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Mar 2013

Volume 84, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 84, 033701 (2013); http://dx.doi.org/10.1063/1.4774387 (7 pages)

E. Nazaretski, Jungdae Kim, H. Yan, K. Lauer, D. Eom, D. Shu, J. Maser, Z. Pešić, U. Wagner, C. Rau, and Y. S. Chu

Computer aided design (CAD) model of the multilayer Laue lenses (MLL) based scanning fluorescence microscope. The inset shows schematic of the MLL setup used to perform scanning fluorescence experiments. The background represents thermal image of the horizontal MLL assembly.

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back to top Sensors and Actuators/MEMS/NEMS

A poly(dimethylsiloxane) based prism for surface plasmon resonance imaging system and its application for gas detection

L. L. Zhang, X. Chen, J. H. Sun, H. Y. Cai, H. Li, Y. P. Chao, and D. F. Cui

Rev. Sci. Instrum. 84, 035001 (2013); http://dx.doi.org/10.1063/1.4792602 (5 pages)

Online Publication Date: 1 March 2013

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This paper presents a surface plasmon resonance (SPR) imaging system based on a low-cost, convenient poly(dimethylsiloxane) (PDMS) prism featured with a close contact with the gold film. Compared to conventional glass prism, both numerical simulations and experimental studies indicated a deeper but wider absorption peak with a higher coupling angle for the PDMS based prism. System repeatability was quantified by the cycled detection of helium and air, with the effect of the flow rate investigated. Furthermore, five types of gases (nitrogen, air, oxygen, hydrogen, and helium) were detected and differentiated by the SPR system, with a calculated sensitivity of 5 × 10−6 RIU.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Bh Lenses, prisms and mirrors

Non-invasive timing of gas gun-launched projectiles using external surface-mounted optical fiber-Bragg grating strain gauges

Peter M. Goodwin, Bruce R. Marshall, Gerald D. Stevens, and Dana M. Dattelbaum

Rev. Sci. Instrum. 84, 035002 (2013); http://dx.doi.org/10.1063/1.4793489 (6 pages)

Online Publication Date: 4 March 2013

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Non-invasive detection methods for tracking gun-launched projectiles are important not only for assessment of gun performance but are also essential for timing a variety of diagnostics, for example, to investigate plate-impact events for shock compression experiments. Measurement of the time of passage of a projectile moving inside of the gun barrel can be achieved by detection of the transient hoop strain induced in the barrel of a light-gas gun by the passage of the projectile using external, barrel surface-mounted optical fiber-Bragg grating strain gauges. Optical fiber-Bragg gratings have been implemented and their response characterized on single-stage and two-stage light gas guns routinely used for dynamic experimentation at Los Alamos National Laboratory. Two approaches, using either broadband or narrowband illumination, were used to monitor changes in the Bragg wavelength of the fiber-Bragg gratings. The second approach, using narrowband laser illumination, offered the highest sensitivity. The feasibility of using these techniques to generate early, pre-event signals useful for triggering high-latency diagnostics was demonstrated.
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89.20.Dd Military technology and weapons systems; arms control
07.10.Pz Instruments for strain, force, and torque
42.79.Dj Gratings
42.81.Pa Sensors, gyros
45.40.Gj Ballistics (projectiles; rockets)

A crossflow filtration system for constant permeate flux membrane fouling characterization

Daniel J. Miller, Donald R. Paul, and Benny D. Freeman

Rev. Sci. Instrum. 84, 035003 (2013); http://dx.doi.org/10.1063/1.4794909 (11 pages)

Online Publication Date: 20 March 2013

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Membrane fouling is often characterized using a crossflow filtration apparatus. Typically, the transmembrane pressure (TMP) difference is fixed, and the flux is allowed to decline as the membrane fouls and the resistance to mass transfer increases. However, as flux varies, so too does the rate at which foulants are brought to the membrane surface, so the observed fouling behavior is not solely the result of membrane/foulant interactions. Constant flux experiments, where the permeate flux is fixed and the TMP difference varies, minimize such variations in the hydrodynamic conditions at the membrane surface, but constant TMP difference experiments dominate the fouling literature because they are more straightforward to execute than constant flux experiments. Additionally, most industrial water purification membrane installations operate at constant flux rather than at constant TMP. Here, we describe the construction and operation of a constant flux crossflow fouling apparatus. System measurement accuracy was validated by comparison of pure water permeance measurements to values specified by the membrane manufacturer, reported elsewhere, and measured by another technique. Fouling experiments were performed with two membrane/foulant systems: polysulfone ultrafiltration membranes with a soybean oil emulsion foulant and PVDF microfiltration membranes with a polystyrene latex bead suspension foulant. Automatic permeate flux control facilitated flux stepping experiments, which are commonly used to determine the threshold flux or critical flux of a membrane/foulant pair. Comparison of a flux stepping experiment with a literature report yielded good agreement.
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88.20.tk Chemicals
06.20.-f Metrology
89.20.Bb Industrial and technological research and development

