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Special Issue "Ultra-Small Sensor Systems and Components"

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A special issue of Sensors (ISSN 1424-8220).

Deadline for manuscript submissions: closed (15 May 2012)

Special Issue Editors

Guest Editor
Prof. Dr. Frances S. Ligler

Lampe Distinguished Professor, Joint Department of Biomedical Engineering, University of North Carolina-Chapel Hill and North Carolina State University, NCSU Engineering Building 3, Room 4307 Mail Stop 7115, Raleigh, NC 27695-7115, USA
Website | E-Mail
Interests: biosensors; immunosensors; fluorescence; multi-analyte sensing; microfluidics; flow cytometry; microarrays
Guest Editor
Prof. Dr. David R. Allee

Director R&D of Backplane Electronics and Professor, Flexible Display Center at Arizona State University, Tempe, AZ 85284, USA
Website | E-Mail
Interests: large area sensing arrays; flexible electronics; thin-film transistors; flexible displays; ultra-small devices; nanolithography

Special Issue Information

Dear Colleagues,

Miniaturization of sensors is accelerating with the increasing sophistication of microfluidics, integrated optics, and consumer electronics. Sensors are becoming more robust and user friendly, with expanding capacity for discriminating targets in complex sample matrices and simultaneous measurement of multiple targets. Integration of sensor systems is producing devices for use outside the laboratory by users without sophisticated technical training for environmental, medical, homeland security, and food safety applications. Networks of distributed sensors are evolving for epidemiological and environmental monitoring, placing an ever increasing emphasis on miniaturization and cost reduction. This special issue collects new reports and reviews on topics related to miniaturization of critical components for sensor systems and the integration of advanced components into portable, user-friendly sensor systems.

Of particular interest are sensors that can achieve high sensitivity, selectivity and low false alarm rates in noisy environments typical of biologically evolved sensors. There is speculation and some recent evidence that the exquisite performance of a dog’s olfaction, energy transfer in photosynthesis, and magnetoreception in birds depend critically on quantum effects. Other quantum sensors based on photon entanglement offer the possibility of enhanced resolution imaging at long wavelengths, and photon counting arrays may enable imaging in extremely low ambient illumination environments. Ultra-miniature micro gas analyzers that integrate gas chromatography and mass spectrometry may enable the detection of chemical agents in the field with laboratory sensitivity and specificity. Uncooled magnetic sensors using multiferroic materials or atomic magnetometers operating at room temperature may rival superconducting quantum interference devices in performance.

Another approach to improve sensitivity is the fabrication of a large array of small sensors to form a large capture cross section for visible photons, x-rays, neutrons, chemical species, or acoustics. Individual sensors may be distributed over large areas or an array of co-localized, multifunctional sensors might enhance specificity. To be practical, the array must be lightweight, rugged and manufacturable at a reasonable cost. Technologies for creating both low cost distributed sensors and integrated sensor arrays are of prime concern.

Papers investigating these and other topics are encouraged.

We invite submission of papers on the following topics:

  • Miniaturization and automation of sample preparation devices
  • Organic electronic devices configured for sensor integration
  • Integration of optical and/or electronic components with sensors
  • Design and fabrication of portable, fully automated sensor systems
  • Utilization of integrated sensor systems at point of use
  • Quantum effect sensors
  • Flexible, large area arrays of small sensors
  • Integration of sensors into distributed networks
  • Use of sensors on unmanned vehicles

Dr. Frances Smith Ligler
Prof. Dr. David R. Allee
Guest Editors

Keywords

  • integrated sensors
  • quantum effect sensors
  • portable sensor systems
  • unmanned vehicle sensors
  • integrated sensor optics
  • multifunctional sensor arrays
  • miniature sensor components
  • automated sample preparation
  • distributed sensing

Published Papers (30 papers)

