Singh Sachin K, Subramanian Arunkumar
Department of Mechanical and Industrial Engineering, University of Illinois at Chicago Chicago IL 60607 USA
RSC Adv. 2020 Jun 30;10(42):25022-25028. doi: 10.1039/d0ra04214e. eCollection 2020 Jun 29.
A numerical simulation is presented for predicting the transient ejection of micro-/nano-scopic jets from microscale nozzles, when a liquid confined within the nozzle is subjected to an external electric field. This simulation is based on the Taylor-Melcher leaky dielectric model, and uses the phase field method for interface tracking. The presented model is able to successfully simulate the deformation of a flat liquid meniscus into a Taylor cone, eventually leading to jet formation and breakup into droplets. Several simulations are performed to understand the effect of process parameters like applied voltage, liquid flow rate and properties on jet ejection dynamics. The results reveal the dependence of the ejected jet diameter and current primarily on the applied electric potential, liquid flow rate and electrical conductivity of the liquid. For high conductivity liquids, it is found that the convection current is of the same order of magnitude as the conduction current. In contrast, the convection current dominates the conduction current during jet ejection in the case of low conductivity liquids, regardless of the flow rate. It is also found that stable jets smaller than 200 nm can be produced from a 2 μm nozzle, which would facilitate patterning structures at the nanoscale. This model presents an approach to analyze the effect of process parameters on electrojet ejections and can effectively guide the design of printheads for e-jet systems that pattern nanoscale features in jetting and nano-dripping modes from microscopic nozzles.
本文提出了一种数值模拟方法，用于预测当喷嘴内的液体受到外部电场作用时，微/纳米尺度喷嘴的瞬态射流情况。该模拟基于泰勒 - 梅尔彻漏电介质模型，并使用相场法进行界面跟踪。所提出的模型能够成功模拟扁平液体弯月面变形为泰勒锥，最终导致射流形成并破碎成液滴的过程。进行了多项模拟，以了解诸如施加电压、液体流速和性质等工艺参数对射流动力学的影响。结果表明，射出射流的直径和电流主要取决于施加的电势、液体流速和液体的电导率。对于高电导率液体，发现对流电流与传导电流具有相同的数量级。相比之下，在低电导率液体的射流过程中，无论流速如何，对流电流都主导传导电流。还发现，从2μm的喷嘴可以产生小于200nm的稳定射流，这将有助于在纳米尺度上进行图案化结构。该模型提供了一种分析工艺参数对电射流影响的方法，并能有效地指导用于电子喷射系统的打印头设计，该系统可从微观喷嘴以喷射和纳米滴模式对纳米尺度特征进行图案化。
