Showing papers in "IEEE Sensors Journal in 2008"
TL;DR: This paper reviews the state-of-the-art in force and tactile sensing technologies applied in minimally invasive surgery and discusses several sensing strategies including displacement-based, current- based, pressure-Based, resistive-based , capacitive-based), piezoelectric-based.
Abstract: Haptic perception plays a very important role in surgery. It enables the surgeon to feel organic tissue hardness, measure tissue properties, evaluate anatomical structures, and allows him/her to commit appropriate force control actions for safe tissue manipulation. However, in minimally invasive surgery, the surgeon's ability of perceiving valuable haptic information through surgical instruments is severely impaired. Performing the surgery without such sensory information could lead to increase of tissue trauma and vital organic tissue damage. In order to restore the surgeon's perceptual capability, methods of force and tactile sensing have been applied with attempts to develop instruments that can be used to detect tissue contact forces and generate haptic feedback to the surgeon. This paper reviews the state-of-the-art in force and tactile sensing technologies applied in minimally invasive surgery. Several sensing strategies including displacement-based, current-based, pressure-based, resistive-based, capacitive-based, piezoelectric-based, vibration-based, and optical-based sensing are discussed.
525 citations
TL;DR: In this article, an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations, is presented. But the proposed generator cannot generate enough energy for proper operation.
Abstract: This paper presents an electromagnetic (EM) vibration-to-electrical power generator for wireless sensors, which can scavenge energy from low-frequency external vibrations. For most wireless applications, the ambient vibration is generally at very low frequencies (1-100 Hz), and traditional scavenging techniques cannot generate enough energy for proper operation. The reported generator up-converts low-frequency environmental vibrations to a higher frequency through a mechanical frequency up-converter using a magnet, and hence provides more efficient energy conversion at low frequencies. Power is generated by means of EM induction using a magnet and coils on top of resonating cantilever beams. The proposed approach has been demonstrated using a macroscale version, which provides 170 nW maximum power and 6 mV maximum voltage. For the microelectromechanical systems (MEMS) version, the expected maximum power and maximum voltage from a single cantilever is 3.97 muW and 76 mV, respectively, in vacuum. Power level can be increased further by using series-connected cantilevers without increasing the overall generator area, which is 4 mm2. This system provides more than an order of magnitude better energy conversion for 10-100 Hz ambient vibration range, compared to a conventional large mass/coil system.
355 citations
TL;DR: A review of acoustic and ultrasonic optical fiber sensors (OFSs) is given in this article, which covers optical fiber sensing methods for detecting dynamic strain signals, including general sound and acoustic signals, high-frequency signals, and other signals such as acoustic emissions, and impact induced dynamic strain.
Abstract: This paper gives a review of acoustic and ultrasonic optical fiber sensors (OFSs). The review covers optical fiber sensing methods for detecting dynamic strain signals, including general sound and acoustic signals, high-frequency signals, i.e., ultrasonic/ultrasound, and other signals such as acoustic emissions, and impact induced dynamic strain. Several optical fiber sensing methods are included, in an attempted to summarize the majority of optical fiber sensing methods used to date. The OFS include single fiber sensors and optical fiber devices, fiber-optic interferometers, and fiber Bragg gratings (FBGs). The single fiber and fiber device sensors include optical fiber couplers, microbend sensors, refraction-based sensors, and other extrinsic intensity sensors. The optical fiber interferometers include Michelson, Mach-Zehnder, Fabry-Perot, Sagnac interferometers, as well as polarization and model interference. The specific applications addressed in this review include optical fiber hydrophones, biomedical sensors, and sensors for nondestructive evaluation and structural health monitoring. Future directions are outlined and proposed for acousto-ultrasonic OFS.
309 citations
TL;DR: In this article, the primary automotive sensor technologies used today and their related system applications are described for sensors that measure speed/timing, mass air flow, and occupant safety/security.
Abstract: This paper focuses on the primary automotive sensor technologies used today and their related system applications. This paper describes new automotive sensors that measure position, pressure, torque, exhaust temperature, angular rate, engine oil quality, flexible fuel composition, long-range distance, short-range distance, and ambient gas concentrations. In addition, new features are described for sensors that measure linear acceleration, exhaust oxygen, comfort/convenience factors, and night vision. New automotive system applications are described for sensors that measure speed/timing, mass air flow, and occupant safety/security.
