Key Engineering Materials Vol. 503

Abstract: A novel silicon based dual-mass vibrating tuning fork vibratory gyroscope (TFG) with differential capacitor structure is designed in this paper. the U-shaped beam is adapted to connecting the two decoupling movement of the framework structure in order to achieve the independent of the movement of drive direction and sense direction. The TFG structure is also optimized to further reduce the mechanical coupling of the device. The drive combs are designed on the mass, while the sense combs are designed on the frame. All the combs in this gyroscope are dominated by slide-film air damping in order to lower the air damping. This gyroscope is designed to obtain robust operation against variations under atmospheric pressure condition. The TFG is tested at atmospheric pressure with a sensitivity of 17.8mV/◦/s and a linearity of 99.989%, capacitance structure sensitivity is 21.5αf/◦/s with an equivalent noise angular rate of 0.028◦/s/Hz1/2, respective.

Abstract: A novel MEMS vector hydrophone with bionics structure was introduced in 2007. As the acoustic-electric transducer infrastructure has been optimized, the performance of the hydrophone has been greatly improved compared with the previous. This hydrophone calibration was finished in National Defense Underwater Acoustics Calibration Laboratory of China. According to test results, the sensitivity of the hydrophone is -165dB（including pre-amplification 20 dB）,The frequency response ranges from 20Hz to 2kHz (±5dB). And this hydrophone has a good directional pattern in form of "8"-shape.

Abstract: This paper is focused on the finite element analysis (FEA) and theoretical calculation of vibration characterization of V-shaped electrothermal microactuator. A vibration mechanical model about V-shaped electrothermal microactuator is presented. By having a comparison between FEA and theoretical calculation about natural frequencies of V-shaped electrothermal microactuator, the maximum error is within 0.19 %. This paper also analyzes the influences of microactuator geometric parameters on natural frequency. The length and thickness have larger effect on the natural frequency of the actuator, while the angle and width have less effect on the natural frequency.

Abstract: Due to many inherently problems of accelerometers on market, such as complex fabrication process and low precision, a monolithic three-axis accelerometer is proposed and fabricated. The 3-axis accelerometer consists of four individual seismic mass, each has a wafer-thick of 240μm and is fabricated by anisotropic wet etching technology. In this paper, the design, fabrication, and characterization of the 3-axis accelerometer are presented. The performance is characterized and demonstrated.

Abstract: In this paper, an interface for low-Q micromachined gyroscope is designed. Based on the testified system architecture, the driving circuit with frequency modulation and PI controller, together with the sensing circuit contained twice demodulation, are designed. The bias stability of the gyroscope is 0.072 o/s, and the noise is 0.02o/s/Hz1/2.

Abstract: In this paper a high-performance closed-loop fourth-order sigma-delta (ΣΔ) micro-accelerometer is presented. After a introduction of sigma-delta accelerometer, system-level analysis and design of a fourth-order sigma-delta micro-accelerometer is given. The simulation result shows that an accelerometer with 107dB signal to noise ratio (SNR) and 17.5 bits effective number of bits (ENOB) is achieved. Through the root locus analysis, it is got that accelerometer is stable when quantization gain is bigger than 0.262. The accelerometer gets a good linearity and it becomes overload when input signal level is greater than -5dBFS.

Abstract: There are two types of coupling structures for the photonic crystal of triangular array of air holes. The two types of coupling structure between dielectric taper waveguide(DTW) and photonic crystal waveguide(PCW) is investigated. The coupling transmission efficiency is calculated for different coupling structure of the input and output, we found that the coupling transmission efficiency is changed with different coupling width and distance. The highest transmission efficiency is 92.6% and 99.6% for the input and output port respectively.

Abstract: For studying DNA electrical double layer in electrolyte solution, the key process is to create the template for DNA processing. In this paper, we described a straightforward method for depositing DNA on a substrate. The mica was chosen as the substrate materials because of its atomically flat and negatively charged surface in solution, and mica was coated by the polylysine to absorb the DNA molecules. Using by AFM, the DNA molecules have been probed obtaining a high resolution in air and liquid, and the method is simple and easy operated. This method can be used for nano-manipulation and the quality of the DNA under physiological conditions.

Abstract: A capacitive accelerometer with triangle cross-section beam fabricated by anisotropic wet etching of (100) silicon is presented in this paper. The feature of this accelerometer is that eight suspension beams with triangle cross-section are formed by anisotropic wet etching of (100) silicon in TMAH solution, without heavy boron doping or Si-Si bonding. When the width of beam is decided, the beam’s geometry is determinate. The formation procedure of the triangle cross-section beam is analyzed in detail. Through this beam-fabrication approach, the beam’s thickness can be well controlled by beam’s width and intrinsic stress in the beams is minimized. Accelerometers with different sensitivities can be easily fabricated by varying the width of the beams. For a device with 23 μm width beams, the resonance frequency and the quality factor are 644 Hz and 32, respectively. The sensitivity of accelerometer is measured as 2 V•g-1.

Abstract: Resonance integrated optical gyroscope, Polarization-maintaining waveguide, Single-mode condition, Birefringence. Abstract. A polarization-maintaining (PM) waveguide used in Resonance Integrated Optical Gyro (RIOG) is theoretically proposed. Three essential factors determining the PM performance, which are the single-mode condition, birefringence and core index, are analyzed and optimized respectively. The single-mode rectangular waveguide is obtained by analyzing the propagation mode of the rectangular waveguide. A high birefringence waveguide design method is brought up according to the theory of geometrical birefringence, realized by changing the cross-sectional shape of the waveguide. The effect that the core index contributes to the birefringence is also discussed, and an optimal core index of the waveguide to reach maximal birefringence is determined in the condition of single-mode transmission. The high birefringence PM Waveguide with geometrical birefringence of 1.5×10-4 is obtained by theoretical analysis, the simulation results shows that the polarization cross-talk in RIOG is obviously improved.