Thursday, November 17, 2005

Machines Behave Like DNA
By Tracy Staedter, Discovery News



Oct. 14, 2005- Just like the biological components inside a cell can replicate a segment of DNA and self-correct when something goes out of whack, so too can a newly developed set of miniature robots.

Created by a team of researchers at the Massachusetts Institute of Technology, the three-inch-long autonomous machines have mechanisms, both physical and computational, that allow them to meet up randomly, latch together, decide if they should stay connected, and then either let go or remain paired.

"The technique simultaneously addresses two of the most challenging requirements in nanoscale manufacturing: error-free assembly and massively parallel assembly of mechanical parts," said Robert A. Freitas Jr., a senior research fellow at the Institute for Molecular Manufacturing in Palo Alto, Calif., and co-author of a recent book on self-replicating machines.

The new method, published by MIT's Joseph M. Jacobson in a recent edition of the journal Nature, could serve as the foundation for systems that assemble themselves, such as machines that break apart to explore tight places and then reassemble later.

To date, self-replicating machines have been realized, but have relied on the well-ordered input of building blocks and do not posses a self-correcting function.

But the approach taken by Jacobson and lead graduate student, Saul Griffith, functions more like a biological system.
For example, inside a cell's nucleus, particles including a variety of chemical compounds and proteins float around randomly.

The proteins copy bits of DNA by assembling the compounds into a specific order. This is not an assembly line where parts are delivered in the correct sequence, yet nature has figured out a way to correctly order the components and self-correct any errors along the way.

"We wanted to mimic nature and make an analogy to the machinery in nature that copies itself," said Jacobson.

In the lab, his team built machines that come in two colors: yellow and green.

They attached five robots together, shoulder to shoulder, to make a "seed" string, for example green, green, yellow, yellow, green.

The seed string, which served as the starting point for assembly, was placed on an air hockey table with a bunch of individual robots.

Even though the robots in the string were attached shoulder to shoulder, the individual robots are designed to latch onto each other front to back.

The goal was to assemble identical rows of robots in the same color order: green, green, yellow, yellow, green.

As the air from the table jostled the little machines here and there, they randomly bumped into each other, as well as the components in the seed string.

When they attached, they automatically sent each other an electronic signal to identify whether they were of the same color. If they were, they stayed together. If they weren't, they released.

In tests, the team got perfect replication of the five-robot strings each time. If they turned off the error-correction program, strings replicated only three percent of the time.


http://dsc.discovery.com/news/briefs/20051010/dnabot.html


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