Electric fields bubbles

Gas Bubble in Liquid Film under External Electric Field... 

In the theoretical section above, the nonlinear polarization induced by the fundamental wave incident on a planar interface for a system made of two centrosymmetrical materials in contact was described. However, if one considers small spheres of a centrosymmetrical material embedded in another centrosymmetrical material, like bubbles of a liquid in another liquid, the nonlinear polarization at the interface of a single sphere is a spherical sheet instead of the planar one obtained at planar surfaces. When the radius of curvature is much smaller than the wavelength of light, the electric field amplitude of the fundamental electromagnetic wave can be taken as constant over the whole sphere (see Fig. 7). Hence, one can always find for any infinitely small surface element of the surface... 

Colver, G. M., Bubble control in gas-fluidized beds with applied electric fields, Powder Technol., 17 9-18(1977)... 

It would therefore be of obvious importance to study the electrical behaviour of a surface liquid-air, since in that case we can determine changes in surface tension directly. Such experiments were already carried out by Quincke, who examined under the microscope the travel of a small air bubble in capillary filled with liquid, in an electric field. The method is therefore substantially cataphoresis, but has the drawback that there is only a minute thickness of liquid between the air surface and the glass wall, and that the portion of liquid film adjacent to the latter also travels in the electric field. Quincke found that air bubbles in water were negatively... 

Dielectric particles show a reduced tendency for bubbling and a larger range of velocities over which particulate expansion occurs when an alternating electrical field is applied. 

Breakup of water drops due to strong electrical forces has been studied in connection with rain phenomena [e.g. (A4, L8, L9, M4, M7)]. As a strong electrical field is imposed on a freely falling drop, marked elongation occurs in the direction of the field and can lead to stripping of charge-bearing liquid. A simple criterion derived by Taylor (T6) can be used to predict the critical condition for instability. It has also been shown (W6) that soap bubbles can be rendered unstable by electric fields. 

Assume now that the ejected ions are distributed isotropically on the surface of the expanding sphere, and that linear electric fields along the z axis project the sphere perfectly onto the PSD. The 3-D bubble of ions will flatten to a disk on the detector with the highest ion intensity lying at the outer edge of the disk, forming a circle of radius... 

In electrophoresis an electric field is applied to a sample causing charged dispersed droplets, bubbles, or particles, and any attached material or liquid to move towards the oppositely charged electrode. Their electrophoretic velocity is measured at a location in the sample cell where the electric field gradient is known. This has to be done at carefully selected planes within the cell because the cell walls become charged as well, causing electro-osmotic flow of the bulk liquid inside the cell. From hydrodynamics it is found that there are planes in the cell where the net flow of bulk liquid is zero, the stationary levels, at which the true electrophoretic velocity of the particles can be measured. 

A platinized Au electrode was used as a decoupler (the decoupling ground electrode for CE) to reduce the interferences of the high separation electric field on the detection current and of H2 bubble formation. However, the lifetime of the decoupler was estimated to be - 10 separations [242]. 

A Pd film decoupler has also been constructed for amperometric detection of catecholamines. The Pd film has been thermally evaporated onto a plastic chip (without the use of the Cr or Ti adhesion underlayers). Owing to the fast diffusion of H2 on a Pd surface, gas bubbles will not form. Pd is able to absorb H2 produced at the cathode up to a Pd/H ratio of 0.6. This reduces one of the interferences to the EC signal, leading to an improvement of LOD to 0.29 pM dopamine [205,375]. With an optimal decoupler size of 500 pm, up to 6 h of operation was achieved with an electric field of 600 V/cm [375]. 

A four-electrode capacitively coupled (contactless) detector has been integrated on a Pyrex glass chip for detection of peptides (1 mM) and cations (5 mM K+, Na+, Li+). The A1 electrode (500 nm Al/100 nm Ti) was deposited in a 600-nm-deep trench and was covered with a thin dielectric layer (30-nm SiC). The other parts of the channel were covered and insulated with Si3 N4 (160 nm). To avoid gas bubble formation after dielectric breakdown, the electric field for separation was limited to 50 V/cm [145]. This four-electrode configuration allows for sensitive detection at different background conductivities without the need of adjusting the measurement frequency [328]. 

Fig. 2.25 illustrates a device for the study of the deformation of a spherical foam film in an electric field, proposed in [130]. The surfactant solution is fed into the glass cell through the tube 2, so that its level reaches the porous plate 4. When air is blown through the tube 3, a foam bubble forms at the capillary orifice. An electric field is created between electrode 1 and 6, which deforms the foam film (bubble). The bubble transforms from spherical to ellipsoidal shape. The value of the deformation A/ depends on the surface tension of the film... 

Platikanov and Nedyalkov [326] have developed another technique for establishing the CBF/NBF transition which is based on measuring the deformation of a foam bubble laying on a horizontal liquid surface in electrical field. 

---