Yun Bo Shi

Study of Surface Raman and Fluorescence Enhancement of RhB Molecules Adsorbed on Au Nanoparticles

In this work, an interesting phenomenon demonstrating the similarities between the results from both Surface Enhanced Raman Spectroscopy (SERS) and Surface Enhanced Fluoresence (SEF) for rhodamine B (RhB) molecules adsorbed on gold nanoparticles was reported. By changing the deposition time, porous Au nanoparticle films with various densities and sizes were deposited. Via thermal annealing, the densities and sizes were modified. It is concluded from the results that the intensity of SERS and SEF varied in parallel with different Au nanoparticle films: different sizes and different densities. We believe that the results obtained can provide us with a reference when developing bio-chemical sensors based on Surface Enhanced Raman Spectroscopy and Surface Enhanced Fluorescence.

Study on the Package of MEMS High-G Acceleration Sensor

A practical packaging structure was designed based on the designed MEMS high-g acceleration sensor, and encapsulation performance was simulated when it used potting. By the result of simulation, the packaging structure can meet the requirements that sensor demand, which can test the namal signal under 200,000 g impact load. From the results of modal and static simulation, potting can not only improve the natural frequency of the package model, but also can reduce the stress when shock load effected on the model. Elastic modulus of the potting materials have the great influence on the package performance, but the density has little effect on it. The simulation results also show that the modal frequency of the package model increases with modulus increases, while the the stress reduce when the same load on the package model. However, the modal frequency is much smaller than the packaging structure without potting when the elastic modulus was too small,which may bring a distortion of the sensor output signal.

Research on Micromachined Gyroscope with Electrostatic Drive and Meso-Piezoresistive Detection

In this paper, the structure design and operating principle is introduced to micromachined gyroscope with electrostatic drive and piezoresistive detection. In the paper, the piezoresistive effect of multi-barrier nano-film is used as detection method, which achieves high piezoresistive sensitivity compared with Silicon piezoresistive device. The gyroscope structure and multi-barrier nano-film device is fabricated by using heteroepitaxy GaAs film on Si substrate which implements the process compatible. The natural frequencies of gyroscope are determined from the modal analysis.

Observation of Ferromagnetic Resonance in Magnetic Exchange Force Microscopy (MExFM)

The atomic spin interaction is very important for understanding the superficially magnetic feature of nanostructure at atomic level. Magnetic exchange force microscopy (MExFM) is an innovative means of measuring surface spin force. But it is difficult to separate the surface topography and spin information. We develop the magnetic exchange force microscopy using ferromagnetic resonance (FMR-MExFM). The theoretical and experimental results demonstrate that this method can separate the two kinds of information effectively. Here, in order to obtain the high sensitivity in detecting the ferromagnetic resonance, we fabricate the microwave irradiation device to optimize the position between the device and the cantilever. We have succeeded in observing the ferromagnetic resonance effect and determining its resonant frequency using the homemade microwave irradiation device and the network analyzer. This research is very important for developing FMR-MExFM and novel magnetic sensor, detecting the magnetic information, etc.

Varistor Characteristic Analysis of the Piezoresistive Sensors

In the process of the piezoresistive sensor design, the placement of varistor has a great influence on the sensitivity of the sensor.In this paper, three theoretical models of piezoresistive sensor are established.The stress simulation analysis of the different varistor path way placed on the cantilever beam is conducted in Ansys software. The sensitivities of the axis and transverse direction are calcuated and compared by Matlab compiler. The results show that the placement of varistor which is parallel to the cantilever beam is the most optimal choice.

Design and Test of High-g MEMS Accelerometer

For measuring the high-g impaction and overload of some conditions, a kind of high-g accelerometer was designed. Testing and analysis to the accelerometer was processed through launching projectile to penetrate concrete target. Four fixed end structure was adopted in the design of the high-g accelerometer and the chamfer was set in the bottom and top part of the beam to divert stress. It is learned that the sensitivity of the accelerometer is 0.1uv/g by calibration. A kind of deceleration measurement device was provided to test the performance of the accelerometer through penetration experiment over concrete target and the design of the measurement device and penetration experiment over concrete target was illustrated. The impaction characteristic of the accelerometer was tested and studied through penetration to the target. MATLAB software is used to analyze the influence of the filter cutoff frequency over the test result and the best cutoff frequency point was set at 6 kHz, under which the maximum penetration acceleration is up to 28526 g.

Design and Testing of In-Plane MEMS High-g Accelerometer

μAiming at the demand of missile fuse and other weapons systems, a high-g piezoresistive accelerometer with two terminal fixed beam-mass structure which can measure in-plane acceleration was designed. The design and simulation were also performed using Matlab and ANSYS. The simulation results show that the sensitivity of the accelerometer of sensitive-axis is 0.1101μV/g, and the transverse sensitivity of accelerometer is eliminated effectively. The key parameters such as impact over-loading signal and sensitivity of in-plane accelerometer were tested by Master hammer and Hopkinson bar. The test results showed that the sensor can work with the impact acceleration up to 117,395.95 g and the sensitivity of the accelerometer is 0.1028μV/g.

Research on the Control Method of Penetration Depth Based on the Acceleration Data

In order to gain the maximum destroy when the concrete facilities are penetrated by projectile, the best detonation position must be controlled. So a signal processor system was designed to record the penetration acceleration. The acceleration character and the control algorithm of penetration depth were studied by simulation. The displacement integrated by acceleration was verified to be effective, which could control the detonation of projectile in the right position.

Consistency of High-g Acceleration Sensor Performance

Based on the designed, packaged high-g acceleration sensor in measuring demonstrated sensor performance between individuals have big difference, Researched this problem, through the analysis that the main reason of this problem appeared in the sensor package process of Die process. Through ANSYS simulation and experimental test on two aspects of the analysis the die adhesive’s amount of Die process is the high-g acceleration sensor in testing large performance differences were the main factors. Packaged high-g acceleration sensors with die process of quantitative die adhesive were designed and tested their performance. The result showed that, the simulation results were consistent with experimental results.

Design and Pspice Simulation on Interface Circuit of Capacitive Micro-Gyroscope

For testing angle velocity, testing system of micromechanical gyroscope is applied widely in both military and civil areas, and it is provided with broad foreground of evolution and application, The characteristics of the application require them have high sensitivity and accuracy, under this conditions, technology development level of interface circuit reach their limits, and restricts test performance improvement of the system of micro-gyroscope. In this paper the equivalent electrical model of capacitive micro-gyroscope is established firstly, then a novel interface circuit is designed, the interface circuit include two part, driving-circuit and detecting- circuit, and the feasibility of the driving-circuit and detecting- circuit is emulated and validated by Pspice respectively. The detecting circuit of static state capacitance is come true , and theoretical accuracy of it is 10-18F.