| Piezoelectric-excited mass sensors can be used to test chemical components of target materials, by detecting resonance frequency shift caused by the mirco-mass of the material attached to the surface of the sensing area, what leads to wide range of applications, including bacteria, virus and microbial particles identification, gas and liquid ingredients detection and concentration measurement. For micro mass sensors, the analytes absorbed or deposited on the cantilever surface are so extremely small that ultra-sensitive sensors are needed. Therefore, sensitivity improvement methods and corresponding structural design theories are necessary prerequisites for high performance mass sensors. On the other hand, in applications sometimes due to the extreme testing environments or requirements of long-term or real-time monitoring, remotely controlled/monitored tests are necessary. This can be achieved via integrating micro-mass sensor with directional wireless transmission contrivance. For such devices, the mass information quality from the wireless micro-mass sensor depends not only on the mass resolution, but also on the effectiveness of the wireless transmission system and the receiver sensitivity. In many cases, directional wireless transmission can improve the quality of the signal as well as securing the safety of the information. With their special wave propagation features, electromagnetic metamaterials including left-handed materials and electromagnetic band-gap materials are ideal materials for developing antennas to exhibit directional transmission properties as well as enhanced transmission quality and safety. Hence, the construction of materials with specific electromagnetic properties, and their application in improving antenna's orientation is also of great significance. Motivated by the two main above-mentioned demands, this thesis discussed the design and manufacturing of micro-mass sensors with high sensitivity and directional wireless transmission system.By analyzing the influence of the cantilever cross sections on the structural stiffness and effective mass distribution systematically, the author proposed methods to improve sensitivity, and also designed and fabricated different types of high-sensitivity micro-mass sensors with innovative elastic structures. On the other hand, the construction mechanisms of the microstructures in the electromagnetic metamaterials with left-hand or band-gap properties have also been studied, as well as the designing methods of microstructures for directional antennas. Furthermore, by utilizing the proposed metamaterial, the structural design technology of the antenna was investigated to realize high quality transmission. Such micro-mass sensors with improved accuracy and integrated directional wireless transmission technology can play an important role in tests under extreme environment/constant monitoring, e.g. detection of nuclear leakage, dangerous chemical products leakage, and environmental pollution monitoring. The main achievements of this thesis are listed below:(1) Sensitivity analysis of the piezoelectric-excited, resonance micro-mass sensor. In this part, the effects of the cantilever structure on the vibration characteristics were analyzed, followed by the description of the sensor sensitivity. Finally, multiple design methods for sensitivity improvement were proposed.(2) Design of the I-shaped cross-section cantilever based micro-mass sensor. First, a sensor configuration incorporating an I-shaped cross-section cantilever was put forward. Then, a sensor sample was designed and fabricated. Next, its sensitivity was analyzed through theoretical deduction and experimental methods. Influences of structural parameters such as cross section area, PZT thickness, and length of the extension part on the sensor's sensitivity were discussed. The comparison between the simulation and experimental results showed that the sensitivity of the I-shaped cross-section cantilever sensor is much higher than that of the rectangular section mass sensor, which verified the feasibility and effectiveness of the introduction I-shaped cross-section cantilever into the design of mass sensor for sensitivity improvement.(3) Sensitivity analysis of micro-mass sensor with the trapezoidal variable cross-section cantilever. The sensitivity of the trapezoidal variable cross-section cantilever sensor was analyzed theoretically and experimentally. Comparing with the uniform section cantilever sensor, sensitivity was improved dramatically by using the trapezoidal cantilever. whose cross-section varies along its neutron-axis. In a word, this section of the thesis proposed and recommended another effective way to improve the sensor's sensitivity:by changing the cross-section along the cantilever's axis.(4) Micro-mass sensor based on the high order resonance mode was designed and fabricated. By selecting suitable thickness ratio between the PZT and elastic layers, a sensor based on the high order resonance mode was designed and fabricated to detect mass of target analyte by measuring the resonance frequency shift of high order modes. A design method was proposed for designing micro-mass sensors with specific high order resonance frequency. Accordingly, a mass sensor operating at the third-order resonance frequency was designed, whose third resonance mode can be excited easily to fulfill the mass detection function. Based on MEMS technology, the fabrication of the microstructures with large thickness ratio and real three-dimensional cantilevers was proposed. A micro-mass sensor with a 50μm thick cantilever was fabricated with this method. Finally, through numerical simulation and experiment, the validity and feasibility of the proposed design method were confirmed. (5) Structural design and analysis of the micro metamaterial based on the transmission line model. A microstructure design method for left-handed material was presented by analogy with the transmission line model. Firstly, based on the existing transmission line model with left-handed or right-handed nature, a new model with left-handed nature was constructed by analogy; then through a qualitative analysis of correspondence between each element of the transmission line network, and shape and size of the microstructure model of continuous medium, the specific sizes of various parts of the model were derived, thus obtained a reasonable left-handed material microstructure and its corresponding transmission line analogy model, which were tested and verified through numerical simulation and experiment. Finally a method to design a structure with two left-handed frequency bands was proposed, and a structure based on the method was given and verified by numerical simulation.(6) A design optimization method for left-handed materials with specific frequency bands. Based on a classical microstructure constructed by a coupling-enhance magnetic resonator and rod, a mathematical model of the microstructure with maximized frequency band-width and lower loss about given frequencies was proposed, and examples were given. Numerical examples confirmed that the optimized model was applicable.(7) The application of electromagnetic super material to microstrip antennas. In order to enhance the quality of information transmission, improvement of orientation and efficiency is the key to the design of microstrip antenna. Inhibiting surface wave propagation is an effective way to improve orientation and efficiency. Utilizing the above proposed design method of specific frequency magnetic resonance material, the author designed material with two-dimensional negative permeability, located it around microstrip antenna and constructed a microstrip antenna with negative permeability structure. Numerical simulation showed that the addition of negative permeability significantly improved gain performance (by 10%) and orientation.The works of this thesis are supported by the National Basic Research Program (973 Program) of China through grant No.2011CB610304 and the National Natural Science Foundation of China through grant No.11172052.The financial contributions are gratefully acknowledged.
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