Researchers at the California Institute of Technology have developed a novel microfabricated device that uses fluorescence detection to size and sort individual DNA molecules at a rate 100-fold faster than conventional gel electrophoresis while requiring a million fold less sample. The device consists of an elastomer microfluidic network, which can be loaded with femtograms of DNA labeled with YOYO-1, an intercalating fluorescent dye. Illumination of the sample with lasers allows researchers to use fluorescence quantitatively to measure the length of individual DNA molecules. Lead investigator, Stephen Quake, explains that the total fluorescence intensity of the sample is directly proportional to the size of the DNA molecule. "We would ultimately like to use this device for nested mapping," he says. This would involve selecting and manipulating a DNA molecule into a specific channel, and then carrying out successive enzymatic reactions directly on the chip. Ultimately, the device could prove useful for bacterial artificial chromosome clone fingerprinting and DNA diagnostics. The findings are reported in Proc. Natl. Acad. Sci. USA (96, 11–13, 1999).