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Proceedings Paper

Dual-fiber optic microcantilever proximity sensor
Author(s): Shawn Goedeke; Stephen W. Allison; R. H. Farahi; Slobodan Rajic; Panos G. Datskos
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Paper Abstract

Microcantilevers are key components of many Micro-Electro- Mechanical Systems (MEMS) and Micro-Optical-Electro- Mechanical Systems (MOEMS) because slight changes to them physically or chemically lead to changes in mechanical characteristics. An inexpensive dual-fiberoptic microcantilever proximity sensor and model to predict its performance are reported here. Motion of a magnetic- material-coated cantilever is the basis of a system under development for measuring magnetic fields. The dual fiber proximity sensor will be used to monitor the motion of the cantilever. The specific goal is to sense induction fields produced by a current carrying conductor. The proximity sensor consists of two fibers side by side with claddings in contact. The fiber core diameter, 50 microns, and cladding thickness, 10 microns, are as small as routinely available commercially with the exception of single mode fiber. Light is launched into one fiber from a light-emitting diode (LED). It emerges from that fiber and reflects from the cantilever into the adjacent receiving fiber connected to a detector. The sensing end is cast molded with a diameter of 3 mm over the last 20 mm, yielding a low profile sensor. This reflective triangulation approach is probably the oldest and simplest fiber proximity sensing approach, yet the novelty here is in demonstrating high sensitivity at low expense from a triangular microstructure with amorphous magnetic coatings of iron, cobalt, permalloy, etc. The signal intensity versus distance curve yields an approximate Gaussian shape. For a typical configuration, the signal grows from 10% to 90% of maximum in traversing from 6 to 50 microns from a coated cantilever. With signal levels exceeding a volt, nanometer resolution should be readily achievable for periodic signals.

Paper Details

Date Published: 27 December 2001
PDF: 10 pages
Proc. SPIE 4468, Engineering Thin Films with Ion Beams, Nanoscale Diagnostics, and Molecular Manufacturing, (27 December 2001); doi: 10.1117/12.452552
Show Author Affiliations
Shawn Goedeke, Oak Ridge National Lab. and Tennessee Technological Univ. (United States)
Stephen W. Allison, Oak Ridge National Lab. (United States)
R. H. Farahi, Oak Ridge National Lab. (United States)
Slobodan Rajic, Oak Ridge National Lab. (United States)
Panos G. Datskos, Oak Ridge National Lab. and Univ. of Tennessee/Knoxville (United States)

Published in SPIE Proceedings Vol. 4468:
Engineering Thin Films with Ion Beams, Nanoscale Diagnostics, and Molecular Manufacturing
Emile J. Knystautas; Wiley P. Kirk; Valerie Browning, Editor(s)

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