In DNA replication, a string of chemical building blocks called nucleotides functions as a template. Enzymes use nucleotides floating around in cells to make new DNA molecules. These enzymes are able to check the copy against the template strand to ensure the two match.
The MIT researchers set out to build a mechanical system based on the same principles. The systemmost of which was developed by Saul Griffithstarts with a five-part plastic string made up of two different colors in a certain sequence.
The template string floats around on a cushion of air like a puck on an air-hockey table and is surrounded by randomly moving building blocks of the two colors. These plastic building blocks are able to talk to each other and have onboard latches that are controlled by little microprocessors.
When two blocks come into contact, they can latch together.
"If a yellow part collides with the first yellow tile in our string, they will talk to each other and they will stick," Jacobson said. "But if a green tile collides with that first yellow tile, they'll exchange information and they'll say, You are of the wrong tile type, I want you to release."
Over time, the number of strings matching the original template can grow exponentially.
"Once we make our first copy it is going to separate, and it will be a template itself to be copied," Jacobson said.
The number of robots that could be built is limited by the supply of available building blocks.
But unlike self-assembling robots, which are assembled in a pre-programmed way, self-replicating robots can degrade themselves or break apart and replicate something else.
"This type of device may find the greatest utility in the manufacturing and assembly of complex machine systems composed of parts at the micro-, and later, nano-size scales," said Robert Freitas, a senior research fellow at the Institute for Molecular Manufacturing in Palo Alto, California.
While the MIT researchers' goal was to illustrate the fundamental aspects of biological replication, they envision that the systems, if suitably miniaturized, could have some exciting practical applications.
"You could have a set of little building blocks, maybe smaller than a millimeter [0.04 inch], in a bottle," Jacobson said. "You load in a program, and it instructs these things to fabricate themselves into a particular entity, maybe a little spider that can go down pipes."
The spider might break itself up into other units, such as a worm that can pass through even smaller holes. The units could then reassemble back into a spider.
On the nano-scale, Jacobson said, "you could imagine robots that go inside the body and are used as diagnostics sensors or even for repairs."
Free E-Mail News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES