Monolithic integration of Knudsen pumps to form a complete, self-sufficient fluidic system for microscale gas chromatography.

This paper reports the first microscale gas chromatography (μGC) system in which all fluidic components are monolithically integrated into a single 15 × 15 mm2 chip, including three Knudsen pumps, a preconcentrator, a separation column, and a capacitive detector. Knudsen pumps utilize thermal transpiration along narrow channels to induce gas flow, providing a compact, motionless solution that enables monolithic integration with high reliability and a long operational lifetime. The flow switching within the system is provided by a unique arrangement of multiple Knudsen pumps that eliminates the need for valves. To realize monolithic integration, the preconcentrator, separation column, and detector are arranged in a planar layout and are designed to be microfabricated using a common fabrication process. Methods to provide heat dissipation and thermal isolation are incorporated. In the experimental evaluation, the fabricated μGC system was operated to analyze the headspace of chemical mixtures, including alkenes, glycol ethers, aromatics, and mercaptans. The results showed a quantification accuracy of ±8.5% for the individual species within the mixtures, which is suitable for specific process monitoring applications in the chemical industry where concentrations of select target species and byproducts must be assessed continuously. The monolithic integration of gas pumps into a μGC system has not been previously reported and is an important step toward further miniaturization of μGC systems.