US researchers have built a team of robots, made entirely out of DNA, that can walk around and sort molecules.

Key points: Researchers have built a team of DNA robots that work together

Researchers have built a team of DNA robots that work together The robots recognise and transport molecules

The robots recognise and transport molecules In the future, DNA robots could help deliver medicine to specific cells, or build nanodevices

In a study published in the journal Science, researchers at the California Institute of Technology designed a group of DNA robots with 'bodies', 'hands', 'arms', and 'feet'.

"We call [them] DNA robots because they can also perform mechanical tasks, but at the nanometre scale," said Lulu Qian, who led the research with graduate student Anupama Thubagere.

The robots worked together to find and collect fluorescent molecules.

"We would like to send molecular robots to miniscule places where humans can't go, such as the bloodstream," Dr Qian said.

What is a DNA robot?

DNA is composed of the nucleotides adenine (A), thymine (T), cytosine (C) and guanine (G).

While these nucleotides can be strung together as a genetic blueprint for living organisms, researchers can also manipulate them to build nanostructures, including DNA robots.

"The DNA robot is just a single-stranded molecule, it's like a floppy rope when it's not attached to anything," Dr Qian said.

"We designed it to have a specific sequence of nucleotides that include what we call a 'hand', 'arm', 'leg' and two 'feet' components."

How do they 'walk'?

Sorry, this video has expired A DNA robot 'walking' (supplied: Caltech)

Because the robots are made entirely of DNA, they can walk around on structures that are also made of DNA — so long as the sequences of A, T, C and G nucleotides on their 'feet' pair up with complementary sequences below their 'feet'.

The team created a testing ground for their DNA robots that included a series of 'pegs' with a complementary code for the robots to step along.

"If the single strand has the right nucleotides in the sequence, it could actually force two partially zipped other strands to unzip," Dr Qian said.

"When it takes a step, the step size is about 6 nanometres, which is roughly only one hundred-millionth of a human step."

Are these the first DNA robots?

Researchers have already created DNA robots that can walk, while others have shown DNA robots can pick up and drop off molecular cargo.

But this new study shows DNA robots can walk, sort, and work together — all at once.

"This is actually one of the first steps towards developing the building blocks for general purpose DNA robots, rather than a robot that can perform one specific task," Dr Qian said.

"It is also one of the first examples that we show we can have multiple DNA robots collectively performing the same task."

Artist's rendition of DNA robots performing cargo sorting task ( Supplied: Demin Liu (www.molgraphics.com) )

How do they pick up their 'cargo'?

The researchers dispersed fluorescent cargo molecules across a nanostructure testing ground, and put one of their DNA robots to work.

"It took almost a day for the robot to go back and forth and find all six different cargo molecules," Dr Qian said.

The researchers then added more DNA robots to the testing ground to see if they could work together.

"The time decreased from roughly a day to roughly just a couple of hours," she said.

Dr Qian said the DNA robots function on this miniature scale in the same way regular-sized robots might work inside a mailroom.

"When there [was] more than one robot, the amount of cargo molecules that were actually correctly delivered to the desired locations increased to very close to 100 per cent," she said.

So the DNA robots were probably more effective than this guy:

What can they be used for?

Nanobionics researcher Wenlong Cheng from Monash University said the new research is exciting, because the team has designed a modular system with highly specific DNA robots.

"They also demonstrated you can have multiple DNA 'walkers' and do this kind of sorting work simultaneously, ensuring this is a scalable approach," said Professor Cheng, who was not involved in the research.

Professor Cheng said there's a range of future applications for this type of technology, including targeted drug delivery.

"If someone gets a tumour, you can have small robotics, small robots walking to that location doing small scale surgery," he said.

"Another application is in the nanoscale device area."

However, given DNA robots have the potential to interact with our own DNA, Professor Cheng said it's unlikely we'll see them in human bodies anytime soon.

"When you deliver them into the human body, it could potentially create risk if that genetic coding integrates into the genome information," he said.

Dr Qian said there are some promising applications in medicine and nanoengineering, but her lab's focused more on building the infrastructure for DNA robots.

"Many of the potential applications I would say are still science fiction," she said.

"My interest and my lab's interest are essentially understanding the engineering principles for how to build these molecular robots."