Chilai Chen

MEMS based sensors for explosive detection: Development and discussion

In this paper, the development of explosive detection with MEMS technology was briefly reviewed. Various detecting methods were classified in microcalorimetric spectroscopy, optical displacement measuring, resonance frequency shift measuring, piezoresistive strain monitoring, heat absorption or release monitoring, and FA-IMS. Advantages and disadvantages of each method were respectively discussed.

Peak Profile Analysis in High Field Asymmetric Wave Ion Mobility Spectrometry

High field asymmetric wave ion mobility spectrometry (FAIMS) is a powerful tool to detect and characterize gas-phase ions, while the unsolvable partial differential equation of ions moving in ion drift tube poses a big challenge to FAIMS spectral peak analysis. In this work, a universal and effective model of FAIMS spectral peak profile has been proposed by introducing ion trajectory and loss height. With this model, the influence of the structure of ion drift tube, dispersion voltages, compensation voltages, and carrier gas flow rate on the FAIMS spectral peak characteristics like peak shape, full width at half maximum and peak height is analyzed and discussed. The results show that the influence of different factors on the FAIMS spectral peak profile can be qualitatively described by the model which agrees with the experimental data.

Design of MEMS electrometer for highly sensitive charge measurement

A new scheme of MEMS vibrating reed electrometer is proposed, which has eliminated bias current leakage of preamplifiers. Its principle stays largely the same to Gunns largescale electrometer proposed in 1932, input Charge is shared between a variable capacitor formed by the vibrating reed and a fixed capacitor, charge is measured by detecting the AC image current caused by charge redistribution. Theoretical calculation showed a charge resolution of 286 electrons in 0.3 Hz bandwidth, showing some compromise between charge resolution and bias current leakage.

Electric Field Interference Simulation of Ionization Electrodes on Ion Filter Electrodes in FAIMS

Using the method of ANSYS finite element analysis, we calculate the electric field interference between the ionization electrodes and ion filter electrodes. The effect of varying the electrodes width and distance on the electric interference field intensity has been investigated. In this paper, a method for selecting the electrodes width and distance is proposed by synthetically considering ions recombination time, electric field interference and detection precision, and shield electrodes configuration is designed for decreasing the electric field interference.