Evaporation-induced cavitation in nanofluidic channels
Evaporation-induced cavitation in nanofluidic channels
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DOI：
10.1073/pnas.1014075109
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发表时间：
2012-03-06
影响因子：
11.1
通讯作者：
Majumdar, Arun
中科院分区：
文献类型：
--
作者：
Duan, Chuanhua;Karnik, Rohit;Majumdar, Arun
空化现象，即液体在张力下形成气泡的现象，在凝聚态科学以及植物学、水利工程和医学等多种应用中引起了极大的兴趣。尽管在散装和微米级限制液体中进行了广泛的研究，但纳米级的空化通常被认为在能量上是不利的，并且从未经过实验证明。在这里，我们报告了在高达 -7 MPa 的巨大负压下，充满水的亲水纳米通道中蒸发引起的空化。与微通道蒸发中观察到的后退弯液面相反，纳米通道中的弯液面被固定在入口处，而蒸汽泡在内部形成并膨胀。研究发现，通道中的蒸发受到平流液体传输的帮助，这导致蒸发速率比宏观和微观蒸发中由菲克蒸气扩散控制的蒸发速率高一个数量级。气泡还表现出不寻常的运动以及平移稳定性和对称性，这是由于热毛细管作用和蒸发驱动的两个相互竞争的质量通量之间的平衡而发生的。我们的研究拓展了我们对空化的理解，并为纳米尺度的相变现象提供了新的见解。
Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7 MPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale.