Closed-Loop, Axial Temperature Control of Etched Silicon Microcolumn for Tunable Thermal Gradient Gas Chromatography

Combining the resolution of conventional gas chromatography systems with the size factor of microGC systems is important for improving the affordability and portability of high performance gas analysis. Recent work has demonstrated the feasibility of high resolution separation of gases in a benchtopscale short column system by controlling thermal gradients through the column. This work reports a microfabricated thermally controllable gas chromatographic column with a small footprint (approximately 6.25 cm 2 ). The design of the 20 cm column utilizes 21 individually controllable thin film heaters and conduction cooling to produce a desired temperature profile. The reported device is capable of heating and cooling rates exceeding 8000 °C/min and can reach temperatures of 350 °C. The control methods allow for excellent disturbance rejection and precision to within +/- 1 °C. Each length of the column between heaters was demonstrated to be individually controllable and displayed quadratic temperature profiles. This paper focuses on the fabrication process and implementation of the thermal control strategy.