Sensor Tip Research Articles

Carbon Nanotube-Based Nanomechanical Sensor: Theoretical Analysis of Mechanical and Vibrational Properties

This paper reviews the recent research of carbon nanotubes (CNTs) used as nanomechanical sensing elements based mainly on theoretical models. CNTs have demonstrated considerable potential as nanomechanical mass sensor and atomic force microscope (AFM) tips. The mechanical and vibrational characteristics of CNTs are introduced to the readers. The effects of main parameters of CNTs, such as dimensions, layer number, and boundary conditions on the performance characteristics are investigated and discussed. It is hoped that this review provides knowledge on the application of CNTs as nanomechanical sensors and computational methods for predicting their properties. Their theoretical studies based on the mechanical properties such as buckling strength and vibration frequency would give a useful reference for designing CNTs as nanomechanical mass sensor and AFM probes.

Improved tactile resonance sensor for robotic assisted surgery

This paper presents an improved tactile sensor using a piezoelectric bimorph able to differentiate soft materials with similar mechanical characteristics. The final aim is to develop intelligent surgical tools for brain tumour resection using integrated sensors in order to improve tissue tumour delineation and tissue differentiation. The bimorph sensor is driven using a random phase multisine and the properties of contact between the sensor's tip and a certain load are evaluated by means of the evaluation of the nonparametric FRF. An analysis of the nonlinear contributions is presented to show that the use of a linear model is feasible for the measurement conditions. A series of gelatine phantoms were tested. The tactile sensor is able to identify minimal differences in the consistency of the measured samples considering viscoelastic behaviour. A variance analysis was performed to evaluate the reliability of the sensors and to identify possible error sources due to inconsistencies in the preparation method of the phantoms. The results of the variance analysis are discussed showing that ability of the proposed tactile sensor to perform high quality measurements.

A chemical sensor for alternative barriers using NIR spectroscopy

Remediation of contaminated sites often includes the use of alternative barriers as a passive treatment method for a variety of contaminants and sites. Alternative barriers, in turn, require a means for monitoring their performance directly, without the need for costly sampling. It is ideal that the monitoring system provide the data in real time and remotely. When combined with optical fibres, near-infrared (NIR) spectroscopy is a promising chemical sensor for in situ, on-site detection of contaminants. This technology has important advantages over other sensors: it can be used to identify hydrocarbons – capable of distinguishing between chemical groups such as alkanes and chlorinated, aromatic and polyaromatic hydrocarbons, as well as distinguishing compounds within the same homologous series of hydrocarbons. Furthermore, with the combined use of lipophilic polymer coatings and tip sensors, the waveguide can be turned into a localised chemical sensor. Coupled with the fact that the new generation of spectrometers are lower in cost and smaller in size than their predecessors, such a sensor can be installed in the field where communications technologies can transmit data from a remote location – ideally suited for alternative barriers as a means of monitoring the subsurface environment and the performance of the barrier.

Fabry–Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of multimode fiber

We demonstrate an optical Fabry–Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of a multimode fiber. The fiber device is miniature and robust, with a convenient reflection mode of operation, a high temperature sensitivity of 202.6 pm/°C within the range from 5°C to 90°C, a good refractive index sensitivity of ∼119 nm/RIU within the range from 1.331 to 1.38, and a gas pressure sensitivity of 0.19 dB/MPa.

Acquisition and Neural Network Prediction of 3D Deformable Object Shape Using a Kinect and a Force-Torque Sensor.

The realistic representation of deformations is still an active area of research, especially for deformable objects whose behavior cannot be simply described in terms of elasticity parameters. This paper proposes a data-driven neural-network-based approach for capturing implicitly and predicting the deformations of an object subject to external forces. Visual data, in the form of 3D point clouds gathered by a Kinect sensor, is collected over an object while forces are exerted by means of the probing tip of a force-torque sensor. A novel approach based on neural gas fitting is proposed to describe the particularities of a deformation over the selectively simplified 3D surface of the object, without requiring knowledge of the object material. An alignment procedure, a distance-based clustering, and inspiration from stratified sampling support this process. The resulting representation is denser in the region of the deformation (an average of 96.6% perceptual similarity with the collected data in the deformed area), while still preserving the object’s overall shape (86% similarity over the entire surface) and only using on average of 40% of the number of vertices in the mesh. A series of feedforward neural networks is then trained to predict the mapping between the force parameters characterizing the interaction with the object and the change in the object shape, as captured by the fitted neural gas nodes. This series of networks allows for the prediction of the deformation of an object when subject to unknown interactions.

