The objective of this proposal is to introduce a new architecture for GC columns named semi-packed and a new method for stationary phase coating. The approach is to use MEMS technology for the fabrication of semi-packed columns and to utilize nanotechnology to uniformly functionalize the column surfaces.
Intellectual Merit: The proposed semi-packed columns consist of a microfluidic channel with an embedded array of ordered pillars (posts). These new columns, which do not have any conventional counterpart, offer both higher sample capacities and higher separation efficiencies. Four specific goals are proposed: 1) fabricating semi-packed columns with on-chip heaters and temperature sensors, 2) depositing functionalized gold nanoparticles or gold thin films on all surfaces of the MEMS-based columns with nanometer resolutions, 3) evaluation of the performance of MEMS columns with their monolayer-protected gold phases, and 4) coating the MEMS columns with commercial phases under industrial conditions to analyze their performance against those coated with proposed stationary phases.
Broader Impacts: The outcome of this project will set an outstanding example of how MEMS and Nanotechnology can become highly complementary methodologies to develop low-cost, low-power, high-performance microdevices. This research will also advance discovery while promoting teaching and learning through research opportunities for undergraduates, recruiting of graduate students into a highly interdisciplinary research program, incorporation of the project results in the courses taught by the PIs in different departments/institutions, and annual joint seminars by Virginia Tech, College of William and Mary, and Restek Corporation on micro gas chromatography and novel stationary phases.
Gas chromatography is a pervasive analytical technique for separation and identification of gaseous compounds with wide variety of applications in homeland security, medical diagnosis, food processing, and environmental monitoring. The heart of a GC system is a separation column whose walls are coated with a stationary phase. As the sample moves through the column by an inert mobile phase (such as helium or nitrogen), different gases spend different amount of time on the stationary phase and hence gets separated. The award provided by the National Science Foundation has resulted in the development of new gas chromatography (GC) columns for hand-held devices enabled by the marriage of microsystems fabrication techniques and nanotechnologies. The so-called "semi-packed" columns developed in this project is a short microfluidic channel having a dense array of pillars. These microstructures are fabricated in a silicon substrate using fabrication techniques similar to those used for integrated circuits (microprocessors) and sealed with a glass substrate. The research has resulted in the integration of nanotechnology and microsystem fabrication to functionalize the interior surfaces of these columns and to efficiently separate gas mixtures into their constituents. The project has utilized techniques such as layer-by-layer assembly of nanoparticles, thiol-functionalization of thin-film gold layers, and atomic layer deposition to achieve separation capability within the microchannels. The research has been carried out within an interdisciplinary environment in which faculty from engineering and science departments, undergraduate students, and graduate students worked together to fulfill the objectives of the proposal. Students were trained to use various state-of-the-art micro/nano fabrication and characterization equipment as well as analytical instruments and were provided unique opportunities to present their finding in national and international conferences. The research outcomes have been part of the dissertation of three doctoral students and has been reported in several reputable journals.
