External Electric Potential Research Articles

Dynamics of an Electrified Multi-layer Film Down a Porous Incline

The nonlinear dynamics of gravity-driven two-layers flow through an oblique microchannel of porous walls subjected to an external electric potential is examined. The evolution equation governing the surface wave deflection is derived in the frame of long wave theory. The stability criteria of the linearized system are investigated. As permeability, inclination or dielectric constant increase, the disturbances become stronger. However, the viscosity ratio plays an irregular role on the stability. Resonant waves propagating on the fluid interface are introduced. The instability of the base flow is simulated. It is observed that the instability onset can be controlled by many physical properties related with the model. The effect of permeability as well as dielectric constant corresponds to linear processing expectations. Viscosity ratio improves stability in certain situations. However, the electric role is generally dominant in the current model. Such results may be useful in practical applications by designing a device in order to control the instability. Solitary waves propagating on the interface are studied. The presence of stable stationary solitons is shown in certain statuses of the model.

Wave propagation in magneto-electro-thermo-elastic nanobeams based on nonlocal theory

In this article, wave based method (WBM) is proposed as a new semi-analytical method to analyze the wave propagation characteristics of the magneto-electro-thermo-elastic nanobeams with arbitrary boundary conditions. According to the Timoshenko beam theory and Hamilton principle, the governing equations of the nanobeam which are related to Eringen’s nonlocal theory are obtained. The displacement and external potential variables are expanded as wave function forms. In the light of the introduction of several type boundary conditions, the total matrix of the nanobeam is constituted. Searching the zero locations of the total matrix determinant by the bisection method, the natural frequencies of the nanobeam under arbitrary boundary conditions are received. To further illustrate the calculation correctness of the presented method, the results are compared with the solutions in reported references. Furthermore, a series of numerical examples are proposed to investigate the effect of each parameter on the free vibration characteristics of the nanobeam with several boundary conditions, such as beam length and thickness, external temperature rise, magnetic and electric potential. Some new numerical solutions and conclusions are presented in this paper to provide the basic foundation for subsequent research.

Prediction in Chaotic Environments Based on Weak Quadratic Classifiers

The problem of prediction in chaotic environments based on identifying analog situations in arrays of retrospective data are considered. Traditional recognition schemes are ineffective and form weak classifiers in cases where the system component of the observed process is represented by a non-periodic oscillatory time series (realization of chaotic dynamics). The objective is to develop a system of such classifiers, which allows for improvements in the quality of forecasts for non-stationary dynamics in flow processes. The introduced technique can be applied for the prediction of oscillatory non-periodic processes with non-stationary noise, i.e., dependence of different relay frequencies, external electric potential and microchannel width in an electrokinetic micromixer.

Rational design of self-supported Cu@WC core-shell mesoporous nanowires for pH-universal hydrogen evolution reaction

Cu@WC core-shell nanowires, as the WC-based materials with Pt-like electronic configurations around the Fermi level, have been successfully fabricated via chemical oxidation and electro-reduction processes followed by magnetron sputtering of WC for pH-universal hydrogen evolution reaction (HER). The Cu@WC catalyst showed low overpotentials of 92, 119 and 173 mV at 10 mA cm−2 in acidic, alkaline and neutral conditions with high exchange current densities. The core-shell structure was verified to increase the WC’s carrier density with the interfacial, strongly delocalised electrons under the external electric potential and matched work functions between Cu and WC preserving the high level of Pt-like electrons in WC. The ΔGH* calculations demonstrated that the lattice mismatch between WC and Cu modifies the atomic and electronic structures of WC and weakens the hydrogen bond during absorption leading to enhanced HER performance. This work provides a deep insight into the WC-based core-shell catalysts for pH-universal HER.

