A collaborative project between physicists from the Joint Quantum Institute (JQI; College Park, MD), the Neils Bohr Institute (Copenhagen, Denmark) and Harvard University (Cambridge, MA) has yielded a theoretical nanosized speaker-like technology capable of detecting weak electrical signals. These nano loudspeakers, if realized, could someday enable more patient-friendly MRI machines.

Researchers have developed a theoretical nano loudspeaker that could lead to improved MRI machines. Image: Taylor/NIST

"We envision coupling a nanomechanical membrane to an electrical circuit so that an electrical signal, even if exceedingly faint, will cause the membrane to quiver slightly as a function of the strength of that signal," explains Jake Taylor, a JQI physicist. "We can then bounce photons from a laser off that membrane and read the signal by measuring the modulation of the reflected light as it is shifted by the motion of the membrane. This leads to a change in the wavelength of the light."

This ability to amplify weak electrical signals using nano loudspeakers could ultimately contribute to the development of more-compact MRI machines that are less intimidating to patients than current models. "MRI machines are so big because they are stuffed with really powerful superconducting magnets. But if we can reduce the strength of the signals we need for a reading, we can reduce the strength—and the size—of the magnets," Taylor says. "This may mean that one could get an MRI while sitting quietly in a room and forgo the tube."

In addition to detecting faint electrical signals, the nano loudspeakers will also feature the ability to cool electrical circuits. The researchers believe that the task of translating the mechanical motion of the nanomechanical membrane into photons will result in the transport of a significant amount of heat out of the system. This cooling capability, they note, will reduce noise in the system and enhance signal detection.

While the theoretical tiny speaker has a lot of potential, the researchers must first prove that their theory is viable through experiments.