<p>Liquid confined in a nanoscale environment exists in a wide variety of natural and engineering systems, such as water confined in cells, transpiration, high heat flux removal devices, and nanofluidic devices. The properties of the confined fluid differ from the corresponding bulk dramatically, due to the appreciable, if not dominant, solid-liquid intermolecular interactions. At the solid-liquid interface, the fluid adopts atom configurations from solid, forming a layered structure. This layer usually associates with high density, and extreme pressure (either positively high or negatively low). Here, we present a molecular dynamics (MD) study of the molecular mechanics and the structure of the this layer, with confinement effect included. We create two systems, one is a thin liquid film, with a free liquid-vapor interface, on a solid surface; the other is a fluid confined in a nanopore, which is connected to the bulk liquid at on end, and the other end connected with bulk vapor. We choose argon (Ar) as the fluid in the systems. In the first system, the surface was chosen as a hydrophilic wall consists of five-layer face centered cubic (FCC) &lt;111&gt; plane atoms. Two cases were run for this system with different film thickness, one is 0.65 nm thick where only solid-liquid interface exists, without any bulk; the other is 4.2 nm thick where bulk liquid presents. In the second system, the nanopore is formed by the same hydrophilic walls as in the first system, and is connected a bulk liquid, which is a 5.2 nm thick continuous film. A 2.2 nm thick hydrophobic wall is present at the left edge of the domain to prevent the direct interaction between bulk liquid and vapor, which is at the other side of the domain. The space between hydrophilic wall and simulation domain is filled with the same atoms in hydrophobic wall. Two cases were run for this system with different pore size, one is 0.9 nm with liquid layers only, the other is 3 nm where bulk liquid exists in the nanopore. All atomic interactions were governed by standard Lennard - Jones potential. The hydrophilic wall is mimicked by using high large potential well in Ar - Wall atom potential, which is 1.5 times as large as that in Ar - Ar potential. The hydrophobic wall atoms is achieved by using small potential well (1% of Ar - Ar potential). The confined effects were investigated by comparing the molecular mechanics and the structures of the liquid layers in nanopore and the in the film.</p>

Confinement Effects on Molecular Mechanics and Structure of the Liquid Layers at Solid-Liquid Interface

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.