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Analysis and Design of a Nano-Electromechanical Vibration Sensor

[+] Author Affiliations
Farbod Khoshnoud

University of British Columbia, Vancouver, BC, Canada; California Institute of Technology, Pasadena, CA

Clarence W. de Silva

University of British Columbia, Vancouver, BC, Canada

Houman Owhadi

California Institute of Technology, Pasadena, CA

Paper No. IMECE2010-37797, pp. 521-529; 9 pages
doi:10.1115/IMECE2010-37797
From:
  • ASME 2010 International Mechanical Engineering Congress and Exposition
  • Volume 10: Micro and Nano Systems
  • Vancouver, British Columbia, Canada, November 12–18, 2010
  • Conference Sponsors: ASME
  • ISBN: 978-0-7918-4447-2
  • Copyright © 2010 by ASME

abstract

Design and analysis of an embedded nano-electromechanical capacitive sensor for vibration monitoring is presented in this paper. In this sensor, vibration sensing is carried out by detecting the oscillations of a Single Walled Carbon Nanotube (SWCNT). The SWCNT is excited when it is subjected to a base motion corresponding to the measured vibration. Acquisition of the sensor signal is performed by a capacitance circuit, using the electric charge generated in the Carbon Nanotube (CNT). A modulation in the charge in the CNT, due to change in the capacitance, leads to a modulation in the CNT’s conductance and is used in measuring the input vibration. Vibration properties of the CNTs are obtained by molecular mechanics and finite element analysis where atoms are modeled as particles with an equilibrium distance equal to the bond length, and the bonded interactions of atoms are modeled as flexible beams. Stiffness coefficients of the atomic bonds are modeled using Morse atomic potential. A bridge circuit is utilized in this sensor to compensate for temperature and other environmental effects. When the CNT is in the vicinity of the gate underneath the tube, at a distance in the range of 1 nanometer to 1 micrometer, Casimir pressure, due to quantum fluctuations in the zero point electromagnetic field, can attract the CNT to the gate. This unwanted applied force on the tube may lead to inaccurate measurement of the vibration. In order to study the effect of Casimir pressure on the CNT a simplified model of the Casimir effect, for parallel surfaces, is adopted. This model can assist in achieving better accuracy in vibration measurement, and the sensor can be calibrated accordingly to account for the Casimir attractive force. The paper presents the physical and operational details of the sensor. This device is particularly useful for precise and effective sensing of vibration for machinery and structural condition monitoring and fault diagnosis.

Copyright © 2010 by ASME
Topics: Sensors , Design , Vibration

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