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Open AccessArticle Label-Free Microcavity Biosensors: Steps towards Personalized Medicine
Sensors 2012, 12(12), 17262-17294; doi:10.3390/s121217262
Received: 16 November 2012 / Revised: 10 December 2012 / Accepted: 11 December 2012 / Published: 13 December 2012
Cited by 1 | PDF Full-text (1074 KB) | HTML Full-text | XML Full-text
Abstract
Personalized medicine has the potential to improve our ability to maintain health and treat disease, while ameliorating continuously rising healthcare costs. Translation of basic research findings to clinical applications within regulatory compliance is required for personalized medicine to become the new foundation for
[...] Read more.
Personalized medicine has the potential to improve our ability to maintain health and treat disease, while ameliorating continuously rising healthcare costs. Translation of basic research findings to clinical applications within regulatory compliance is required for personalized medicine to become the new foundation for practice of medicine. Deploying even a few of the thousands of potential diagnostic biomarkers identified each year as part of personalized treatment workflows requires clinically efficient biosensor technologies to monitor multiple biomarkers in patients in real time. This paper discusses a critical component of a regulatory system, a microcavity optical biosensor for label-free monitoring of biomolecular interactions at physiologically-relevant concentrations. While most current biosensor research focuses on improving sensitivity, this paper emphasizes other characteristics a biosensor technology requires to be practical in a clinical setting, presenting robust microcavity biosensors which are easy to manufacture and integrate with microfluidics into flexible and redesignable platforms making the microcavity biosensors deployable for continuous monitoring of biomarkers in body fluids in the clinic,  in dense 2D random arrays for high-throughput applications like drug-library screening in interactomics, and of the secretory behavior of single cells in the laboratory. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Low Cost Matching Motion Estimation Sensor Based on the NIOS II Microprocessor
Sensors 2012, 12(10), 13126-13149; doi:10.3390/s121013126
Received: 27 July 2012 / Revised: 5 September 2012 / Accepted: 11 September 2012 / Published: 27 September 2012
Cited by 15 | PDF Full-text (1737 KB) | HTML Full-text | XML Full-text
Abstract
This work presents the implementation of a matching-based motion estimation sensor on a Field Programmable Gate Array (FPGA) and NIOS II microprocessor applying a C to Hardware (C2H) acceleration paradigm. The design, which involves several matching algorithms, is mapped using Very Large Scale
[...] Read more.
This work presents the implementation of a matching-based motion estimation sensor on a Field Programmable Gate Array (FPGA) and NIOS II microprocessor applying a C to Hardware (C2H) acceleration paradigm. The design, which involves several matching algorithms, is mapped using Very Large Scale Integration (VLSI) technology. These algorithms, as well as the hardware implementation, are presented here together with an extensive analysis of the resources needed and the throughput obtained. The developed low-cost system is practical for real-time throughput and reduced power consumption and is useful in robotic applications, such as tracking, navigation using an unmanned vehicle, or as part of a more complex system. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Ultra Small Integrated Optical Fiber Sensing System
Sensors 2012, 12(9), 12052-12069; doi:10.3390/s120912052
Received: 21 June 2012 / Revised: 10 August 2012 / Accepted: 20 August 2012 / Published: 3 September 2012
Cited by 11 | PDF Full-text (25147 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces a revolutionary way to interrogate optical fiber sensors based on fiber Bragg gratings (FBGs) and to integrate the necessary driving optoelectronic components with the sensor elements. Low-cost optoelectronic chips are used to interrogate the optical fibers, creating a portable dynamic
[...] Read more.
This paper introduces a revolutionary way to interrogate optical fiber sensors based on fiber Bragg gratings (FBGs) and to integrate the necessary driving optoelectronic components with the sensor elements. Low-cost optoelectronic chips are used to interrogate the optical fibers, creating a portable dynamic sensing system as an alternative for the traditionally bulky and expensive fiber sensor interrogation units. The possibility to embed these laser and detector chips is demonstrated resulting in an ultra thin flexible optoelectronic package of only 40 μm, provided with an integrated planar fiber pigtail. The result is a fully embedded flexible sensing system with a thickness of only 1 mm, based on a single Vertical-Cavity Surface-Emitting Laser (VCSEL), fiber sensor and photodetector chip. Temperature, strain and electrodynamic shaking tests have been performed on our system, not limited to static read-out measurements but dynamically reconstructing full spectral information datasets. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Open AccessArticle Sensors Based on Plasmonic-Photonic Coupling in Metallic Photonic Crystals
