltage amplification across the DE capacitor. In turn, this leads the DE membrane to oscillate with a remarkable large motion using a small voltage which is of one-tenth the magnitude of the input voltage required to drive such systems in the absence of electro-mechanical (EM) resonance syntonization. The efficiency of the proposed approach is demonstrated in the context of nonlinear vibration analysis. The results show that the voltage amplitude across the DE capacitor is amplified substantially while the electrical mode is syntonized with the mechanical one, and as a result, the DE motion’s amplitude is at least two hundred times greater than that of the unmatched system. Furthermore, for unbiased AC voltages with large amplitudes, the electro-mechanical modal interaction causes the system to exhibit the formation of frequency combs in the frequency spectrum of the system’s response. The implementation of this method using a simple electrical circuit just requires adequate matching between the electrical and the mechanical natural frequencies that depends on the inductance value. Our proposal effectively eliminates the need for a high source voltage generator which has been the main limitation in designing DE-based capacitors.

Sound Generation by Metro Trains during Braking and Its Suppression Method

The causes of acoustic noise occurring during braking of electric vehicles, in particular, in the metro, were analyzed. The spectrum of such noise was measured, and it is shown that high-frequency discrete tones are excited by braking resistors, applied for electrodynamic braking of electric vehicles. Three proposed mechanisms of electromechanical interaction in a Fecral plate, which is a braking resistor element, were considered: the Ampère force and linear and nonlinear magnetostriction. It was shown that predominant odd harmonics indicate the presence of a significant piezomagnetic effect and the inverse effect of linear magnetostriction in the Fecral alloy. A phenomenological approach was used to calculate the piezomagnetic tensor elements for Fecral. Calculations by the finite element method showed that asymmetric cuts introduced into the plate may significantly decrease intensity of acoustic vibrations excited by the braking resistor.

XFEM for semipermeable crack in piezoelectric material with Maxwell stress

In this work, extended finite element method (XFEM) is implemented to model the semipermeable cracks in the piezoelectric material with Maxwell stresses. This Maxwell stress is induced due to the presence of an electric field at the crack faces and boundary of the piezoelectric material. To model the semipermeable crack with Maxwell stress, the crack tip is enriched with six-fold enrichment functions. The electro-mechanical interaction integral is modified and implemented for several crack configurations to compute the stress intensity factor (SIF). The accuracy of the XFEM-based semipermeable crack model in the presence of Maxwell stresses is demonstrated by validating with the analytical solution. The effects of crack length, far-field loading, Maxwell stress, and poling direction are investigated on the normalized SIF.

Rotor instability due to electromechanical interactions in synchronous machines

Rotor instability due to electromechanical interactions in synchronous machines

Quantifiable Relationship Between Antibacterial Efficacy and Electro-Mechanical Intervention on Nanowire Arrays.

Physical disruption is an important antibacterial means as it is lethal to bacteria without spurring antimicrobial resistance. However, it is very challenging to establish a quantifiable relationship between antibacterial efficacy and physical interactions such as mechanical and electrical forces. Herein, titanium nitride (TN) nanowires with adjustable orientations and capacitances are prepared to exert gradient electro-mechanical forces on bacteria. While vertical nanowires show the strongest mechanical force resulting in an antibacterial efficiency of 0.62 log reduction (vs 0.22 for tiled and 0.36 for inclined nanowires, respectively), the addition of electrical charges maximizes the electro-mechanical interactions and elevates the antibacterial efficacy to more than 3 log reduction. Biophysical and biochemical analyses indicate that electrostatic attraction by electrical charge narrows the interface. The electro-mechanical intervention more easily stiffens and rips the bacteria membrane, disturbing the electron balance and generating intracellular oxidative stress. The antibacterial ability is maintained in vivo and bacteria-challenged rats are protected from serious infection. The physical bacteria-killing process demonstrated here can be controlled by adjusting the electro-mechanical interactions. Overall, these results revealed important principles for rationally designing high-performance antibacterial interfaces for clinical applications.

In silico analysis of the contribution of cardiomyocyte-fibroblast electromechanical interaction to the arrhythmia.

