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MEMS Self-focused Piezoelectrical Acoustic Transducers

Author: ZhuJie
Tutor: WangGaoFeng；YuHongYu
School: Wuhan University
Course: Communication and Information System
Keywords: Microelectromechanical systems Micro-fabrication Microstructures Micro - transducer Microfluidic system
CLC: TB552
Type: PhD thesis
Year: 2010
Downloads: 180
Quote: 0
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Abstract

Micro-electromechanical systems (Micro-Electrical-Mechanical Systems, acronym MEMS) based micro-fabrication technology, the set of micro-mechanical structure, micro sensors, micro actuators, and microelectronic circuits is equal to one of the micro-devices and systems. With the mature development of integrated circuit manufacturing technology, the researchers also used a chemical and mechanical processes to manufacture micro-structure and micro-devices. For the traditional mechanics, micro-electromechanical systems technology not only whom to open the door to a new field of \Since 1988, since the launch of the first silicon micro electrostatic drive motor, the research and development of micro-electromechanical systems technology increasingly widespread concern in the international. For the study of micro-electromechanical systems, usually divided into two categories: micro-structures and micro-change energy converter. The micro-structure typically contains a micro-lens, micro-nozzles, the micro-probe and the microfluidic system; micro transducer usually contains micro-sensors and micro-actuator. Fresnel self-focusing piezoelectric acoustic transducer as a MEMS transducer has been Kim, Ph.D., of the University of Southern California team developed and manufactured. This article widely discussed in depth the basic principles of microelectromechanical systems, self-focusing Fresnel piezoelectric acoustic transducer, and the design and development, respectively, apply to the local cell exfoliation and high-frequency ultrasound imaging and Doppler detection of micro-electromechanical transducer control system. Not only that, we also creatively controllable curvature radius of surface production and packaging technology for microfluidic systems. Below, four aspects of this article work done while I walk. A traditional cell exfoliation method, either acting on a large cell, not actually used in the treatment of small samples or precise control; either need people manual, cumbersome and labor-intensive. We design and manufacture of the Fresnel self-focusing piezoelectric acoustic transducer capable of generating a highly focused acoustic beam, excited ultrasonic cavitation bubble, to achieve a local cell exfoliation. The transducer to the acoustic wave is focused on the radius of only 60 microns in a small region, which produces a peak pressure can reach nearly three atmospheres, sufficient up to 12 MHz at the high frequency excitation of cavitation bubbles. Cavitation bubbles in the blasting process produces a great deal of energy, the focus area of ??nearly 200 cells were knocked down, and outside the region of the cells intact. The technology for the possible realization of the local cell exfoliation, and can be applied to the small sample sampling and local biomedical treatment. High-frequency ultrasound imaging because of its high spatial resolution, and has become an important medical tool. In the ultrasound imaging system, the transducer is the most important part. Subject to the limitations of the conventional manufacturing techniques, the transducer is difficult to work at high frequencies, so that the imaging resolution creating a bottleneck. Paper developed manufacturing Fresnel self-focusing piezoelectric acoustic transducer, using a thickness of lead zirconate titanate (Lead Zirconate Titanate, abbreviated as PZT) as a substrate, and its working base frequency of 20 megahertz. As the design of the Fresnel lens has an air reflector cavity, the transducer can operate at its resonant mode. Transducer triples (60 megahertz) and five times the frequency (100 MHz), we have been strong acoustic signals. The experimental results and theoretical analysis prove that the transducer can be applied to up to 100 MHz high-frequency ultrasound imaging and Doppler system. We developed on the silicon wafer with a new micro-fabrication technology, to achieve a controlled radius of curvature surface of manufacturing. The micro-structure having a three-dimensional arbitrary shape having a very wide range of applications, the MEMS device including the optical element, the needle array, and any other required strict control of its structure. The traditional method of etching can do in this situation, the gray mask method is extremely expensive. Based sputtering theory, by the occlusion of the shadow mask, is deposited on a silicon wafer having a different radius of the convex spherical surface structure of the silica. Deep reactive ion etching (Deep Reactive Ion Etching, abbreviated as DRIE) because of its excellent directionality and selectivity, is used to etch silicon dioxide and silicon substrate, thereby convex spherical silica structure is transferred to the silicon. We refer to this as a mold having a different radius of the spherical surface of a silicon wafer using polyimide (Polyimide) film forming, a polyimide having a spherical radius of the recessed structure. It can be used to manufacture a three-dimensional self-focusing piezoelectric acoustic transducer. We use poly paraxylene-C (Parylene-C) for the microfluidic system package provides a good solution. The microfluidic system usually contains a micro-channel and micro-sink microstructure, they need to package in order to protect the liquid sample is not contaminated. In the previous package with Parylene-C, the thick photoresist and wax were used as the sacrificial material is used for the micro-structure of the filler. And rotation, and the deposition of these two methods are used on a silicon wafer covered like polytetrafluoroethylene (Polytetrafluoroethene abbreviated as PTFE, trade name, a Teflon (?), Commonly known as Teflon), an amorphous polymer, and its The role is to make the silicon surface rendered hydrophobic state, so that the wax filling. Experimental results show that, compared with a photoresist, wax can help to improve the flatness of the film of Parylene-C, and is very suitable for mass production. After removing wax, Parylene-C is heated to 120 ℃, to thereby obtain a more flat surface so that the film has a greater tension. This thesis involves two of the most important aspects of microelectromechanical systems - micro structure and micro-change energy converter. Inheritance, development and application of the self-focusing piezoelectric acoustic transducer Fresnel, the innovation of of 3D arbitrary curvature radius of the curved manufacturing method beneficial exploration and packaging technology for microfluidic systems.

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