Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor

doi:10.1073/pnas.0712129105

Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor

*Ecole Normale Supérieure de Lyon, 69364 Lyon Cedex 07, France;
^†Departments of Physics and
^‡Chemistry, University of California, Berkeley, CA 94720-7300; and
^§Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Contributed by Alexander Pines, December 21, 2007 (received for review December 14, 2007)

Abstract

We report the detection of nuclear magnetic resonance (NMR) using an anisotropic magnetoresistive (AMR) sensor. A “remote-detection” arrangement was used in which protons in flowing water were prepolarized in the field of a superconducting NMR magnet, adiabatically inverted, and subsequently detected with an AMR sensor situated downstream from the magnet and the adiabatic inverter. AMR sensing is well suited for NMR detection in microfluidic “lab-on-a-chip” applications because the sensors are small, typically on the order of 10 μm. An estimate of the sensitivity for an optimized system indicates that ≈6 × 10¹³ protons in a volume of 1,000 μm³, prepolarized in a 10-kG magnetic field, can be detected with a signal-to-noise ratio of 3 in a 1-Hz bandwidth. This level of sensitivity is competitive with that demonstrated by microcoils in superconducting magnets and with the projected sensitivity of microfabricated atomic magnetometers.

Footnotes

^¶To whom correspondence should be addressed at:
Department of Chemistry, Hildebrand Hall D64, University of California, Berkeley, CA 94720-7300.
E-mail: pines{at}berkeley.edu
Author contributions: F.V., M.P.L., C.H., L.-S.B., D.B., and A.P. designed research; F.V., M.P.L., S.X., D.J.M., C.H., L.-S.B., S.A., and D.B. performed research; F.V., M.P.L., S.X., L.-S.B., and D.B. analyzed data; and F.V., M.P.L., L.-S.B., and D.B. wrote the paper.
The authors declare no conflict of interest.