DNA robot takes its first steps

New Scientist ^ | 5/6/04

[LibWhacker]

A microscopic biped with legs just 10 nanometres long and fashioned from fragments of DNA has taken its first steps.

The nanowalker is being hailed as a major breakthrough by nanotechnologists. The biped's inventors, chemists Nadrian Seeman and William Sherman of New York University, say that while many scientists have been trying to build nanoscale devices capable of bipedal motion, theirs is the first to succeed.

"It's an advance on everything that has gone before," says Bernard Yurke of Bell Labs in New Jersey, part of the team that made one of the best-known molecular machines to date: a pair of "tweezers" also constructed from DNA strands (New Scientist print edition, 12 August 2000). Like similar molecular-scale efforts, the tweezers' arms merely open and close: they can not move around.

But for nanoscale manufacturing to become a realistic prospect, mobile microscopic robots will be needed to assemble other nanomachines and move useful molecules and atoms around.

Pairing up

The New York team's biped can "walk" because its DNA-based legs are able to detach themselves from a DNA-based track, move along a bit, then reattach themselves.

Why DNA? Two reasons. First, unlike other polymers, DNA chains like to pair up. However, two DNA strands will only "zip" together if the sequences of bases in each strand complement each other in the right way - so by tweaking the sequences chemists get a high degree of control over where each strand attaches. Second, researchers hope that cells can one day be engineered to manufacture these DNA-based machines.

Each of the legs in the walker is 36 bases long and is made from two strands of DNA that pair up to form a double helix. At the top, a springy portion of each DNA strand runs across from the left leg to the right, linking them together. At the bottom, one of the two strands pokes out of the helix to serve as a sticky foot.

The track, or "footpath", the walker travels on is also made of DNA, and is designed so that unpaired sections of DNA strands stick up like spikes along its length. These act as footholds for the walker. The feet attach to the footholds via "anchor" strands of DNA that match up with the foot sequence at one end and with the foothold at the other.

Because the left and right foot/foothold sequences are unique, each requires a different anchor. So to make the walker take a step, a free piece of DNA called an unset strand is introduced to peel away one of the anchors (see graphic), releasing the foot.

Shuffling forward

The anchor has a handle at the top - a short length of the DNA strand which does not bind to the foot or foothold. The unset strand sticks to this handle and then binds with the anchor all the way down. The anchor comes away easily because it prefers to have partners for all its base pairs - including the sequence in the handle.

The free foot grabs a new anchor sequence, which latches onto the next foothold, stepping the foot forward. Repeating the procedure to move the back foot forward completes the walker's shuffle.

The walker takes its nanostroll in a bath of a liquid called a "nondenaturing buffer", which stops the DNA falling apart. To start with, millions of walkers and tracks are floating around freely in this liquid. Only when the researchers add the DNA anchors do the bipeds' feet fix onto the footpaths. Then the unset strands can be added to begin the walking process.

The researchers were able to confirm that the nanowalkers had taken their first steps by taking small samples of the solution after each DNA addition. By feeding the material through a gel which separates DNA molecules by size and shape, they confirmed where the feet were attached - it is the same technique that gives "DNA fingerprints" in forensics.

Persuading the walker to ferry a load, such as a metal atom, is the team's next challenge.

[Centurion2000]

Fascinating

[Harpo Speaks]

The question is, how will they find pants that small?

[Brett66]

Singularity bump.

[LibWhacker]

Lol!

I'm guessing they won't need them; nanorobots will have nanomodesty. :-)

[LibWhacker]

BTW, Harpo . . . Welcome to FR!

[Harpo Speaks]

Honk!

[freebilly]

The question is, how will they find pants that small?

Forget the pants. I want to see the nano-thongs....

[freebilly]

As long as they don't open a Nano-Hooters....

[festus]

Why do I fear that nothing good will come of this ?

[RightWhale]

Is this a robot?

[freebilly]

Why do I fear that nothing good will come of this ?

Hey, we've already got a nanny state. A nano-state won't do any more damage.

I'm all for nano-government....

[The Duke]

For some reason I've always thought that "nanotechnology" was the biggest scam on the planet. (How convenient that one can work an entire decade and literally have *nothing* to show for it!)

[SauronOfMordor]

There are a number of nanotech-based products. Do a google search for MEMS (Micro-electro-mechanical-systems). Or just go to http://www.memsoptical.com/ and look thru their product catalogue

[MonroeDNA]

It's the Devil!

[LibWhacker]

I know from your homepage you are an engineer. I'm not, so I'll defer to you on this . . . But isn't it at least potentially very impressive that they have nano-grippers, nano-rotors and gears, nano-conveyor belts, nano-walkers, nano-memory, nano-circuits and other circuit elements, etc.? Personally, I think it's fascinating and expect soon we'll start seeing lots of nano-devices that will have amazing properties and that will be built up from these components. Where am I going wrong?

[LibWhacker]

Here's a nanotech site I haven't seen mentioned on FR before: Nanopicture of the day.

Description:

New flat screens based on carbon nanotube technology will be longer lasting, more energy efficient and more convenient than current screens. There will also be the opportunity to make them both thinner and flexible.

Carbon nanotubes are arrangements of carbon atoms that are formed into tiny tubes about a millionth of a millimeter in diameter. In screens they work as an intermediary, focussing electrons onto a surface where they react with a fluorescent material to produce light for picture displays. A major challenge for researchers is how to get control of the way they form. In order to use nanotubes for panel displays it is important that the tubes are either aligned or formed into patterns. The bunches of nanotubes shown here are aligned in vertical groups on a star or cross type of pattern.

[The Duke]

I know from your homepage you are an engineer. I'm not, so I'll defer to you on this . . .

Actually, please don't necessarily defer to me on this. I'm still smarting from many years ago predicting that "computer viruses were all just a bunch of hype". :(

However, we in the US have a rich history of hyping technology advances that never live up to their promise, and I must say that before I am an engineer I am a cynic.

[LibWhacker]

However, we in the US have a rich history of hyping technology advances that never live up to their promise . . .

Boy, you're right about that! When I see some of the predictions about the future that have been made in the past, they always seem so naive -- if not so completely wrong, lol.

Here's hoping the promise of nanotech fairs better. If it doesn't, I'm sure something even better and more wonderful will come along. :-)

[William Tell]

The Duke said: "For some reason I've always thought that "nanotechnology" was the biggest scam on the planet. "

I think you are confusing "nanotechnology" with "cold fusion".

Nanotechnology has the potential to make dramatic changes to how some very important things get done in our world.

One example might be in the creation of food. Almost all of the food we eat is created by some other animal or plant. The process by which such food is created is determined by what is useful to that animal or plant and not on what is most useful to humans.

In the future, carbohydrates, proteins, sugars, and fats may be created in giant vats using "nanomachines". Bacteria may be harnessed to provide part of such machines, but the process of making the foodstuffs will be designed to efficiently create "food".

Pharmaceuticals and other useful chemicals can also be created this way.

I have read descriptions of using DNA to accomplish decryption using a massively parallel approach. Computation in general may be furthered by nanotechnology.

Another post describes using nanotubes to create improved video displays. Imagine such a display which might be manufactured using nanomachines. It might not only be inexpensive to create but possible to repair using nanomachines. No more dead pixels.