Design And Fabrication Of FAIMS Sensor

High-field asymmetric waveform ion mobility spectrometry is a kind of wide-band ions separation technology. The mechanism of FAIMS technology bases on the differential ion mobility at high and low electric field. This technology has lots advantages, such as quick response, high resolution, large range of application, small in size, etc.. FAIMS has wide application areas such as environment monitoring, explosives detecting, metabolite chemicals detecting, etc. For example, FAIMS can be applied in detecting the concentration of acetone in expired air, which can be used as a method in early diabetes diagnosis.Many foreign institutes have made lots of research in FAIMS theory, and some companies have produced FAIMS instruments. However, the research of FAIMS has just started in the past few years in China, and no FAIMS instruments have been reported so far. So the design and research of FAIMS sensor have great significance in developing the FAIMS technology and increasing the ability of chemicals accurate detecting.Considering the prospects of FAIMS technology and the backwardness of FAIMS research in China, a FAIMS sensor chip is designed in this thesis.In this thesis, a micro FAIMS sensor is designed based on MEMS technology, and the main research contents are listed as follows. The deflection of ions drift tube in high electric field is analyzed by theoretical calculation and finite element analysis (FEA). An interdigitated ions drift tube is designed based on the results of calculation and simulation. An ionization method is proposed to ionize the chemicals through analyzing the demands of FAIMS. A method of micro electric current detecting circuit is designed to detect the electric current that results from the discharge of ions. The layout of FAIMS sensor chip is designed based on the parameters of the interdigitated drift tube. At last the interdigitated drift tube, which is the key part of FAIMS sensor, is fabricated by the technology of photo lithography and inductively coupled plasma (ICP) etching.The main innovation of this paper is the design of microfabricated interdigitated ions drift tube, which is the heart of FAIMS sensor chip. This interdigitated structure reduces the deflection of the electrodes of drift tube, which can increase the reliability of the ions tube. The interdigitated structure can also increase the effective area of the drift tube, which will increase the resolution and accuracy. Since the space between the ions drift tube microfabricated by MEMS technology is very small, the utmost electric field in the drift tube become very high, which means the ion mobility of sample chemicals could be changed in a larger range. Thus the drift tube can separate more types of chemicals and simultaneously increase the ions separation ability.