Sensors 2012, 12(9), 12082-12097; doi:10.3390/s120912082
Received: 18 July 2012 / Revised: 16 August 2012 / Accepted: 17 August 2012 / Published: 3 September 2012
Cited by 14 | PDF Full-text (2200 KB) | HTML Full-text | XML Full-text
Abstract
An optical sensor based on the coupling between the plasmonic and photonic resonance modes in metallic photonic crystals is investigated. Large-area metallic photonic crystals consisting of periodically arranged gold nanostructures with dimensions down to sub-100 nm are fabricated using solution-processible gold nanoparticles in
[...] Read more.
An optical sensor based on the coupling between the plasmonic and photonic resonance modes in metallic photonic crystals is investigated. Large-area metallic photonic crystals consisting of periodically arranged gold nanostructures with dimensions down to sub-100 nm are fabricated using solution-processible gold nanoparticles in combination with interference lithography or interference ablation, which introduces a variety of fabrication techniques for the construction of this kind of sensor device. Sensitivity of the plasmonic response of the gold nanostructures to the changes in the environmental refractive index is enhanced through the coupling between the narrow-band photonic resonance mode and the relatively broad-band plasmon resonance, which is recognized as a Fano-like effect and is utilized to explore sensors. Theoretical modeling shows the characterization and the optimization of the sensitivity of this kind of sensor device. Theoretical and experimental results are demonstrated for the approaches to improve the sensitivity of the sensor device. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Alignment and Position Sensors Based on Split Ring Resonators
Sensors 2012, 12(9), 11790-11797; doi:10.3390/s120911790
Received: 10 July 2012 / Revised: 16 August 2012 / Accepted: 20 August 2012 / Published: 29 August 2012
Cited by 28 | PDF Full-text (454 KB) | HTML Full-text | XML Full-text
Abstract
In this paper compact alignment and position sensors based on coplanar waveguide (CPW) transmission lines loaded with split ring resonators (SRRs) are proposed. The structure consists of a folded CPW loaded with two SRRs tuned at different frequencies to detect both the lack
[...] Read more.
In this paper compact alignment and position sensors based on coplanar waveguide (CPW) transmission lines loaded with split ring resonators (SRRs) are proposed. The structure consists of a folded CPW loaded with two SRRs tuned at different frequencies to detect both the lack of alignment and the two-dimensional linear displacement magnitude. Two additional resonators (also tuned at different frequencies) are used to detect the displacement direction. The working principle for this type of sensor is explained in detail, and a prototype device to illustrate the potential of the approach has been designed and fabricated. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessCommunication In Vivo Histamine Optical Nanosensors
Sensors 2012, 12(9), 11922-11932; doi:10.3390/s120911922
Received: 7 June 2012 / Revised: 20 August 2012 / Accepted: 24 August 2012 / Published: 29 August 2012
Cited by 4 | PDF Full-text (488 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this communication we discuss the development of ionophore based nanosensors for the detection and monitoring of histamine levels in vivo. This approach is based on the use of an amine-reactive, broad spectrum ionophore which is capable of recognizing and binding to
[...] Read more.
In this communication we discuss the development of ionophore based nanosensors for the detection and monitoring of histamine levels in vivo. This approach is based on the use of an amine-reactive, broad spectrum ionophore which is capable of recognizing and binding to histamine. We pair this ionophore with our already established nanosensor platform, and demonstrate in vitro and in vivo monitoring of histamine levels. This approach enables capturing rapid kinetics of histamine after injection, which are more difficult to measure with standard approaches such as blood sampling, especially on small research models. The coupling together of in vivo nanosensors with ionophores such as nonactin provide a way to generate nanosensors for novel targets without the difficult process of designing and synthesizing novel ionophores. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Open AccessArticle A Fully Integrated Humidity Sensor System-on-Chip Fabricated by Micro-Stamping Technology
Sensors 2012, 12(9), 11592-11600; doi:10.3390/s120911592
Received: 27 July 2012 / Revised: 17 August 2012 / Accepted: 24 August 2012 / Published: 27 August 2012
Cited by 6 | PDF Full-text (942 KB) | HTML Full-text | XML Full-text
Abstract
A fully integrated humidity sensor chip was designed, implemented, and tested. Utilizing the micro-stamping technology, the pseudo-3D sensor system-on-chip (SSoC) architecture can be implemented by stacking sensing materials directly on the top of a CMOS-fabricated chip. The fabricated sensor system-on-chip (2.28 mm ×
