Papers by Author: Zheng You

Abstract: The stable range of MEMS electrostatically actuated beam during the pull-in process is crucial to the device performance. Different devices have specific requirements for stable pull-in region based on their applications. In this paper, Rayleigh-Ritz energy method is used to establish dynamic pull-in model of electrostatic cantilever actuated by a step voltage. Modified trial function is derived according to different position of bottom electrode. The model takes into account the effects of fringe capacitance and variable cross-sectional beam. Published numerical methods and experimental data are used to verify the model . The impact of bottom electrode position on pull-in parameters is analyzed in present model. With fitting empirical equations, pull-in parameters can be easily satisfied through the distribution of bottom electrode, which provide an effective reference for the design of MEMS electrostatically actuated beam under given pull-in parameters .

Abstract: Identification and characterization of CTCs can be used as a tool for the study of cancer metastases. A novel design of microfluidic chip used for enrichment of circulating tumor cells is presented in this paper. An integration of DLD method and negative enrichment method were designed to improve the throughput and recovery rate while getting intact CTCs. The DLD stage is used to separate CTCs from blood cells preliminarily, and the negative enrichment stage is used to acquire purified CTCs. Both of them were simulated with COMSOL Multiphysics. Simulation results showed that triangular micro-posts have better performance in DLD stage, and wave structures could generate better disturbance effect than herringbone structures. This chip provides a potential approach with high throughput and purity for the enrichment of CTCs.

Abstract: In this paper, a modeling and simulation method for planar interdigitated ruthenium oxide MEMS supercapacitor was proposed based on the electrochemical reaction mechanism of supercapacitor. The study simulated the planar interdigitated ruthenium oxide MEMS super capacitor using Comsol software. The highly accurate charge and discharge curves of the super capacitor, electric potential distribution graph and the concentration distribution graph were got through simulation. The effects of two structure-parameters were discussed in the research.

Abstract: A chemical gas sensor for volatile organic compounds (VOCs) detection at trace level is proposed. In this paper, the development and demonstration of the sensor prototype are presented. The prototype is based on a microcantilever resonator that is fabricated from direct bonding silicon-on-insulator (SOI) wafer. The resonant cantilever employs integrated thermal driving and piezoresistive detecting units, and operates in a self-oscillation system. Polyethylenevinylacetate (PEVA) is deposited on top of the cantilever as gas sensitive layer through a spraying method. The responses of the prototype to relative humidity (RH) and six common VOCs: toluene, benzene, ethanol, acetone, hexane and octane have been tested. The PEVA-coated prototype has trace sensitivity to toluene, benzene, hexane and octane, while is insensitive to humidity. The experimental results provide confirmation that the microcantilever resonator is an excellent platform for chemical gas sensor.

Abstract: This paper presents design methodology, dynamics simulation and fabrication process of a magnetically actuated two-dimensional MOEMS scanning mirror with piezoresistor sensors. In the device, the mirror has two gimbal structures with two integrated driving coils and piezoresistors for the control and measurement of the both tilt angles, respectively. The dynamic model is established and the FEM simulation results show that the resonant frequencies for both directions are 254Hz and 523Hz, respectively. The two-dimensional MOEMS scanning mirror has advantages of tilt angles control and measurement feedback for the both directions.

Abstract: In this paper, a MEMS surface resonant magnetometer based on Lorentz force is presented. This magnetometer has three current carriers to sense the magnetic field and changes into deflection of beams which will be detected by the comb-capacitance. The alternating current carried by oscillate beams has the same frequency as resonant frequency of the magnetometer structure to make the deflection magnified Q (Quality-factor) times, therefore, it becomes more easily to measure. In this paper, the mechanical model of the sensitive element is established. The equations of stiffness of the system, deflection, first-order resonance frequency and sensitivity are setup and simulated in ANSYS, as well as second-order to fourth-order modal, and harmonic excitation response simulation. It can be seen that the simulation results are in good accordance with the theoretical calculations, which proves the feasibility and the rationality of the theoretical model. The dimensions of the structure are designed, as well as the processing sequence Anodic Silicon-Glass Bonding and Silicon DRIE Multi-user Bulk Micromachining Process which will be used to manufacture the magnetometer. The MEMS surface resonant magnetometer has a high sensitivity, simple structure and easy to manufacture. The prototype sensors are being manufactured in NEDI now.

Abstract: In this paper, a comb-driving tunneling magnetometer based on the tunneling effect is introduced. The designation, manufacture and tests of this magnetometer are discussed, including its structure, FEA analysis, machining processes and test results. The test results indicate that the chip is coincidental with the tunneling effect and the chip is capable of sensing the magnetic signal.