243 citations
TL;DR: Three sensors embedded into medical textiles for the monitoring of respiratory movements in a magnetic resonance imaging environment can successfully sense textile elongations between 0% and 3%, while maintaining the stretching properties of the textile substrates for a good comfort of the patients.
Abstract: The potential impact of optical fiber sensors embedded into medical textiles for the monitoring of respiratory movements in a magnetic resonance imaging environment is presented. We report on three different designs, all textile based: a macrobending sensor, a Bragg grating sensor, and a time reflectometry sensor. In all three cases, the sensing principle is based on the measure of the elongation of the abdominal circumference during breathing movements. We demonstrate that the three sensors can successfully sense textile elongations between 0% and 3%, while maintaining the stretching properties of the textile substrates for a good comfort of the patients.
216 citations
TL;DR: An Environmental Air Pollution Monitoring System (EAPMS) for monitoring the concentrations of major air pollutant gases has been developed, complying with the IEEE 1451.2 standard as mentioned in this paper.
Abstract: An Environmental Air Pollution Monitoring System (EAPMS) for monitoring the concentrations of major air pollutant gases has been developed, complying with the IEEE 1451.2 standard. This system measures concentrations of gases such as CO, NO2, SO2, and O3 using semiconductor sensors. The smart transducer interface module (STIM) was implemented using the analog devices' ADuC812 microconverter. Network Capable Application Processor (NCAP) was developed using a personal computer and connected to the STIM via the transducer independent interface. Three gas sensors were calibrated using the standard calibration methods. Gas concentration levels and information regarding the STIM can be seen on the graphical user interface of the NCAP. Further, the EAPMS is capable of warning when the pollutant levels exceed predetermined maxima and the system can be developed into a low cost version for developing countries.
211 citations
TL;DR: In this paper, the authors describe the characteristics and performance of a distributed feedback (DFB) fiber laser strain sensor and discuss the technological developments necessary to obtain comparable performance from a multiplexed array of laser sensors.
Abstract: The distributed feedback (DFB) fiber laser strain sensor has demonstrated strain resolution comparable to that obtained from high-performance fiber-optic interferometry. This manuscript describes the characteristics and performance of this fiber laser strain sensor and discusses the technological developments necessary to obtain comparable performance from a multiplexed array of laser sensors. The design of the Bragg grating and doped fiber are discussed, where possible providing simplified equations to quantify the relevant design parameters. Techniques based on fiber-optic interferometry to decode the wavelength shifts of the laser are presented and potential noise sources are described. Measurements conducted on a test laser demonstrate the capability of the DFB fiber laser to resolve effective length changes to less than 0.76 fm/Hz1/2 at 2 kHz. The accuracy of the strain measurement, calculated by subtracting the output of two lasers subjected to the same strain, is found to be less than 1%. Issues relating to multiplexing lasers, such as pump power depletion and optical feedback, are described along with methods to maximize the number of lasers serially multiplexed on a single fiber. Finally, the strain transduction mechanism and methods to mount the laser sensor are described. It is shown that for certain applications, the DFB fiber laser sensor provides significant performance benefits when compared with remotely interrogated fiber-optic interferometric sensing techniques.
182 citations
TL;DR: A WSN-based intelligent light control system for indoor environments that considers two requirement models, namely, binary satisfaction and continuous satisfaction models, and proposes two decision algorithms to determine the proper illuminations of devices and to achieve the desired optimization goals.
Abstract: Recently, wireless sensor networks (WSNs) have been widely discussed in many applications. In this paper, we propose a WSN-based intelligent light control system for indoor environments. Wireless sensors are responsible for measuring current illuminations. Two kinds of lighting devices, namely, whole lighting and local lighting devices, are used to provide background and concentrated illuminations, respectively. Users may have various illumination requirements according to their activities and profiles. An illumination requirement is as the combination of background and concentrated illumination demands and users' locations. We consider two requirement models, namely, binary satisfaction and continuous satisfaction models, and propose two decision algorithms to determine the proper illuminations of devices and to achieve the desired optimization goals. Then, a closed-loop device control algorithm is applied to adjust the illumination levels of lighting devices. The prototyping results verify that our ideas are practical and feasible.