[...] Read more.
A fully integrated humidity sensor chip was designed, implemented, and tested. Utilizing the micro-stamping technology, the pseudo-3D sensor system-on-chip (SSoC) architecture can be implemented by stacking sensing materials directly on the top of a CMOS-fabricated chip. The fabricated sensor system-on-chip (2.28 mm × 2.48 mm) integrated a humidity sensor, an interface circuit, a digital controller, and an On-Off Keying (OOK) wireless transceiver. With low power consumption, i.e., 750 μW without RF operation, the sensitivity of developed sensor chip was experimentally verified in the relative humidity (RH) range from 32% to 60%. The response time of the chip was also experimentally verified to be within 5 seconds from RH 36% to RH 64%. As a consequence, the implemented humidity SSoC paves the way toward the an ultra-small sensor system for various applications. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Design and Fabrication of a Large-Stroke Deformable Mirror Using a Gear-Shape Ionic-Conductive Polymer Metal Composite
Sensors 2012, 12(8), 11100-11112; doi:10.3390/s120811100
Received: 10 June 2012 / Revised: 24 July 2012 / Accepted: 31 July 2012 / Published: 9 August 2012
Cited by 3 | PDF Full-text (1006 KB) | HTML Full-text | XML Full-text
Abstract
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. A
[...] Read more.
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. A deformable mirror (DM) provides a good opportunity to improve these issues. The DM is a reflective type optical component which can alter the optical power to focus the lights on the two dimensional optical image sensors. It can make the camera system operate rapidly. Ionic polymer metal composite (IPMC) is a promising electro-actuated polymer material that can be used in micromachining devices because of its large deformation with low actuation voltage. We developed a convenient simulation model based on Young’s modulus and Poisson’s ratio. We divided an ion exchange polymer, also known as Nafion®, into two virtual layers in the simulation model: one was expansive and the other was contractive, caused by opposite constant surface forces on each surface of the elements. Therefore, the deformation for different IPMC shapes can be described more easily. A standard experiment of voltage vs. tip displacement was used to verify the proposed modeling. Finally, a gear shaped IPMC actuator was designed and tested. Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts. The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Aircraft Aerodynamic Parameter Detection Using Micro Hot-Film Flow Sensor Array and BP Neural Network Identification
Sensors 2012, 12(8), 10920-10929; doi:10.3390/s120810920
Received: 25 April 2012 / Revised: 29 June 2012 / Accepted: 1 August 2012 / Published: 7 August 2012
Cited by 11 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text
Abstract
Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic parameters
[...] Read more.
Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic parameters are inferred using a micro hot-film flow sensor array mounted on the surface of the wing is proposed. A back-propagation neural network is used to model the coupling relationship between readings of the sensor array and aerodynamic parameters. Two different sensor arrangements are tested in wind tunnel experiments and dependence of the system performance on the sensor arrangement is analyzed. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Wireless Magnetic Resonance Energy Transfer System for Micro Implantable Medical Sensors
Sensors 2012, 12(8), 10292-10308; doi:10.3390/s120810292
Received: 16 May 2012 / Revised: 11 July 2012 / Accepted: 16 July 2012 / Published: 30 July 2012
Cited by 20 | PDF Full-text (1091 KB) | HTML Full-text | XML Full-text
Abstract
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and
[...] Read more.
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm3. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessCommunication A Micro-Machined Gyroscope for Rotating Aircraft
Sensors 2012, 12(7), 9823-9828; doi:10.3390/s120709823
Received: 1 April 2012 / Revised: 23 May 2012 / Accepted: 1 June 2012 / Published: 23 July 2012
PDF Full-text (633 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we present recent work on the design, fabrication by silicon micromachining, and packaging of a new gyroscope for stabilizing the autopilot of rotating aircraft. It operates based on oscillation of the silicon pendulum between two torsion girders for detecting the
[...] Read more.
