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

摘要提案题目：微气相色谱用SGER mems纳米结构预富集剂。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，其中的成分在空间和时间上是有区别的。传统的gc往往是大型、易碎、相对昂贵的台式仪器，功耗高，但它们可以提供准确和选择性的分析。使用MEMS技术进行GC开发是一种很有前途的微型仪器方法，具有成本更低，尺寸更小，功耗更低，分析速度更快，并且大大增加了现场使用的可移植性。这样的系统将使气相色谱法成为一种普遍的气体分析方法，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富集器自动对环境气体进行采样，并将测量灵敏度提高10-1000倍。利用硅微加工技术实现预浓缩器的小型化，可以通过减小设备尺寸、功耗、死体积和热质量，克服传统方法（使用窄孔金属管）的局限性。尽管取得了令人满意的结果，但在实现高吸附剂容量（1000）、低功耗（峰值功率1W）和窄注入塞宽度（0.2s）的预富集剂方面，微制备预富集剂仍然面临着艰巨的挑战。在此，我们将通过结合和弥合自上而下的小型化处理和自下而上的自组装方法之间的差距来解决这些挑战，首次开发小型化预富集剂。这项工作的目的是利用MEMS技术制造具有片上热脱附能力的预富集器，并利用纳米技术在预富集器的内部表面涂覆纳米结构材料，如离子自组装薄膜。提出了三个具体目标：1)利用高宽高比硅蚀刻技术和玻璃上硅工艺制造集成加热器和温度传感器的低质量（低功率）预富集器，用于热分解；2)在预富集器壁上沉积离子自组装多层（ISAM）作为吸附剂，厚度只有几十纳米；3)从突破时间和体积、浓度因子和温度要求方面评估预富集器性能。我们设想使用具有高表面体积比的纳米结构吸附剂（如纳米颗粒）确保预富集器有足够的表面积来捕获样品流。这减少了预浓缩器的体积，从而降低了结构的总质量。低质量预富集器允许快速热解吸产生窄带进气相色谱柱。考虑到GC仪器的全球市场估计每年约为10亿美元，这个探索性项目的广泛影响将为MEMS和纳米技术如何成为高度互补的方法来开发低成本、低功耗、高性能的设备树立一个杰出的榜样。这项研究还将促进发现，同时促进本科和研究生水平的教学。这包括从代表性不足的群体中招募研究生参加一个高度跨学科的研究项目，并将项目成果纳入三个不同部门的pi教授的课程，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广泛传播给工程界和科学界。

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.