Nanoscale patterning of gold-coated optical fibers for improved plasmonic sensing

Merging surface plasmon resonance (SPR) to fiber optic (FO) technology has brought remarkable achievements in the field by offering attractive advantages over the conventional prism-based SPR platforms, such as simplicity, cost-effectiveness and miniaturization. However, the performance of the existing FO-SPR instruments mainly depends on the device surface condition and in particular on the structural aspect of the thin gold (Au) plasmonic film deposited on the FO substrate. In this work, a simple cost-effective colloidal lithography technique (CLT) was adapted and applied for the first time to the micrometer-sized FO substrate, to design end reflection-type FO-SPR sensors with periodic arrays of Au triangularly-shaped nanostructures on the Au mirror FO tip distal end. The nanopatterned FO-SPR sensor tips were afterwards subjected to refractometric measurements in a sucrose dilution series and subsequently compared with their non-patterned counterparts. It was observed that the spectral dips of the nanopatterned FO-SPR sensor tips were shifted towards longer wavelengths after CLT patterning. Moreover, the sensor sensitivity was improved with up to 25% compared to the conventional non-patterned FO-SPR devices. The obtained results represent important steps in the development of a new generation of FO-SPR sensors with improved performance, which can ultimately be used in various applications, ranging from food analysis and environmental monitoring, to health control and medical diagnosis.

Explosive sensing by using polymer tip on the end of optical fiber

The present study developed a new optical chemical sensor for detection of nitro-aromatic explosives in liquid phase. The method is based on the fluorescence quenching of conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Polymer tip on the one end of single mode optical fiber was fabricated by photo polymerization reaction method. The tip was coated with MEH-PPV and used as sensor head to detect nitro-aromatic explosives. Compared to the normal end cut fiber this kind of sensor head can gather more fluorescence signal which indicate higher sensitivity. The sensing characteristics of the tip sensor head to dinitrobenzene (DNB) which is chemically similar to the common explosive TNT was studied. The optical sensor head coated with fluorescence indicator showed strong fluorescence quenching when exposed to DNB. A Stern-Volmer graph for DNB was constructed and showed that the range of concentration from 6mM to 30mM was linear and the response time of the sensor was within 1min.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation. Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

Determination of High-affinity Antibody-antigen Binding Kinetics Using Four Biosensor Platforms

Label-free optical biosensors are powerful tools in drug discovery for the characterization of biomolecular interactions. In this study, we describe the use of four routinely used biosensor platforms in our laboratory to evaluate the binding affinity and kinetics of ten high-affinity monoclonal antibodies (mAbs) against human proprotein convertase subtilisin kexin type 9 (PCSK9). While both Biacore T100 and ProteOn XPR36 are derived from the well-established Surface Plasmon Resonance (SPR) technology, the former has four flow cells connected by serial flow configuration, whereas the latter presents 36 reaction spots in parallel through an improvised 6 x 6 crisscross microfluidic channel configuration. The IBIS MX96 also operates based on the SPR sensor technology, with an additional imaging feature that provides detection in spatial orientation. This detection technique coupled with the Continuous Flow Microspotter (CFM) expands the throughput significantly by enabling multiplex array printing and detection of 96 reaction sports simultaneously. In contrast, the Octet RED384 is based on the BioLayer Interferometry (BLI) optical principle, with fiber-optic probes acting as the biosensor to detect interference pattern changes upon binding interactions at the tip surface. Unlike the SPR-based platforms, the BLI system does not rely on continuous flow fluidics; instead, the sensor tips collect readings while they are immersed in analyte solutions of a 384-well microplate during orbital agitation.Each of these biosensor platforms has its own advantages and disadvantages. To provide a direct comparison of these instruments' ability to provide quality kinetic data, the described protocols illustrate experiments that use the same assay format and the same high-quality reagents to characterize antibody-antigen kinetics that fit the simple 1:1 molecular interaction model.

High sensitivity fiber acoustic sensor tip working at 1550 nm fabricated by two-photon polymerization technique

An ultracompact fiber acoustic sensor tip was fabricated by using two-photon polymerization technique. The fiber sensor tip was consisted of two sidewalls on the end surface of the single mode fiber and a film held up by the sidewalls, which forms fiber inline Fabry-Pérot micro-cavity. Owing to the fabrication advantages of two-photon polymerization technique, the quadrature phase bias point can be controlled at fix wavelength of 1550nm by matching the cavity length with the film thickness accurately. At laser wavelength of 1550nm, the acoustic pressure of the fiber sensor tip reaches 0.0508±0.0052nm/Pa. The fiber acoustic sensor tip can be suitable for both industrial and biomedical applications due to its high sensitivity, excellent biocompatibility, ultracompact size and independent of laser wavelength tuning.