In this paper we present recent work on the design, fabrication by silicon micromachining, and packaging of a new gyroscope for stabilizing the autopilot of rotating aircraft. It operates based on oscillation of the silicon pendulum between two torsion girders for detecting the Coriolis force. The oscillation of the pendulum is initiated by the rolling and deflecting motion of the rotating carrier. Therefore, the frequency and amplitude of the oscillation are proportional to the rolling frequency and deflecting angular rate of the rotating carrier, and are measured by the sensing electrodes. A modulated pulse with constant amplitude and unequal width is obtained by a linearizing process of the gyroscope output signal and used to control the deflection of the rotating aircraft. Experimental results show that the gyroscope has a resolution of 0.008 °/s and a bias of 56.18 °/h. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Design and Analysis of a Compact Precision Positioning Platform Integrating Strain Gauges and the Piezoactuator
Sensors 2012, 12(7), 9697-9710; doi:10.3390/s120709697
Received: 14 May 2012 / Revised: 7 June 2012 / Accepted: 10 July 2012 / Published: 17 July 2012
Cited by 3 | PDF Full-text (1201 KB) | HTML Full-text | XML Full-text
Abstract
Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as static
[...] Read more.
Miniaturization precision positioning platforms are needed for in situ nanomechanical test applications. This paper proposes a compact precision positioning platform integrating strain gauges and the piezoactuator. Effects of geometric parameters of two parallel plates on Von Mises stress distribution as well as static and dynamic characteristics of the platform were studied by the finite element method. Results of the calibration experiment indicate that the strain gauge sensor has good linearity and its sensitivity is about 0.0468 mV/μm. A closed-loop control system was established to solve the problem of nonlinearity of the platform. Experimental results demonstrate that for the displacement control process, both the displacement increasing portion and the decreasing portion have good linearity, verifying that the control system is available. The developed platform has a compact structure but can realize displacement measurement with the embedded strain gauges, which is useful for the closed-loop control and structure miniaturization of piezo devices. It has potential applications in nanoindentation and nanoscratch tests, especially in the field of in situ nanomechanical testing which requires compact structures. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle The Development of an UAV Borne Direct Georeferenced Photogrammetric Platform for Ground Control Point Free Applications
Sensors 2012, 12(7), 9161-9180; doi:10.3390/s120709161
Received: 2 May 2012 / Revised: 4 June 2012 / Accepted: 29 June 2012 / Published: 4 July 2012
Cited by 22 | PDF Full-text (1460 KB) | HTML Full-text | XML Full-text
Abstract
To facilitate applications such as environment detection or disaster monitoring, the development of rapid low cost systems for collecting near real time spatial information is very critical. Rapid spatial information collection has become an emerging trend for remote sensing and mapping applications. In
[...] Read more.
To facilitate applications such as environment detection or disaster monitoring, the development of rapid low cost systems for collecting near real time spatial information is very critical. Rapid spatial information collection has become an emerging trend for remote sensing and mapping applications. In this study, a fixed-wing Unmanned Aerial Vehicle (UAV)-based spatial information acquisition platform that can operate in Ground Control Point (GCP) free environments is developed and evaluated. The proposed UAV based photogrammetric platform has a Direct Georeferencing (DG) module that includes a low cost Micro Electro Mechanical Systems (MEMS) Inertial Navigation System (INS)/ Global Positioning System (GPS) integrated system. The DG module is able to provide GPS single frequency carrier phase measurements for differential processing to obtain sufficient positioning accuracy. All necessary calibration procedures are implemented. Ultimately, a flight test is performed to verify the positioning accuracy in DG mode without using GCPs. The preliminary results of positioning accuracy in DG mode illustrate that horizontal positioning accuracies in the x and y axes are around 5 m at 300 m flight height above the ground. The positioning accuracy of the z axis is below 10 m. Therefore, the proposed platform is relatively safe and inexpensive for collecting critical spatial information for urgent response such as disaster relief and assessment applications where GCPs are not available. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Design Parameters of a Miniaturized Piezoelectric Underwater Acoustic Transmitter
Sensors 2012, 12(7), 9098-9109; doi:10.3390/s120709098
Received: 15 May 2012 / Revised: 7 June 2012 / Accepted: 27 June 2012 / Published: 2 July 2012
Cited by 5 | PDF Full-text (685 KB) | HTML Full-text | XML Full-text
Abstract
PZT ceramics have been widely used in underwater acoustic transducers. However, literature available discussing the design parameters of a miniaturized PZT-based low-duty-cycle transmitter is very limited. This paper discusses some of the design parameters—the backing material, driving voltage, PZT material type, power consumption
[...] Read more.
