Electro-wetting behavior of Imidazolium based Hydrophilic Ionic Liquid on Rough surface: A molecular dynamics study

Abstract

In this work, we study the electro-wetting behavior of aqueous Imidazolium based Ionic Liquids (ILs) using classical molecular dynamics (MD) simulation, with a particular focus on 1-Ethyl-3-methylimidazolium tetrafluoroborate ([EMIM] [BF4]) under intrinsically rough surfaces. The roughness of the surfaces is modelled using two parameters which are pillar fraction (f) and pillar height (H). It is essential to comprehend how ILs behave when subjected to an external electric field (EEF) because of the diverse range of uses they have in the engineering and biomedical fields. Electro-wetting on dielectric surfaces (EWOD), which can result in the controlled manipulation of liquid droplets, is one of the phenomenon's essential uses. First, we compute the contact angle of the IL droplets on rough surfaces, and then we perform a thorough examination of the density and charge distributions inside the droplets to understand how the molecules align themselves when subjected to an EEF. The investigation helps us comprehend how water molecules align when exposed to varying field intensities and how this affects droplet behavior. Positive and negative electric field strengths applied in the z-direction vary from (±0.03 to-±0.07 V/Å) with the key aim to assess whether a wetting transition happens under the effect of the applied electric field or not. In addition, we do a hydrogen bonding (HB) analysis to study the interaction between water molecules and ILs when EEF is applied, this can reveal information about the system's structural characteristics. By means of these investigations, we hope to evaluate the electro-wetting responsiveness of these ILs and investigate the viability of applying an electric field to induce a wetting transition.