179 citations
TL;DR: This paper presents an integrated optical sensor based upon the heterogeneous integration of an InGaAs-based thin-film photodetector with a digital microfluidic system, the first step toward the heterogeneity integration of entire planar optical sensing systems on this platform.
Abstract: The advent of digital microfluidic lab-on-a-chip (LoC) technology offers a platform for developing diagnostic applications with the advantages of portability, increased automation, low-power consumption, compatibility with mass manufacturing, and high throughput. However, most digital microfluidic platforms incorporate limited optical capabilities (e.g., optical transmission) for integrated sensing, because more complex optical functions are difficult to integrate into the digital microfluidic platform. This follows since the sensor must be compatible with the hydrophobic surfaces on which electrowetting liquid transport occurs. With the emergence of heterogeneous photonic component integration technologies such as those described herein, the opportunity for integrating advanced photonic components has expanded considerably. Many diagnostic applications could benefit from the integration of more advanced miniaturized optical sensing technologies, such as index of refraction sensors (surface plasmon resonance sensors, microresonator sensors, etc.). The advent of these heterogeneous integration technologies, that enable the integration of thin-film semiconductor devices onto arbitrary host substrates, enables more complex optical functions, and in particular, planar optical systems, to be integrated into microfluidic systems. This paper presents an integrated optical sensor based upon the heterogeneous integration of an InGaAs-based thin-film photodetector with a digital microfluidic system. This demonstration of the heterogeneous integration and operation of an active optical thin-film device with a digital microfluidic system is the first step toward the heterogeneous integration of entire planar optical sensing systems on this platform.
156 citations
TL;DR: In this paper, a wireless, passive embedded sensor was applied for real-time monitoring of water content in civil engineering materials such as sands, subgrade soils, and concrete materials, which can be used for long-term monitoring of localized water content inside soils and sands to understand the environmental health in these media.
Abstract: A wireless, passive embedded sensor was applied for real-time monitoring of water content in civil engineering materials such as sands, subgrade soils, and concrete materials. The sensor, which comprised of a planar inductor-capacitor (LC) circuit, was embedded in test samples so that the internal water content of the samples could be remotely measured with a loop antenna by tracking the changes in the sensor's resonant frequency. Since the dielectric constant of water was much higher compared with that of the test samples, the presence of water in the samples increased the capacitance of the LC circuit (capacitance of the capacitor was proportional to the dielectric constant of the medium between its electrodes), thus decreasing the sensor's resonant frequency. Using the described sensor, a study was conducted to investigate the drying rate of sand samples of different grain sizes. A study was also conducted to measure the curing rate of a portland cement concrete slab during casting, and its drying rate after it has been soaked in water. The described sensor technology can be applied for long-term monitoring of localized water content inside soils and sands to understand the environmental health in these media. In addition, this sensor will be useful for monitoring water content within concrete supports and road pavements. The measurement of water content is important for civil engineering infrastructure since excess water may hasten their degradation.
144 citations
TL;DR: In this article, a prototype of a multifunctional tactile sensor using ionic polymer metal composites (IPMCs) is proposed, designed, and tested, which can detect the presence of a material in contact with it and to measure its stiffness.
Abstract: In this paper, a first prototype of a multifunctional tactile sensor using ionic polymer metal composites (IPMCs) is proposed, designed, and tested. Two IPMC strips are used, one as an actuator and one as a sensor, both positioned in a cantilever configuration; working together they enable the system to detect the presence of a material in contact with it and to measure its stiffness. These sensing capabilities can be exploited in various biomedical applications, such as catheterism, laparoscopy and the surgical resection of tumors. Moreover, the simple structure of the proposed tactile sensor can easily be extended to devices in which a sensing tip for exploration of the surrounding environment is required. Compared with other similar tools, the one proposed works with a very low-power supply (the order of magnitude being a few volts), it needs very simple electronics, it is very lightweight and has a low cost.
TL;DR: In this paper, a monolithically integrated CMOS-MEMS three-axis capacitive accelerometer with a single proof mass was developed, which provided robust single-crystal silicon (SCS) structures in all three axes and greatly reduced undercut of comb fingers.
