Mems Ultrasonic Two-dimensional Sound Field Separator And The Production Process

There are great advantages in separating suspending particles from small dosage by ultrasonic radiation force compared with conventional separations. There is more extensive application foreground by associating this method with Micro Electro-Mechanical System (MEMS). The research on MEMS ultrasonic micro-separator is proceeding with some progresses, but there are also some inherent defects, such as the difficulty of disposing outlets, the turbulence of clean and turbid stream. The two dimensional normal mode exited by anti-phase PZT supplies a feasible approach to overcome the inherent defects of the MEMS ultrasonic separator based on layer resonance mode.Based on the research of sound and radiation force in fluid layer of separating cavity, the MEMS separator is fabricated and the separating experiment is partly put out in this paper. The main contents are as follows:1. From theory of normal wave in acoustics,the sound field in separating cavity is analyzed. The two dimensional normal mode in the MEMS separator based on plane standing wave is explored, and the influence to the sound field of fluid layer imposed by anti-phase emitting source is studied. The (1, 1) normal frequency is chosen as exciting frequency of the separator. The standing wave is regarded as summation of progressive waves to confirm the thickness of the separator's layers, based on the transmission of sound wave in the medium layer. At last, according to the calculation of radiation force, the relation between the properties of particles and the conglomeration position is listed.2. According to the comparison of diversified etching methods of separating cavity, the mixed gas containing SF6, C2F6 and the top layer of SOI is selected to form separating cavity, which ensures the precision of depth and the smoothness of bottom and walls. Based on the manufacturing engineering of MEMS, the fabrication processes of micro-separator, which include etching cavity, laser drilling and bonding, are studied and analyzed. And the quality of fabrication is checked by instruments such as surface profilometry and microscope. 3. The scheme of separating experiment is put forward and the pedestal and tie-in is designed. The anti-phase vibration of two PZT is realized by Conductive Adhesive and Function Signal Generator. According to the comparison of the suspended particles'conglomeration positions between single PZT and two anti-phase PZT in the separating experiment, the advantages of latter on exciting two dimensional normal mode in separating cavity is proved. Several problems in the experiment are also listed, along with the improvements.