Electrical Potential Response Research Articles

Nonlinear Analysis of Electric Potential in a Piezoelectric Thin Plate as Pressure Sensor

Piezoelectric materials are widely applied in electronic components due to their ability to couple electric and mechanical fields. For the piezoelectric thin plate as a pressure sensor, we extend the modified first-order piezoelectric plate theory to explore the nonlinear solution of electric potential and discuss the relevant regulation mechanisms. Based on the piezoelectric effect, the electric potential generated by deformation is not linear with thickness. A quadratic function of electric potential across thickness is introduced. However, the electric potential on upper and lower electrodes is an unknown constant, which can be determined by the nonlinear complementary equation based on the Gauss theorem. It is shown that the nonlinear results of electric potential are consistent with outcomes by the three-dimensional finite element method. Furthermore, relevant regulation mechanisms are discussed on electric potential, including supported conditions, plate thickness, and load area. In addition, the influence of load locations on the electric potential response is analyzed. It is expected that these findings will be instructive to the structural design of piezoelectric pressure sensors.

The multi-dimensional joint response of the electric potential time–frequency-field in the fracture process of flawed coal under dynamic load

The fracture failure of flawed coal has always been a problem in underground engineering. Therefore, it is necessary to monitor crack propagation and damage evolution during coal fracture. In this study, the split Hopkinson pressure bar (SHPB) and digital image correlation (DIC) were combined to analyze the impact failure electric potential (EP) of flawed coal samples. The multi-dimensional joint response characteristics of coal EP time–frequency-field under dynamic load were studied and the differential expression and multi-fractal characteristics of EP responses at different measuring points were analyzed. Based on the EP signals, the evolution of damage to the coal was calculated. The results show that the time series evolution of EP and stress–strain curves during coal failure is consistent. The generation of fracture zones will excite the high-value area of local EP, and the spectral distribution of EP signals in this area shows the characteristics of low frequency and high amplitude. Each channel’s EP signal and the degree of deformation at the corresponding place are perfectly matched. The multi-fractal spectrum of the EP signal close to the fracture zone has a higher Δα and a lower Δf, which demonstrates the dominance of the large-scale EP signal produced in this region by the destruction of sample. Theoretical study indicates that the main causes of the anomalous distribution of the EP field are crack tip potential, diffusion potential, etc. The results can provide theoretical basis for the evaluation of coal fracturing by EP technology.

Electric Potential Response Characteristics of Coal Under Stress Wave Loading

Electric Potential Response Characteristics of Coal Under Stress Wave Loading

Study on electric potential response’s spatial distribution characteristics to damaging localization evolution of gas-bearing coal under load

Study on electric potential response’s spatial distribution characteristics to damaging localization evolution of gas-bearing coal under load

Experimental investigation of the fracture and damage evolution characteristics of flawed coal based on electric potential and acoustic emission parameter analyses

Flawed coal is the most common construction object in the mining process, and understanding its mechanical behavior and damage evolution is crucial for monitoring the stability of underground projects. In this work, uniaxial compression experiments on flawed coal were conducted, and the electric potential (EP) and acoustic emission (AE) signals were recorded synchronously. An in-depth study of the fracture mode and damage evolution characteristics of coal samples based on EP and AE responses was conducted. The results showed that (1) as loading proceeds, the coal body stress increases, the EP and AE values increase, and EP and AE are excited whenever the stress drop phenomenon occurs. With the gradual expansion of the initial flaws, the EP field and AE event distributions show regional differences. High-intensity EP anomaly bands are generated in the path of the main crack formation, and many high-energy AE events are generated. (2) The fractured behavior of the coal sample is dramatically altered by flaw inclination. When the flaw inclination increases, the AE signals show a shift from the common distributions of the six types to the concentrated distributions of the low amplitude–low frequency (LA–LF) and high amplitude–low frequency (HA–LF) types, the coal sample destruction modes are transformed from dominantly tensile to mixed tensile and shear, and the destruction mode is increasingly complicated. (3) It is possible to evaluate and analyze the damage evolution characteristics of the coal samples by defining the coefficient of variation (CV value) of the EP and the b value of the AE. Both a sudden increase in the CV value and a sudden decrease in the b value can be used as precursor information for coal failure. A two-parameter joint monitoring approach can be used to precisely and promptly warn about coal instability damage. The research results can provide theoretical support for the stability assessment of coal structures during the deep coal seam mining process and early warning of the occurrence of dynamic disasters.

