AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Wednesday Sessions
       Session MM-WeA

Paper MM-WeA10
MEMS-Based Force Detected Nuclear Magnetic Resonance Spectrometer

Wednesday, October 27, 1999, 5:00 pm, Room 620

Session: Micro-Science and Tribology
Presenter: T. George, Jet Propulsion Laboratory
Authors: T. George, Jet Propulsion Laboratory
W. Tang, Jet Propulsion Laboratory
A. Chang-Chien, Jet Propulsion Laboratory
D.W. Elliott, Jet Propulsion Laboratory
L. Madsen, California Institute of Technology
G. Leskowitz, California Institute of Technology
D. Weitekamp, California Institute of Technology
Correspondent: Click to Email
A novel nuclear magnetic resonance (NMR) spectrometer was recently demonstrated. In contrast to conventional NMR spectroscopy, which involves the detection of RF absorption, the force-detection technique works on the principle of using the RF to resonantly invert the magnetization of the sample of interest. The magnetization inversion is carried out at the mechanical resonance frequency of a microfabricated harmonic oscillator consisting of a silicon "diving board" on which a sensor magnet is mounted. The motion of the oscillator in response to the inversion of the sample magnetization is detected using fiber-optic interferometry. A two pronged approach was undertaken to develop the MEMS-based instrument. Microfabrication techniques including deep reactive etching of silicon and micro-electroplating of Fe-Ni alloys are being developed for the 2 mm diameter MEMS instrument. In parallel, a 25 mm diameter, conventionally machined magnet array mounted on a microfabricated silicon "diving board" has been used successfully to demonstrate the proof-of-concept. NMR spectroscopy has been conducted using this device, on millimeter-sized water droplets. Spin-echo experiments have also been undertaken to reduce the linewidth of the NMR peaks to below <1 Hz. The results of these experiments and the fabrication process will be described in detail. Applications of FDNMR spectroscopy in planetary exploration will also be discussed.