Rapid bioparticle concentration and detection by combining a discharge driven vortex with surface enhanced Raman scattering

Rapid concentration and detection of bacteria in integrated chips and microfluidic devices is needed for the advancement of lab-on-a-chip devices because current detection methods require high concentrations of bacteria which render them impractical. We present a new chip-scale rapid bacteria concentration technique combined with surface-enhanced Raman scattering (SERS) to enhance the detection of low bacteria count samples. This concentration technique relies on convection by a long-range converging vortex to concentrate the bacteria into a packed mound of 200 mu m in diameter within 15 min. Concentration of bioparticle samples as low as 104 colony forming units (CFU)/ml are presented using batch volumes as large as 150 mu l. Mixtures of silver nanoparticles with Saccharomyces cerevisiae, Escherichia coli F-amp, and Bacillus subtilis produce distinct and noticeably different Raman spectra, illustrating that this technique can be used as a detection and identification tool. (C) 2007 American Institute of Physics.