Study of preconcentration of non-polar compounds in microchannels with constrictions

The influence of the presence of constrictions in microchannels was investigated in this work, numerically and experimentally, aiming at to obtain preconcentrator microstructures for non-polar compounds that can be present as a contaminant in the air. The flow behavior inside the microstructures was analyzed using the ANSYS FLOTRAN 8.1 and EVOLVER 2.14 simulations packages. The experimental tests for evaluation of preconcentration characteristics were performed using gas mixtures with n-hexane (C6H14) inserted in a microchannel with a length of 30 cm, width of 100 μm and depth of 30 μm. The microchannels were defined using RIE plasma etching and sealed with glass. Preconcentration was effectively observed and it was also demonstrated that the constrictions may favor the occurrence of capillary effects, as compared to adsorption effects, defining the dynamical behavior of the preconcentrator microstructure as a function of geometric and flow conditions. So far, these microstructures can be useful for the preconcentration process at high-contaminated environments, in which the human interference is not safe or small devices with high portability are required.