| The Micro Electro-Mechanical System (MEMS) as a kind of optical-electronic-machinery integrated high technology has broad application prospects in the related fields of national defense and economy. After30years of development, MEMS has forward to the integration of the multi-functional complex hybrid system with multi-component and multi-structure from focusing on the production of micro components or a single feature in the past. The further development of this technology should rely on the improvement and application of the micro-assembly technology. Especially, with many challenges due to the dimension miniaturization of the application objects, the three-dimensional manufacture with high depth-to-width ratio, the diversity of manufacture process and material in MEMS, the micro-assembly technology becomes even more important and urgent. Hence, exploring new theories and mechanisms to develop this technology is the most basic and key research subject in MEMS area at present.According to the technical characteristics of the micro-assembly, a kind of non-destructive and noncontact micro-assembly technology should be the main trend in the current research and development. As a kind of mechanical wave, ultrasonic has shown good application potential and advantage in micro-particles trapping, agglomeration and separation by its characteristics of mechanical effects. Hence, using acoustic radiation force and torque as the driving force to develop a noncontact micro-assembly technology should has its own technical superiority. However, the theoretic research of this technology is still limited to ideal sound field and regular scatters, and there is little theoretical model for micro-assembly applications. Moreover, the existing application of acoustic radiation force and torque is based on the steady state and qualitative analysis. And because precise and quantitative control should be satisfied in preparing, locating, posture adjusting and releasing of the micro-component during micro-assembling process, the current related methodology and application failed to meet the needs of micro-assembly technology. Therefore, considering the characteristics of MEMS, the key technologies of non-contact micro-assembly based on acoustic radiation force and torque were studied in this dissertation, which is supported by National High Technology Research and Development Program " Research on Key technologies of3D tele-manipulation for micro and nano components based on ultrasonic radiation force (No.2006AA04Z329)" and Key Project of Natural Science Foundation of Zhejiang Province "Research on theory and application of automatic3D micro-assembly technology based on acoustic manipulation (No. Z1110393)". The mechanical model of the unit procedure in micro-assembly, the mechanism and influencing factors of the acoustic radiation force under assembling condition have been theoretically analyzed and experimentally studied. A multi-mode noncontact tele-driving source has been built by using ultrasonic phased array to flexibly and precisely synthesize the acoustic radiation force field which meets the needs of each unit procedure in micro-assembling process. The technology of detaching the micro-components on the rigid surface, quantitative transportation at a long range, adjusting the posture of the micro-components and releasing to the target position have been realized. This new technology can be applied in the micro-assembly of MEMS and provide a general solution for the research and manufacturing of MEMS. The detailed contents and innovative points of this dissertation are presented as below:In chapter one, the significance to conduct the research on the micro-assembly technology was described by discussing its role and status in MEMS and other fields. And through elaborating the present research status and development trends of micro-assembly technology at home and abroad, the technology of micro-assembly based on acoustic radiation force and torque was proposed. Meanwhile, the achievements of the theory and the applications of acoustic radiation force and torque were summarized to illustrate the feasibility and advantage of applying them to micro-assembly. And its problems were observed and the research direction was pointed out.In chapter two, the technologies of detaching the micro-components on a rigid surface and releasing it to the target position were studied in order to realize the unit procedures of preparing and releasing the micro-component. On the basis of the systemic study on the theoretical model of the acoustic radiation force acting on the rigid spherical Reyleigh scatter near a rigid surface in the sound field which was synthesized by several incident wave, detaching the particle from the surface and releasing it to the target position were realized by two ultrasonic wave with crossed wave vectors.In chapter three, the methodology of controllable and quantitative transporting micro-component at a long range was proposed. On the basis of precisely synthesizing the sound field, the micro-component trapped at the acoustic potential well can be transported at different velocity and trajectories by changing the phase of the ultrasonic wave to shift the distribution of the sound field. The feasibility and applicability of this method has been verified by numerical simulation of the theory, measurements of the sound field with a hydrophone and the results of transporting silica bead with50μm radius. Meanwhile, the status of the bead in the transporting process and the influence on it was analyzed.In chapter four, the stability of the micro-component in the long range transporting process was systematically studied aiming at the possible position fluctuation and the phenomenon of slipping off during the transporting course. On the basis of analyzing the influence of acoustic streaming on the performance of micro-component transporting, the relationship between the characteristics of the acoustic potential well and the stability of the transporting was developed. A method to quantitatively evaluate the performance of the acoustic potential well was proposed and the basis properties of an ideal acoustic potential well were also presented. Meanwhile, the characteristics of the acoustic potential well in several different sound field was analyzed using this method and the micro-component transporting method proposed in chapter three was optimized. The experimental results illustrate that the position fluctuation of the micro-component in the transporting process has been obviously suppressed after optimization.In chapter five, a stepless method to adjust the two-dimensional posture of the micro-component was proposed. While the theory on the acoustic radiation force and torque of the long-stripe shape micro-component in the sound field was studied, two-dimensional posture adjusting was realized using circular transducer array which was grouped to several sub-arrays. On the basis of trapping the micro-component in the sound field synthesized by one group, the sound field was rotated by alternately using different sub-arrays, and the micro-component was rotated with the sound field. The experiment on posture adjusting was conducted and the anticipated effect was achieved. And the experiment results showed that the accuracy of the posture adjusting can be improved by adding more transducers in the circular array.In chapter six, on the basis of confirming the function target and entire design of the system, the functional modules of the multi-channel ultrasonic signal generator, the linear power amplifier, the data acquisition card and the CMOS camera were developed, and an experiment setup is established using the architecture of the virtual instrument and the strategy of modular design. Meanwhile, the experiment was performed to verify the feasibility and applicability of the methodology proposed in this dissertation.In chapter seven, the research results and the innovative points of this dissertation were summarized, and the future research works were also forecasted. |
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