Nanolestnik for sorting nanoparticles and biomolecules
Experts from the National Institute of Standards and Technology (NIST) and Cornell University have created the latest device for size separation of nanoparticles and large biomolecules suspended in a liquid. Moreover, the development, despite the fact that it is the next step in the development of nanotechnology, is easy to manufacture.
Schematic representation of the "ladder" created by the Americans. Separated DNA molecules are indicated in green, explanations are given below in the text (illustration by NIST-Cornell).
Devices that would be able to separate nanoparticles and even individual molecules by size have been created over the past few years. And this industry is still at an early stage of development.
Usually, multilayer photolithography is used for these purposes. The process is similar to the creation of integrated circuits: an extensive network of rectangular channels (most often of the same depth, which significantly limits their functionality) is etched on a silicon or glass plate in several stages.
In this case, a group of researchers from NIST used a single-stage process. A stencil is applied to the surface of the photoresistor, which transmits only a certain amount of light. Then the "excess" substance is washed out by etching, and a multi-level surface is formed. The result is a cavity, part of which resembles a staircase of 30 steps.
The figure shows the step structure of the device: due to the interference of light, each stage is colored in its own color (photo NIST).
The principle of particle separation is as follows: the liquid passes from the widest (620 nanometers) to the narrowest (10 nanometers) place. The electric field "pushes" it, forcing the particles suspended in the liquid to climb higher and higher up the stairs. It is clear that only those of them that pass by the size of the next "step" can move higher. Those who are unable to climb further remain on the last platform available to them.
To make sure that the device works, the scientists ran two solutions up the stairs containing polystyrene spheres with a diameter of 100 nanometers or virus DNA molecules about 20 micrometers in size, marked with fluorescent markers.
With the help of a microscope, scientists determined that in the first case, there was an empty space where the "width" of the steps was less than 100 nanometers. In the second case, the folded DNA molecules occupied wider areas, the same ones that unfolded were able to occupy narrower "slits".
The upper micrograph shows that all polystyrene spheres stopped at the border of 100 nanometers (top view of the device). Below: the folded and unfolded DNA strands have diverged in space, as they differ in "thickness" and the second is able to go deeper (photo by NIST-Cornell).
At the moment, scientists are trying to separate and study mixtures of particles of different sizes. "Nanoseparators" are necessary for science for one simple reason: it is impossible to "take" individual molecules even with the smallest forceps in the world. Meanwhile, in modern chemistry, biology and medicine, such capabilities are extremely necessary for the analysis of DNA, protein structures and toxic compounds, for the development of methods for accurate drug delivery and gene therapy.
One of the authors of this work, Samuel Stavis from NIST, believes that such technology can be used to create more complex devices and reliefs (curved, for example).
Read more about the new technology in the NIST press release and an article in the journal Nanotechnology.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of the "Membrane"10.04.2009