A complete analysis of the laser beam deflection systems used in cantilever-based systems.

Department of Physics and Physical Oceanography, Memorial University. St. John's, NL., Canada A1B 3X7.
Ultramicroscopy (Impact Factor: 2.47). 01/2007; 107(4-5):422-30. DOI: 10.1016/j.ultramic.2006.11.001
Source: PubMed

ABSTRACT A working model has been developed which can be used to significantly increase the accuracy of cantilever deflection measurements using optical beam techniques (used in cantilever-based sensors and atomic force microscopes), while simultaneously simplifying their use. By using elementary geometric optics and standard vector analysis it is possible, without any fitted or adjustable parameters, to completely and accurately describe the relationship between the cantilever deflection and the signal measured by a position sensitive photo-detector. By arranging the geometry of the cantilever/optical beam, it is possible to tailor the detection system to make it more sensitive at different stages of the cantilever deflection or to simply linearize the relationship between the cantilever deflection and the measured detector signal. Supporting material and software has been made available for download at so that the reader may take full advantage of the model presented herein with minimal effort.

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    ABSTRACT: The impressive developments in micro / nano-electro-mechanical-systems (MEMS; NEMS) have led to a new class of chemical and biological sensors based on micro and nano cantilevers. This work focuses on fabrication challenges of flat cantilevers exhibiting well-controlled, uniform and reproducible mechanical performance. Our experimental study is based on cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk micromachining. Experimental results on fabrication and characterization of composite porous silicon-crystalline silicon microcantilevers made of SOI wafers are also presented, where the porous silicon surface provides an excellent interface for immobilization of the biosensing layer. The optimal geometric design of microcantilevers depending on the application as well on the selected sensing mode (static or dynamic) is considered. The innovative aspects and open issues of NEMS/MEMS cantilever-based biosensors are addressed.
    Proc SPIE 01/2008;
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    ABSTRACT: Laser beam deflection is a well known method commonly used in detecting resonance frequencies in atomic force microscopes and in mass/force sensing. The method focuses a laser spot on the surface of cantilevers to be measured, which might change the mechanical properties of the cantilevers and affect the measurement accuracy. In this work we showed that the joule heating of the laser, besides other extrinsic effects such as surface contamination, can cause a significant amount of shift in the resonator. The longer and softer the cantilever is, the more significant the effect. We suggest that the laser effects on the resonant response of sensors have to be taken into account.
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