Thermokinetic transport of dilatant/pseudoplastic fluids in a hydrophobic patterned micro-slit

The flow enhancement and convective heat transfer along with entropy generation analysis are studied numerically in a micro-slit with alternating hydrodynamic slip patches. The advances in molecular simulations and micro-scale experiments confirmed that the slip of fluid on the solid surfaces occurred at small scale flows and the traditional no-slip boundary conditions cannot be applicable for the flow simulation at the micro- and nano-scale. The coupled Poisson–Boltzmann–Navier–Stokes equations dealing with an external electric potential are involved for the flow enhancement and entropy generation analysis of non-Newtonian fluids in a micro-slit with periodic slips. From the finite volume simulation, it is observed that the drag force effect is very strong along the wall for the transportation and mixing of fluids. This effect is found to be minimized by imposing periodic hydrophobic slippage along the boundary. An additional pressure gradient is generated by imposing electrokinetic pumping, resulting in a higher velocity gradient in the flow direction in the presence of viscous dissipation and Joule heating effects. The results are predicted in terms of the flow enhancement factor (Ef) (which provides maximum species transport), the average heat transfer rate (Nu), and the average entropy generation due to fluid friction, heat transfer, and Joule heating effects. The advantages and disadvantages of utilizing slip conditions are discussed, which has large scale applications on drug delivery and DNA analysis and sequencing, since cell damage due to pumping will be minimized.

Modeling of novel nanoscale mass sensor made of smart FG magneto-electro-elastic nanofilm integrated with graphene layers

This paper is devoted to presenting theoretical modeling for a novel nano-mass sensor system composed of smart core integrated with graphene layers in its top and bottom surfaces. The smart core is made of a functionally graded (FG) magneto-electro-elastic (MEE) nanofilm. On the basis of the nonlocal strain gradient theory and first-order shear deformation plate theory, the size-dependent governing equations for this graphene/FG-MEE/graphene nanofilm based nano-mass sensor system are derived. The frequency shift behavior of this system is investigated with consideration of different distribution configurations, different attaching locations, and different total masses of the attached nanoparticles. Furthermore, the influences of graphene faces, FG index of the MEE core, nonlocal and strain gradient parameters, as well as external electric and magnetic potentials on the frequency shift behavior of the nanoscale mass sensor are examined in detail. Significant enhancement of the frequency shift and frequency shift ratio can be observed for the nano-mass sensor system by covering graphene in the top and bottom surfaces of FG-MEE nanofilm. The theoretical model and conclusion presented in this paper may serve as an inspiration to researchers for exploiting nanoscale mass sensors with high sensitivities.

Multiphysics cross-section analysis of smart beams

The cross-section response of smart beams under electric, magnetic and thermal fields is investigated. The method predicts the generalized cross-section stiffness of prismatic smart beams, and allows recovering the three dimensional multiphysics fields variables. The semi-analytical procedure divides the contributions of the non-homogeneous governing equation into a homogeneous solution, which resorts to computing the de Saint-Venant solution, and a set of particular solutions which describe the beam cross-section behaviors when external electric potential, magnetic potential and boundary temperature are imposed. The generalized cross-section stiffness is computed by means of an energy equivalence equation.

Buckling and Vibration Analysis of a Double-layer Graphene Sheet Coupled with a Piezoelectric Nanoplate

In this article, the vibration and buckling of a double-layer Graphene sheet (DLGS) coupled with a piezoelectric nanoplate through an elastic medium (Pasternak and Winkler models) are under consideration. DLGS are subjected to biaxial in-plane forces and van der Waals force existing between each layer. Polyvinylidene fluoride (PVDF) piezoelectric nanoplate is subjected to an external electric potential. For the sake of this study, sinusoidal shear deformation theory of orthotropic plate expanded with Eringen’s nonlocal theory is selected The results indicate that nondimensional frequency and nondimensional critical buckling load rise, when the ratio of width to thickness increases. Furthermore, incrementing the effect of elastic medium parameter results in increasing the stiffness of the system and, consequently, rising nondimensional frequency and critical buckling load.

Revealing Transient Shuttling Mechanism of Catalytic Ion Transport through Liquid-Liquid Interface.

Hard, hydrophilic ions that hardly transport over the water-oil interface by imposing external electric potential could undergo facile transport with a trace of ligand. Such phenomena, called "shuttling", are elucidated by microscopic investigation with molecular dynamics simulations. The catalytic role manifests itself in a 2-D free-energy surface within the nanometer range of the interface. The free-energy landscape clearly distinguishes the condition that the catalytic shuttling plays a vital role in the ion transport. The mechanism associated with transient complex formation at the interface is shown to be widely relevant to the ion kinetics and extends the conventional concept of facilitated ion transport.