PZT ceramics have been widely used in underwater acoustic transducers. However, literature available discussing the design parameters of a miniaturized PZT-based low-duty-cycle transmitter is very limited. This paper discusses some of the design parameters—the backing material, driving voltage, PZT material type, power consumption and the transducer length of a miniaturized acoustic fish tag using a PZT tube. Four different types of PZT were evaluated with respect to the source level, energy consumption and bandwidth of the transducer. The effect of the tube length on the source level is discussed. The results demonstrate that ultralow-density closed-cell foam is the best backing material for the PZT tube. The Navy Type VI PZTs provide the best source level with relatively low energy consumption and that a low transducer capacitance is preferred for high efficiency. A 35% reduction in the transducer length results in 2 dB decrease in source level. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Analysis of Building Envelope Insulation Performance Utilizing Integrated Temperature and Humidity Sensors
Sensors 2012, 12(7), 8987-9005; doi:10.3390/s120708987
Received: 14 May 2012 / Revised: 12 June 2012 / Accepted: 25 June 2012 / Published: 29 June 2012
Cited by 3 | PDF Full-text (847 KB) | HTML Full-text | XML Full-text
Abstract
A major cause of high energy consumption for air conditioning in indoor spaces is the thermal storage characteristics of a building’s envelope concrete material; therefore, the physiological signals (temperature and humidity) within concrete structures are an important reference for building energy management. The
[...] Read more.
A major cause of high energy consumption for air conditioning in indoor spaces is the thermal storage characteristics of a building’s envelope concrete material; therefore, the physiological signals (temperature and humidity) within concrete structures are an important reference for building energy management. The current approach to measuring temperature and humidity within concrete structures (i.e., thermocouples and fiber optics) is limited by problems of wiring requirements, discontinuous monitoring, and high costs. This study uses radio frequency integrated circuits (RFIC) combined with temperature and humidity sensors (T/H sensors) for the design of a smart temperature and humidity information material (STHIM) that automatically, regularly, and continuously converts temperature and humidity signals within concrete and transmits them by radio frequency (RF) to the Building Physiology Information System (BPIS). This provides a new approach to measurement that incorporates direct measurement, wireless communication, and real-time continuous monitoring to assist building designers and users in making energy management decisions and judgments. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Direct Measurement of Mammographic X-Ray Spectra with a Digital CdTe Detection System
Sensors 2012, 12(6), 8390-8404; doi:10.3390/s120608390
Received: 8 May 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 18 June 2012
Cited by 14 | PDF Full-text (487 KB) | HTML Full-text | XML Full-text
Abstract
In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate X-ray spectroscopy in mammography (1–30 keV). The DPP system performs a height and shape analysis of the detector pulses, sampled
[...] Read more.
In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate X-ray spectroscopy in mammography (1–30 keV). The DPP system performs a height and shape analysis of the detector pulses, sampled and digitized by a 14-bit, 100 MHz ADC. We show the results of the characterization of the detection system both at low and high photon counting rates by using monoenergetic X-ray sources and a nonclinical X-ray tube. The detection system exhibits excellent performance up to 830 kcps with an energy resolution of 4.5% FWHM at 22.1 keV. Direct measurements of clinical molybdenum X-ray spectra were carried out by using a pinhole collimator and a custom alignment device. A comparison with the attenuation curves and the half value layer values, obtained from the measured and simulated spectra, from an ionization chamber and from a solid state dosimeter, also shows the accuracy of the measurements. These results make the proposed detection system a very attractive tool for both laboratory research, calibration of dosimeters and advanced quality controls in mammography. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture
Sensors 2012, 12(6), 8338-8354; doi:10.3390/s120608338
Received: 30 April 2012 / Revised: 30 May 2012 / Accepted: 1 June 2012 / Published: 15 June 2012
Cited by 11 | PDF Full-text (1140 KB) | HTML Full-text | XML Full-text
Abstract
Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to
[...] Read more.
Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si3N4 membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Open AccessArticle Flexible Graphite-on-Paper Piezoresistive Sensors
Sensors 2012, 12(5), 6685-6694; doi:10.3390/s120506685
Received: 20 March 2012 / Revised: 3 May 2012 / Accepted: 14 May 2012 / Published: 22 May 2012
Cited by 17 | PDF Full-text (1738 KB) | HTML Full-text | XML Full-text
Abstract
