Abstract
The freezing of water can initiate at electrically conducting electrodes kept at a high electric potential or at charged electrically insulating surfaces. The microscopic mechanisms of these phenomena are unknown, but they must involve interactions between water molecules and electric fields. This paper investigates the effect of uniform electric fields on the homogeneous nucleation of ice in supercooled water. Electric fields were applied across drops of water immersed in a perfluorinated liquid using a parallel-plate capacitor; the drops traveled in a microchannel and were supercooled until they froze due to the homogeneous nucleation of ice. The distribution of freezing temperatures of drops depended on the rate of nucleation of ice, and the sensitivity of measurements allowed detection of changes by a factor of 1.5 in the rate of nucleation. Sinusoidal alternation of the electric field at frequencies from 3 to 100 kHz prevented free ions present in water from screening the electric field in the bulk of drops. Uniform electric fields in water with amplitudes up to (1.6 ± 0.4) × 10(5) V/m neither enhanced nor suppressed the homogeneous nucleation of ice. Estimations based on thermodynamic models suggest that fields in the range of 10(7)-10(8) V/m might cause an observable increase in the rate of nucleation.
Highlights
The nucleation of ice in water is ubiquitous in nature, and is relevant to phenomena ranging from the formation of atmospheric precipitation[1,2], and ice accretion on the wings of airplanes[3], to the cryopreservation of tissues[4]
Our experiments show that the homogenous nucleation of ice in drops of water cannot be influenced by external electric fields in air at ambient pressure; upon increasing the strength of the applied field, dielectric breakdown of air will occur before any changes in the rate of nucleation can be observed
We investigated the freezing of water in the presence of electric fields for three reasons. i) Previous experiments suggested that electrical phenomena can cause freezing, but the exact mechanism in which electric field might influence the nucleation of ice remains unclear
Summary
The nucleation of ice in water is ubiquitous in nature, and is relevant to phenomena ranging from the formation of atmospheric precipitation[1,2], and ice accretion on the wings of airplanes[3], to the cryopreservation of tissues[4]. While traveling along the channel, the drops supercooled until they froze due to the homogenous nucleation of ice. Across the drops of water, we applied sinusoidal alternating electric fields with frequencies from 3 to 100 kHz and a range of amplitudes. Electric fields with amplitudes above this value influenced the trajectory and the shape of the drops due to dielectrophoretic forces and made accurate observations of freezing impossible. Based on these experiments, we conclude that the homogeneous nucleation of ice is neither enhanced nor suppressed by electric fields with amplitudes up to 1.6±0.4×105 V/m
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