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Date Oct. 30 2005-Nov. 3 2005

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Displaying Results 1 - 25 of 359
  • Foreword

    Page(s): 0_1
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  • Conference Committees

    Page(s): 0_2 - 0_7
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  • Sensors 2005: Highlights

    Page(s): 0_8 - 0_10
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  • Participants List

    Page(s): 0_11 - 1_58
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  • Table of contents

    Page(s): 1_59 - 1_89
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  • Author index

    Page(s): 1_90 - 1_116
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  • Nanostructured sensors

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (923 KB) |  | HTML iconHTML  

    We summarize prior development of nanostructured strain sensors formed by electrostatic self-assembly (ESA) processing. The sensors may be used to measure strains from 1 microstrain to more than 50% strain, over gauge lengths ranging from approximately 1 millimeter to tens of centimeters View full abstract»

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  • Whispering gallery mode biosensors using semiconductor quantum dots

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    We are constructing optically coupled biosensors from microspheres and semiconductor quantum dots (QDs). Detection will be accomplished through the resonance shift of whispering gallery modes (WGMs) in the microspheres as an analyte is adsorbed to the surface of the microsphere. The use of QDs in such a system allows us to remotely couple to the biosensors with an external optical system. Because the QDs have a high quantum yield and a broad absorption band, the biosensors may be excited with a low light flux well outside the spectral detection region. The resonant effect will permit sensitive detection due both to the WGM's narrow spectral linewidths as well as to multiple sampling as light circulates in the resonant cavity. Detection is local to the microsphere surface as changes in index are sampled via the WGM's evanescent field outside the microcavity. Since the microspheres are smaller than many cells, we anticipate that the system will be useful in both in vitro and in vivo environments View full abstract»

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  • Wireless soil moisture sensor based on fringing capacitance

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB) |  | HTML iconHTML  

    A soil moisture sensor was developed which was based on fringing capacitance and the increase in dielectric constant of a soil-water mixture with water content. The frequency shift of an RC oscillator connected to the capacitance sensor electrode was measured by a microcontroller. The data, in IEEE 1451 format, is communicated by a built-in RF transmitter (433MHz) to a receiver or base station for logging and display. This battery-operated sensor/transmitter is expected to have an operational life of several years View full abstract»

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  • A Wireless Pressure Measurement System Based on TiO2 Interdigitated Sensors

    Page(s): 12 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB) |  | HTML iconHTML  

    The ability to monitor pressure remotely is of particular importance in medical and environmental applications as it is less labour intensive, safer and offers peace of mind to the general public. To meet this demand, a prototype system using TiO2 thick film interdigitated capacitors has been developed. The circuit is based on the principle of capacitance-frequency-voltage conversion and has been designed to minimize power consumption. The sensor was tested under hydrostatic pressure ranging from 0-17 kPa and high sensitivity (DeltaV=47 mV) with low hysteresis (4 %) was recorded. It can be seen that this approach may provide cost effective, reliable devices for wireless sensing applications View full abstract»

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  • Wireless frequency-tuned generation and measurement of shear horizontal waves using magnetostrictive gratings in plates

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    The wave transduction method can be used in various nondestructive evaluation applications if shear horizontal (SH) waves are generated and measured successfully in plate structures. We consider using the principle of magnetostriction as an efficient means for generating and measuring SH waves, because the energy conversion between magnetic energy and acoustic energy in magnetostrictive material can take place wirelessly. A grating-type magnetostrictive transducer was considered because SH waves at desired frequencies can be tuned by changing grating size and distance. Experiments showed that grating width should be selected appropriately to avoid generating unwanted wave modes such as the Lamb wave modes. The experiments confirmed that the grating distance controls the center (or tuning) frequency of the grating transducer View full abstract»

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  • A wireless implantable passive strain sensor system

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    A design study of a novel passive strain-sensor technology for the in-situ measurement of small strains on implants, bones or fixation systems is presented. The sensing principle is based on hydro-mechanical strain amplification which allows for the abandonment of any electrical circuits. Thus, the sensor can be fabricated applying solely biocompatible or bioresorbable polymeric materials. Finite element simulations are employed to validate the basic sensing principle and to optimize design parameters according to the required target specifications. Remote wireless and passive signal read-out of the sensor signal can be achieved by advanced ultrasound imaging technologies View full abstract»

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  • Characterization and Application of Wireless Magnetostrictive Micro-Sensors

    Page(s): 24 - 27
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    Magnetostrictive materials have been investigated extensively for the application of physical, chemical and biological sensors recently. Higher precision and higher detection sensitivity requires microsensors or nanosensors to be used. In this research, the mass sensitivity and size effect of the free-standing magnetostrictive sensors is investigated down to the micro level both experimentally and theoretically. A highly efficient wireless signal query system is designed and employed. The procedure of the fabrication of micro-sized sensors is investigated to ensure optimum sensor surface for immobilization and excellent frequency signals. The damping effect in liquid is tested and the high Q factor promises potential application in chemical and biological areas. A numerical approach is also used for sensor modeling and related to experimental results View full abstract»