Electric Potential Response Characteristics and Constitutive Model of Coal Under Axial Static Load–Dynamic Load Coupling

Electric Potential Response Characteristics and Constitutive Model of Coal Under Axial Static Load–Dynamic Load Coupling

Scalable and Degradable Dextrin-Based Elastomers for Wearable Touch Sensing.

Elastomer-based wearables can improve people's lives; however, frictional wear caused by manipulation may pose significant concerns regarding their durability and sustainability. To address the aforementioned issue, a new class of advanced scalable supersoft elastic transparent material (ASSETm) is reported, which offers a unique combination of scalability (20 g scale), stretchability (up to 235%), and enzymatic degradability (up to 65% in 30 days). The key feature of our design is to render native dextrin hydrophobic, which turns it into a macroinitiator for bulk ring-opening polymerization. Based on ASSETm, a self-powered touch sensor (ASSETm-TS) for touch sensing and non-contact approaching detection, possessing excellent electrical potential (up to 65 V) and rapid response time (60 ms), is fabricated. This work is a step toward developing sustainable soft electronic systems, and ASSETm's tunability enables further improvement of electrical outputs, enhancing human-interactive applications.

Response Characteristics of Electric Potential and Its Relationship with Dynamic Disaster during Mining Activities: A Case Study in Xuehu Coal Mine, China.

Across the world, coal resource is widely utilized in industrial production. During coal mining activities, dynamic disasters may be induced, such as coal and gas outbursts, or rock burst, resulting in serious accidents or disasters. Previous studies have shown that electric potential (EP) signals can be produced during the deformation and fracture process of coal and rock mass under load. The abnormal response characteristics of EP can reveal the damage evolution and failure feather of coal mass. In this paper, the response characteristics of EP signals are analyzed with high gas testing during mining activities within deep coal seams, and the relationship between the EP response and outburst disaster hazard is studied. The results show that: (1) Under the comprehensive action of mining stress and gas effect, the coal mass was damaged and fractured, which can produce abundant EP signals, while the temporal EP response characteristics can reflect the loading state and damage evolution process inside the coal seam. (2) When coal cannon and a sudden increase of gas concentration occurred in the coal mass, the EP signal was at a high level and fluctuated violently. This can be regarded as precursory information for an outburst risk, which was verified by monitoring the results of mining stress and electromagnetic radiation (EMR). (3) Based on the unilateral inversion imaging method, EP spatial distribution law was studied and abnormal zones with high-value were identified. The zone is close to, or coincident with, the high value interval of EMR intensity and count indexes, which revealed the distribution characteristics of coal damage localization. Hence, EP monitoring results can forecast precursor information of outburst hazards temporally, and identify local zones with outburst hazard spatially. This study provides a new idea and application basis for using the EP method to monitor and prevent coal and rock dynamic disaster hazards in the field.

Experimental Test and Field Observations of an Electric Potential Monitoring Device for Dynamic Hazards during Mining Activities

The EP (electric potential) signals can be generated during the deformation and fracture process of coal and rock mass. Meanwhile, the EP response is closely related to its stress state and damage evolution, which is expected to be used in monitoring and coal and rock dynamic disaster hazards. Based on this, this paper developed an EP monitoring device for mining to continuously monitor the temporal response characteristics and spatial distribution of coal seam internal EP signals in real time. Further, the experimental tests were carried out, whose results showed that the device has high monitoring sensitivity and little error for the EP signals and can reveal the loading state and damage degree of the coal and rock specimens during the deformation and fracture process. Moreover, the tests and application of EP monitoring were carried out during mining activities in the field. The results showed that the EP signals fluctuate during the coal mining stage and remain relatively stable during the maintenance stage. When the abnormal mining stress or the coal cannon phenomenon occurs, the intensity of EP signals increases rapidly and fluctuates violently, which has precursory response information for the hazards of dynamic disasters. Considering the advantages of sensitive response and nearly non-destructive monitoring, the study results can provide key monitoring equipment and research basis for field testing the EP signals during the mining process, to monitor and forecast the hazards of coal and rock dynamic disasters.

