How does an electric field create velocity in a water bridge?

[HelloCthulhu]

I've been researching water bridges and electrowetting to learn the effects of electric fields on water molecules but something continues to confuse me: if polar molecules can only rotate in an electric field, how is the water moving? Anyone familiar with this phenomenon? Any help is greatly appreciated!

https://www.academia.edu/18092509/B...trohydrodynamics_of_the_floating_water_bridge

 

[Drakkith]

Quick guess is that the polarization places negative or positive charges closer to the source of the electric field, causing the molecules to experience a net force. Similar to the Van der Waals force between closely spaced atoms/molecules. Not sure if that's correct or not, so I hope someone with more knowledge on the topic can answer.

 

[TeethWhitener]

Water (even completely pure water) isn't just water molecules. It undergoes a process called autoionization, which very simplified looks like
$$2H_2O \rightleftharpoons OH^-+H_3O^+$$
with the caveat that these species are actually significantly more complicated than the above equation makes them seem. The point is that water self-ionizes (this is the reason that water has a pH at all), and it is these ionic species that migrate under the influence of an electric field.

 

[HelloCthulhu]

I'm not sure if this will help, but this article, "Dynamics Behaviors of Droplet on Hydrophobic Surfaces Driven by Electric Field" (2019), describes in section 3. Results and Discussion that a water droplet on a substrate within an electric field is "mainly affected by the inertial force, viscous force, electric field force, surface tension and substrate adhesion". Granted the surfaces are hydrophobic, but I thought the data might still be useful since I'm interested in electrowetting as well.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6915515/