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  • Self-Powered Wireless Sensor by Collecting Electromagnetic Energy in Inhomogeneous Structure

    Page(s): 28 - 31
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    This paper presents a new scheme of self-powered sensor by collecting electromagnetic energy. A unidirectional transducer group and an inhomogeneous piezoelectric structure are created inside the transducer while propagating the unidirectionality required for low loss and receiving the convergent acoustic wave with higher power output. The acoustic waves may be converged by modifying the angle of the slope boundary and the wavelength of the incident wave. Almost all energy in a wave period is converged and gathered in a flash. Therefore the peak power output in receiving IDT may be much larger than that in input UDT. The electromagnetic energy collected from antenna can be gathered and accumulated ceaselessly, then burst in short time, thus the sensor can be deployed in longer distance than that of ordinary passive SAW sensors. Simulation and measurement demonstrate that the maximum sensing distance of the self-powered sensor is more than that of ordinary passive sensors View full abstract»

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  • Micro and nano fluidic chips for biosensors

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    Micro and nanofluidics provide very controlled delivery of reagents and samples for highly sensitive biosensors. Two fluidic platforms are introduced in this paper, the microfluidic droplet emulsion and the electrical field-based microfluidics. Traditional issues in microfluidics such as mixing in low Reynolds numbers can be mitigated using some of our active microfluidic techniques View full abstract»

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  • Micro analysis system with an integrated microfluidic system based on electrowetting

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    Electrowetting was used to fabricate an integrated highly efficient microfluidic transport system. As an option, a row of elongated gold working electrodes were used to generate a driving force to mobilize a solution in a flow channel. Flow velocity could be changed by changing the potential of the working electrode. The solutions could be transported to any desired direction without using any valves. In another option, a working electrode was formed in a hydrophilic flow channel and used as a valve. When the valve was switched on, a solution in the flow channel passed the area and went forward by capillary action. Furthermore, two solutions transported through two flow channels could be mixed based on the same principle. Integrated biosensing systems could easily be constructed using these microfluidic components. In this study, the concentration of L-amino acids was determined by generating electrochemical luminescence (ECL) on an integrated platinum working electrode. Also, the activity of protease could be determined using an integrated potentiometric pH-sensing system View full abstract»

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  • A novel immunosensing technique based on the thermal properties of biochemicals

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    A new and independent method to investigate biological reactions and their products based upon the accurate and real-time measurement of the thermal conductivity of the reacting samples is presented. A micromachined thermopile based thermal sensor integrated with a planar heater and microfluidic channel has been fabricated for these measurements. The device was calibrated by measuring the thermal conductivity of standard fluids such as DI water and isopropyl alcohol. The calibrated device was then used to measure the thermal properties of biological molecules such as glucose, urea, Bovine Serum Albumin (BSA), Human Fibrinogen (HF), their antibodies, and the bound product. To the best of our knowledge, this is the first report of the observation of the real-time monitoring of antibody-antigen binding based on the change in the thermal properties of the reacting fluids View full abstract»

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  • Two-terminal longitudinal hotwire sensor for in-line monitoring of sub-nanoliter volume in microfluidic channels

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    We report a simple and practical sensor for monitoring both the absolute position and advancing speed of liquid front in a microfluidic channel. The sensor consists of a longitudinal hot wire element - a two-terminal electrical device, with its length spanning the entire channel. The design, materials, fabrication method, and use of this sensor are extremely simple. Characterization results are presented View full abstract»

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  • Microfluidic chips for viral RNA extraction & detection

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    Sensing biomolecules at minute quantities demands laborious and skill-laden laboratory protocols for sample preparation and amplification in order to improve signal-to-noise ratio. Nucleic-acid-based detection of viral particles in whole blood requires separation of viral particles from blood cells followed by extraction, amplification, and detection of viral nucleic acids. Here, three microfluidic chips have been independently shown to be capable of performing each critical step. Separation of viral particles involves a flow-through, shear-type microfilter chip that can handle large volume of blood. The remaining chips, although developed for genomic DNA, have been adopted for extraction and amplification of viral RNA. In the extraction chip, protein coatings around viral particles are chemically broken to liberate viral RNA which can reversibly bind to the chip surface under high-salt conditions. Viral RNA can be eluted out with a low-salt buffer after removal of unwanted debris. In the amplification chip, viral RNA is first transcribed into cDNA and then multiplied exponentially in copies by a continuous, isothermal, enzyme-based technique known as Nucleic Acid Sequence-Based Amplification (NASBA). The amplicons are detected on the same chip using DNA probes conjugated with horse radish peroxide (HRP) for colorimetry View full abstract»

