Redistribution Of Electric Potential Research Articles

Asymmetric electrode capacitive deionization for energy efficient desalination

Capacitive deionization (CDI) is an emerging technology as a sustainable low energy process for desalination of brackish water. Activated carbon electrodes are often used in the CDI devices. Electrosorption capacity was found to be improved on asymmetric electrode configuration using activated carbon cloth doped with fluorine due to redistribution of electric potential. This led to improvement in desalination performance up to 12.4 mg/g for a desalination cycle of 6 min employing an asymmetric fluorinated electrode as cathode (ACC//F-ACC). A relatively high charge efficiency of 77 % was obtained representing 92 % charge efficiency neglecting the leakage currents. Furthermore, the ion adsorption rate was found to improve substantially due to an increased surface conductivity of the fluorinated electrode confirmed by Mott-Schottky analysis. Energy consumption during desalination of 1000 ppm sodium chloride solution of 0.71kWh/m3 for symmetric electrode configuration was found to reduce by 36 % upon employing asymmetric configuration. This study shows some of the benefits of asymmetric configuration to achieve an optimal operation of CDI device, as well as improvements related to energy consumption.

Touch position identification based on a flexible array-less supercapacitive tactile sensor

Flexible tactile sensors with simple structures, minimal peripheral electric connections and straightforward data processing will benefit the human-machine interactions in which the contact information is crucial. However, it is still hard to balance the easy fabrication, full flexibility, large measurement area and minimal electric connection in existed tactile sensing systems. This study introduces an innovative positioning method based on a flexible supercapacitive tactile sensor. A 100 mm×100 mm prototype sensor, which contains two layers of flexible electrodes and a layer of ionic gel membrane in the middle to construct electrostatic double-layer capacitors (EDLCs), is developed to study the underlying physical principles. Following the established method, minimized electric connections are needed to achieve the mm-scale touch position/movement trace identification. Under the touch pressure, the formation of supercapacitors around the touch area leads to re-distribution of electric potential within the sensor. The electrical voltage variation is gauged at four points, and the data are calculated to estimate the touch positions following a two-step protocol. The developed method demonstrates high accuracy of position identification (around 5% in the 100 mm×100 mm flexible sensor), superior anti-disturbance capability (more than ∼104 variation of capacitance) and fast response (∼ms level). At the same time, it has no dependency on complex fabrication, redundant electric circuit or sensing unit arrays. These promising characteristics can benefit various application fields, such as intelligent robotics, biomedical devices and wearable equipment.

Electric potential redistribution due to time-dependent creep in thick-walled FGPM cylinder based on Mendelson method of successive approximation

In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semianalytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.

The analysis of time-dependent creep in FGPM thick walled sphere under electro-magneto-thermo-mechanical loadings

Time-dependent creep response of a smart sphere made of functionally graded piezoelectric material (FGPM) is investigated. The vessel is subjected to an internal pressure, a uniform temperature field, an electric potential and a uniform magnetic field. Under such a loading condition initial elastic stresses are locked in the vessel at zero time. Due to high temperature, creep evolution causes stress redistribution in the sphere which is followed by electric potential redistribution across the thickness of the sphere. History of radial stresses is always reflected by history of electric potential which can be used for condition monitoring of the smart sphere. From the initial elastic stresses it has been found that imposing an electric potential decreases effective stresses. It has also been concluded from history of electric potential that electric potential redistribution is decreasing due to creep evolution and therefore this is followed by increasing effective stresses.

Dynamic electric potential redistribution and its influence on the development of a dielectric barrier plasma jet

We investigate the initiation and development of a streamer-like plasma jet generated in a single-electrode dielectric barrier configuration at atmospheric pressure. The influence of dielectric boundary conditions on discharge propagation dynamics, morphology and current distribution was studied using spatially and temporally resolved emission spectroscopy and wide-bandwidth current measurements. A Phantom high-frame-rate camera system was used to visualize discharge inception as a function of pulse repetition frequency, which was varied between 1 and 20 kHz. At discharge inception, with the copper ring anode located 20 mm behind the capillary tip, the discharge propagated along the 2 mm diameter inner wall of the glass capillary regardless of pulse repetition frequency. The steady-state morphology remained annular below 6 kHz, but gradually transitioned to an axial morphology with the expansion of a dark wall sheath towards the anode as the pulse repetition frequency was increased to 10 kHz. In the axial mode, the ionization front steadily decelerated with a corresponding decrease in peak emission intensity, while emission from the residual plasma channel increased. This indicated a dynamic redistribution of electric potential from the ionization front into the residual plasma channel that was attributed to charge accumulation on the dielectric surface between discharge pulses.

Enhancement of electromechanical coupling coefficient by proton exchange in Z-cut LiNbO3

The electromechanical coupling coefficient K for surface acoustic waves (SAWs) in proton-exchanged Z-cut X-propagation lithium niobate has been experimentally investigated by the method of evaporating a thin metal film and measuring in situ the SAW attenuation. The enhancement in K2 value by as much as two times caused by the proton exchange has been observed. It is attributed to the redistribution of electric potential of the acoustic wave due to formation of a HxLi1−xNbO3 layer at the surface. The change of electromechanical coupling coefficient in samples fabricated under different conditions depends on the acoustic wavelength–layer thickness product kd. The K2 value attains a maximum of about 0.8×10−2 at kd≈0.4, whereas it is equal to 0.46×10−2 in nonexchanged lithium niobate. The increase in electromechanical coupling coefficient can be applied for enhancement of the SAW interdigital transducer efficiency.

Cell electroporation: Part 3. Theoretical investigation of the appearance of asymmetric distribution of pores on the cell and their further evolution

The appearance of an asymmetric pore distribution in the spherical cell membrane and further evolution of the pores under the influence of the external electric field are investigated theoretically.It is shown that, depending on the electroporation conditions (cell size, resting potential, and intensity and duration of the pulse) and the radius of the first pores to appear, either asymmetric (anodic or cathodic) or symmetric pore distribution is possible.The behaviour of a cell possessing asymmetrically distributed hydrophilic pores is investigated for the case when the electric potential redistribution on the cell membranes takes place much faster than the change in pore size. The electric potential distribution on each of the pores is found. Analytical expressions for the forces acting on the pore walls are derived. It is shown that under influence of these forces the cell tends to a stable state in which pores are larger in the hemisphere in which there are fewer pores, while the fraction of the membrane area occupied by pores is greater in the opposite hemisphere. The total conductances of the pores on both sides of the cell are almost the same: RCE ≈ RAE.The influence of the methods used to investigate cell electroporation on the results obtained is also discussed.