Abstract
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 mum in diameter within 15 min. Concentration of bioparticle samples as low as 10(4) colony forming units (CFU)ml are presented using batch volumes as large as 150 mul. 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.