Multimode fiber tip Fabry-Perot cavity for highly sensitive pressure measurement

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on an etched end of multimode fiber filled with ultraviolet adhesive. The fiber device is miniature (with diameter of less than 60 μm), robust and low cost, in a convenient reflection mode of operation, and has a very high gas pressure sensitivity of −40.94 nm/MPa, a large temperature sensitivity of 213 pm/°C within the range from 55 to 85 °C, and a relatively low temperature cross-sensitivity of 5.2 kPa/°C. This device has a high potential in monitoring environment of high pressure.

In vivo characterization of magnesium alloy biodegradation using electrochemical H2 monitoring, ICP-MS, and XPS.

Biodegradable devices based on magnesium and its alloys are promising because they gradually dissolve and thereby avoid the need for subsequent removal by surgery if complications arise. In vivo biodegradation rate is one of the crucial parameters for the development of these alloys. Promising alloys are first evaluated in vivo by being implanted subcutaneously in mice for 1month. Here, we evaluated several magnesium alloys with widely varying corrosion rates in vivo using multiple characterization techniques. Since the alloys biodegrade by reacting with water forming H2 gas, we used a recently demonstrated, simple, fast and noninvasive method to monitor the biodegradation process by just pressing the tip of a H2 sensor against the skin above the implant. The analysis of 9 organs (intestine, kidney, spleen, lung, heart, liver, skin, brain and skull) for accumulation of Mg and Zn revealed no significant accumulation of magnesium in these organs. Zinc accumulation in intestine, kidney and lung was observed for the faster corroding implant ZJ41. The surfaces of explanted alloys were analyzed to determine the composition of the insoluble biodegradation products. The results suggest that these tested alloys are potential candidates for biodegradable implant applications.

Using electromagnetic articulography with a tongue lateral sensor to discriminate manner of articulation.

This study examined the contributions of the tongue tip (TT), tongue body (TB), and tongue lateral (TL) sensors in the electromagnetic articulography (EMA) measurement of American English alveolar consonants. Thirteen adults produced /ɹ/, /l/, /z/, and /d/ in /ɑCɑ/ syllables while being recorded with an EMA system. According to statistical analysis of sensor movement and the results of a machine classification experiment, the TT sensor contributed most to consonant differences, followed by TB. The TL sensor played a complementary role, particularly for distinguishing /z/.

Photoplethysmograph measurement using mail tip sensor in daily life environment

Photoplethysmograph measurement using mail tip sensor in daily life environment

Particle cluster sizing in downer units. Applicable methodology across downer scale units

Data analysis from downers requires a comprehensive methodology in order to set the data baseline. This analysis can be accomplished by using a mathematical approach based on solid mass balances and an iterative calculation. Each signal baseline is defined asX+n∙σx, where X is the signal average; σx is the signal standard deviation; and “n” is a baseline parameter. By using this methodology, the noise resulting from secondary reflections is eliminated and all valuable data is kept in the time series.More than 500 experiments with >50 million data records were obtained using two independent gas-solid circulating fluidized bed downer units of 3m height and two different diameters (2.54-cm and 5.08-cm ID). The solid used was a FCC catalyst with a mean particle diameter of 84.42μm and a particle density of 1722kg/m3. Measurements were effected using a CREC-GS-Optiprobe, an optical sensor equipped with a GRIN lens. This lens focus radiation in a 118±34μm diameter highly irradiated volume, placed at 4.5mm away from the sensor tip. CREC-GS-Optiprobe sensors do not require calibration and offer minimum intrusion.On the basis of the data obtained, this study reports a valuable methodology, applicable to downer units of different diameters. This leads for the two downers studied to particle clusters with very close asymmetric distributions.

