Elmar C. Fuchs

The floating water bridge

When high voltage is applied to distilled water filled in two glass beakers which are in contact, a stable water connection forms spontaneously, giving the impression of a floating water bridge. A detailed experimental analysis reveals static and dynamic structures as well as heat and mass transfer through this bridge.

Dynamics of the floating water bridge

When high voltage is applied to distilled water filled into two beakers close to each other, a water connection forms spontaneously, giving the impression of a floating water bridge (Fuchs et al 2007 J. Phys. D: Appl. Phys. 40 6112–4). This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. The build-up mechanism, the chemical properties and the dynamics of this bridge as well as related additional phenomena are presented and discussed.

Neutron scattering of a floating heavy water bridge

When high voltage is applied to distilled water filled into two beakers close to each other, a water connection forms spontaneously, giving the impression of a floating water bridge (Fuchs et al 2007 J. Phys. D: Appl. Phys. 40 6112–4, 2008 J. Phys. D: Appl. Phys. 41 185502). This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the first data on neutron scattering of a floating heavy water bridge are presented and possible interpretations are discussed. D2O was measured instead of H2O because of the very strong incoherent scattering of H. The obtained data support the ‘bubble hypothesis’ suggested earlier (Fuchs et al 2008).

Two-dimensional neutron scattering in a floating heavy water bridge

When a high voltage is applied to pure water in two filled beakers kept close to each other, a connection forms spontaneously, giving the impression of a floating water bridge. This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the first two-dimensional structural study of a floating heavy water bridge is presented as a function of the azimuthal angle. A small anisotropy in the angular distribution of the intensity of the first structural peak was observed, indicating a preferred orientation of a part of the D2O molecules along the electric field lines without breaking the local tetrahedral symmetry. The experiment is carried out by neutron scattering on a D2O bridge.

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Colour change of co-doped yttrium aluminium borate crystals under illumination with different white light sources

A colour change of doped YAB crystals and microcrystalline powders takes place upon illumination with different white light sources. This paper presents extensive experimental data on the new materials Ho,Nd:YAB; Ho,Cr:YAB, Nd,Cr:YAB and Ho,Nd,Cr:YAB, resulting in a chart providing the observed crystal colours and chromaticity differences of the materials under illumination with seven different types of white light sources. The microcrystalline powders could be used as coatings in order to produce a special colour changing effect. Furthermore, the colour table presented enables the observer to discriminate the investigated light sources at one glance.

The behaviour of a floating water bridge under reduced gravity conditions

When high voltage is applied to pure water filled into two beakers close to each other, a connection forms spontaneously, giving the impression of a floating water bridge (Armstrong 1893 The Electrical Engineer pp 154?45, Uhlig W 2005 personal communication, Fuchs et al 2007 J. Phys. D: Appl. Phys. 40 6112?4, Fuchs et al 2008 J. Phys. D: Appl. Phys. 41 185502, Fuchs et al 2009 J. Phys. D: Appl. Phys. 42 065502, Fuchs et al 2010 J. Phys. D: Appl. Phys. 43 105502, Woisetschl?ger et al 2010 Exp. Fluids 48 121?31, Nishiumi and Honda 2009 Res. Lett. Phys. Chem. 2009 371650). This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the behaviour of this phenomenon under reduced gravity conditions during a parabolic flight is presented by the means of high speed imaging with fringe projection. An analysis of the behaviour is presented and compared with theoretical considerations.

Aqueous phenol and ethylene glycol solutions in electrohydrodynamic liquid bridging

The formation of aqueous bridges containing phenol and ethylene glycol as well as bisphenol-A, hydrochinone and p-cresol under the application of high voltage DC (“liquid bridges”) is reported. Detailed studies were made for phenol and glycol with concentrations from 0.005 to 0.531 mol L−1. Conductivity as well as substance and mass transfers through these aqueous bridges are discussed and compared with pure water bridges. Previously suggested bidirectional mass transport is confirmed for the substances tested. Anodic oxidation happens more efficiently when phenol or glycol are transported from the cathode to the anode since in this case the formation of a passivation layer or electrode poisoning are retarded by the electrohydrodynamic (EHD) flow. The conductivity in the cathode beaker decreases in all experiments due to electrophoretic transport of naturally dissolved carbonate and bicarbonate to the anode. The observed electrochemical behavior is shortly discussed and compared to known mechanisms.

Methanol, Ethanol and Propanol in EHD liquid bridging

When a high-voltage direct-current is applied to two beakers filled with water or polar liquid dielectrica, a horizontal bridge forms between the two beakers. In this work such bridges made of methanol, ethanol, 1-propanol and 2-propanol are investigated with polarimetry and thermography. Whereas methanol, ethanol and 1-propanol bridges become warm like a water bridge, a 2-propanol bridge cools down relative to the surroundings. It is shown how the different stability of the primary and secondary alcoholate ions and the resulting small difference in conductivity between 1-propanol and 2-propanol is responsible for this novel effect.

Mass and charge transfer within a floating water bridge

When high voltage is applied to pure water filled into two beakers close to each other, a connection forms spontaneously, giving the impression of a floating water bridge 1-8. This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the charge and mass transfer through the water bridge are investigated with schlieren visualization and laser interferometry. It can be shown that the addition of a pH dye increases the H+ and OH- production with subsequent electrolysis, whereas schlieren and interferometric methods reveal another mechanism where charge and mass transfer appear to be coupled. Whereas this mechanism seems to be responsible for the electrolysis-less charge and mass transfer in the water bridge, it is increasingly superseded by the electrochemical mechanism with rising conductivity. Thus it can be shown that a pH dye does only indirectly visualize the charge transfer in the water bridge since it is dragged along with the water flow like any other dye, and additionally promotes conventional electrochemical conduction mechanisms, thereby enhancing electrolysis and reducing the masscoupled charge transport and thus destabilizing the bridge.