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RESEARCH PROFILES Reliable dispensing of attoliter volumes of fluid
Waste
Sample
milliseconds and that diffusion could In the tiny wonderland where nanowires nect to the sample, buffer, analysis, and occur in ~0.5 milliseconds. and nanopores serve as sensors, scientists waste reservoirs. The researchers switched to a modiThe researchers first tested gated infeel their way through a landscape domified pinched injection, in which the jection, which Jacobson, Lance Koutny, nated by unfamiliar forces. Stephen Jawaste channel is directly across from the Roland Hergenröder, Alvin Moore, and cobson has been in the thick of it, hashsample channel, and the analysis channel Mike Ramsey pioneered for microfluing out some of the basic infrastructure is positioned at a 90° of this nanorealm. An angle. In this apinitial step “is to see how (a) Sample (b) proach, 10 V is apwell things from the miplied to the buffer, crofluidic regime scale to sample, and analysis the nanofluidic regime,” reservoirs, while the Jacobson says. “What can waste reservoir reyou transfer from microNanochannels Analysis Buffer mains grounded durfluidics to nanofluidics, Buffer ing loading. To inject and does it work?” a sample plug, the In the February 15 analysis reservoir is issue of Analytical Chem- Nanochannels then grounded. istry (pp 1655–1660), he “This valve works and graduate student extremely well, and Microchannels Michelle Kovarik at Indi20 µm Microchannels the volumes that we’re ana University Bloomable to dispense are as ington address the fun(a) Schematic of the microfluidic channels overlaid on the nanofluidic cross in the low as 40 aL,” says damental issue of reliably modified pinched injection scheme and (b) an image of an assembled device. Jacobson. “That’s the delivering fluids at this smallest-scale electrokinetic dispensing idics while they worked at Oak Ridge scale. They describe a device that can that we know of.” He notes that other National Laboratory. In this approach, dispense volumes as small as ~40 aL in the sample is loaded into the top arm of researchers have discussed electrokinetic 10–100 milliseconds from channels that transport in nanochannels, but the new the cross-shaped intersection; the analyare
