Nanoflows induced by MEMS and NEMS: Limits of two-dimensional models
Nanoflows induced by MEMS and NEMS: Limits of two-dimensional models
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DOI：
10.1103/physrevfluids.6.024201
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发表时间：
2021-02-02
影响因子：
2.7
通讯作者：
Ekinci, Kamil L.
中科院分区：
文献类型：
--
作者：
Liem, Alyssa T.;Ari, Atakan B.;Ekinci, Kamil L.
在这里，我们研究粘性振荡纳米流体中产生的小型化谐振器的机械振荡。特别是，我们专注于二维圆柱体理论的限制，它近似细长的纳米谐振器，如原子力显微镜微悬臂梁或纳米梁谐振器，作为在流体中振荡的圆柱体。圆柱体理论是微纳机电系统文献中的中流砥柱，但仅在某些情况下是准确的。我们观察和解释两个不同的路线，以打破圆筒理论。首先，当存在衬底时，挤压膜效应变得显著，并且圆柱体理论低估了施加到谐振器的流体力。第二，当轴向流变得相对较大时，圆柱体理论高估了流体力。这发生在更高的弯曲模式下，其中沿梁的空间梯度沿着更大。引入无因次挤压数和轴向流数，以便于深入研究二维柱体理论的局限性。实验和三维有限元模型的结果，以说明在二维流动模型打破。
Here we study viscous oscillatory nanoflows generated in a fluid by mechanical oscillations of miniaturized resonators. In particular, we focus on the limits of two-dimensional cylinder theory, which approximates a slender nanoresonator, such as an atomic force microscopy microcantilever or a nanobeam resonator, as a cylinder oscillating in a fluid. The cylinder theory is the mainstay in the micro- and nanoelectromechanical systems literature, but is only accurate in certain regimes. We observe and explain two distinct routes to the breakdown of the cylinder theory. First, when a substrate is present, squeeze film effects become significant and the cylinder theory underpredicts the fluid force applied to the resonator. Second, the cylinder theory overpredicts the fluid force when axial flow becomes relatively large. This occurs at higher bending modes where the spatial gradients along the beam are larger. A dimensionless squeeze number and axial flow number are introduced to facilitate in-depth investigations into the limitations of the two-dimensional cylinder theory. Results from experiments and three-dimensional finite-element models are presented in order to illustrate where two-dimensional flow models break down.