Abstract: This paper reports a monolithically integrated CMOS-MEMS three-axis capacitive accelerometer with a single proof mass. An improved DRIE post-CMOS MEMS process has been developed, which provides robust single-crystal silicon (SCS) structures in all three axes and greatly reduces undercut of comb fingers. The sensing electrodes are also composed of the thick SCS layer, resulting in high resolution and large sensing capacitance. Due to the high wiring flexibility provided by the fabrication process, fully differential capacitive sensing and common-centroid configurations are realized in all three axes. A low-noise, low- power dual-chopper amplifier is designed for each axis, which consumes only 1 mW power. With 44.5 dB on-chip amplification, the measured sensitivities of x-, y-, and z-axis accelerometers are 520 mV/g, 460 mV/g, and 320 mV/g, respectively, which can be tuned by simply changing the amplitude of the modulation signal. Accordingly, the overall noise floors of the x-, y-, and z-axis are 12 mug/radicHz , 14 mug/radicHz, and 110 mug/radicHz, respectively, when tested at around 200 Hz.
TL;DR: The basic operating principles of various implantable sensors are reviewed and categorized into groups to delineate their differences and key design questions are proposed for future progress.
Abstract: Continuous measurement of intraocular pressure is important in the detection and treatment of glaucoma. While a point check of intraocular pressure in a doctor's office using indirect measurements such as the tonometer is helpful, it is inadequate to track circadian variation. Circadian variation is an independent risk factor in addition to elevated pressure levels. This paper is aimed at providing an up-to-date review of various intraocular pressure sensing techniques and in vivo sensor design approaches. The basic operating principles of various implantable sensors are reviewed and categorized into groups to delineate their differences. A discussion is presented identifying the drawbacks of existing designs and key design questions are proposed for future progress.
TL;DR: Capacitive humidity sensors were fabricated using countersunk interdigitated electrodes coated with amorphous nanostructured TiO2, SiO2 and Al2O3 thin films grown by glancing angle deposition.
Abstract: Capacitive humidity sensors were fabricated using countersunk interdigitated electrodes coated with amorphous nanostructured TiO2, SiO2, and Al2O3 thin films grown by glancing angle deposition. The capacitive response and response times for each sensor were measured. The sensor utilizing TiO2 exhibited the largest change in capacitance, increasing exponentially from ~ 1 nF to ~ 1muF for an increase in relative humidity from 2% to 92%. Adsorption and desorption response times were measured using flow rates of 2.5 l/min and were between 90 ms and 300 ms for the sensors studied here. A simple model of the capacitive response of the devices has been developed and used to calculate the dielectric constant of the combined system of our films and adsorbed water. The obtained dielectric constants are found to be much higher than bulk or literature values for similar systems.
TL;DR: A biocompatible neural microprobe constructed using well-established SU-8 microfabrication techniques is described that was designed to record fiber spike signals from regenerated axons within peripheral nerves, without any signs of tissue damage or inflammatory reaction.
Abstract: A biocompatible neural microprobe constructed using well-established SU-8 microfabrication techniques is described that was designed to record fiber spike signals from regenerated axons within peripheral nerves. These microprobes features bipolar longitudinal gold electrodes recessed below the surface within ldquogroovesrdquo designed to guide the growth of regenerating axons along the length of the grooves and limit the number of fibers that come in contact with the longitudinal electrodes. In addition, screening microprobe toxicity using cultures of human skin fibroblasts, the biocompatibility of these SU-8 microprobes for neural interface applications, in particular, was specifically verified using primary cultures of two sensitive cell types found in peripheral nerves: purified Schwann cells and explanted dorsal root ganglion (DRG) neurons and their fibers. The SU-8 microprobes were surgically implanted into transected rat Sciatic nerves within a unique peripheral nerve regeneration tube. Long-term fiber spike signals were recorded with these SU-8 microprobes in 13 chronically implanted rats for periods from 4 to 51 weeks without any signs of tissue damage or inflammatory reaction.
TL;DR: In this paper, a wide range of methods and materials used for in vivo measurement of pH levels, such as using the optical fibers, pH-sensitive polymers, ion-sensitive field effect transistors, near infrared spectroscopy, nuclear magnetic resonance, and fluorescent pH indicators.