We demonstrate novel graphite-on-paper piezoresistive devices. The graphite was used as sensing component. The fabrication process can be finished in a short time with simple tools (e.g., a scissor and a pencil). A small array of six paper-based piezoresistive devices is made. The
[...] Read more.
We demonstrate novel graphite-on-paper piezoresistive devices. The graphite was used as sensing component. The fabrication process can be finished in a short time with simple tools (e.g., a scissor and a pencil). A small array of six paper-based piezoresistive devices is made. The whole device is flexible. The test results showed that the change of resistance was proportional to the applied force. A paper-based weighing balance was also made as an example of applications. This novel array of paper-based piezoresistive devices will open wide applications in force and acceleration sensing areas. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Open AccessArticle Energy Performance Assessment of Virtualization Technologies Using Small Environmental Monitoring Sensors
Sensors 2012, 12(5), 6610-6628; doi:10.3390/s120506610
Received: 13 March 2012 / Revised: 1 May 2012 / Accepted: 14 May 2012 / Published: 18 May 2012
Cited by 9 | PDF Full-text (754 KB) | HTML Full-text | XML Full-text
Abstract
The increasing trends of electrical consumption within data centres are a growing concern for business owners as they are quickly becoming a large fraction of the total cost of ownership. Ultra small sensors could be deployed within a data centre to monitor environmental
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The increasing trends of electrical consumption within data centres are a growing concern for business owners as they are quickly becoming a large fraction of the total cost of ownership. Ultra small sensors could be deployed within a data centre to monitor environmental factors to lower the electrical costs and improve the energy efficiency. Since servers and air conditioners represent the top users of electrical power in the data centre, this research sets out to explore methods from each subsystem of the data centre as part of an overall energy efficient solution. In this paper, we investigate the current trends of Green IT awareness and how the deployment of small environmental sensors and Site Infrastructure equipment optimization techniques which can offer a solution to a global issue by reducing carbon emissions. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Structure and Process of Infrared Hot Electron Transistor Arrays
Sensors 2012, 12(5), 6508-6519; doi:10.3390/s120506508
Received: 10 April 2012 / Revised: 9 May 2012 / Accepted: 14 May 2012 / Published: 16 May 2012
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Abstract
An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark
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An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark current ratio compared to the basic quantum well infrared photodetector (QWIP), and hence it improved the array S/N ratio by the same factor. The study also showed for the first time that there is no electrical cross-talk among individual detectors, even though they share the same emitter and base contacts. Thus, the IHET structure is compatible with existing electronic readout circuits for photoconductors in producing sensitive focal plane arrays. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Humidity-Induced Charge Leakage and Field Attenuation in Electric Field Microsensors
Sensors 2012, 12(4), 5105-5115; doi:10.3390/s120405105
Received: 15 March 2012 / Revised: 6 April 2012 / Accepted: 9 April 2012 / Published: 19 April 2012
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Abstract
The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the Boltzmann
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The steady-state zero output of static electric field measuring systems often fluctuates, which is caused mainly by the finite leakage resistance of the water film on the surface of the electric field microsensor package. The water adsorption has been calculated using the Boltzmann distribution equation at various relative humidities for borosilicate glass and polytetrafluoroethylene surfaces. At various humidities, water film thickness has been calculated, and the induced charge leakage and field attenuation have been theoretically investigated. Experiments have been performed with microsensors to verify the theoretical predictions and the results are in good agreement. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessCommunication Direct Measurement of Lateral Force Using Dual Cantilevers
Sensors 2012, 12(3), 3200-3203; doi:10.3390/s120303200
Received: 27 January 2012 / Revised: 29 February 2012 / Accepted: 2 March 2012 / Published: 7 March 2012
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Abstract
We have constructed an experimental system to measure a piconewton lateral force using dual cantilevers which cross with each other. The resolution of the lateral force is estimated to be 3.3 p ± 0.2 pN, which is comparable to forces due to thermal