Flux concentration and modulation based magnetoresistive sensor with integrated planar compensation coils

Wugang Tian, Jiafei Hu, Mengchun Pan, Dixiang Chen, and Jianqiang Zhao

Rev. Sci. Instrum. 84, 035004 (2013); http://dx.doi.org/10.1063/1.4796094 (6 pages)

Online Publication Date: 26 March 2013

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1/f noise is one of the main noise sources of magnetoresistive (MR) sensors, which can cause intrinsic detection limit at low frequency. To suppress this noise, the solution of flux concentration and vertical motion modulation (VMM) has been proposed. Magnetic hysteresis in MR sensors is another problem, which degrades their response linearity and detection ability. To reduce this impact, the method of pulse magnetization and magnetic compensation field with integrated planar coils has been introduced. A flux concentration and VMM based magnetoresistive prototype sensor with integrated planar coils was fabricated using microelectromechanical-system technology. The response linearity of the prototype sensors is improved from 0.8% to 0.12%. The noise level is reduced near to the thermal noise level, and the low-frequency detection ability of the prototype sensor is enhanced with a factor of more than 80.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.16.-c Methods of micro- and nanofabrication and processing
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
05.40.Ca Noise

An air flow sensor for neonatal mechanical ventilation applications based on a novel fiber-optic sensing technique

L. Battista, S. A. Sciuto, and A. Scorza

Rev. Sci. Instrum. 84, 035005 (2013); http://dx.doi.org/10.1063/1.4798298 (9 pages)

Online Publication Date: 29 March 2013

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In this work, a simple and low-cost air flow sensor, based on a novel fiber-optic sensing technique has been developed for monitoring air flows rates supplied by a neonatal ventilator to support infants in intensive care units. The device is based on a fiber optic sensing technique allowing (a) the immunity to light intensity variations independent by measurand and (b) the reduction of typical shortcomings affecting all biomedical fields (electromagnetic interference and patient electrical safety). The sensing principle is based on the measurement of transversal displacement of an emitting fiber-optic cantilever due to action of air flow acting on it; the fiber tip displacement is measured by means of a photodiode linear array, placed in front of the entrance face of the emitting optical fiber in order to detect its light intensity profile. As the measurement system is based on a detection of the illumination pattern, and not on an intensity modulation technique, it results less sensitive to light intensity fluctuation independent by measurand than intensity-based sensors. The considered technique is here adopted in order to develop two different configurations for an air flow sensor suitable for the measurement of air flow rates typically occurring during mechanical ventilation of newborns: a mono-directional and a bi-directional transducer have been proposed. A mathematical model for the air flow sensor is here proposed and a static calibration of two different arrangements has been performed: a measurement range up to 3.00 × 10−4 m3/s (18.0 l/min) for the mono-directional sensor and a measurement range of ±3.00 × 10−4 m3/s (±18.0 l/min) for the bi-directional sensor are experimentally evaluated, according to the air flow rates normally encountered during tidal breathing of infants with a mass lower than 10 kg. Experimental data of static calibration result in accordance with the proposed theoretical model: for the mono-directional configuration, the coefficient of determination r2 is equal to 0.997; for the bi-directional configuration, the coefficient of determination r2 is equal to 0.990 for positive flows (inspiration) and 0.988 for negative flows (expiration). Measurement uncertainty δQ of air flow rate has been evaluated by means of the propagation of distributions and the percentage error in the arrangement of bi-directional sensor ranges from a minimum of about 0.5% at −18.0 l/min to a maximum of about 9% at −12.0 l/min.
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87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.81.Pa Sensors, gyros
87.19.Wx Pneumodyamics, respiration

Compact prototype apparatus for reducing the circle of confusion down to 40 nm for x-ray nanotomography

Jungdae Kim, K. Lauer, H. Yan, Y. S. Chu, and E. Nazaretski

Rev. Sci. Instrum. 84, 035006 (2013); http://dx.doi.org/10.1063/1.4798546 (4 pages)

Online Publication Date: 29 March 2013

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We have constructed a compact prototype apparatus for active correction of circle of confusion during rotational motion. Our system combines fiber optic interferometry as a sensing element, the reference cylinder along with the nanopositioning system, and a robust correction algorithm. We demonstrate dynamic correction of run-out errors down to 40 nm; the resolution is limited by ambient environment and accuracy of correcting nanopositioners. Our approach provides a compact solution for in-vacuum scanning nanotomography x-ray experiments with a potential to reach sub-nm level of correction.
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07.85.Tt X-ray microscopes
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