Reduced Graphene Oxide nano-composites layer on fiber optic tip sensor reflectance response for sensing of aqueous ethanol

In this study, the used of tapered optical fiber tip as sensors coated with reduced Graphene Oxide (rGO) is investigated. The resultant rGO nanocomposites coated on the tapered fiber sensor were characterized by X-ray Diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM). Optimization of the rGO layer and the tapering parameters are found and the sensing capability of the device is tested using different concentrations of ethanol in water. The nanocomposite layer improved the performance of the sensor by demonstrating high sensitivity to aqueous ethanol when interrogated in the visible region using a spectrometer in the optical wavelength range of 500–700 nm. The reflectance response of the rGO coated fiber tip reduced linearly, upon exposure to ethanol concentrations ranging between 20-80 %.

Development of the droplet-capable conductivity probe for measurement of liquid-dispersed two-phase flow

A new conductivity probe design has been developed in order to measure dispersed liquid particles in churn-turbulent and annular flows which cannot be detected by the conventional conductivity probes. The probe incorporates a common sensor near the measurement point to detect the local conductance signals between two sensor tips that are 150µm apart. Once fully developed, the probe is capable of measuring local two-phase parameters of various fields including small and large bubbles, large liquid droplets and a continuous liquid field. Preliminary benchmarking studies of the probe have been performed with a specially designed droplet dispensing setup. A high speed imaging system is used to provide benchmarking data such as droplet diameter, velocity, and chord length, for individual droplets, and the time-averaged data such as droplet volume fraction, volumetric flux and interfacial area concentration. Reasonable agreement has been obtained by comparing individual droplets with a diameter range of 1.4–4.0mm, and a velocity range of 1.6–4.8m/s. For time- and area-averaged parameters, the results from two test runs show that the maximum absolute relative errors are 6.42%, 7.43% and 5.72% for droplet volume fraction, interfacial area concentration and volumetric flux, respectively. The error is within 5% compared with the global droplet flow rate measurement.

Visuomotor pursuit tracking accuracy for intraoral tongue movement

Visuomotor pursuit tracking (VMT) tasks are used to study the movement of the articulators in order to better understand the processes involved in speech motor planning and execution. Because most of this research has focused on lip/jaw tracking of sinusoids visually presented on a screen, little is known about the tracking capabilities of the tongue, or for visual targets placed in the oral cavity. The present study used a novel technique for measuring tongue (and jaw) VMT based on a 3D electromagnetic articulography (EMA) system. Streaming EMA data from oral sensors were used to construct a real-time avatar of the tongue which was shown to subjects on a computer monitor. Subjects also viewed a (virtual) intra-oral spherical target that they were required to “hit” with the tongue tip sensor. The target was programmed to move in a sinusoidal direction and was varied in frequency (Hz), direction, and predictability. Preliminary results suggest that tracking accuracy is inversely related to target frequency...

Abstract PR507

Background & Objectives: The deformation of spinal needles during clinical use can affect the safe and timely conduct of anaesthesia. The strength profile of needles is measured by industry standard tests, which do not necessarily reflect clinical use (1). Testing is done by individual manufacturers and there are few objective, comparative studies of different needle brands (2). We aimed to compare the resistance to deformation in commonly used brands of spinal needles of a set length and gauge (27G 90mm) using both industry standard approaches and our own. Materials & Methods: We designed a testing rig incorporating a force transducer which measured the registered force during calibrated deflection of a sensor tip. A horizontal three-point bend test (A) was performed as a common industry standard test and a separate vertical test was designed by the group (B). During horizontal testing the sensor was pushed onto the needle shaft and in the vertical test the sensor was pushed onto the needle tip. Final needle deformation was measured (C). 27G 90mm luer spinal needles were tested from 4 popular, global brands. Each needle brand was tested 8 times in random order. Results: Only the vertical testing showed a significant difference in the deformation of the needles where Brand C showed significantly greater deformation than the other brands (p<0.05).Conclusion: Currently employed manufacturer tests may not identify differences in needle strength that could be clinically relevant. Our study identified differences between manufacturers in our specially designed test of axial strength but not in the standard industrial test. An awareness of such differences is important for clinicians when using or purchasing needles from different manufacturers.

Quantification of the fluorescence sensing performance of microstructured optical fibers compared to multi-mode fiber tips.

Microstructured optical fibers, particularly those with a suspended-core geometry, have frequently been argued as efficient evanescent-field fluorescence-based sensors. However, to date there has not been a systematic comparison between such fibers and the more common geometry of a multi-mode fiber tip sensor. In this paper we make a direct comparison between these two fiber sensor geometries both theoretically and experimentally. Our results confirm that suspended-core fibers provide a significant advantage in terms of total collected fluorescence signal compared to multi-mode fibers using an equivalent experimental configuration.