Vibrations of graphene nanoplatelet reinforced functionally gradient piezoelectric composite microplate based on nonlocal theory

This paper investigates the small-scale effect on the linear and nonlinear vibrations of the graphene nanoplatelet (GNPL) reinforced functionally gradient piezoelectric composite microplate based on the nonlocal constitutive relation and von Karman geometric nonlinearity. The GNPL reinforced functionally gradient piezoelectric composite microplate is resting on the Winkler elastic foundation and is subjected to an external electric potential. The parallel model of Halpin Tsai is used to compute the effective Young’s modulus of the GNPL reinforced functionally gradient piezoelectric composite microplate. The Poisson’s ratio, mass density and piezoelectric properties of the GNPL reinforced functionally gradient piezoelectric composite microplate are calculated by using the rule of mixture. Hamilton’s principle is adopted to obtain the higher-order nonlinear partial differential governing equations of motion for the GNPL reinforced functionally gradient piezoelectric composite microplate. The partial differential governing equations of motion are reduced to a system of the nonlinear algebraic eigenvalue equations by using the differential quadrature (DQ) method and are solved by an iteration progress. The efficiency and accuracy of the present approach are verified by comparing with the existed results. Both uniformly and functionally distributing graphene nanoplatelets (GNPLs) are considered to investigate the effects of the GNPL concentration, external voltage, nonlocal parameter, geometrical and piezoelectric characteristics of the GNPLs as well as the elasticity coefficient of the Winkler elastic foundation on the linear and nonlinear dynamic behaviors of the GNPL reinforced functionally gradient piezoelectric composite microplate with various boundary conditions. The numerical results clearly manifest that the GNPLs can significantly enhance the structural stiffness of the micro-electro-mechanical system (MEMS).

Immobilization of surface non-affinitive protein onto a metal surface by an external electric field

We investigated an alternate technique to coat the surface with a protein having no surface affinity, without the use of any exotic chemical agents. An external electric field was utilized to prepare the protein coating on a metal substrate. Stainless steel (St) substrate and lysozyme (LSZ) were used as the surface to be coated and the model non-adsorptive protein, respectively. Dynamics of the adsorption of LSZ on the St surface in the presence and absence of an external electric potential (EEP) were monitored by in-situ ellipsometry. Applying negative surface potential (-0.4V vs Ag/AgCl) forced the adsorption of LSZ onto the St surface where LSZ did not adsorb without applying any EEP. The repetition of the EEP-application and -cut-off indicated the controllability of the LSZ coating amount depending on the total duration of the EEP-application. The coated LSZ largely remained bound to the surface even by the cut-off of the external electric field, the ratio of which to the detached amount was roughly constant (approximately 7:3). Furthermore, the LSZ coated surface on the St substrate was found to be reversibly switched between being affinitive and non-affinitive to a typical model protein adsorbate (bovine serum albumin) by the EEP-application and cut-off.

The Feynman Path Integral to Characterize and Anticipate Bacteria Chemotaxis in a Host Healthy Body

In this paper the idea of Feynman’s path integral is introduced inside a nano biological system such as bacteria population where due to their property of chemotaxis, a stochastic modeling might be drawn to describe their mobility due essentially to electrical interactions among them as a recurrent resource to protect themselves against antibacterial agents such as macrophages. Due to composition of K+, Cl− and Na+ exists there a net charge along the internal and external phospholipid membrane of bacteria.The model of path’s integration invented by Richard Feynman has been extensively used to tackle crucial problems in quantum mechanics for various decades essentially in atomic physics and nano physics. The idea of the path’s integral assumes a space-time pathway where the space­time bacteria displacements are governed by physics interactions that gives rise to changes of position in the space-time plane in a fully accordance to biological and physics laws. We worked out the idea of the Feynmans path integral to describe space-time dynamics of aggregations of bacteria trying to host a healthy body. We assumed that the bacteria interactions is governed by electric fields and potentials.While the net charge is predominantly positive due to the high concentrations of Cl+, there are clearly external electric fields and potentials that might seriously affect the behavior of bacteria space-time dynamics. In this manner this phenomenology would fit the path integral theory. Therefore the change of the net charge in bacteria due to the presence of others charged nano organisms would affect their translational dynamics by being vulnerable to macrophages. Thus the knowledge of the pathway of these bacteria populations is seen as an advantage to tackle the beginning of diseases inside the framework of Internet of Bio-nano Things that targets to anticipate infections using electromagnetic pulses through advanced software-hardware interfaces. In order to assess possible advantages and disadvantages of this theory we use the Machine Learning algorithm.

