Analysis of droplet stability after ejection from an inkjet nozzle
Analysis of droplet stability after ejection from an inkjet nozzle
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DOI：
10.1017/jfm.2018.251
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发表时间：
2018-04-26
影响因子：
3.7
通讯作者：
Dong, Xuran
中科院分区：
文献类型：
--
作者：
Zhong, Yonghong;Fang, Haisheng;Dong, Xuran
喷墨技术在图形打印、生物工程和微电子机械系统(MEMS)等许多应用中都是一种值得称赞的工具。液滴稳定性是影响喷墨性能的关键因素。稳定性可以用通常结合热物理性质和系统尺寸的无量纲数来分析。本文建立了一套按需滴墨(DOD)喷墨实验系统。建立了一个数值模型，研究了操作条件对液滴稳定性的影响，包括喷嘴尺寸、驱动参数(用于驱动液滴形成的脉冲幅度和宽度)和流体性质。结果表明，减小脉冲幅度和脉宽，减小流体密度和粘度，增大喷嘴直径和流体表面张力，均可提高稳定性。基于实例分析和模拟，数值确定了稳定液滴在4-8范围内的Ohnesorge数的倒数Z。为了明确地结合驱动参数，进一步提出了一个新的稳定性判据Pj。提出了在已知喷嘴和流体的情况下，选择合适的驱动参数，同时考虑PJ和Z的一般规律，并通过实验进行了验证。
Inkjet technology is a commendable tool in many applications including graphics printing, bioengineering and micro-electromechanical systems (MEMS). Droplet stability is a key factor influencing inkjet performance. The stability can be analysed using dimensionless numbers that usually combine thermophysical properties and system dimensions. In this paper, a drop-on-demand (DOD) inkjet experimental system is established. A numerical model is developed to investigate the influence of the operating conditions on droplet stability, including nozzle dimensions, driving parameters (the pulse amplitude and width used to drive droplet formation) and fluid properties. The results indicate that the stability can be improved by decreasing the pulse amplitude and width, decreasing the fluid density and viscosity or increasing the nozzle diameter and fluid surface tension. Based on case analysis and modelling, a dimensionless number (Z), the reciprocal of the Ohnesorge number, is numerically determined for a stable droplet to lie in a range between 4 and 8. To explicitly combine the driving parameters, a new stability criterion, Pj, is further proposed. A general rule taking into account both Pj and Z is proposed for choosing appropriate driving parameters to eject stable droplets for a known nozzle and fluid, which is further validated by experiments.