An experimental study on precursor identification for gas-bearing coal failure from electric potential responses in the loading process

The occurrence of coal and rock dynamic disasters threatens and restricts the safe production of underground coal mining activities seriously. For the prevention and control of the dynamic disasters, it is the foundation and premise to monitor the damage evolution and forecast the failure of coal mass under joint action of loading stress and gas pressure. For this, the stress loading and electric potential (EP) measuring experimental system of gas-bearing coal specimen was established, to test and analyze the precursor information for the failure of gas-bearing coal from EP response. The results show that the EP intensity of gas-bearing coal is positively correlated with loading stress level. The EP signals show step-like changes once the specimen is severely damaged at local moment. Based on mathematical statistics, the multifractal and critical slowing down paratemers of temporal EP data were analyzed, to reveal the nonlinear characteristics of gas-bearing coal during the loading and damaging process. In the critical failure stage, the multifractal parameter Δα rapidly increases to the peak and another parameter Δfm changes significantly to a negative value. Furthermore, the variance (V), as a critical slowing down parameter, rapidly rises to the peak value very shortly (0.3 s) before the failure occurs. Simultaneously, the autocorrelation coefficient (ac) also exhibits abnormal responses. Analysis combining the above indexes enables comprehensive monitoring and identification of precursor information for the failure of gas-bearing coal from temporal EP data.

Can the electrical potential of acupoints be used to assess the functional state of meridians and the effects of therapeutics? An exploratory data analysis

IntroductionAcupoints have bioelectrical properties distinct from common skin. Besides the higher electrical conductivity and lower resistance, acupoints show capacitor-like properties, which can be related to their endogenous electrical potential. Traditional Chinese Medicine (TCM) postulates that meridians are physiological structures connecting acupoints and working as a conduit for the flow of two essential substances known as qi and xue. Objectives: This pilot study was focused in evaluating whether the electrical potential of acupoints can be correlated objectively to the functional properties as described by ancient Chinese medical theories, such as the theories of coupled meridians of the same phase ('elements'), and the principle of coupled points. Methods: Direct needle moxibustion on LU5 and needle dispulsion of LI4 were performed in 21 subjects. The electrical potential of each acupoint was measured with a high-resolution data acquisition system taking to reference the acupoint SP6 of the Spleen conduit. Results: The results may indicate a functional relationship between the therapeutics and the electrical potential response on the selected acupoints. These effects seem to be explainable considering the specific properties of each acupoint, the relationship between TCM phases, and the dynamics between coupled conduits. Conclusion: The evaluation of the endogenous electrical potential of acupoints and the changes caused by an external stimulus might contribute to the understanding of TCM concepts, mechanisms, and the effects of associated therapeutics. The observed phenomena encourage the systematic assessment of the functional vegetative status via skin electrophysiology and using objective measurements.

Experimental Study of Electric Potential Response Characteristics of Different Lithological Samples Subject to Uniaxial Loading

Electric potential (EP) signals are detected when coal or rock materials are subjected to mechanical loading. Such signals are attributed to the generation and accumulation of free charges under externally applied loads. Due to the excellent correlation between EP and damage evolution, EP methods have great potential in rock mass structural engineering damage monitoring. To systematically study the EP response of different materials, four kinds of samples were prepared for experiments. Moreover, the coefficient of variation (CV) and correlation coefficient were introduced to study the EP response characteristics in different loading stages. Furthermore, characterizations based on atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) were used to reveal the reasons for electrification from a microproperty perspective. The results showed that the EP response characteristics were dominated by the main electrification factors in different loading stages, while these factors were influenced by the microstructure and composition of the different samples. Additionally, crack propagation was a significant mechanism for the EP response, which included electron escape induced by stress concentration at the crack tip, charge separation due to crack propagation, and discharge in the crack tip. Finally, the surface potential was a critical EP generation factor. Different samples were characterized by weak electrical properties in the 5 μm × 5 μm scanning area, and the unevenly distributed surface potential regions can affect the accumulation and migration of the free charges. This study offers new insights into the EP response characteristics and the causes of electrification from macro- and microperspectives.

Electrode insertion generates slow propagating electric potentials in Myriophyllum aquaticum plants

ABSTRACTThe insertion of microelectrodes into plants to record electric potentials can generate electric potential responses due to disturbance of plant tissues. Here, the electric potential triggered by Ag/AgCl glass microelectrode insertion into the stele of Myriophyllum aquaticum (parrot feather) plants was recorded. A system potential was triggered upon the electrode insertion and was propagated along the stele of the stem. The microelectrode detected this electric potential that was triggered by its own insertion and the electric potential was identical among the plants assessed. The temporal variation in electric potential registered two prominent peaks at 31.9 ± 1.8 and 17.1 ± 4.3 mV. The electric potential was repolarized after approximately 50–70 min and the stabilized electric potential was 6.5 ± 2.5 mV higher than the initial electric potential of plants. Control experiments conducted using a non-biological spongy rod wetted with distilled water or 1 M KCl confirmed that the peaks were solely due to the electric potential in the stem. These signals can be recognized as system potentials. The systematic EP could develop stimuli responses in distant locations, which is to be tested in further studies.

