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(GC)一直是分析挥发性混合物的常用方法。使用微电子机械系统(MEMS)技术进行GC开发是一种很有前途的方法，与传统的方法相比，它具有成本更低、体积更小、功耗更低、分析速度更快、以及极大地提高了现场使用的便携性等优点。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方面都有应用。由于挥发性和半挥发性有机化合物(VOC)在GC中的浓度很低，因此需要在实时化学传感器测量之前进行预浓缩步骤。理想的预浓缩器将自动采样环境气体，并在低功耗的情况下将测量灵敏度提高10-1000倍。我们将通过结合和弥合自上而下的微型化处理(MEMS)和自下而上的自组装方法(纳米技术)之间的差距来应对这一挑战。本工作的目标是利用MEMS技术开发具有集成热解吸能力和高比表面积比的VOC预浓缩器芯片，并利用纳米技术在其上涂覆纳米结构的吸附剂。提出了四个具体的目标：1)利用高深宽比硅刻蚀技术和玻璃上硅片工艺，制作具有片上加热器和温度传感器的低质量(低功率)预浓缩器；2)在MEMS基预浓缩器的所有表面上沉积离子自组装多层膜(ISAM)或烷烃功能化的金纳米颗粒；3)用OV-1和Tenax等传统吸附剂覆盖MEMS预浓缩器，从脱附宽度、突破体积和温度分布等方面评价它们的性能，并开发新的模型来预测此类预浓缩器的行为。以及4)通过与Convergent Engineering Inc.(CE)的合作，表征用于监测呼吸中生物分析物的PC及其相应吸附剂的性能，并将微芯片的性能与传统的行业标准预浓缩器进行比较。我们预计将展示正构烷烃(C5-C16)和多环芳烃的浓缩和解吸，以及环大小不同的呼气分析物，其浓缩系数为200，解吸宽度为0.2s，在50°C/秒的温度坡道下的功耗为1W。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性地浓缩分析物，即环境监测、国土安全和生物医学。该项目的成果将树立一个杰出的榜样，说明MEMS和纳米技术如何成为开发影响全球工业的低成本、低功耗、高性能设备的高度互补的方法，考虑到全球GC仪器的市场估计每年约为10亿美元。这项研究还将促进发现，同时促进高中、本科生和研究生的教与学。这包括：1)为弗吉尼亚理工大学开发使用带有纳米结构吸附的MEMS预浓缩器的气相色谱演示？S物理学会学生向弗吉尼亚大学农村和西南部高中生推广计划，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收研究生加入高度跨学科的研究计划，以及4)将项目成果纳入不同系/机构的PI教授的课程中，即VT？S MEMS：从制造到应用和纳米技术，以及W&AMP；M？S仪器分析和高级分析化学；4)VT、W&M和CE关于微系统在生物医学中的应用的年度联合研讨会。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的陈述中广泛传播给工程界和科学界，向CE和其他使用或开发气相色谱和VOC预浓缩器(微捕集器)的行业广泛传播，并在网页中作为校外教员的资源，这些教员将教授与分离科学有关的本科生和研究生分析化学课程

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