Magnetic resonance imaging of flow and mass transfer in electrohydrodynamic liquid bridges

Here, we report on the feasibility and use of magnetic resonance imaging-based methods to the study of electrohydrodynamic (EHD) liquid bridges. High-speed tomographic recordings through the longitudinal axis of water bridges were used to characterize the mass transfer dynamics, mixing, and flow structure. By filling one beaker with heavy water and the other with light water, it was possible to track the spread of the proton signal throughout the total liquid volume. The mixing kinetics are different depending on where the light nuclei are located and proceeds faster when the anolyte is light water. Distinct flow and mixing regions are identified in the fluid volumes, and it is shown that the EHD flow at the electrodes can be counteracted by the density difference between water isotopes. MR phase contrast imaging reveals that within the bridge section, two separate counter-propagating flows pass one above the other in the bridge. Graphical Abstract