Although fibroblasts are about 5-10times smaller than cardiomyocytes, their number in the ventricle is about twice that of cardiomyocytes. The high density of fibroblasts in myocardial tissue leads to a noticeable effect of their electromechanical interaction with cardiomyocytes on the electrical and mechanical functions of the latter. Our work focuses on the analysis of the mechanisms of spontaneous electrical and mechanical activity of the fibroblast-coupled cardiomyocyte during its calcium overload, which occurs in a variety of pathologies, including acute ischemia. For this study, we developed a mathematical model of the electromechanical interaction between cardiomyocyte and fibroblasts and used it to simulate the impact of overloading cardiomyocytes. In contrast to modeling only the electrical interaction between cardiomyocyte and fibroblasts, the following new features emerge in simulations with the model that accounts for both electrical and mechanical coupling and mechano-electrical feedback loops in the interacting cells. First, the activity of mechanosensitive ion channels in the coupled fibroblasts depolarizes their resting potential. Second, this additional depolarization increases the resting potential of the coupled myocyte, thus augmenting its susceptibility to triggered activity. The triggered activity associated with the cardiomyocyte calcium overload manifests itself in the model either as early afterdepolarizations or as extrasystoles, i.e., extra action potentials and extra contractions. Analysis of the model simulations showed that mechanics contribute significantly to the proarrhythmic effects in the cardiomyocyte overloaded with calcium and coupled with fibroblasts, and that mechano-electrical feedback loops in both the cardiomyocyte and fibroblasts play a key role in this phenomenon.

Reaching new levels of wave scattering via piezoelectric metamaterials and electro-momentum coupling

Piezoelectric materials are materials that can convert mechanical energy into electrical energy (and vice versa). In addition to the well-known electromechanical interaction between mechanical deformation and electric fields, a recent discovery revealed that the macroscopic linear momentum of piezoelectric materials is also coupled with the electric field. This means that their kinetic movement can be controlled by the electric field. This effect is termed electro-momentum (EM) coupling and provides a new design degree of freedom for piezoelectric devices with better properties and dynamic performance. In this talk, theoretical bounds of EM coupling in wave scattering will be discussed, which can provide valuable information on estimating the performance space of piezoelectric metamaterials for various applications such as acoustic sensing and energy harvesting. The results show that scattering performance from EM coupling can be of the same order of magnitude as that of the scatterer’s geometric features, such as shape and size, which are considered major factors for scattering performance. Furthermore, its capability of promising wave manipulation will be demonstrated, i.e., tunable scattering-cloaking piezoelectric devices via EM coupling. Moreover, how material properties and geometrical microstructures affect EM coupling will be investigated, which allows researchers to precisely control EM coupling in piezoelectric materials.

Remote-refocusing light-sheet fluorescence microscopy enables 3D imaging of electromechanical coupling of hiPSC-derived and adult cardiomyocytes in co-culture

Improving cardiac function through stem-cell regenerative therapy requires functional and structural integration of the transplanted cells with the host tissue. Visualizing the electromechanical interaction between native and graft cells necessitates 3D imaging with high spatio-temporal resolution and low photo-toxicity. A custom light-sheet fluorescence microscope was used for volumetric imaging of calcium dynamics in co-cultures of adult rat left ventricle cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes. Aberration-free remote refocus of the detection plane synchronously to the scanning of the light sheet along the detection axis enabled fast dual-channel 3D imaging at subcellular resolution without mechanical sample disturbance at up to 8 Hz over a ∼300 µm × 40 µm × 50 µm volume. The two cell types were found to undergo electrically stimulated and spontaneous synchronized calcium transients and contraction. Electromechanical coupling improved with co-culture duration, with 50% of adult-CM coupled after 24 h of co-culture, compared to 19% after 4 h (p = 0.0305). Immobilization with para-nitroblebbistatin did not prevent calcium transient synchronization, with 35% and 36% adult-CM coupled in control and treated samples respectively (p = 0.91), indicating that electrical coupling can be maintained independently of mechanotransduction.

An electrometric method for the interface stress and contact resistance of pancake coil under winding force.