Bidirectional Optogenetically-Induced Plasticity of Evoked Responses in the Rat Medial Prefrontal Cortex Can Impair or Enhance Cognitive Set-Shifting.

Chronic stress compromises cognition, including executive function mediated in the medial prefrontal cortex (mPFC). To investigate mechanisms underlying these processes, we use chronic unpredictable stress (CUS), which reduces activity in the mPFC and impairs cognitive set-shifting, a measure of cognitive flexibility in laboratory rats. It has been shown that CUS attenuates the local electrical field potential response evoked in the mPFC by stimulation of the ascending excitatory afferent from the mediodorsal thalamus (MDT). Thus, in this study, to investigate the role that such changes in afferent-evoked responsivity of the mPFC might play in the cognitive deficits induced by CUS, we used optogenetics to directly induce plastic changes in the thalamic-mPFC afferent pathway. Glutamatergic neurons in the MDT were virally-induced to express the ChETA variant of channelrhodopsin. Then, to first validate the optogenetic induction of plasticity, long-term depression (LTD) or long-term potentiation (LTP) were induced by laser stimulation of ChETA-expressing terminals in the mPFC of anesthetized rats. In subsequent experiments, induction of opto-LTD in awake animals produced set-shifting deficits similar to those induced by CUS. By contrast, inducing opto-LTP in rats that had received prior CUS treatment corrected the stress-induced deficit in set-shifting. These results suggest that stress-induced plasticity in the thalamic-mPFC pathway is sufficient to produce stress-induced cognitive deficits, and may represent a novel target for effective therapeutic intervention to correct cognitive impairment in stress-related psychiatric disorders.

An experimental study on the precursory characteristics of EP before sandstone failure based on critical slowing down

The electric potential (EP) generated during coal rock deformation and fracture reflects coal rock mass stress and damage states. However, identifying the EP signal precursory signs that characterize a coal rock mass tending toward instability and failure is difficult. In this paper, we established an acoustic-electric multiparameter test experimental system, synchronously tested and collected acoustic emission (AE), surface potential (SP), and axial strain (AS) and observed surface crack propagation during the sandstone sample failure process. Meanwhile, by introducing the critical slowing down theory, the EP signal precursory characteristics before the sandstone sample unstable failure were explored. The results showed that EP signal time series autocorrelation coefficients and variances increased abruptly and continuously before the main fracture of the sandstone samples, which could be used as sandstone failure precursory information. Compared with the autocorrelation coefficient, the variance mutation point was easy to identify and was not affected by lag length selection, which was an effective precursory point to predict sandstone sample failure. From the precursory point to the main fracture of the sandstone samples, the AE events gradually gathered at the fracture damage location, high-energy AE events gradually increased, and the crack propagation rate gradually accelerated. Compared with the AE count time series, the variance mutation point (precursory point) of the EP signal time series appeared earlier. The research results were of theoretical significance for the monitoring and early warning of coal rock mass instability and failure and for identifying precursory characteristics using the EP response.

Experimental Study on the Damage Evolution of Gas-Bearing Coal and Its Electric Potential Response

Previous studies indicate that an electric potential (EP) signal is generated during the loading process of coal and that the EP response is related to the damage evolution. When coupled with gas, EP changes the pore structure and mechanical properties of a coal mass, promoting crack generation and growth and accelerating damage evolution. To study the EP response characteristics and investigate the damage of gas-bearing coal, a triaxial test was carried out with a gas-controlled confining pressure, and multiple types of data were measured and analyzed. The results show that with the change in stress, the EP response increases and fluctuates. This response reflects the stress and reveals the damage evolution, which could be verified with the variation in the acoustic emission response. For the mechanism analyses, the failure of the sample is caused by crack expansion and propagation under the coupling action of stress and gas. Consequently, microscopic charge separation and electron emission are the dominant mechanisms controlling the EP response. Furthermore, the constitutive damage equation of gas-bearing coal is established based on the EP response in view of continuous damage theory and the stress intensity distribution hypothesis. The calculation results of damage and stress based on the EP response are utilized for verification; the results indicate that the damage expressed by the EP response is reasonable and useful. This finding is helpful for understanding the damage evolution mechanism of gas-bearing coal.

