A fast-response microfluidic gas concentrating device for environmental sensing

This paper describes the design, fabrication and characterization of a microfluidic gas centrifuge for separating dilute gas mixtures based on the molecular weights of their constituents. The principal advantage of this approach is its fast response time compared to other methods that are based on permeation or adsorption/desorption. This would allow it to serve as a real-time preconcentrator for improving the sensitivity of miniature chemical sensors. Devices with nozzle throat widths as small as 3.6 Rm have been fabricated using photolithography, deep reactive ion etching (DRIE) and silicon-glass anodic bonding. Measurements of the device's performance show that a single stage can achieve a two-fold enrichment of an initially 1% mixture of SF6 in N-2 in 0.01 ms. These experimental findings are consistent with the results of two-dimensional numerical simulations of the flow through the device. The simulations suggest that the performance of a single stage could be improved significantly by changing the geometry of the entrance flow. Further improvements in performance could be achieved by cascading the devices. (C) 2006 Elsevier B.V. All rights reserved.