SGER: MEMS-Based Preconcentrators with Nano-Structured Adsorbents for Micro Gas Chromatography

摘要提案标题：用于微气相色谱的基于SGER MEMS的带有纳米结构吸附的预浓缩器。建议编号：CTS-0610213首席研究员：Masoud Agah，机构：弗吉尼亚理工学院和州立大学自20世纪50年代以来，气相色谱(GC)一直是分析挥发性混合物的常用方法，其中的组分在空间和时间上有所区别。传统的GC往往是体积大、易碎、相对昂贵的桌面仪器，耗电量高，但众所周知，它们能够提供准确和选择性的分析。利用MEMS技术开发的微型仪器具有成本低、体积小、功耗低、分析速度快、便于现场使用等优点，具有广阔的应用前景。这些系统将使气相色谱成为气体分析的普遍方法，应用于国土安全、监测食品新鲜度、工业过程控制、生物医学诊断和改善环境质量。在气相色谱中，由于环境中挥发性和半挥发性有机化合物的浓度较低，需要在实时化学传感器测量之前使用预浓度器来自动采样环境气体，将测量灵敏度提高10-1000倍。采用硅微机械加工技术的预浓缩器小型化可以通过减小设备尺寸、功耗、死体积和热质量来克服传统方法(使用窄口径金属管)的局限性。尽管取得了可喜的成果，但在实现高吸附容量(1000)、低功耗(1W峰值功率)和窄注入塞宽度(0.2s)的预浓缩器方面，微细预浓缩器仍然面临着严峻的挑战。在这里，我们将通过首次结合和弥合自上而下小型化处理和自下而上自组装方法之间的差距来解决这些挑战，以开发小型化预浓缩器。这项工作的目的是利用MEMS技术制造具有片上热解吸能力的预浓缩器，并利用纳米技术在预浓缩器内表面涂覆一层纳米结构材料，如离子自组装膜。提出了三个具体的目标：1)制造具有集成加热器和温度传感器的低质量(低功率)预浓缩器，利用高深宽比硅刻蚀技术和玻璃上硅工艺，2)在预浓缩器壁上沉积离子自组装多层膜(ISAM)作为只有几十纳米厚的吸附剂，以及3)从突破时间和体积、浓度因数和温度要求方面评价预浓缩器的性能。我们设想，使用具有高表面积与体积比的纳米结构吸附剂(如纳米颗粒)可确保预浓缩器有足够的表面积来捕获样品流。这减小了预浓缩器的体积，从而降低了结构的总质量。低质量预浓缩器允许快速热解吸产生窄带注入GC柱。考虑到全球GC仪器市场估计每年约10亿美元，这一探索性项目的更广泛影响将树立一个突出的例子，说明MEMS和纳米技术如何成为高度互补的方法，以开发影响全球工业的低成本、低功耗、高性能设备。这项研究还将促进发现，同时促进本科生和研究生的教与学。这包括从代表性不足的群体中招收研究生参加高度跨学科的研究计划，并将项目成果纳入三个不同系的PIS教授的课程中，即MEMS：从制造到应用、纳米技术和高级分析化学-分离科学。此外，这项研究的结果将在期刊和多学科会议上向工程界和科学界广泛传播。

Abstract Proposal Title: SGER MEMS-Based Preconcentrators with Nano-Structured Adsorbents for Micro Gas Chromatography. Proposal Number: CTS-0610213 Principal Investigator: Masoud Agah, Institution: Virginia Polytechnic Institute and State UniversitySince the 1950s, gas chromatography (GC) has been a common approach for analysis of volatile mixtures in which the components are differentiated in space and time. Conventional GCs tend to be large, fragile, and relatively expensive table-top instruments with high power consumption, but they are known to deliver accurate and selective analysis. The use of MEMS technology for GC development is a promising approach to micro-instruments having lower cost, smaller size, lower power consumption, faster analysis, and greatly increased portability for in-field use. Such systems will make gas chromatography a pervasive method for gas analysis, with applications in homeland security, monitoring food freshness, industrial process control, biomedical diagnostics, and improving environment quality. In GCs, due to low concentration of volatile and semivolatile organic compounds in the environment, a preconcentrator prior to real-time chemical sensor measurement is needed to automatically sample the ambient gas and improve the measurement sensitivity by 10-1000 folds. Miniaturization of preconcentrators using silicon micromachining techniques can overcome the limitations of conventional methods (using a narrow bore metal tubing) by reducing the device size, power consumption, dead volume, and thermal mass. Although achieving promising results, microfabricated preconcentrators still face difficult challenges in achieving a preconcentrator with high adsorbent capacity (1000), low power consumption (1W peak-power), and narrow injection plug width (0.2s). Herein, we will address these challenges by combining and bridging the gap between top-down miniaturized processing and bottom-up self-assembly approaches for the first time to develop miniaturized preconcentrators. The objective of this work is to employ MEMS technology to fabricate preconcentrators having on-chip thermal desorption capability and to utilize nanotechnology to coat the preconcentrator interior surfaces with nano- structured materials such as ionically self-assembled films. Three specific aims are proposed: 1) Fabrication of lowmass (low-power) preconcentrators having integrated heaters and temperature sensors for thermal desportion using high-aspect-ratio silicon etching techniques and a silicon-on-glass process, 2) Deposition of ionic self-assembled multilayers (ISAM) on the preconcentrator walls as adsorbents only a few tens of nanometers thick, and 3) Evaluation of the preconcentrator performance in terms of breakthrough time and volume, concentration factor, and temperature requirements. We envision that the use of nanostructured adsorbents (such as nanoparicles) with high surface to volume ratio ensures that the preconcentrator has sufficient surface area for trapping the sample stream. This reduces the preconcentrator volume and hence decreases the overall mass of the structure. The low-mass preconcentrator allows rapid thermal desorption to generate narrow bands for injection into the GC column.The broader impacts of this exploratory project will set an outstanding example of how MEMS and Nanotechnology can become highly complementary methodologies to develop low-cost, low power, high-performance devices that impact industries across the globe considering that the worldwide market for GC instruments is estimated to be around $1 billion annually. This research will also advance discovery while promoting teaching and learning at undergraduate and graduate levels. This includes recruiting of graduate students from under-represented groups into a highly interdisciplinary research program, and incorporation of the project results in the courses taught by the PIs in three different departments, namely MEMS: from fabrication to application,Nanotechnology, and Advanced Analytical Chemistry-Separation Science. Additionally, the outcome of this research will be widely disseminated to the engineering and scientific communities in journals and in presentation at multidisciplinary conferences.