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Apr 2012

Volume 83, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 041101 (2012); http://dx.doi.org/10.1063/1.3697599 (19 pages)

Michael A. Duncan

The laser vaporization cluster source in the "cutaway" configuration. The sample rod is mounted from above with a flexible nylon screw in a holding block. The pulsed gas valve is mounted in the stainless steel can (left) and the skimmer is mounted on the opposite wall.

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back to top Sensors and Actuators/MEMS/NEMS

Channelling optics for high quality imaging of sensory hair

C. Skupsch, T. Klotz, H. Chaves, and C. Brücker

Rev. Sci. Instrum. 83, 045001 (2012); http://dx.doi.org/10.1063/1.3697997 (13 pages) | Cited 1 time

Online Publication Date: 3 April 2012

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A long distance microscope (LDM) is extended by a lens and aperture array. This newly formed channelling LDM is superior in high quality, high-speed imaging of large field of views (FOV). It allows imaging the same FOV like a conventional LDM, but at improved magnification. The optical design is evaluated by calculations with the ray tracing code ZEMAX. High-speed imaging of a 2 × 2 mm2 FOV is realized at 3.000 frames per second and 1 μm per pixel image resolution. In combination with flow sensitive hair the optics forms a wall shear stress sensor. The optics images the direct vicinity of twenty-one flow sensitive hair distributed in a quadratic array. The hair consists of identical micro-pillars that are 20 μm in diameter, 390 μm in length and made from polydimethylsiloxane (PDMS). Sensor validation is conducted in the transition region of a wall jet in air. The wall shear stress is calculated from optically measured micro-pillar tip deflections. 2D wall shear stress distributions are obtained with currently highest spatiotemporal resolution. The footprint of coherent vortical structures far away from the wall is recovered in the Fourier spectrum of wall shear stress fluctuations. High energetic patterns of 2D wall shear stress distributions are identified by proper orthogonal decomposition (POD).
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42.79.Pw Imaging detectors and sensors
07.60.Pb Conventional optical microscopes
42.79.Bh Lenses, prisms and mirrors

Fiber optic displacement sensor with a large extendable measurement range while maintaining equally high sensitivity, linearity, and accuracy

Yeon-Gwan Lee, Yoon-Young Kim, and Chun-Gon Kim

Rev. Sci. Instrum. 83, 045002 (2012); http://dx.doi.org/10.1063/1.3698586 (5 pages)

Online Publication Date: 3 April 2012

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This paper presents a fiber optic displacement sensor composed of a transmissive grating panel, a reflection mirror, and two optical fibers as a transceiver. The proposed fiber optic displacement sensor guarantees a stable reflected signal acquisition for application in real industrial fields. Through a parametric study of the grating pitch of the transmissive grating panel, the signal-to-noise ratio, linearity, resolution, accuracy error, and sensitivity of the proposed sensor were investigated. The measured bidirectional movement demonstrated a peak to peak accuracy of 10.5 μm, high linearity of 0.9996, resolution of 3.1 μm at the full bandwidth, signal-to-noise ratio of 27.7, and high sensitivity of 31.8 μm/rad during a movement of 16 004.0 μm using the transmissive grating panel, which had a grating pitch of 200 μm. Even for an extended measurement range, the proposed scheme enables the same accuracy, linearity, and sensitivity to be maintained when compared with conventional laser displacement sensors and fiber optic displacement sensors.
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42.81.Pa Sensors, gyros
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

The design and analysis of beam-membrane structure sensors for micro-pressure measurement

Bian Tian, Yulong Zhao, Zhuangde Jiang, and Bin Hu

Rev. Sci. Instrum. 83, 045003 (2012); http://dx.doi.org/10.1063/1.3702809 (8 pages) | Cited 1 time

Online Publication Date: 18 April 2012

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This paper reports the design and analysis of a type of piezoresistive pressure sensor for micro-pressure measurement with a cross beam-membrane (CBM) structure. This new silicon substrate-based sensor has the advantages of a miniature structure and high sensitivity, linearity, and accuracy. By using the finite element method to analyze the stress distribution of the new structure and subsequently deducing the relationship between structural dimensions and mechanical performances, equations used to determine the CBM structure are established. Based on the CBM model and our stress and deflections equations, sensor fabrication is then performed on the silicon wafer via a process including anisotropy chemical etching and inductively coupled plasma. The structure's merits, such as linearity, sensitivity, and repeatability, have been investigated under the pressure of 5 kPa. Our results show that the precision of these equations is ±0.19%FS, indicating that this new small-sized structure offers easy preparation, high sensitivity, and high accuracy for micro-pressure measurement.
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06.30.-k Measurements common to several branches of physics and astronomy
02.70.Dh Finite-element and Galerkin methods
81.65.Cf Surface cleaning, etching, patterning
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

An ultrasonic stage for controlled spin of micro particles

Yujie Zhou, Huaqing Li, and Junhui Hu

Rev. Sci. Instrum. 83, 045004 (2012); http://dx.doi.org/10.1063/1.3701369 (5 pages) | Cited 1 time

Online Publication Date: 27 April 2012

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In this work, we proposed and developed an ultrasonic stage which can make different kinds of micro particles spin at its center. The stage consists of a circular copper plate and two piezoelectric half-rings bonded onto the bottom surface of the copper plate. The two piezoelectric half-rings have the same size and property, but opposite polarization in the thickness direction. They form a ring concentric with the copper plate. The spin direction of micro particles can be reversed by changing the operating frequency of stage. The spin speed can be controlled by operating frequency and voltage of the stage, and it reaches 955 rpm for a single glass ball with 0.51 mm diameter. The spin of micro particles is caused by travelling waves around the center of the stage, and the travelling waves are generated by anti-symmetric flexible vibration of the stage, excited by the two piezoelectric half-rings.
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43.38.-p Transduction; acoustical devices for the generation and reproduction of sound

In-situ comprehensive calibration of a tri-port nano-electro-mechanical device

E. Collin, M. Defoort, K. Lulla, T. Moutonet, J.-S. Heron, O. Bourgeois, Yu. M. Bunkov, and H. Godfrin

Rev. Sci. Instrum. 83, 045005 (2012); http://dx.doi.org/10.1063/1.4705992 (12 pages) | Cited 1 time

Online Publication Date: 30 April 2012

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We report on experiments performed in vacuum and at cryogenic temperatures on a tri-port nano-electro-mechanical (NEMS) device. One port is a very nonlinear capacitive actuation, while the two others implement the magnetomotive scheme with a linear input force port and a (quasi-linear) output velocity port. We present an experimental method enabling a full characterization of the nanomechanical device harmonic response: the nonlinear capacitance function C(x) is derived, and the normal parameters k and m (spring constant and mass) of the mode under study are measured through a careful definition of the motion (in meters) and of the applied forces (in Newtons). These results are obtained with a series of purely electric measurements performed without disconnecting/reconnecting the device, and rely only on known dc properties of the circuit, making use of a thermometric property of the oscillator itself: we use the Young modulus of the coating metal as a thermometer, and the resistivity for Joule heating. The setup requires only three connecting lines without any particular matching, enabling the preservation of a high impedance NEMS environment even at MHz frequencies. The experimental data are fit to a detailed electrical and thermal model of the NEMS device, demonstrating a complete understanding of its dynamics. These methods are quite general and can be adapted (as a whole, or in parts) to a large variety of electromechanical devices.
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07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
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