Abstract: Advances in semiconductor sensor technology, medical diagnostics, and health care needs a rapid boost in research into novel miniaturized pH sensors, which can be used in vivo for continuous patient monitoring. Requirements for the in vivo sensor are materials biocompatibility, high measurement precision, a response time of an order of less than seconds, and the possibility of continuous 24-h monitoring. Monitoring of the pH values is important in the study of tissue metabolism, in neurophysiology, cancer diagnostics, and so forth. Muscle pH can be used to triage and help treat trauma victims as well as to indicate poor peripheral blood flow in diabetic patients. Clearly, to avoid infection and spread of diseases, all in vivo monitoring devices should be single-use/disposable, which puts strict requirement on their price. This paper reviews the wide range of methods and materials used for in vivo measurement of pH levels, such as using the optical fibers, pH-sensitive polymers, ion-sensitive field effect transistors, near infrared spectroscopy, nuclear magnetic resonance, and fluorescent pH indicators.
TL;DR: In this paper, a magnetically controlled wireless sensor device is proposed for minimally invasive intraocular oxygen concentration measurements, which works based on quenching of luminescence in the presence of oxygen.
Abstract: The influence of oxygen on various ophthalmological complications is not completely understood and intraocular oxygen measurements are essential for better diagnosis and treatment. A magnetically controlled wireless sensor device is proposed for minimally invasive intraocular oxygen concentration measurements. This device will make it possible to make measurements at locations that are currently too invasive for human intervention by integrating a luminescence optical sensor and a magnetic steering system. The sensor works based on quenching of luminescence in the presence of oxygen. A novel iridium phosphorescent complex is designed and synthesized for this system. A frequency-domain lifetime measurement approach is employed because of the intrinsic nature of the lifetime of luminescence. Experimental results of the oxygen sensor together with magnetic and hydrodynamic characterization of the sensor platform are presented to demonstrate the concept. In order to use this sensor for in vivo intraocular applications, the size of the sensor must be reduced, which will require an improved signal-to-noise ratio.
TL;DR: In this paper, a periodic array of apertures with subwavelength dimensions and submicron periodicity was fabricated on gold-coated tips of silica optical fibers using focused ion beam (FIB) milling.
Abstract: Periodic arrays of apertures with subwavelength dimensions and submicron periodicity were fabricated on gold-coated tips of silica optical fibers using focused ion beam (FIB) milling. Interaction of light with subwavelength structures such as an array of nanoapertures in an optically thick metallic film leads to the excitation of surface plasmon waves at the interfaces of the metallic film and the surrounding media, thereby leading to a significant enhancement of light at certain wavelengths. The spectral position and magnitude of the peaks in the transmission spectra depend on the refractive index of the media surrounding metallic film containing the nanohole array. This lays the foundation for the development of fiber-optic chemical and biological sensors that sense the change in refractive index of the medium around the metallic film. This is demonstrated by testing the sensors with solutions of alcohols with different refractive indices and by the attachment of biomolecules to the sensor surface. The bulk refractive index sensitivity of these nanoaperture array-based sensors is shown to be higher than what has been typically reported for metallic nanoparticle-based plasmonic sensors.
TL;DR: In this paper, a model for predicting photonic crystal label-free biosensor performance based primarily on the spatial distribution of electromagnetic near fields at device resonance is presented, and the effect of each property on the resonant mode profile, and consequently on sensor performance, is illustrated.
Abstract: We present a model for predicting photonic crystal label-free biosensor performance based primarily on the spatial distribution of electromagnetic near fields at device resonance. To achieve maximum device sensitivity, the resonant fields can be shaped by careful choice of material and geometrical parameters. The effect of each property on the resonant mode profile, and consequently on sensor performance, is illustrated. A comparison of device sensitivity calculated by both the proposed model and direct rigorous coupled wave analysis simulation supports the validity of our model.
TL;DR: In this article, a two-dimensional accelerometer based on a simple fiber cantilever constructed from a short length of multicore optical fiber is demonstrated up to 3 kHz, and differential measurement between fiber Bragg gratings written in the multicore fiber provides temperature-insensitive measurements.
Abstract: We report a compact two-dimensional accelerometer based upon a simple fiber cantilever constructed from a short length of multicore optical fiber. Two-axis measurement is demonstrated up to 3 kHz. Differential measurement between fiber Bragg gratings written in the multicore fiber provides temperature-insensitive measurements.
TL;DR: In this paper, a review of transport phenomena in nanofluidics with a focus on several systems and applications important to problems of public health and welfare is presented, focusing on the role of the electric double layer and the molecular-scale interactions that occur within confined nanoscale systems.
