Analysis of crosstalk between fluid coupled cmut membranes

P. Eccardt, A. Lohfink, H. Garssen
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引用次数: 38

Abstract

Crosstalk between array elements is an important and intensively discussed topic for CMUTs. For operation in fluids crosstalk effects significantly influence the dynamic range at pulse-echo mode, directivity pattern and frequency response and are highly undesired for medical application. On the other hand, crosstalk effects between the membranes and the surrounding fluid are used for other CMUT applications like pumping and mixing in micro fluidic channels. So far, coupling between the membranes and the surrounding fluid was mostly described as Stonely or Scholte waves at the CMUT surface. This paper presents an analytical description of this crosstalk effect between CMUT membranes. The basic idea is that the elastic membranes act as a complex load onto the fluid. Waves at such an interface are comparable to gravitational waves at a free water surface. Considering a homogeneously stiff and mass loaded interface, the speed of sound of an evanescent fluid wave at this interface will be described analytically with a simple formula for a fluid half space bounded by a complex acoustical impedance. The approach was validated with FEM simulations. Investigations with respect to the influence of discretisation and size of typical membranes are discussed as well as the influence of membrane stiffness, membrane mass and inactive area between membranes onto the speed of sound and the intensity distribution of this surface wave. The wave is highly dispersive, its speed of sound increases with increasing stiffness and with decreasing frequency. Both effects are monotonic but nonlinear for frequencies above the membrane resonance. Near membrane resonance the speed of sound approaches zero. FEM simulations of typical CMUT membranes show that these surface waves have a significant influence onto the array behavior and can be well described by the presented analytical approach.
流体耦合膜间串扰分析
阵列元素间的串扰是cmut研究的一个重要课题。在流体中操作时,串扰效应会显著影响脉冲回波模式下的动态范围、指向性模式和频率响应,这在医疗应用中是非常不希望的。另一方面,膜与周围流体之间的串扰效应用于其他CMUT应用,如微流体通道中的泵送和混合。到目前为止,膜与周围流体之间的耦合主要被描述为CMUT表面的斯通利波或肖尔特波。本文对CMUT膜间的串扰效应进行了分析描述。其基本思想是弹性膜作为流体的复杂负载。这种界面上的波与自由水面上的引力波相当。考虑一个均匀的刚性和质量加载界面,用一个简单的公式来解析描述在这个界面上消失的流体波的声速,这个公式适用于以复杂声阻抗为界的流体半空间。通过有限元仿真验证了该方法的有效性。讨论了典型膜的离散化和尺寸的影响,以及膜刚度、膜质量和膜间非活动面积对声速和表面波强度分布的影响。波具有高色散性,其声速随刚度的增大和频率的减小而增大。这两种效应都是单调的,但在膜共振以上的频率上是非线性的。在膜共振附近,声速接近于零。典型CMUT膜的有限元模拟表明,这些表面波对阵列行为有显著的影响,并且可以用所提出的分析方法很好地描述。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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