3D打印高频超声换能器中的关键科学问题研究

The increasing demands for miniature, complex, and high-performance high-frequency transducer arrays have imposed huge challenges on traditional 'subtractive manufacturing’, including mechanical dicing, micromachining etc. Microstereolithography, an additive manufacturing approach, has simple system requirements, fast printing speed and low cost, and can realize precise, complex structures without additional machining steps. It is a promising technique to fabricate high-frequency transducers. However, it is primarily limited to printing piezoelectric elements of transducers..The objectives of this research aim to 1) make individualized composite slurries for transducer components; 2) develop processing procedures for DMD based microstereolithography manufacturing of transducer arrays' piezo-elements, electrical interconnection, matching layers, and backing layers; 3) and eventually realize the process-reliable manufacture of high-frequency transducer arrays. The significance and innovation highlights of the study include 1) making composite slurries using thick film hybrid circuits technology for reference, 2) employing a novel bottom-up DMD projection setup, 3) building a mathematical prediction model for microstereolithography manufacturing of ceramics. Technical barriers preventing the implementation of all-printed high-frequency piezoelectric ultrasonic transducers, which include multi-material printing, high printing resolution, and the need of sintering, were broken through thereafter.

现代高频超声领域需求微型、 结构复杂 、性能优越的新型换能器，这给传统的机械切割、微加工等减法制造带来新的技术挑战。微立体光刻成型增材制造技术系统简单、制造速度快、成本低，可实现高精度复杂结构器件，且成型器件结构完整，契合高频超声换能器制备的需求。.本课题志于突破目前微立体光刻成型技术局限于打印压电陶瓷阵元局面，拟以高频压电超声换能器为研究对象，制备适用换能器各部件打印浆料；发展新颖数字微镜投射技术，探索微型压电陶瓷换能器压电阵元、电极连接 、匹配层、 背衬层的微立体光刻成型技术及后处理工艺；最终实现高频压电换能器的可控打印制备。 关键科学问题和创新点包括 1）提出借鉴厚膜混合电路技术制备换能器部件浆料，2）采用创新的自下而上的DMD投射装置 ，3）建立微立体光刻成型陶瓷部件预测模型；从而解决了全打印高频压电超声换能器面临的多材料打印、打印精度要求高、器件需高温烧结处理等关键技术难题。

现代高频超声领域需求微型、结构复杂、性能优越的新型换能器，这给传统的加工制造带来很多技术挑战。以微立体光刻成型技术为代表的增材制造技术系统简单、制造速度快、成本低，可实现高精度复杂结构器件，且成型器件结构完整，契合高频超声换能器制备的需求。本课题志于突破目前微立体光刻成型技术局限于打印压电陶瓷阵元局限，取得了如下的研究成果：.（1）制备适用于超声换能器的光固化浆料，着重探索微型压电陶瓷换能器阵元的微立体光刻成型技术及后处理工艺，克服打印压电陶瓷需要高浓度的浆料与高浓度瓷浆料黏稠性高、散射强影响固化成型之间的矛盾，和打印精度要求高与器件固化成型皱缩变形、热处理变形之间的矛盾，实现尺寸精细、形状复杂、性能优异的PZT和KNN压电陶瓷的可控制备；.（2）研究了基于超材料的声学梯度折射率器件，包括声波导和声透镜。在声波导的研究过程中开发三维拟共形变换优化算法，成功得到了真实空间与虚拟空间之间材料参数的映射关系，结合3D打印技术制作声波导实物。实验表明所设计的波导能够维持声波的传输模态，进一步设计了基于声学超材料的水声伦伯透镜。以微结构作为基本单元，通过调整单元的尺寸以实现梯度变化的声学参数，仿真和实验结果证明了它广视角、无像差的特性。.（3）将贝叶斯统计建模和逆向设计方法用于陶瓷的形变预测和补偿研究，使用三维扫描仪配合Geomagic后处理软件获取打印件的三维轮廓，结合MATLAB编程，实现形变的快速测量、反馈、和逆向设计补偿。形变补偿后，圆柱状陶瓷的尺寸精度可以提高80%，正棱柱状陶瓷的尺寸精度可以提高70%。采用新的切片函数，对形变预测模型进行优化，缓解正多边形截面的圆角化现象。