Interface stress and contact resistance play key roles in the safety and stability assessment of non-insulated superconducting pancake coils. An electrometric method for the interfacial stresses and contact resistance of multi-turn coils of different materials has been established, which is further applied to the measurement and analysis of contact stresses and resistances of the composite superconducting coils under the extremely low temperature environment. The mechanical and electrical behaviors are coupled through an extended electro-mechanical contact model, which also reveals the electro-mechanical interaction mechanism of the coil. The extended contact model was verified by comparison with experimental results, and the proposed electrometric method was verified by comparing the interface stresses calculated by two approaches. The contact stresses and resistances of superconducting coils with different turns are successfully obtained through the proposed electrometric method, which provides bases for the evaluation of the transport and mechanical performance of superconducting coils.

Dynamic modelling and dynamic characteristics of wind turbine transmission gearbox-generator system electromechanical-rigid-flexible coupling

The design of large wind turbine drivetrain systems is trending towards light weight and integration. To ensure the safe operation of the drivetrain system, investigating the electromechanical–rigid–flexible interaction of wind turbine transmission systems is necessary. This study proposed an electromechanical–rigid–flexible coupling dynamic model that can be used for variable speed and load operating conditions. The model considered the time-varying mesh stiffness, structural flexibility, magnetic saturation characteristics, and electromagnetic radial force. The effects of the flexibility of the housing and high-speed shaft on the electromechanical interaction of the system under steady and unsteady conditions are discussed. There is a strong coupling between the gear system and the generator system. The resonance speed at the generator is affected by the gear excitation, and the vibration signal of the gear system is affected by electromagnetic excitation. The flexibility of the high-speed shaft and housing has apparent effects on the vibration characteristics of the integrated systems. It directly affects the stability and safety of the system particularly under gust conditions. Thus, studying the electromechanical–rigid–flexible coupling characteristics is significant for wind turbine drivetrain design.

Distributed Electro-Mechanical Coupling Effects in a Dielectric Elastomer Membrane Array

BackgroundDielectric elastomer (DE) transducers permit to effectively develop large-deformation, energy-efficient, and compliant mechatronic devices. By arranging many DE elements in an array-like configuration, a soft actuator/sensor system capable of cooperative features can be obtained. When many DE elements are densely packed onto a common elastic membrane, spatial coupling effects introduce electro-mechanical interactions among neighbors, which strongly affect the system actuation and sensing performance. To effectively design cooperative DE systems, those coupling effects must be systematically characterized and understood first.ObjectiveAs a first step towards the development of complex cooperative DE systems, in this work we present a systematic characterization of the spatial electro-mechanical interactions in a 1-by-3 array of silicone DEs. More specifically, we investigate how the force and capacitance characteristics of each DE in the array change when its neighbors are subject to different types of mechanical or electrical loads. Force and capacitance are chosen for this investigation, since those quantities are directly tied to the DE actuation and sensing behaviors, respectively.MethodsAn electro-mechanical characterization procedure is implemented through a novel experimental setup, which is specifically developed for testing soft DE arrays. The setup allows to investigate how the force and capacitance characteristics of each DE are affected by static deformations and/or electrical voltages applied to its nearby elements. Different combinations of electro-mechanical loads and DE neighbors are considered in an extensive experimental campaign.ResultsThe conducted investigation shows the existence of strong electro-mechanical coupling effects among the different array elements. The interaction intensity depends on multiple parameters, such as the distance between active DEs or the amount of deformation/voltage applied to the neighbors, and provides essential information for the design of array actuators. In some cases, such coupling effects may lead to changes in force up to 9% compared to the reference configuration. A further coupling is also observed in the DE capacitive response, and opens up the possibility of implementing advanced and/or distributed self-sensing strategies in future applications.ConclusionBy means of the conducted experiments, we clearly show that the actuation and sensing characteristics of each DE in the array are strongly influenced by the electro-mechanical loading state of its neighbors. The coupling effects may significantly affect the overall cooperative system performance, if not properly accounted for during the design. In future works, the obtained results will allow developing cooperative DE systems which are robust to, and possibly take advantage of, such spatial coupling effects.