The influence of bend geometry on the performance of a MicroGC

A definite need for fast, reliable, handheld, low power equipments for environmental monitoring is realized in many areas. A Micro-GC with on-chip devices is a strong potential solution. The separation column forms an important part of the GC where segregation of analytes occur. For quick and efficient separation of analytes it is very important to know how micro-columns need to be designed. Bends are unavoidable features in microfluidic systems due to design or technological constraints. However, these bends induce pressure drop and dispersion that decreases the separation time and efficiency. This paper shows how microfabricated columns with different bend designs perform differently. The following designs were fabricated on chip with DRIE technology: simple circular bends, faceted designs with expansion at bends, faceted designs with contraction at bends, a contraction-expansion design and a contraction-expansion design with race-track compensation. Different designs give different degrees of separation. A pressure drop comparison is made using the obtained carrier mass flow rate at constant inlet pressure. Dispersion is characterized using the peak asymmetry from an FID detector signal. The results indicate that dispersion in the contraction-expansion design with racetrack compensation is minimum at the expense of pressure drop.