With magnetic resonance microscopy

Microscopy with magnetic resonance (in English, magnetic resonance force microscopy) is a nano-MRI process developed since the beginning of the 1990s.


The process relies firstly on the phenomenon of resonance magnetic, already implemented by MRI: a field magnetic radiofrequency switches out of balance spin if it is the Larmor frequency. A magnetic field gradient spatially code this resonance frequency with proportional to amplitude spatial resolution. It builds second atomic force microscopy techniques, invented in 1986 by IBM researchers. The nanodétecteur detects the resonance of the spins with a lever mechanical, able to vibrate from a very low energy absorption.


Recognize a utility to put the sample in an inhomogeneous field is a somewhat counter-intuitive concept for a magnetic resonance spectroscopist. The first mechanical detection of resonance (NMR) nuclear magnetic was obtained by D.F. Evans in 1955 long was perceived as a simple feat technical lack have exploited this interest of space coding.

At the time, Evans was looking for new ways to measure the static component of nuclear susceptibility. Inspired by the balance of Faraday, he proposed placing the sample in an inhomogeneous field to carry a top force. It notes that the sensitivity of the device is comparable to that of inductive detection. In his conclusion commentary, he writes however, that his technique is probably no practical use: the use of an inhomogeneous field being necessary, the spectral resolution is inherently bad.

There in 1961, a reference to a. Abragam in the introduction to his famous book , then in 1967, the attempt by Alzetta et al. mechanically detect electron spin resonance of the Diphenylpicrylhydrazyl signal (en) (DPPH (en)). In this case, the sample is placed in a homogeneous field and the torque is measured.

In 1973 two physicists, Paul Lauterbur and Peter Mansfield, proposes to use this gradient to a spatial encoding, giving rise to magnetic resonance (MRI) imaging.

This discovery was awarded a Nobel Prize. Side mechanical detection, little work are to follow for several decades. They were delivered to the taste of the day by J.A. Sidles in 1991 in the light of the progress achieved both in MRI but also in atomic force (AFM) microscopy.

Sidles stressed the advantage of using a sensor proportional to the field gradient, to strongly increase the spatial resolution without deterioration of the sensitivity, operating in a very inhomogeneous field. Several significant progress after the first demonstrations of feasibility. Consecutive studies showed the remarkable improvement of the spatial resolution in Imaging ESR, NMR, and RFM.

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