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Journal of Sensors
Volume 2012, Article ID 580939, 7 pages
Research Article

An Astigmatic Detection System for Polymeric Cantilever-Based Sensors

1Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan
2Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan
3Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Lyngby, Denmark

Received 15 July 2011; Accepted 20 August 2011

Academic Editor: Martin Hegner

Copyright © 2012 En-Te Hwu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We demonstrate the use of an astigmatic detection system (ADS) for resonance frequency identification of polymer microcantilever sensors. The ADS technology is based on a DVD optical head combined with an optical microscope (OM). The optical head has a signal bandwidth of 80 MHz, allowing thermal fluctuation measurements on cantilever beams with a subnanometer resolution. Furthermore, an external excitation can intensify the resonance amplitude, enhancing the signal- to-noise ratio. The full width at half maximum (FWHM) of the laser spot is 568 nm, which facilitates read-out on potentially submicrometer-sized cantilevers. The resonant frequency of SU-8 microcantilevers is measured by both thermal fluctuation and excited vibration measurement modes of the ADS.