The Research On The Preparation Of MEMS Micro Gas-preconcentrator

Monitoring of the air component is necessary to the safety of human life and property in the explosive, high traffic occasions. Meanwhile in the current international context of counterterrorism, chemical weapon attacking becomes a sensitive topic, and trace level of the toxic gas could cause life-threatening to people. So, the more sensitive analysis-detection system is essential. The gas preconcentrator is installed at the front-end of the analysis-detection system. And the capability of analysis-detection system can be improved by several times to hundred times through its two stages: enrichment and desorption.The conventional preconcentrator is a tubular structure which can achieve a high preconcentration factor. However, it has disadvantages of large dead-volume, high heat capacity and high power consumption. And the preconcentrator using MEMS technology has advantages of micro-volume, small heat capacity, high heating rate, low power consumption. Besides, it’s easy to be integrated into handheld device.This paper based on the relevant reports in the field of MEMS preconcentrators abroad introduces the MEMS technology and applications, the research progress and development of gas preconcentrator in detail. This paper describes the principle of preconcentrator and gas adsorption. And several major factors that affect the preconcentration factor are analyzed. Based on the different MEMS preconcentrator structures, we designed a crisscross pillar MEMS preconcentrator with three-layers that has a high surface to volume ratio that can increase the area of the adsorbent material and improve preconcentration factor. The MEMS preconcentrator with 200 μm inlet/outlet ports was etched 3500 micropillars with dimentions of 120 μm×30 μm×240 μm on the silicon substrate by DRIE technology. It has two kinds of size 7 mm×7 mm and 14 mm×14 mm. In order to seal the MEMS preconcentrator, a pyrex glass was covered on the silicon substrate by anodic bonding technology. The Pt thin-film resistive heaters were sputtered on the backside of the silicon and patterned by the lift-off technique.Tenax-TA was used as adsorbent material and it was dissolved in chloroform. And it was formed a layer of adsorbent film on the pillar structure by perfusion. Finally the MEMS preconcentrator was connected to the FID by capillary and tested. The preconcentration factor was tested by ethanol, acetone, chloroform and DMMP. This MEMS device achieved preconcentration factors of 2~3 using ethanol, 3~4 using acetone, 9~12 using chloroform. And FID signal significantly increased using DMMP.