A wrench or a screwdriver of a single size is useful for some jobs, but for a more complicated project, you need a set of tools of different sizes. Following this guiding principle, researchers at the National Institute of Standards and Technology (NIST) have engineered a nanoscale fluidic device that functions as a miniature "multi-tool" for working with nanoparticlesobjects whose dimensions are measured in nanometers, or billionths of a meter.
First introduced in March 2009 (see "NIST-Cornell Team Builds World's First Nanofluidic Device with Complex 3-D Surfaces", the device consists of a chamber with a cascading "staircase" of 30 nanofluidic channels ranging in depth from about 80 nanometers at the top to about 620 nanometers (slightly smaller than an average bacterium) at the bottom. Each of the many "steps" of the staircase provides another "tool" of a different size to manipulate nanoparticles in a method that is similar to how a coin sorter separates nickels, dimes and quarters.
In a new article in the journal Lab on a Chip*, the NIST research team demonstrates that the device can successfully perform the first of a planned suite of nanoscale tasksseparating and measuring a mixture of spherical nanoparticles of different sizes (ranging from about 80 to 250 nanometers in diameter) dispersed in a solution. The researchers used electrophoresisthe method of moving charged particles through a solution by forcing them forward with an applied electric fieldto drive the nanoparticles from the deep end of the chamber across the device into the progressively shallower channels. The nanoparticles were labeled with fluorescent dye so that their movements could be tracked with a microscope.
As expected, the larger particles stopped when they reached the steps of the staircase with depths that matched their diameters of around 220 nanometers. The smaller particles moved on until they, too, were restricted from moving into shallowe
|Contact: Michael E. Newman|
National Institute of Standards and Technology (NIST)