Droplet formation and ejection from a micromachined ultrasonic droplet generator: Visualization and scaling
Droplet formation and ejection from a micromachined ultrasonic droplet generator: Visualization and scaling
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DOI：
10.1063/1.1921249
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发表时间：
2005-10-01
影响因子：
4.6
通讯作者：
Fedorov, AG
中科院分区：
文献类型：
--
作者：
Meacham, JM;Varady, MJ;Fedorov, AG
按需滴和连续射流流体雾化的水的可视化和缩放，以阐明喷射过程的流体物理和表征一种新型的微机械超声波液滴发生器的操作模式。该装置包括在体陶瓷压电换能器和湿蚀刻到（100）硅中的液体喇叭结构阵列之间形成的流体贮存器。在共振时，换能器在腔内产生超声压力驻波，并且该波通过喇叭结构聚焦在喷嘴的尖端处。通过在1至5 MHz之间的多个谐振频率下从5至10 μ m孔中喷射水滴来演示设备操作。聚焦的超声压力波和毛细管波之间的密切相互作用，形成在液体-空气界面位于喷嘴尖端被发现支配的喷射动力学，导致不同的喷射方式，从个别液滴连续射流。具体来说，我们报告的结果高分辨率频闪光学成像的液体-空气界面的演变过程中的声泵，以阐明毛细波的作用，在液滴的形成和喷射过程。通过仔细的可视化和缩放获得的管理物理的基本理解形成了改进的理论模型的基础上发展的液滴形成和喷射过程中占的关键流体力学特性的现象。(c)2005年美国物理学会。
Visualization and scaling of drop-on-demand and continuous-jet fluid atomization of water are presented to elucidate the fluid physics of the ejection process and characterize the modes of operation of a novel micromachined ultrasonic droplet generator. The device comprises a fluid reservoir that is formed between a bulk ceramic piezoelectric transducer and an array of liquid horn structures wet etched into (100) silicon. At resonance, the transducer generates a standing ultrasonic pressure wave within the cavity and the wave is focused at the tip of the nozzle by the horn structure. Device operation has been demonstrated by water droplet ejection from 5 to 10 mu m orifices at multiple resonant frequencies between 1 and 5 MHz. The intimate interactions between focused ultrasonic pressure waves and capillary waves formed at the liquid-air interface located at the nozzle tip are found to govern the ejection dynamics, leading to different ejection modalities ranging from individual droplets to continuous jet. Specifically, we report the results of high-resolution stroboscopic optical imaging of the liquid-air interface evolution during acoustic pumping to elucidate the role of capillary waves in the droplet formation and ejection process. A basic understanding of the governing physics gained through careful visualization and scaling forms the basis for development of improved theoretical models for the droplet formation and ejection processes by accounting for key fluid mechanical features of the phenomena. (c) 2005 American Institute of Physics.