Wen Dong Zhang

Design and Analysis of Capacitive Micromachined Ultrasonic Transducers Based on SU-8

In this paper, a new capacitive micromachined ultrasonic transducer (CMUT) is designed by using SU-8 material, and the theory of elastic thin plate is used to deduce the relationship between the pressure and capacitance of the structure. Simulation has been done about SU-8 CMUT by finite element method software ANSYS. The deformation of CMUT under acoustic pressure, the relationship between frequency, thickness and sensitivity, as well as the acoustic impedance and reflection coefficient of SU-8 material also have been studied through the simulation. The results turn out that SU-8 has the advantages of big dynamic range, high sensitivity and small acoustic impedance, so it has broad application in the ultrasonic field.

Phase Transition Characterization Dependent on Temperature and DC Electric Field for (Pb, La) (Zr, Ti)O3 Antiferroelectric Thick Films

Pb0.97La0.02(Zr0.95Ti0.05)O3 antiferroelectric thick films were prepared on platinized silicon substrates by sol–gel methods. Films showed polycrystalline perovskite structure with a strong (100) preferred orientation. The antiferroelectric nature of the films was confirmed by the double hysteresis behaviors versus applied field. The temperature dependence of dielectric constant and loss displayed the Curie temperature was 225oC.The current caused by the polarization and depolarization of polar was detected at coupling application of electric field and temperature. The phase transition characterization could be effectively adjusted by electric field and temperature.

Structures and Dielectric Properties of (Pb, La)(Zr, Ti)O3 Antiferroelectric Thick Films Prepared by Different Sintering Procedures

(Pb,La)(Zr,Ti)O3 antiferroelectric thick films were prepared on Pt (111)/ Ti/SiO2/Si (100) substrates by a sol-gel process. The effects of single annealing and multistep annealing on the structures and electric properties of the films were investigated. The crystal orientation and structure of the antiferroelectric thick films were studied. The thick films by multistep annealing have higher (100)-preferred orientation than them by single annealing. The surface of the films was more smooth, compact and uniform by single annealing. The antiferroelectric nature of the (Pb,La)(Zr,Ti)O3 antiferroelectric thick films by various sintering procedures was demonstrated by P(polarization)-E(electric field) and C(capactitance)-E(electric field). The temperature dependent of the dielectric constant and loss was measured under the frequency 1, 10, and 100 kHz and comparing with traditional signal annealing, the films have phase transition from antiferroelectric state to paraelectric state by multistep annealing.

Fabrication and Growth Mechanism of Star-Shaped Gold Nanoparticles via Seed-Mediated Growth Method

In this paper, gold nanoparticles with branches were prepared in aqueous solutions using seed-mediated growth method. The mean diameter of the seeds chosen for these studies is 6~8nm. The influence of reducing agent used in synthesis gold sphere as seeds was investigated. A reaction mechanism of fabrication gold nanostar particles was systematically described. The nanoparticles synthesized were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. In order to investigate their optical property, Surface Enhanced Raman Scattering (SERS) spectrums were tested, which showed quite good Raman enhencement.

Fabrication of Planar Microtoroid Cavities Using High-Power Laser

Planar Microtoroid cavities have important application in many researching and application domains due to their ultrahigh quality factor (Q). But the special toroid structure can not be fabricated through traditional technology. In this paper, a novel processing method for fabricating microtoroid cavities using high-power CO2 laser after a series of traditional processing steps is introduced. The processing details are discussed including light path, focusing system and other important parameters. Test using scanning electronic microscope and laser-Raman spectrum shows that fabrication of planar microtoroid cavity using CO2 laser is feasible. The final microtoroid cavity is fabricated with slight impact to the silicon strut-beam, ensuring excellent optical performance in Planar Microtoroid cavity.

Design and Experiment Research on MEMS Vector Hydrophone Vibration Damping Structure

A novel vibration damping structure is designed based on the existing package structure of MEMS vector hydrophone. It is desirable that this novel structure can isolate the vibration noise caused by working platform so as to improve the anti-noise ability of hydrophone. This novel structure is made of “dow corning” damping silicone rubber which is manufactured with a certain proportion because of its small Young’s Modulus. The hydrophone is fabricated in the form of original packaging structure firstly and then in vibration-isolation packaging structure. Laboratory tests by means of the shaking table test and standing-wave tube test are performed to validate the theoretical results. The test results prove that the vibration damping structure can effectively isolate the interference signal produced by working platform without affecting the sensitivity of hydrophone obviously.

Design of a New Multi-Channel High-Low Pressure Micro-Ejection System

According to the structural characteristics of the multi-channel high-low pressure micro-ejection system,this paper sets up mathematical model of the trajectory based on the classical trajectory theory,makes numerical analysis to prove the rationality of the structural design,tests the pressure and bullet velocity of the launching system.The results show that the analysis and design methods of the multi-channel high-low pressure micro-ejection system are reasonable and reliable.

A Monolithic Three-Axis Accelerometer with Low Cross-Axis Sensitivity

A 50,000g three-axis accelerometer using a single proof mass is presented. The sensitive structure is made of a single proof mass and eight cantilever beams. Twelve piezoresistors are placed on the cantilevers symmetrically, which can be used to detect 3-dimensional acceleration. The symmetric placement of the piezoresistors brings the reasonable sensitivity and simultaneously decreases the cross-axis sensitivity significantly. Simulation results show that the sensitivity in X-, Y- and Z-axis are 0.806uV/g, 0.806uV/g and 3.71uV/g respectively with 5V supply and the cross-axis sensitivities are all less than 2.4%, which ensures the high performance of the three-axis accelerometer.

The Design and Simulation of Vibratory Ring Gyroscope

This paper deals with design and simulation of vibratory ring gyroscope which has good performance as resisting vibration, resisting impact, small temperature drift because of the inherent symmetry of structure. The good performance of gyroscope has verified by detailed modeling and simulation. The manufacture of gyroscope using wafer level vacuum packaging technology making the gyroscope has high quality factor .At last we test the gyroscope and the Q factor is 20300 by detecting the resonant state of the gyroscope.

Embedded Seal Cavity Fabricated in HTCC MEMS Technology

This article presents a design and fabrication method of a embedded cavity using alumina casting-belt. This method is based on HTCC (high-temperature co-fired ceramic) MEMS technology with using fugitive materials. The test structures are fabricated using two different fugitive materialsPolyimide film and ESL4900 film and two different lamination pressures (15MPa and 21MPa). The final stack was sintered by selecting different temperature process parameters in the high-temperature sintering process. Complete the analysis of the sample cavity structure using a SEM (scanning electron microscope). The manufacturing method is available for structural integrity and good air tightness of ceramics sealed cavity and it will be applied to the fabrication of flow sensors, capacitance pressure sensors etc.