Membrane-suspended microgrid as a gas preconcentrator for chromatographic applications

A micro-preconcentrator unit has been fabricated on silicon technology. The unit consists of a 3D-microheater surrounded by an insulating membrane. The preconcentrator is made up of a grid of suspended silicon bars underneath a polysilicon resistor. The grid was formed by 40-μm wide, 520-μm depth, 3000-μm long silicon bars fabricated by deep reactive ion etching covering a 3 mm × 3 mm area. This type of silicon grid structure allows to hold large amount of absorbent materials and provides efficient heat diffusion. The dimensions of the μ-preconcentrator were defined to achieve good thermal isolation and high absorbent content to yield a high gas concentration factor. Thermal characterization of the heater showed a low heat capacity of the structure and therefore, fast response and high power efficiency.