Nano-scale MRI could peer inside molecules

Harvard researchers have developed a magnetic resonance imaging (MRI) system that can produce nano-scale images, and may one day allow scientists to peer into the atomic structure of individual molecules.
For decades, scientists have used techniques like X-ray crystallography and nuclear magnetic resonance imaging (NMR) to gain invaluable insight into the atomic structure of molecules.
However, such efforts have been hampered as they demand large quantities of a specific molecule and often in ordered and crystallised form to be effective - making it all but impossible to peer into the structure of most molecules.
A team of scientists, led by Professor of Physics and of Applied Physics Amir Yacoby, has developed a magnetic resonance imaging (MRI) system that can produce nano-scale images.

"What we've demonstrated in this new paper is the ability to get very high spatial resolution, and a fully operational MRI technology. This work is directed towards obtaining detailed information on molecular structure," Yacoby said.
"If we can image a single molecule and identify that there is a hydrogen atom here and a carbon there we can obtain information about the structure of many molecules that cannot be imaged by any other technique today," Yacoby said.

Though not yet precise enough to capture atomic-scale images of a single molecule, the system has already been used to capture images of single electron-spins.

As the system is refined, Yacoby said he expects the system will eventually be precise enough to peer into the structure of molecules.
"What we've done, essentially, is to take a conventional MRI and miniaturise it," Yacoby said.
"Functionally, it operates in the same way, but in doing that, we've had to change some of the components, and that has enabled us to achieve far greater resolution than conventional systems," he said.
While conventional systems, Yacoby said, can achieve resolutions of less than a millimetre, they are effectively limited by the magnetic field gradient they can produce.
Since those gradients fade dramatically within just feet, conventional systems built around massive magnets designed to create a field large enough to image an object - like a human - that may be a metre or more in length.

The nano-scale system devised by Yacoby and colleagues, by comparison, uses a magnet that's just 20 nanometres in diameter - about 300 times smaller than a red blood cell - but is able to generate a magnetic field gradient 100,000 times larger than even the most powerful conventional systems.
The difference, Yacoby explained, is that the nano-scale magnet can be brought incredibly close - to within a few billionths of a metre - to the object being imaged.
"By doing that, we can achieve spatial resolution that's far better than one nanometre," Yacoby said.
The study is published in the journal Nature Nanotechnology.