Wireless Nanobioelectronics for Electrical Intracellular Sensing

For the field of bioelectronics to make an impact on healthcare, there is an urgent requirement for the development of “wireless” electronic systems to enable modulation of chemistry inside of cells. Herein we report on an intracellular wireless electronic communication system. This is based on modulating the electrochemistry on gold nanoparticles without the nanoparticles having any physical electrical connection to a power supply at relatively low externally applied potentials. The system is made functional by modifying water-soluble gold nanoparticles (ws-AuNPs) with a Zn(II) meso-tetrakis(4-carboxyphenyl)porphyrin sodium salt (Na-ZnTCPP). Na-ZnTCPP modified ws-AuNPs are taken up by cells and are shown to be noncytotoxic. It is demonstrated that the redox state of the Zn-porphyrin modified gold nanoparticles is controlled, and a fluorescent output can be used to measure this during the application of an external electrical potential. When the porphyrin modified nanoparticles were located intracellularly and external potentials were applied, the same effect was observed. This provides an attractive “wireless” approach to develop bioelectronic devices for modulating and sensing cellular behavior.

Towards electrically tunable nanofiltration membranes: polyaniline-coated polyvinylidene fluoride membranes with tunable permeation properties

Conductive polyaniline (PANI)-coated polyvinylidene fluoride (PVDF) composite nanofiltration (NF) membranes were synthesized by an in situ chemical oxidative interfacial polymerization (solution and diffusion cell polymerization) to produce pressure filtration membranes with tunable separation selectivity through applying an external electrical potential. The diffusion cell polymerization technique was found to be superior with ability to coat a greater thin layer PANI film (120% mass increase) than solution polymerization (13% mass increase) after 48 h of reaction time. Furthermore, the conductivity of the PANI membrane synthesized by diffusion cell polymerization was far higher than that of the solution polymerization membrane, which was up to 6.711 S/cm compared to 7.61 × 10–2 S/cm, respectively, showing that a continuous film with good electrical connectivity has been formed. Meanwhile, a modified dynamic contact angle test showed that the membranes were electrically tunable with about 30–40% decrement on the contact angle values after an external electrical potential was applied. Moreover, the membranes with a complete surface PANI coverage (around 30–80 mass percentages) confirmed to have their permeability for neutral species (polyethylene glycols) electrically tuned under cross-flow conditions. Overall, this work demonstrated that the diffusion cell polymerization method produced membranes that have the potential to be applied as electrically tunable NF membranes.

Cross property connection between the electric and the thermal conductivities of copper graphite composites

The cross property relationship between thermal and electrical conductivity of the copper matrix–graphite composite was characterised in the composition range up to 100 vol.% of graphite. It was observed that the investigated cross property is linear in the whole composition range. This linearity averages out nonlinear dependence of single conductivity on composition. It means also that the behaviour of investigated composite under applied external electric potential and thermal gradient are qualitatively identical. Both conductivities are realised by free electrons in copper and in basal plane of graphite. The only difference between both cases is phonon thermal conductivity in graphite phase. The possible explanation for linear cross property is that all non linear effects are probably ruled by the scattering of valence electrons on copper–graphite interface via converting of some part of kinetic electron energy to the vibrations of phonons in graphite phase. Further Wiedemann–Franz law was used to determine composition threshold above which the phonon conductivity in graphite phase starts to play significant role. This threshold was observed around 25 vol.% of graphite. As linearity of cross property is valid also above the composition threshold it means probably that above this composition electrical conductivity composition dependence start to be nonlinear as well.

Suppressing Photoinduced Charge Recombination via the Lorentz Force in a Photocatalytic System.

