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

自20世纪50年代以来，气相色谱法（GC）一直是分析挥发性混合物的常用方法。使用微机电系统（MEMS）技术进行GC开发（ìGC）是一种很有前途的方法，可以开发成本更低，尺寸更小，功耗更低，分析速度更快的微型仪器，并且与传统仪器相比，大大提高了现场使用的便携性。这些仪器在国土安全、工业过程控制、生物监测和改善环境质量等方面都有应用。由于ìGCs中挥发性和半挥发性有机化合物（VOC）的浓度低，因此需要在实时化学传感器测量之前进行预浓缩步骤。理想的预富集器能自动对环境气体进行取样，测量灵敏度提高10-1000倍，同时功耗低。我们将通过结合和弥合自上而下的微型化加工（MEMs）和自下而上的自组装方法（纳米技术）之间的差距来解决这一挑战。本研究的目的是利用MEMS技术开发具有集成热解吸能力和高表面体积比的VOC预富集芯片，并利用纳米技术在其表面涂覆纳米结构吸附剂。提出了四个具体目标：1)采用高宽高比硅蚀刻技术和玻璃上硅晶圆工艺，利用片上加热器和温度传感器制造低质量（低功耗）预聚光器；2)在基于mems的预聚光器的所有表面以纳米分辨率沉积离子自组装多层（ISAM）或烷烃功能化金纳米粒子；3)用OV-1和Tenax等传统吸附剂涂覆MEMS预富集剂，对比涂覆纳米结构材料的预富集剂在解吸宽度、突破体积和温度分布方面的性能，并开发新的模型来预测预富集剂的行为；4)表征ìPCs及其相应的吸附剂的性能，用于监测呼吸中存在的生物分析物，并通过与Convergent Engineering Inc. （CE）合作，将微芯片的性能与传统的工业标准预富集器进行比较。我们期望通过在50°C/秒温度梯度下实现浓度系数为200，解吸宽度为0.2s，功耗为1W，来证明正烷烃（C5-C16）和多芳烃的浓度和解吸以及环大小不同的呼吸分析物。自组装极性和非极性吸附材料的能力将使我们能够在广泛的应用中选择分析物的浓度，即环境监测，国土安全和生物医学。考虑到GC仪器的全球市场估计每年约为10亿美元，这个项目的结果将为MEMS和纳米技术如何成为开发低成本、低功耗、高性能设备的高度互补方法树立一个杰出的榜样。这项研究还将促进发现，同时促进高中、本科和研究生水平的教学。这包括：1)为弗吉尼亚理工大学开发使用mems预富集器和纳米结构吸附剂的气相色谱演示。2)为弗吉尼亚理工大学（VT）和威廉与玛丽学院（W&amp；M）的本科生提供研究机会；3)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；4)将项目成果纳入不同部门/机构（即弗吉尼亚理工学院）的pi教授的课程中。s MEMS：从制造到应用和纳米技术，以及W&amp；M？4) VT、W&amp；M和CE联合举办的微系统在生物医学中的应用年度研讨会。此外，这项研究的结果将在同行评议的期刊和多学科会议上广泛传播给工程和科学界，传播给使用或开发气相色谱法和挥发性有机化合物预浓缩器（微捕集器）的CE和其他行业，并在网页上广泛传播给教授分离科学的本科生和研究生分析化学课程的校外教师

0854242AgahSince the 1950s, gas chromatography (GC) has been a common approach for analysis of volatile mixtures. The use of microelectromechanical systems (MEMS) technology for GC development (ìGC) is a promising approach for developing micro-instruments having lower cost, smaller size, lower power consumption, faster analysis, and greatly increased portability for in-field use compared to their conventional counterparts. These instruments have applications in homeland security, industrial process control, bio-monitoring, and in improving environment quality. Due to the low concentration of volatile and semi-volatile organic compounds (VOC) in ìGCs, a preconcentration step prior to real-time chemical sensor measurement is needed. The ideal preconcentrator would automatically sample the ambient gas and improve the measurement sensitivity by 10-1000 fold while having low power consumption. We will address this challenge by combining and bridging the gap between top-down miniaturized processing (MEMs) and bottom-up self-assembly approaches (nanotechnology). The objective of this work is to employ MEMS technology to develop VOC preconcentrator chips with integrated thermal desorption capability and high surface-to-volume-ratio and to utilize nanotechnology to coat them with nano-structured adsorbents. Four specific goals are proposed: 1) fabricate low-mass (low-power) preconcentrators with on-chip heaters and temperature sensors using high-aspect-ratio silicon etching techniques and a silicon-on-glass wafer process, 2) deposit ionic self-assembled multilayers (ISAM) or alkane functionalized gold nanoparticles on all surfaces of the MEMS-based preconcentrators with nanometer resolutions, 3) coat MEMS preconcentrators with conventional adsorbents such as OV-1 and Tenax and evaluate their performance against those coated with nano-structured materials in terms of desorption width, breakthrough volume, and temperature profile as well as develop new models to predict the behavior of such preconcentrators, and 4) characterize the performance of ìPCs and their corresponding adsorbents for monitoring bioanalytes present in breath and compare the performance of the microchips with conventional industry-standard preconcentrators through collaboration with Convergent Engineering Inc. (CE). We expect to demonstrate the concentration and desorption of n-alkanes (C5-C16) and polyaromatic hydrocarbons as well as breath analytes that vary in ring-size by achieving a concentration factor of 200, desorption widths 0.2s, and power consumptions 1W at 50°C/sec temperature ramps. The ability to self-assemble both polar and non-polar adsorbent materials will enable us to have selective concentration of analytes in a wide range of applications, namely environmental monitoring, homeland security, and biomedicine. The outcome of this project will set an outstanding example of how MEMS and Nanotechnology can become highly complementary methodologies for developing 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 the high school, undergraduate, and graduate levels. This includes: 1) development of gas chromatographic demonstrations using the MEMS-based preconcentrators with nano-structured adsorbents for Virginia Tech?s Society of Physics Students outreach programs to rural, southwestern Virginia high school students, 2) research opportunities for undergraduates at Virginia Tech (VT) and the College of William and Mary (W&M), 3) recruiting of graduate students from under-represented groups into a highly interdisciplinary research program, and 4) incorporation of the project results in the courses taught by the PIs in different departments/institutions, namely VT?s MEMS: from fabrication to application and Nanotechnology, and W&M?s Instrumental Analysis and Advanced Analytical Chemistry and 4) annual joint seminars by VT, W&M, and CE on microsystems applications in biomedicine. Additionally, the outcome of this research will be widely disseminated to the engineering and scientific communities in peer-reviewed journals and in presentation at multidisciplinary conferences, to CE and other industries that use or develop gas chromatography and VOC preconcentrators (microtraps), and in web pages that will serve as resources for off-campus faculty who are teaching undergraduate and graduate analytical chemistry courses that deal with separation science