UC Merced

We present our study of the behavior of water at the molecular level in the presence of an external electric field. We develop two model systems using the theory of molecular dynamics (MD) and demonstrate how the tendency of interfacial water molecules to reorganize explains the structural behavior of the systems.

Water molecules can interact with external electric fields. This interaction can be observed in various processes such as formation of raindrops in thunderclouds, lightning strikes and electrofreezing. Understanding of this interaction is relevant to variety of applications, like for example, electrospinning, electrospray ionization, crop spraying, spray painting, and inkjet printing. Furthermore, the interaction of water molecules with an external electric field plays an important role in the electroporation process.

First, we present a novel theory of electroporation that provides insight into initiation pore formation in biological cell membranes when they are exposed to an external electric field. Using thorough structural and energetic analysis, we demonstrate that the formation of a pore is driven by the reorganization of the interfacial water molecules into energetically favorable structures.

Second, we present our study of nano-sized water droplets placed in an external electric field. Our analysis exposes the molecular mechanism behind the nanodroplet shape change from a spheroid to a highly prolate ellipsoid. We demonstrate that a droplet extends its shape as water dipoles align with the electric field while simultaneously restructuring to minimize the dipole-related interaction energy. A new semi-empirical model is developed to predict the critical electric field value which separates the two states. We show that the new model sheds more light onto the dynamics of the system compared to previous theoretical results.

Finally, we conclude with a possible future research work.