Patent ID: 7399449
Filing Date: 2008-07-15
Classification: B01L,G01N

Abstract:
1. A microfabricated diffusion source to provide a controlled diffusion rate of a vapor, comprising: a substrate having a hollow cavity formed therein, a lid bonded to the cavity-side of the substrate to enclose the hollow cavity, a porous reservoir formed in the cavity of the substrate to hold a liquid, a headspace formed in the cavity in fluidic communication with the porous reservoir to provide an equilibrium vapor of the liquid therein, a diffusion channel, having a cross-section, a length, an entrance end in fluidic communication with the headspace and an exit end for controlled diffusion of the vapor therethrough, wherein the cross-section and length are selected so that the diffusion rate of the vapor through the diffusion channel is in the molecular flow regime and wherein the diffusion rate R of the vapor through the diffusion channel in the molecular flow regime is given approximately by R=2.216×10 an outlet formed through the lid at the exit end of the diffusion channel for release of the vapor to a gas stream.