Microfluidic devices for rapid and highly sensitive detection of living organisms were developed for two applications. First, a zebrafish embryo genotyping system was developed and shown to be able to genotype embryos in the first 48 hours of the embryos life without damaging the embryos in any apparent way. Second, a highly sensitive bacteria detection platform has been developed for the rapid detection of pathogens. The system relies on a magnetic bead extraction followed by secondary bead attachment. The secondary beads are barcoded with DNA sequences highly enriched for Gs. The guanine molecules generate an electrochemical response after they are released from the secondary beads and detected at a sensing location downstream from the beads. The amplification with the efficient washing procedures leads to a limit of detection of 3 CFU in 100 mL of water.