面向壁面剪应力测量的底层隔板微敏感结构设计与制造

 采用MEMS技术加工的底层隔板能够为壁面剪应力的测量提供新的手段。利用有限元法(FEM)建模仿真、正交实验设计以及各因素的极差分析,考查了微敏感结构宽度、厚度和凸出壁面高度对底层隔板固有频率和压阻灵敏度的影响规律,完成了底层隔板的结构优化设计。仿真结果显示:微敏感结构厚度对隔板固有频率和灵敏度影响最大,提升敏感结构高度能够有效提高压阻灵敏度,固有频率和压阻灵敏度受微敏感结构宽度变化影响很小。基于绝缘体上硅技术,利用电感耦合等离子体刻蚀工艺形成底层隔板结构,反应离子刻蚀工艺完成对敏感结构的释放,所加工底层隔板的整体尺寸为5.9 mm×10.1 mm×0.39 mm。底层隔板的动态特性测试表明样件固有频率为1 453.1 Hz,与有限元仿真结果的最大偏差为4.4%。

Design and Fabrication of Sensitive Elements of Sublayer Fence for Wall Shear Stress Sensor

MEMS sublayer fence provides a new method for wall shear stress measurement. In order to determine the influence of a fence's structural parameters on its natural frequency and piezoresistive sensitivity, the finite element method (FEM), orthogonal experimental design, and range analysis are adopted to optimize the parameters of the fence. The simulation results demonstrate that the natural frequency and sensitivity of a fence are more easily affected by its thickness than other parameters. Piezoresistive sensitivity can be improved more effectively than natural frequency by increasing the height of a sensitive element. The width of the element has less impact on the natural frequency and sensitivity of the fence. Inductive couple plasma etching process is used to form the structure of a sensitive element. The releasing process of the fence is accomplished by reactive ion etching technology. The dimension of the sublayer fence is 5.9 mm×10.1 mm×0.39 mm. Dynamic measurement results show that the natural frequency of the fence is 1 453.1 Hz, featuring a deviation of less than 4.4% as compared with finite element simulation.