Why the water bridge does not collapse

Abstract

In 2007 an interesting phenomenon was discovered: a thread of water, the so-called water bridge (WB), can hang between two glass beakers filled with deionized water if voltage is applied to them. We analyze the available explanations of the WB stability and propose a completely different one: the force that supports the WB is the surface tension of water and the role of electric field is not to allow the WB to reduce its surface energy by means of breaking into separate drops.PACS numbers: 47.55.nk, 47.20.Dr, After the WB (see Fig. 1) was rediscovered in 2007 [1] (it had been first time observed in 1893 [2]) it immediately captured attention and even entered some TV shows because the experiment is easy to reproduce and it can be treated as an evidence of some unique properties of water. What keeps WB stable against gravity? The first thing one can suppose is that the water in WB has properties similar to those of a polymer melt; i.e. in the electric field water molecules are arranged in quasi polymer chains that play the role of the WB load-carrying structure [3]. It has been also supposed that hydrogen bonds are the driving force of WB formation [4]. But in the computer simulation carried out in the work [4] the WB consisted of only 10 3 molecules and it could be formed if the electric field was at least ≈ 10 3 times stronger than the one necessary for formation of macroscopic WBs in real experiments [1,[5][6][7][8][9]. Some attempts have been made to reveal a specific structure of WB by means of neutron scattering and Raman scattering [5,8], but no exhaustive explanation of the WB stability has been found on this way. An interesting feature of WB is the complicated spiral flow of water and formation of tiny bubbles inside it [6]. But it has not been proved yet that the dynamics of WB can be related to its stability. It has been even supposed that WB stability against gravity is a quantum effect [10].However, the best explanation of a newly discovered phenomenon is the simplest one based on well known formulas. It has been stated already [7,11] that not specific properties of water but just its high dielectric permittivity is likely to be the reason of the WB phenomenon. The convincing evidence of the statement is the "water bridge" (dielectric liquid bridge (DB)) formation of another low molecular polar dielectric liquid (DL): glycerine [9]. A good hint for the discovery with glycerine is the necessity to deionize water for forming WB. How can the high dielectric permittivity of a DL cause the DB stability? It is straightforward to assume that DB is kept stable against gravity by tension as a hanging flexible cable [11], the tension being somehow produced by electric field. Let us imagine a DL cylinder in a uniform electrostatic field (EF) E parallel to its axis. This is possible if the cylinder bases touch two infinite conducting planes to which voltage ∆ϕ is applied (see Fig. 2). To simplify the explanation we have depicted in Fig. 2 gaps between the bases and the planes. The gaps are supposed to be infinite...

Structure of the floating water bridge and water in an electric field

“…Other molecular dynamics simulations have suggested that it is the polarization of hydrogen bonds that induces the formation of the water bridge above a threshold field of 1.2 × 10 9 V∕m (19): which is much higher than the approximately 10 6 V∕m required to form the bridge experimentally. Alternatively, it has been proposed that ordinary surface tension holds the bridge together rather than the electric field directly (20). In this work we have performed high-energy X-ray diffraction experiments, with a submillimeter sized beam, on different parts of the floating water bridge (Fig.…”

Floating and flying ferrofluid bridges induced by external magnetic fields

“…The study of this phenomenon was revived by Fuchs et al 2 in 2007. Thereafter, a number of research works [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have been devoted to the floating water bridges between the deionized water in two containers induced by the high voltages applied to the deionized water. However, the interpretations to the origin of the floating water bridges are different at present stage, 3 for example, dielectric tension, 4 surface tension, 5 or both.…”

Behavioral study of selected microorganisms in an aqueous electrohydrodynamic liquid bridge

“…Formal relationships between the physical fluid parameters, electric field intensity, and experimental configuration have been worked out by Marín and Lohse [7] . Aerov [8] on the other hand proposes a model where surface tension is responsible for holding the bridge against the gravity, whereas the electric field assures stability with respect to decomposition into droplets (the Rayleigh-Plateau instability). Woisetschläger et al [9] present a macroscopic theory based on the works of Widom et al [6] and Marín and Lohse [7] .…”