In MIT’s Technology Review report about ten emerging technologies to watch for, we read about magnetic-resonance force microscopy:
In nanotechnology and molecular biology, researchers are often severely limited by the inability to observe atoms and molecules in three dimensions. Proteins, for instance, fold into complex patterns that are largely invisible to the biologists trying to work out their functions of the biomolecules.
So researchers are working to develop a tool that could provide a 3-D view of the nanoworld. The technology–called magnetic-resonance force microscopy (MRFM)–is a hybrid of magnetic-resonance imaging (MRI) and atomic force microscopy (AFM), which is widely used in nanotech. Physicists at the IBM Almaden Research Center in San Jose, CA, led by Daniel Rugar, recently used MRFM to detect the faint magnetic signal–the “spin”–of a single electron. While that accomplishment is still far from the goal of a 3-D snapshot of an atom or molecule, it is a critical step in proving that MRFM could perform atomic-scale imaging.
IBM Almaden Research Center describes how MRFM works:
The magnetic resonance force microscope (MRFM) uses an ultrathin silicon cantilever (yellow) with a nanometer size magnetic tip (blue) to detect the magnetic signal from an individual electron buried below the surface of the sample. Because the electron has a quantum mechanical property called “spin,” it acts like a tiny bar magnet and can either attract or repel the magnetic tip. The interaction between the spin and the tip is localized to the bowl-shaped region in the sample called the “resonant slice,” which moves as the cantilever vibrates. With the aid of a high-frequency magnetic field generated by a coil (right, background), the orientation of the electron (green arrow) flips as the resonant slice passes through. The magnetic force between the electron and magnetic tip alternates between attraction and repulsion every time the electron flips its orientation, causing the cantilever frequency to change slightly. A laser beam (left) is used to measure precisely the variations in cantilever vibration frequency.