%0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2008 %T Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor %A Verpillat, F. %A Ledbetter, M. P. %A Xu, S. %A Michalak, D. J. %A Hilty, C. %A Bouchard, L. S. %A Antonijevic, S. %A Budker, D. %A Pines, A. %K mri %X

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 mu m. An estimate of the sensitivity for an optimized system indicates that approximate to 6 x 10(13) protons in a volume of 1,000 mu m(3), 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.

%B Proceedings of the National Academy of Sciences of the United States of America %V 105 %P 2271-2273 %8 Feb 19 %@ 0027-8424 %G English %U ://WOS:000253469900006 %N 7 %M WOS:000253469900006 %! Remote detection of nuclear magnetic resonance with an anisotropic magnetoresistive sensor %R Doi 10.1073/Pnas.0712129105 %0 Journal Article %J Physical Review A %D 2008 %T Submillimeter-resolution magnetic resonance imaging at the Earth's magnetic field with an atomic magnetometer %A Xu, S. %A Crawford, C. W. %A Rochester, S. %A Yashchuk, V. %A Budker, D. %A Pines, A. %K nmr %X

Magnetic resonance imaging in the Earth's magnetic field is achieved using a sensitive atomic magnetometer for detection. We demonstrate images with a submillimeter resolution by recording the flow of two water paths meeting at a T-shaped mixer. The high homogeneity of the Earth's field allows the use of weak gradient fields which circumvent the concomitant-field effect. To distinguish the two input channels, we employed selective polarization, which is a unique and noninvasive labeling method for low-field magnetic resonance imaging. Our technique imposes minimal physical constraints on the object under study, in contrast to conventional high-field magnetic resonance imaging. This technique is applicable for microfluidic imaging in laboratory-on-a-chip devices.

%B Physical Review A %V 78 %8 Jul %@ 1050-2947 %G English %U ://WOS:000258180300141 %N 1 %M WOS:000258180300141 %! Submillimeter-resolution magnetic resonance imaging at the Earth's magnetic field with an atomic magnetometer %R Doi 10.1103/Physreva.78.013404 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2008 %T Zero-field remote detection of NMR with a microfabricated atomic magnetometer %A Ledbetter, M. P. %A Savukov, I. M. %A Budker, D. %A Shah, V. %A Knappe, S. %A Kitching, J. %A Michalak, D. J. %A Xu, S. %A Pines, A. %K mri %X

We demonstrate remote detection of nuclear magnetic resonance (NMR) with a microchip sensor consisting of a microfluidic channel and a microfabricated vapor cell (the heart of an atomic magnetometer). Detection occurs at zero magnetic field, which allows operation of the magnetometer in the spin-exchange relaxation-free (SERF) regime and increases the proximity of sensor and sample by eliminating the need for a solenoid to create a leading field. We achieve pulsed NMR linewidths of 26 Hz, limited, we believe, by the residence time and flow dispersion in the encoding region. In a fully optimized system, we estimate that for 1 s of integration, 7 x 10(13) protons in a volume of 1 mm(3), prepolarized in a 10-kG field, can be detected with a signal-to-noise ratio of approximate to 3. This level of sensitivity is competitive with that demonstrated by microcoils in 100-kG magnetic fields, without requiring superconducting magnets.

%B Proceedings of the National Academy of Sciences of the United States of America %V 105 %P 2286-2290 %8 Feb 19 %@ 0027-8424 %G English %U ://WOS:000253469900009 %N 7 %M WOS:000253469900009 %! Zero-field remote detection of NMR with a microfabricated atomic magnetometer %R Doi 10.1073/Pnas.0711505105 %0 Journal Article %J Applied Physics Letters %D 2006 %T Application of atomic magnetometry in magnetic particle detection %A Xu, S. %A Donaldson, M. H. %A Pines, A. %A Rochester, S. M. %A Budker, D. %A Yashchuk, V. V. %K system %X

The authors demonstrate the detection of magnetic particles carried by water in a continuous flow using an atomic magnetic gradiometer. Studies on three types of magnetic particles are presented: a single cobalt particle (diameter similar to 150 mu m, multidomain), a suspension of superparamagnetic magnetite particles (diameter similar to 1 mu m), and ferromagnetic cobalt nanoparticles (diameter similar to 10 nm). Estimated detection limits are 20 mu m diameter for a single cobalt particle at a water flow rate of 30 ml/min, 5x10(3) magnetite particles at 160 ml/min, and 50 pl for the ferromagnetic fluid of cobalt nanoparticles at 130 ml/min. Possible applications of their method are discussed.

%B Applied Physics Letters %V 89 %8 Nov 27 %@ 0003-6951 %G English %U ://WOS:000242538500151 %N 22 %M WOS:000242538500151 %! Application of atomic magnetometry in magnetic particle detection %R Doi 10.1063/1.2400077