Two-Port Static Coated Micro Gas Chromatography Column With an Embedded Thermal Conductivity Detector

This paper reports a microfabricated 2 x 4 cm gas chromatography chip to separate and detect gases in a two-port structure by embedding a microthermal conductivity detector (mu TCD) within a separation column. A circular on-chip heater is placed on the backside of the monolithic device enabling temperature programming and consequently faster analysis of the heavier components. A unique process enhanced by reactive ion etching lag (RIE lag) is used to achieve multiple etch depths in silicon and restrict the process flow to just three masks. The silicon substrate contains the separation column, the heater, and the tunnels for the TCD electric feed throughs. A Pyrex wafer containing the TCD elements is anodically bonded to the silicon substrate to seal the structure. Performance of a standalone mu TCD fabricated in the same process and integrated in a hybrid fashion is also described. The single-chip design demonstrates successful separation and identification of multicomponent gas mixtures with a performance comparable to that obtained through a flame ionization detector connected in series. Further, on-chip temperature programming capability was utilized to elevate the column temperature to 75 degrees C to exhibit analysis in less than a minute.