Abstract: Nanofluidics presents growing and exciting opportunities for conducting fundamental studies for processes and systems that govern molecular-scale operations in science and engineering. In addition, nanofluidics provides a rapidly growing platform for developing new systems and technologies for an ever-growing list of applications. This review presents a summary of the transport phenomena in nanofluidics with a focus on several systems and applications important to problems of public health and welfare. Special emphasis is afforded to the role of the electric double layer and the molecular-scale interactions that occur within confined nanoscale systems.
TL;DR: In this article, a new optical fiber humidity sensor based on superhydrophilic coating is proposed, which has demonstrated a good linearity in the range from 40% to 98% of relative humidity (RH).
Abstract: In this paper, a new optical fiber humidity sensor based on superhydrophilic coating is proposed. The electrostatic self-assembly technique has been used to create a nanometric scale surface on the tip of a standard single-mode pigtail. The fabricated sensor has demonstrated a good linearity in the range from 40% to 98% of relative humidity (RH). A variation of 10 dB in reflected optical power is achieved with a response time of only 150 ms. Among other applications, this sensor is intended to be used for monitoring the human breathing, so high dynamic performances are required, specially in the higher RH ranges.
TL;DR: This paper describes research work currently being undertaken to detect, model, and track the shape of a contaminant cloud boundary using air borne sensor swarms using a splinegon.
Abstract: In this paper, we describe research work currently being undertaken to detect, model, and track the shape of a contaminant cloud boundary using air borne sensor swarms. A model of the contaminant cloud boundary is first developed using a splinegon, defined by a set of vertices linked by segments of constant curvature. This model is then used in an estimator to predict the evolution of the contaminant cloud. This approach is efficient in that only the vertices and segment curvatures are required to define the cloud boundary, rather than using a distribution function to represent the dispersion density.
TL;DR: In this paper, the spectral shift of the intrinsic Rayleigh backscatter signal along the optical fiber was measured and converted to temperature using swept wavelength interferometry for distributed fiber-optic temperature measurements in a nuclear reactor.
Abstract: We present the use of swept wavelength interferometry for distributed fiber-optic temperature measurements in a nuclear reactor. The sensors consisted of 2-m segments of commercially available, single mode optical fibers. The interrogation technique is based on measuring the spectral shift of the intrinsic Rayleigh backscatter signal along the optical fiber and converting the spectral shift to temperature.
TL;DR: In this paper, a transmission-based surface plasmon resonance (SPR) sensor for label-free detection of protein-carbohydrate and protein-protein binding proximate to a perforated gold surface is demonstrated.
Abstract: A transmission-based surface plasmon resonance (SPR) sensor for label-free detection of protein-carbohydrate and protein-protein binding proximate to a perforated gold surface is demonstrated. An SPR instrument makes real-time measurements of the resonant wavelength and/or the resonant angle of incidence of transmitted light; both are influenced by the presence of proteins at the gold surface-liquid interface. Ethylene glycol solutions with known refractive indexes were used to calibrate the instrument. A paired polarization-sensitive detector achieved an overall detection resolution of ~ 6.6 times 10-5 refractive index units (RIU). Proof of principle experiments was performed with concanavalin A (Con A) binding to gold-adsorbed ovomucoid and anti-bovine serum albumin (BSA) binding to gold-adsorbed BSA.
TL;DR: In this paper, a long period grating (LPG) coated with polyvinyl alcohol has been developed and evaluated through exposure to a range of relative humidity (RH) levels (from 33%RH to 97%RH).
Abstract: A long period grating (LPG) coated with polyvinyl alcohol has been developed and evaluated through exposure to a range of relative humidity (RH) levels (from 33%RH to 97%RH). The conditions for the creation of the sensor probes are described and the response of the device in terms of changes in the resonance loss of several of the spectral loss bands has been monitored. In order to make comparative measurements, a noncoated LPG was exposed to various known refractive index (RI) conditions and the grating response was monitored, analyzed and the results evaluated. This is then related to the change in RH when the sensor is exposed to various RH levels, as the coating RI changes, leading to the change in resonance loss. The PVA coated LPG sensor is showing a relatively fast response time of ~ 80 s to reach 97%RH from 33%RH and inducing ~ 2 dB change in transmission of resonance loss band.
