A novel microfluidic/SERS platform has been developed for real time sensing of 2,4-DNT. The fundamental research is being conducted at UCSB, commercialized by SpectraFluidics, and validated at ECBC. The system leverages phenomena at multiple length scales, ranging from tens of micrometers to several nanometers. The key enabling technology is a newly developed invention termed Free-Surface Fluidics (FSF), where one or more fluidic surfaces are confined by surface tension forces, and exposed to the surrounding atmosphere. The free-surface fluidic architecture is combined with surface-enhanced Raman spectroscopy (SERS) for detection of 2,4-DNT. Once 2,4-DNT analyte molecules are absorbed into the flow, they can interact with gold or silver colloidal particles. This architecture allows for analysis and deterministic control of SERS 'hot spot' aggregation, which can increase Raman scattering signal strength by up to 10 orders in magnitude. We have successfully measured DNT vapor at concentrations as low as ~1 ppb. This sensitivity value is confirmed by orthogonal measurements using GC-mass spectroscopy at ECBC.