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This story is from the category Pure Research
Date posted: 03/12/2008 Researchers working with Clemens Bechinger who is a Professor at the University of Stuttgart and a Fellow at the Max Planck Institute for Metals Research, and David Marr, a professor at the Colorado School of Mines, have constructed micromachines using the same trick that model makers use to get ships into a bottle where the masts and rigging of the sailing ship are not erected until it is in the bottle. In the same way, the scientists link the valves, pumps and stirrers of a microlaboratory to create a micro device on a chip. To do this, they introduce colloidal particles - tiny magnetizable plastic spheres - as components into the channels on the chip. A rotating magnetic field is used to link the components into larger aggregates and set them into motion as micromachines. (Proceedings of the National Academy of Sciences (PNAS), December 2, 2008) The geometry also determines the function of the aggregates. By tipping backwards and forwards, a rhombus creates openings and acts like a valve. On the other hand, if it rotates in a chamber with two inflows, it mixes the incoming liquids. The micro stirrer is also driven by a magnetic field that rotates clockwise or anticlockwise parallel to the chip. In the same way, the researchers in Stuttgart roll a cog wheel through a channel with a serrated wall. The cog wheel, which completely shuts the channel off, agitates liquid back and forth and only in combination with two valves, acts like a pump. "Compared to other approaches to equipping microlaboratories with moving parts, our ship-in-a-bottle technique has several advantages," says David Marr. Some scientists use pneumatic systems to pump liquids through microchannels, for example. However, this requires each component to be connected with a separate hose to the outside so that it can be supplied with compressed air. This is very complex and limits the integration density on microfluidic devices considerably, i.e. the total number of components on the chip. With the new method, it is possible to accommodate up to 5,000 pumps on one square centimetre. Moreover, the new approach does not rely on elastic materials as are required for pneumatic pumps. "It is much easier to produce suitable chips for applications if they only consist of a single material, silicon, if at all possible," says Clemens Bechinger. As the electrical control components like the mini-coils can be fabricated based on silicon, it would be ideal to make the microchannels from the same material. This would allow for integration of all the components on one chip, as in microelectronics," says Bechinger. See the full Story via external site: www.physorg.com Most recent stories in this category (Pure Research): 08/02/2017: New algorithms by U of T researchers may revolutionize drug discoveries |
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