Free surface transition and momentum augmentation of liquid flow in Micro/Nano-scale channels with hydrophobic and hydrophilic surfaces

• Published in: Journal of mechanical science and technology Vol. 22; no. 12; pp. 2554 - 2562
• Main Authors: Budiono, Byun, Doyoung, Nyugen, Vu dat, Kim, Jihoon, Ko, Han Seo
• Format: Journal Article
• Language: English
• Published: Seoul Korean Society of Mechanical Engineers 01.12.2008; Springer Nature B.V; 대한기계학회
• Subjects: Adsorption and desorption kinetics; evaporation and condensation; Applied fluid mechanics; Applied sciences; Augmentation; Computational fluid dynamics; Condensed matter: structure, mechanical and thermal properties; Control; Dynamical Systems; Engineering; Exact sciences and technology; Fluid dynamics; Fluidics; Fundamental areas of phenomenology (including applications); Hydrodynamic stability; Hydrophobic surfaces; Industrial and Production Engineering; Liquids; Mechanical Engineering; Mechanical engineering. Machine design; Nanocomposites; Nanomaterials; Nanostructure; Nozzles; Physics; Precision engineering, watch making; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Vibration; 기계공학; Hydrophilic surface; Nano channel; Computational fluid dynamics; Molecular dynamics; Flow instability; Micro channel; Hydrophobic surface; Free surface; Hydrophobicity; Nanostructures; Liquid meniscus; Nanometer scale; Non equilibrium conditions; Flow control; Liquid flow; Modelling; Nanofluidics; Hydrophilic compound; Microelectromechanical device; Head; Non equilibrium system; Hydrophobic compound; Momentum; Hydrodynamic instability; Microstructure; Microfluidics; Nanotechnology
• ISSN: 1738-494X; 1976-3824
• DOI: 10.1007/s12206-008-0751-8

We propose a novel micro/nano-scale nozzle structure, featuring an interfacial line between the hydrophilic and the hydrophobic surfaces for a jetting system, such as an inkjet head or electrospray devices. This research will investigate the impact of the interfacial line on flow instability and momentum augmentation as the liquid meniscus moves across the line. The research methods used in this paper, in respect to micro-and nano-scale channels, are computational fluid dynamics (CFD) and non-equilibrium molecular dynamics (MD), respectively. With the growing interest in micro/nano electromechanical systems (MEMS/NEMS), many studies have been conducted to develop an advanced micro/nanofluidic system. However, until now, there have been few in-depth studies on passive flow control in micro and nano nozzles using the hydrophilic and hydrophobic surface characteristics. In this research, the sequential arrangement of hydrophilic and hydrophobic surfaces in the nozzle is presented along with an investigation into how flow instability and momentum augmentation are going to be applied to an efficient micro/nano jetting system. When a liquid meniscus arrives at the interfacial line between hydrophilic and hydrophobic surfaces, the meniscus shape changes from concave to convex and the fluid motion near the wall stops until the concave shape is fully converted. Because the momentum should be conserved, the lost momentum near the wall transfers to the center region, and therefore the liquid at the center region is accelerated as it crosses the line. If we use this nozzle structure and the augmentation of the momentum near the center, a tiny droplet can be easily generated.