MIT researchers use light to move tiny particles

Taking up the sci-fi staple of “tractor beams,” scientists have developed a way to use light to grab and move minuscule particles on a microchip. The research could lead to fine-grained biological sensors and other precisely built nanoscale devices.

The work by Massachusetts Institute of Technology researchers could extend the possibilities for “optical tweezers” — super-focused beams of light that have been used for years to study and manipulate tiny biological structures or even individual atoms.

Optical tweezers have been used on transparent media — like a microscope slide — that let the light shine through and hold objects in a tractor beam-like embrace. This is possible because light’s individual photons transfer minuscule amounts of force to particles they hit.

What’s new in the optical tweezer from MIT’s Matt Lang and David Appleyard is that they used infrared light to move particles on silicon, the basis of microchips. (Unlike visible light, the infrared does not bounce off the silicon.) That means that MIT’s optical tweezer can be used not just for study but to build structures on the surface of chips.

Lang and Appleyard proved their technique by getting 16 live E. coli cells to spell out “MIT” on a chip. The long-term potential is more practical: Lang envisions using the system to cram high-resolution sensors in very small spaces — for disease detectors, for example — and to connect silicon-based electronics to living tissues and other “biological interfaces.”

“That’s sort of wide open,” said Lang, a professor of biological engineering and mechanical engineering. The research is being published in an academic journal, Lab on a Chip.

Arthur Ashkin, a retired Bell Laboratories scientist who is considered the father of optical tweezers, cautioned that the MIT work could not be considered a breakthrough, since no devices using the technology have yet been built.

http://www.usatoday.com/tech/news/techinnovations/2007-10-30-mit-optical-tweezers_n.htm

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