Nanofluidics Takes a New StepNanofluidics Takes a New Step
April 13, 2009
Scientists at the National Institute of Standards and Technology (NIST; Gaithersburg, MD) have developed a nanofluidics device that sorts and separates nanoparticles according to size. Researchers believe that a device with this capability may be able to prepare nanoparticles for a range of applications, from gene therapy and drug delivery to toxicity analysis. In contract, current-generation nanofluidic devices lacking the ability to separate particles of different sizes are mainly used to analyze DNA and proteins.The new device consists of a chamber with 30 different depths. Seen in profile, it resembles a staircase, the bottom of which is 10 nm high and the top of which is 620 nm high. After placing nanoparticles at the bottom, researchers use an electric field to push the particles upward. The particles can only move up to the next step if they are smaller than the depth of the step. As a result of this process, nanoparticles of different sizes become separated at the different steps of the device.According to NIST's Samuel Stavis, "If you want to do experiments where you're investigating the dependence of a nanoparticle's function on its size, it would be nice to have a tool to take a mixture of nanoparticles, separate them, sort them, and deliver them."In addition to its breakthrough performance benefits, the new nanofluidic device is fabricated using a novel one-step engineering method that differs from the traditional method of using multilayer lithography for making integrated circuits. In the one-step process, a mask allows different levels of light to fall on the photoresist. Then different amounts of photoresist are washed away, etching the substrate so that device features of varying depths are created.Stavis remarks that the technique could be used to make much more complicated devices than currently exist, including ones with with smooth curves. Such devices, he says, could provide new lab-on-a-chip tools for DNA analysis, biotechnology, and medicine.
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