Imaging Research, Sunnybrook Health Sciences Center, Toronto, Canada.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010 Apr;57(4):957-68. doi: 10.1109/TUFFC.2010.1500.
Piezocomposite materials are used extensively in biomedical transducer array fabrication. However, developing high-frequency piezocomposite materials for imaging systems is still a challenge due to the extremely small pillar dimensions required to avoid the interference from lateral resonances. The use of triangular pillar piezocomposite material has been shown to suppress lateral resonances that appear in square pillar composite designs. To further understand how the geometry of the pillars affects the lateral resonances, piezocomposite materials with triangular pillars of different angles have been simulated and fabricated. Simulations were performed on composite transducers of 70-microm pitch, 18-microm kerf width, and 100-microm thickness with isosceles triangular pillars in which the isosceles angle varied from 30 degrees to 60 degrees using a finite-element analysis. By varying the pillar geometry, the composite transducers show large differences in lateral resonances. The simulation results demonstrate that the composite with 45 degrees angle pillars has the lowest secondary pulse amplitude. The secondary pulse becomes larger when the pillar angle deviates from 45 degrees . To study whether the pillar height (which determines the resonance frequency) and aspect ratio would change the optimum angle, composites with 40-mum pitch, 15-microm kerf width, and 45-microm thickness were also simulated. Finally, the composite with triangle pillars was compared with composites with square and round pillars. The simulation results show that the 45 degrees triangular pillar geometry is, for high-frequency applications, the best configuration among all investigated in this work. Composite samples have also been fabricated to confirm results from finite-element modeling. Acoustical and electrical measurements were carried out to compare with theoretical predictions. Three composite transducers with pillar angles of 30 degrees, 45 degrees, and 60 degrees were fabricated using a dice-and-fill technique. The measured electrical impedances and one-way pulse responses agreed well with the theoretical predictions and confirm the optimal nature of the 45 degrees design.
压电器件复合材料广泛应用于生物医学换能器阵的制造。然而，由于为避免横向共振的干扰而需要非常小的支柱尺寸，开发用于成像系统的高频压电器件复合材料仍然是一个挑战。已经证明，使用三角形支柱压电器件复合材料可以抑制在方形支柱复合材料设计中出现的横向共振。为了进一步了解支柱的几何形状如何影响横向共振，已经对具有不同角度的三角形支柱的压电器件复合材料进行了模拟和制造。在有限元分析中，对具有等腰三角形支柱的复合换能器进行了模拟，等腰三角形的等腰角度从 30 度变化到 60 度，复合换能器的 70 微米节距、18 微米切缝宽度和 100 微米厚度保持不变。通过改变支柱的几何形状，复合换能器在横向共振方面表现出很大的差异。模拟结果表明，具有 45 度角支柱的复合换能器具有最低的二次脉冲幅度。当支柱角度偏离 45 度时，二次脉冲会变大。为了研究支柱高度（决定共振频率）和纵横比是否会改变最佳角度，还对具有 40 微米节距、15 微米切缝宽度和 45 微米厚度的复合材料进行了模拟。最后，将三角形支柱复合材料与方形和圆形支柱复合材料进行了比较。模拟结果表明，对于高频应用，45 度三角形支柱几何形状是本文研究中所有几何形状中最佳的配置。还制造了复合材料样本以验证有限元建模的结果。进行了声学和电气测量以与理论预测进行比较。使用划片和填充技术制造了具有 30 度、45 度和 60 度支柱角度的三个复合换能器。测量的电阻抗和单程脉冲响应与理论预测吻合良好，证实了 45 度设计的最佳性质。