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

Coal mass is deformed and fractured under stress to generate electrical potential (EP) signals. The mechanical properties of coal change with the adsorption of gas. To investigate the EP response characteristics of gas-bearing coal during deformation and fracture, a test system to monitor multi-parameters of gas-bearing coal under load was designed. The results showed that abundant EP signals were generated during the loading process and the EP response corresponded well with the stress change and crack expansion, and validated this with the results from acoustic emission (AE) and high-speed photography. The higher stress level and the greater the sudden stress change led to the greater EP abnormal response. With the increase of gas pressure, the confining action and erosion effect are promoted, causing the damage evolution impacted and failure characteristics changes. As a result, the EP response is similar while the characteristics were promoted. The EP response was generated due to the charge separation caused by the friction effect etc. during the damage and deformation of the coal. Furthermore, the main factors of the EP response were different under diverse loading stages. The presence of gas promoted the EP effect. When the failure of the coal occurred, EP value rapidly rose to a maximum, which could be considered as an anomalous characteristic for monitoring the stability and revealing failure of gas-bearing coal. The research results are beneficial for further investigating the damage-evolution process of gas-bearing coal.

Modeling the Impact of pH- and Oxygen-Coupled Stimuli on Osmotic Pressure and Electrical Potential Responses of Hemoglobin-Loaded Polyampholyte Hydrogel.

A unique character of (bio) responsive materials is their capability to convert specific environmental biochemical cues into an electromechanical response. Thereby, this paper describes the impact of pH- and oxygen-coupled stimuli on osmotic pressure and electrical potential responses of hemoglobin-loaded polyampholyte hydrogel. Herein, a multiphysics model is developed for elucidating the multiphysical interaction between immobile functional components bounded onto polymeric network chains of the hydrogel and hydrogen ion-oxygen-enriched environmental solution. Two constitutive relationships are incorporated into the model to capture: (1) ionization of fixed charge group as a function of its ionization strength coupled with hydrogen ion concentration and (2) bioactivity of hemoglobin as a function of both its ionization and saturation states. The multiphysics model is verified by comparing with experimental observations in open-literature, capturing the oxygen-induced hemoglobin saturation and the pH-actuated deformation of polyampholyte hydrogel. The numerical finding demonstrates that the pH-activated osmotic pressure response of the present hemoglobin-loaded polymeric system is independent of ambient oxygen O2, whereas its electrical potential response is insensitive of ambient oxygen O2 level at pH neutral conditions. Furthermore, the pH-induced swelling deformation of initially balanced polyampholyte hydrogel changes from a "V-" to a "bowl"-shaped like pattern with increase in fixed acidic and basic group ionization strength, whereas the initially unbalanced polyampholyte hydrogel achieves a collapse state at environmental pH coinciding with acid-base dissociation constant of dominant immobile charge group, if the initial dominant immobile charge group density is twice that of its counter one.

Similar simulation study on the characteristics of the electric potential response to coal mining

Similar simulation study on the characteristics of the electric potential response to coal mining

3D coupled multifield magneto-electro-elastic contact modelling

The present work deals with the general contact problem for coupled magneto-electro-elastic materials. Despite of the relevant technological applications, this topic of research has been treated only in some analytical works. But analytical solutions lack the generality of numerical methodologies, being restricted typically to simple geometries, loading conditions, idealized contact conditions and mostly taking into account transversely isotropic material symmetry with the symmetry axis normal to the contact surface. In this work, a numerical procedure for the three-dimensional frictional contact modelling of anisotropic coupled magneto-electro-elastic materials in presence of both electric and magnetic fields is presented for the first time. An orthotropic frictional law is considered, so anisotropy is present both in the bulk and in the surface. The methodology uses the boundary element method with explicit evaluation of the fundamental solutions in order to compute the magneto-electro-elastic influence coefficients. The contact model is based on an augmented Lagrangian formulation and it uses an iterative Uzawa scheme of resolution. Conducting, semi-conducting and insulated electric and/or magnetic indentation conditions, as well as orthotropic frictional contact conditions are considered. The methodology is validated by comparison with benchmark analytical solutions. Then, additional exploration examples are presented and discussed in detail, revealing that magneto-electric material coupling, conductivity contact conditions lead to a significant effect on the indentation force and contact pressure distributions. The influence of friction in electric and magnetic potential responses has been also proved to be very significant. Moreover, tangential loads exhibit an important influence both on the maximum values of the electric and magnetic potentials as well as on their distributions.