High-field Asymmetric Waveform Ion Mobility Spectrometry Based On MEMS Technology

As a mature technology for ion separation in gas phase, in recent years, field asymmetric waveform ion mobility spectrometry (FAIMS) technology has been intensively explored for the applications in detecting and monitoring explosives, chemical warfare and illicit drugs and environmental monitoring. Although, FAIMS technology has reported for a widely application in the field of chemical analysis and biological molecules, but only as the filter device, coupled with HPLC and MS, to identify the ions.FAIMS is a trace gas detection technology that operated under the atmosphere environment. Due to its fast detection, simple operation and achieving positive and negative mode scanning at the same time, FAIMS has been proved to rival a number of mainstream ion detection technologies. Motivated by the progress and advance of the micro-electromechanical systems (MEMS) technology, the FAIMS drift region can be etched on the silicon wafer through deep reaction ion etching (DRIE), achieving the miniaturization of the FAIMS core parts, which makes the realization of the portable gas detection device possible. Besides, compared to traditional FAIMS, the chip-based FAIMS has incomparable advantages such as, low cost, low voltage and so on.In this thesis, based on micro-electromechanical systems (MEMS) technology, a FAIMS chip was designed and fabricated on a low-cost 4 inch silicon wafer. The FAIMS electrode and channel was fabricated through the lift-off and DRIE technology respectively. Based on this, a micro-chip based FAIMS spectrometry system was built and tested. By using the microchip-based FAIMS instrument, various explosives, drugs and hazardous chemicals were conducted FAIMS measurements and their FAIMS spectrum were also obtained. Recognition algorithm is also developed for the FAIMS fingerprint spectral of those explosives, drugs and hazardous chemicals. Furthermore, it was noticed situations for the microchip-based FAIMS were completely different compared to the traditional FAIMS systems due to the much narrower channel size. Since the effect of compensation voltage on microchip-based FAIMS systems would no longer be ignored and was studied in depth. Also the flow rate across the micro-channels could be very different due to the blockage of gas flow or laminar effect by the micro-channels, which may lead to different gas number densities. Based on this, non-linear function based on the first principle and a general model was deduced and the accurate specific alpha coefficients for explosives, drugs and hazardous chemicals were obtained. Which benefit for revealing the effective discrimination regions.Besides, the application of micro-chip based FAIMS in the field of medical biotechnology was also investigated. The metal diffusion tube-microchip FAIMS system was introduced as the standalone device for rapid analysis of phenylalanine (PHE) with different concentrations for the first time. The ion characteristic spectra are acquired under the optimized conditions while the quantitative linear detection range of phenylalanine concentration and the limit of detection (LOD) for phenylalanine are determined. The whole process of the spectrum scanning is within 30 seconds. This investigation shows the feasibility of FAIMS technique for rapid detection of phenylalanine, and provides an important reference for the rapid detection of phenylalanine.