- 4:30 PM

On-Chip High Speed Gas Chromatograph (Gc) with Carbon Nanotube Sensors

Adarsh D. Radadia1, Mark A. Shannon1, Keith Cadwallader1, Michael S. Strano2, and Richard I. Masel1. (1) Chemical and Biomolecular Engineering, University of Illinois, 600 S. Mathews St., Urbana, IL 61801, (2) 66-566 Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139

A micro-GC allows for small, handheld, low power equipments with on-chip devices for environmental sampling. In order to use a micro-GC as a fast chemical warfare agent scanner in highly industrious places like airports, there is a definite need for reduction in analysis times from the current state of the art. Current technology cannot scan (separate and detect) air samples in relatively short times (~ 4 seconds). High speed analysis GC requires 1) a continuous sampling part , 2) a preconcentration part, 3) micro-columns with high separation efficiency and resolution ability and 4) a detector with fast analysis time.

We use standard microfabrication techniques to create each of the components and test individual performance. Integration of the fabricated parts will not be demonstrated. A MEMS pump with a fluctuating polyimide membrane is fabricated to form the continuous sampling component of the GC. Preconcentration principle is demonstrated in a microfluidic processor with valves using metal-organic framework molecules as the adsorbing species. Micro-columns are fabricated in silicon using DRIE technique. Micro-columns are coated with modified polydimethylsiloxane films to perform the gas phase separation. High speed separation on chromatography has been targeted to build a highly sensitive and specific sensor. High resolution columns are fabricated after studying effects of 1) various micro-channel bend geometries and 2) micro-channel configurations on chip. The detector side effort is focused on building a carbon nanotube based chemi-sensors. Carbon nanotubes are highly promising materials for sensing chemical species like thionyl chloride and dimethylmethylphosphonate, a simulant for chemical warfare agent sarin. Results of individual operational components are evaluated using an ordinary modified GC.