Silica sputtering as a novel collective stationary phase deposition for microelectromechanical system gas chromatography column: Feasibility and first separations

Since the late 1970s, approaches have been proposed to replace conventional gas chromatography apparatus with silicon-based microfabricated separation systems. Performances are expected to be improved with miniaturization owing to the reduction of diffusion distances and better thermal management. However, one of the main challenges consists in the collective and reproducible fabrication of efficient microelectromechanical system (MEMS) gas chromatography (GC) columns. Indeed, usual coating processes or classical packing with particulate matters are not compatible with the requirements of collective MEMS production in clean room facilities. A new strategy based on the rerouting of conventional microfabrication techniques and widely used in electronics for metals and dielectrics deposition is presented. The originality lies in the sputtering techniques employed for the deposition of the stationary phase. The potential of these novel sputtered stationary phases is demonstrated with silica sputtering applied to the separation of light hydrocarbons and natural gases. If kinetic characteristics of the sputtered open tubular columns were acceptable with 2500 theoretical plates per meter, the limited retention and resolution of light hydrocarbons led us to consider semipacked sputtered columns with rectangular pillars allowing also significant reduction of typical diffusion distances. In that case separations were greatly improved because retention increased and efficiency was close to 5000 theoretical plates per meter.