TL;DR: In this paper, a fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated, which is a segment of twin core fiber acting as cylinder cantilever beam.
Abstract: A novel fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated. The sensor only is a segment of twin-core fiber acting as cylinder cantilever beam. The force exerted on the cylinder by the slow flow speeds of order mm/s of the fluid with unknown velocity bends the fiber, which corresponds to the shift of the phase of the twin-core in-fiber integrated Michelson interferometer.
TL;DR: It is demonstrated that ultrasonic waves generated by surface acoustic wave (SAW) devices remove nonspecifically bound proteins from the sensing and nonsensing regions of the microarrays using 128 YX lithium niobate, chosen for its high coupling coefficient and efficient power transfer to mechanical motion.
Abstract: Nonspecific binding of proteins is an ongoing problem that dramatically reduces the sensitivity and selectivity of biosensors. We demonstrate that ultrasonic waves generated by surface acoustic wave (SAW) devices remove nonspecifically bound proteins from the sensing and nonsensing regions of the microarrays. We demonstrate our approach for controllably and nondestructively cleaning the microarray interface. In this work, SAWs were generated using 128 YX lithium niobate, chosen for its high coupling coefficient and efficient power transfer to mechanical motion. These waves propagating along the surface were coupled into specifically bound and nonspecifically bound proteins on a patterned surface of 40 mum feature size. Fluorescence intensity was used to quantify cleaning efficacy of the microarrays. Our results have shown that excess protein layers and aggregates are removed leaving highly uniform films as evidenced by fluorescence intensity profiles. Selected antigen-receptor interactions remained bound during the acoustic cleaning process when subjected to 11.25 mW of power and retained their efficacy for subsequent antigen capture. Results demonstrate near-complete fluorescence signal recovery for both the sensing and nonsensing regions of the microarrays. Of significance is that our approach can be integrated into existing array technologies where sensing and nonsensing regions are extensively fouled. We believe that this technology will be pivotal in the development and advancement of microsensors and their biological applications.
TL;DR: In this paper, a template-free chemical route was used to synthesize polypyrrole nanofibers for hydrogen gas sensing at room temperature, and the results showed that the resulting polypolymorphic mat is comparable to bulk polypoly(poly(n) poly(n), and the sensor performance was tested through programmable exposure towards different concentrations of hydrogen gas diluted in synthetic air in an environmental cell.
Abstract: Polypyrrole nanofibers are synthesized through a template-free chemical route and used as the active component for hydrogen gas sensing at room temperature. The synthesis of polypyrrole nanofibers was achieved by using bipyrrole as an initiator to speed up the polymerization of pyrrole with FeCl as the oxidizing agent. Scanning and transmission electron microscopy studies indicate that the resulting polypyrrole forms a nanofibrous mat with average nanofiber diameter of 18 nm. Fourier transform infrared spectroscopy and elemental analysis confirms that the structure of the nanofibers is comparable to bulk polypyrrole. Gas sensing properties of polypyrrole nanofibers were investigated by depositing nanofiber dispersions on an interdigited conductometric transducer. The sensor performance was tested through programmable exposure towards different concentrations of hydrogen gas diluted in synthetic air in an environmental cell at different temperatures. A short response time of 43 s was observed upon exposure to a concentration of 1% hydrogen with a decrease in film resistance of 312 at room temperature. The sensor sensitivity was analyzed with gradual elevation of the operating temperature.
TL;DR: A new low cost converter topology is proposed for sinusoidal position encoders that enables determination of the angle from the sine and cosine signals of the encoder without using LUT, A/D, and D/A converters.
Abstract: A new low cost converter topology is proposed for sinusoidal position encoders. The converter enables determination of the angle from the sine and cosine signals of the encoder. When used with resolvers, the implementation of the present scheme takes advantage of the available excitation signal used to operate the device. This trigonometric reference signal is optimally used to generate an analogue signal equivalent to a digital look-up table (LUT). This enables determination of the mechanical angle without using LUT, A/D, and D/A converters. The scheme is optimized in order to achieve highest possible precision. Beside simplicity of its implementation, the proposed converter offers the advantage of robustness to amplitude fluctuation of the transducer excitation signal. The converter was implemented using ordinary low-cost analog components. The theory of operation, computer simulation, and experimental results are given.