Novel technique delivers 10 nanometer

[Adopted from Materials Toady News, 30 September 2013]

A team from the University of Illinois at Urbana-Champaign and Northwestern University has devised a novel nuclear magnetic resonance imaging (MRI) technique that delivers a roughly 10­nanometer spatial resolution. This represents a significant advance in MRI sensitivity—modern MRI techniques commonly used in medical imaging yield spatial resolutions on the millimeter length scale, with the highest-resolution experimental instruments giving spatial resolution of a few micrometers.

MRI is used widely in clinical practice to distinguish pathologic tissue from normal tissue. It is noninvasive and harmless to the patient, using strong magnetic fields and non-ionizing electromagnetic fields in the radio frequency range, unlike CT scans and tradiational X-rays, which both use more harmful ionizing radiation.

MRI uses static and time-dependent magnetic fields to detect the collective response of large ensembles of nuclear spins from molecules localized within millimeter-scale volumes in the body. Increasing the detection resolution from the millimeter to nanometer range would be a technological dream come true.

The team’s breakthrough—the new technique introduces two unique components to overcome obstacles to applying classic pulsed magnetic resonance techniques in nanoscale systems. First, a novel protocol for spin manipulation applies periodic radio-frequency magnetic field pulses to encode temporal correlations in the statistical polarization of nuclear spins in the sample. Second, a nanoscale metal constriction focuses current, generating intense magnetic field-pulses.

In their proof-of-principal demonstration, the team used an ultrasensitive magnetic resonance sensor based on a silicon nanowire oscillator to reconstruct a two-dimensional projection image of the proton density in a polystyrene sample at nanoscale spatial resolution.

“We expect this new technique to become a paradigm for nanoscale magnetic-resonance imaging and spectroscopy into the future,” added the researcher. “It is compatible with and can be incorporated into existing conventional MRI technologies.”

This story is reprinted from material from University of Illinois, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.