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  • A novel angular joint-sensor using a fluxgate magnetometer

    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    We present a new angular joint-sensor by using a microfabricated fluxgate magnetometer. Fluxgates are normally used for geodetic measurements, navigation of satellites or as an electronic compass. For use as an angular joint-sensor the rotation of a permanent magnet, which transmits the rotation of the joint axis, can be detected by the fluxgate. The measuring range is 180deg. The basic configuration of the fluxgate consists of a helical excitation coil with a soft magnetic toroidal core and a sensing coil wound around the whole body of the core. The integration of the sensor into the joint requires application of miniaturization techniques. The fluxgate is fabricated either monolithically or by mounting the soft magnetic core, for which a new mounting method without gluing is presented. For the optimization of the measured magnetic field self fabricated polymer magnets are used. The sensor works contactless and the output signal is proportional to the angle position of the joint View full abstract»

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  • Coupling nonlinear sensors for enhanced sensitivity: a prototype using the 3 coupled-core fluxgate magnetometer

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    Recently, we have shown the emergence of oscillations in overdamped undriven nonlinear dynamic systems subject to carefully crafted coupling schemes and operating conditions [In, 2003], [Bulsara, 2004]. Here, we present results obtained from a system of N equiv 3 coupled-core fluxgate magnetometer system; the oscillatory behavior is triggered when the coupling constant exceeds a threshold value (bifurcation point), and the oscillation frequency exhibits a characteristic scaling behavior with the "separation" of the coupling constant from its threshold value, as well as with an external target dc magnetic flux signal. The oscillations, which can be induced at frequencies ranging from a few Hz to high-kHz, afford a novel new detection scheme for target signals; in addition, the coupled-core system offers the possibility of significantly enhanced responsivity over its single fluxgate counterpart View full abstract»

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  • New Field Sensors Based on Combined Fluxgate- Hall Effect Magneto-Transport Arrangement

    Page(s): 61 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    A novel 2D magnetic field sensor is presented that is based on a combined Fluxgate/Hall-Effect arrangement. The proposed device involves a thin, isotropic, circular magnetic core, the magnetization of which is driven to saturation, by means of a rotating excitation-field produced by four printed planar coils. That way, the core magnetization rotates, without Barkhausen jumps inducing two orthogonal harmonic flux-density signals that are sensed respectively by two pairs of Hall devices positioned at the edge of the core. The presented sensor incorporates discrete Hall devices and electronic circuitry, as well as a 200 mm diameter amorphous core, packaged on a PCB board. However, the system can easily be implemented on a single silicon-chip, by means of standard CMOS technologies. In this case, the amorphous core is attached onto the chip that contains the Hall devices, planar coils, and electronic circuitry, according to a state-of-art low-temperature post-process View full abstract»

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  • Low-cost epoxy packaging of CMOS Hall-effect compasses

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    For the first time, a compass using CMOS Hall-sensors in a low-cost epoxy package is presented. Due to the high mechanical stress sensitivity of CMOS Hall-sensors, such low-cost plastic or epoxy mold packages have not been a viable option for low-offset applications like the compass application. Instead, expensive ceramic packages have been used. A recently developed, stress insensitive, CMOS Hall-sensor, shows only a 1.65muT offset shift after epoxy molding, while maintaining its low 3muT (3a) offset spread. After repeated thermal shock, the Hall sensor's offset returns almost completely to its original value. For the compass application, the two horizontal plane components of the earth's magnetic field have to be measured. So a package with two orthogonally aligned Hall-sensors was developed View full abstract»

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  • Orthogonal fluxgate effect in electroplated wires

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    Orthogonal fluxgate sensor was built using copper wire covered by electroplated permalloy. This type of sensor core has significant advantage over the sensors based on amorphous wires: it has no magnetic material in the central part, where the excitation field is low. 11 muV/nT sensitivity and less than 1 muT perming error were achieved for the first sensor prototype. The used core geometry also allows to measure both longitudinal and circumferencial hysteresis curves, which is important for further development View full abstract»

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  • Microfabricated atomic magnetometers

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    Using the techniques of microelectromechanical systems, we are developing chip-scale atomic sensors based on laser excitation of alkali atoms. Recently, we demonstrated a magnetometer physics package based on coherent population trapping that had a sensitivity of 50 pT/Hzfrac12 at 10 Hz, had a volume of 12 mm3, and used 195 mW of power as presented by Schwindt et al. (2004). To improve the sensitivity and reduce the power consumption of the magnetometer, we are evaluating other methods of interrogating the atoms for use in microfabricated devices. One of these methods uses frequency modulated nonlinear magneto-optical rotation (FM NMOR). We demonstrate that an FM NMOR magnetometer can be made to self-oscillate, offering simple construction and low power consumption View full abstract»

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