AVS 51st International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM6
MEMS-based Force-Detected Nuclear Magnetic Resonance Spectrometer

Tuesday, November 16, 2004, 10:00 am, Room 213C

Session: MEMS and NEMS: Enabling Tools for Scientific Research
Presenter: T. George, Jet Propulsion Laboratory
Authors: T. George, Jet Propulsion Laboratory
K. Son, Jet Propulsion Laboratory
C. Lee, Jet Propulsion Laboratory
N.V. Myung, Jet Propulsion Laboratory
E.R. Urgiles, Jet Propulsion Laboratory
L.A. Madsen, California Institute of Technology
G.M. Leskowitz, California Institute of Technology
R.A. Elgammal, California Institute of Technology
D.P. Weitekamp, California Institute of Technology
Correspondent: Click to Email
NMR Spectroscopy is the premier spectroscopic method used for identification of chemical compounds. A miniaturized portable NMR spectrometer is highly desirable for field investigation of materials and in-situ planetary exploration. We are developing a novel microfabricated force-detected nuclear magnetic resonance (FDNMR) spectrometer with predicted sensitivity superior to conventional NMR at micron scales. This higher sensitivity arises from the signal-to-noise ratio scaling as d@super 0.5@ for the force detection technique, and as d@super 2@ for conventional NMR (d: sample diameter). Other force detection approaches suffer from broadening of the NMR lines and losses in sensitivity due to the magnetic field gradient imposed on the sample. We overcome this problem by producing a homogenous magnetic field across the sample using a symmetric magnet assembly. Our FDNMR detector consists of a harmonic oscillator comprised of a detector magnet mounted on a microfabricated Si beam. The detector magnet sits within an annular magnet and thus provides a uniform magnetic field over the entire sample volume. Rf pulses applied to the sample modulate the dipole-dipole interaction between the nuclear magnetic moment of the sample and the detector magnet at the mechanical resonance frequency of the oscillator. We detect the resulting motion of the mechanical oscillator at the Brownian-motion limit using a fiber-optic interferometer. In this paper, we present the microfabricated detector assembly of the MEMS-based force-detected nuclear magnetic resonance (FDNMR) spectrometer.