Suppressing the recombination of photogenerated charges is one of the most important routes for enhancing the catalytic performance of semiconductor photocatalysts. In addition to the built‐in field produced by semiconductor heterostructures and the photo‐electrocatalysis realized by applying an external electrical potential to photocatalysts assembled on electrodes, other strategies are waiting to be scientifically explored and understood. In this work, a Lorentz force–assisted charge carrier separation enhancement strategy is reported to improve the photocatalytic efficiency by applying a magnetic field to a photocatalytic system. The photocatalytic efficiency can be improved by 26% just by placing a permanent magnet beneath the normal photocatalytic system without any additional power supply. The mechanism by which the Lorentz force acts oppositely on the photogenerated electrons and holes is introduced, resulting in the suppression of the photoinduced charge recombination. This work provides insights into the specific role of the Lorentz force in suppressing the recombination of electron–hole pairs in their initial photogenerated states. This suppression would increase the population of charge carriers that would subsequently be transported in the semiconductor. It is believed that this strategy based on magnetic effects will initiate a new way of thinking about photoinduced charge separation.

Nonlinear vibration of magnetoelectroelastic nanoscale shells embedded in elastic media in thermoelectromagnetic fields

This study investigates the nonlinear vibration of magnetoelectroelastic composite cylindrical nanoshells embedded in elastic media for the first time. The small-size effect and thermoelectromagnetic loadings are considered. Based on the nonlocal elasticity theory and Donnell’s nonlinear shell theory, the nonlinear governing equations and the corresponding boundary conditions are derived using Hamilton’s principle. Then, the Galerkin method is utilized to transform the governing equations into a nonlinear ordinary differential equation and subsequently the method of multiple scales is employed to obtain an approximate analytical solution to nonlinear frequency response. The present results are verified by the comparison with the published ones in the literature. Finally, an extensive parametric study is conducted to examine the effects of the nonlocal parameter, the external magnetic potential, the external electric potential, the temperature change, and the elastic media on the nonlinear vibration characteristics of magnetoelectroelastic composite nanoshells.

Vibration Analysis of Magneto-Electro-Thermo NanoBeam Resting on Nonlinear Elastic Foundation Using Sinc and Discrete Singular Convolution Differential Quadrature Method

Magneto-Electro-Thermo nanobeam resting on a nonlinear elastic foundation is presented. This beam is subjected to the external electric voltage and magnetic potential, mechanical potential and temperature change. Also, we added the new material PTZ-5H-COFe2O4. The governing equations and boundary conditions are derived using Hamilton principle. These equations are discretized by using three differential quadrature methods and iterative quadrature technique to determine the natural frequencies and mode shapes. Numerical analysis is introduced to explain the influence of computational characteristics of the proposed schemes on convergence, accuracy and efficiency of the obtained results. The obtained results agreed with the previous analytical and numerical ones. A detailed parametric study is conducted to investigate the influences of different boundary conditions, various composite materials, nonlinear elastic foundation, nonlocal parameter, the length-to-thickness ratio, external electric and magnetic potentials, axial forces, temperature and their effects on the vibration characteristics of Magneto-Electro-Thermo-Elastic nanobeam.

Multi-responsive fluorescent polymer microparticles in response to temperature, electricity and hydrogen oxide

Multi-responsive fluorescent materials have attracted much attention in recent years, but the synthesis routes were always complicated. In this work, a simple method was proposed to fabricate multiple responsive fluorescent microparticles, which could respond to tree types of external stimuli, including temperature, electric potential and H2O2 to change particle size and morphology. These microparticles were easily fabricated from radical polymerization of vinylidene ferrocene and N-isopropylacrylamide. Interestingly, when fluorescein (FITC) was encapsulated in the polymeric microparticles, fluorescence intensity of the obtained assemblies could change significantly with the three stimuli mentioned above. This work may provide a new path for the simple synthesis and construction of multi-responsive fluorescent microparticles.

Nonlinear free vibration of piezoelectric cylindrical nanoshells

The nonlinear vibration characteristics of the piezoelectric circular cylindrical nanoshells resting on a viscoelastic foundation are analyzed. The small scale effect and thermo-electro-mechanical loading are taken into account. Based on the nonlocal elasticity theory and Donnell’s nonlinear shell theory, the nonlinear governing equations and the corresponding boundary conditions are derived by employing Hamilton’s principle. Then, the Galerkin method is used to transform the governing equations into a set of ordinary differential equations, and subsequently, the multiple-scale method is used to obtain an approximate analytical solution. Finally, an extensive parametric study is conducted to examine the effects of the nonlocal parameter, the external electric potential, the temper-ature rise, and the Winkler-Pasternak foundation parameters on the nonlinear vibration characteristics of circular cylindrical piezoelectric nanoshells.