敞开式离子源和微型气泵集成的微型针-柱放电结构芯片设计与实验分析

采用LIGA(Lithographie,Galvanoformung,Abformung)工艺设计加工了一种微型针-柱放电结构芯片,可实现敞开式离子源和微型气泵的系统集成。此微型放电结构由采用电镀铜加工而成的针电极、上圆柱电极和下圆柱电极组成,针-柱间距有1mm、2mm两种规格。在室温、大气压环境、无外界通入气流的条件下,通过在针-柱电极上加载负直流高压,可产生稳定的气体放电。利用风速计testo 405-V1测量芯片气体放电产生的离子风风速,结果表明针-柱间距为2mm时产生的离子风流速最大,可达0.79m/s。对针-柱间距2mm规格的微型芯片进行乙酸进样电离实验,当针-柱之间产生稳定的电晕放电后,可发现位于芯片出口处已被去离子水润湿的PH试纸变红。此时利用微弱电流检测系统采集电离产生的离子,当放电电压为-3300V时,通过微弱电流采集系统检测到的电流信号可达120pA。采用LTQ XL离子阱质谱仪,对芯片电离丙酮、无水乙醇和乙酸乙酯的离子产物进行检测,所得到的主要物质为质子化单体离子和二聚物离子。放电产生离子风风速以及乙酸的进样和电离实验表明,基于LIGA的微型针-柱结构芯片可实现大气压环境下敞开式离子源和微型气泵的双重功能。

Design and experiment analysis for micro needle-cylinder discharge chip integrated by open-type ion source and micro pump

The LIGA (Lithographie,Galvanoformung, Abformung) technology was adopted to design and process a micro needle-cylinder discharge structure chip, by doing this, system integration of open-type ion source and micro air pump was realized. The micro discharge structure was composed of pin electrode, upper cylinder electrode and bottom cylinder electrode which were fabricated by copper electroplating. There were two types of needle-cylinder clearances, separately were 1 mm and 2 mm. Under the condition of room temperature, atmospheric pressure environment and no airflow from outside, by loading negative direct current and high voltage on the needle-cylinder electrode, stable gas discharge could be generated. The wind speed of ionic wind caused by chip gas discharge could be measured through testo 405-V1 anemometer. The result shows that if the needle-cylinder clearance is 2 mm, the maximum flow velocity of the ionic wind will reach 0.79 m/s. Acetic acid sample injection ionization experiment of microchip with the needle-cylinder clearance of 2 mm was conducted. We found that when there was stable corona discharge between needle and cylinder, PH test paper located at the chip exit and has been moistened by de-ionized water would be red. At this time, the weak current detection system was used to collect ions generated by ionization, if the discharge voltage was -3 300 V, the current signal detected by weak current collection system reached 120 pA. LTQ XL ion trap mass spectrometer was applied to detect products of ions for chip ionization acetone, absolute ethyl alcohol and ethyl acetate, the main obtained substances were protonation monomer ion and biopolymer ion. Speed of ionic wind generated by discharge and sample injection and ionization of acetic acid experiments show that dual functions of open-type ion source and micro air pump can be realized under atmospheric pressure environment based on LIGA micro needle-cylinder structure chip.