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We have constructed an experimental system to measure a piconewton lateral force using dual cantilevers which cross with each other. The resolution of the lateral force is estimated to be 3.3 p ± 0.2 pN, which is comparable to forces due to thermal fluctuation. This experimental apparatus works so easily that it will enable us to determine forces during nano-manipulation and nano-tribological measurements. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Local Area Water Removal Analysis of a Proton Exchange Membrane Fuel Cell under Gas Purge Conditions
Sensors 2012, 12(1), 768-783; doi:10.3390/s120100768
Received: 9 December 2011 / Revised: 24 December 2011 / Accepted: 4 January 2012 / Published: 11 January 2012
Cited by 2 | PDF Full-text (1360 KB) | HTML Full-text | XML Full-text
Abstract
In this study, local area water content distribution under various gas purging conditions are experimentally analyzed for the first time. The local high frequency resistance (HFR) is measured using novel micro sensors. The results reveal that the liquid water removal rate in a
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In this study, local area water content distribution under various gas purging conditions are experimentally analyzed for the first time. The local high frequency resistance (HFR) is measured using novel micro sensors. The results reveal that the liquid water removal rate in a membrane electrode assembly (MEA) is non-uniform. In the under-the-channel area, the removal of liquid water is governed by both convective and diffusive flux of the through-plane drying. Thus, almost all of the liquid water is removed within 30 s of purging with gas. However, liquid water that is stored in the under-the-rib area is not easy to remove during 1 min of gas purging. Therefore, the re-hydration of the membrane by internal diffusive flux is faster than that in the under-the-channel area. Consequently, local fuel starvation and membrane degradation can degrade the performance of a fuel cell that is started from cold. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle BIPV-Powered Smart Windows Utilizing Photovoltaic and Electrochromic Devices
Sensors 2012, 12(1), 359-372; doi:10.3390/s120100359
Received: 22 November 2011 / Revised: 24 December 2011 / Accepted: 29 December 2011 / Published: 30 December 2011
Cited by 7 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
Abstract
A BIPV-powered smart window comprising a building-integrated photovoltaic (BIPV) panel and an all-solid-state electrochromic (EC) stack is proposed. In the proposed device, the output voltage of the BIPV panel varies in accordance with the intensity of the incident light and is modulated in
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A BIPV-powered smart window comprising a building-integrated photovoltaic (BIPV) panel and an all-solid-state electrochromic (EC) stack is proposed. In the proposed device, the output voltage of the BIPV panel varies in accordance with the intensity of the incident light and is modulated in such a way as to generate the EC stack voltage required to maintain the indoor illuminance within a specified range. Two different EC stacks are fabricated and characterized, namely one stack comprising ITO/WO3/Ta2O5/ITO and one stack comprising ITO/WO3/lithium-polymer electrolyte/ITO. It is shown that of the two stacks, the ITO/WO3/lithium-polymer electrolyte/ITO stack has a larger absorptance (i.e., approximately 99% at a driving voltage of 3.5 V). The experimental results show that the smart window incorporating an ITO/WO3/lithium-polymer electrolyte/ITO stack with an electrolyte thickness of 1.0 μm provides an indoor illuminance range of 750–1,500 Lux under typical summertime conditions in Taiwan. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle Characterization of a Low-Cost Optical Flow Sensor When Using an External Laser as a Direct Illumination Source
Sensors 2011, 11(12), 11856-11870; doi:10.3390/s111211856
Received: 21 November 2011 / Revised: 16 December 2011 / Accepted: 17 December 2011 / Published: 20 December 2011
Cited by 5 | PDF Full-text (871 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a low cost optical flow sensor is combined with an external laser device to measure surface displacements and mechanical oscillations. The measurement system is based on applying coherent light to a diffuser surface and using an optical flow sensor to
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In this paper, a low cost optical flow sensor is combined with an external laser device to measure surface displacements and mechanical oscillations. The measurement system is based on applying coherent light to a diffuser surface and using an optical flow sensor to analyze the reflected and transferred light to estimate the displacement of the surface or the laser spot. This work is focused on the characterization of this measurement system, which can have the optical flow sensor placed at different angles and distances from the diffuser surface. The results have shown that the displacement of the diffuser surface is badly estimated when the optical mouse sensor is placed in front of the diffuser surface (angular orientation >150°) while the highest sensitivity is obtained when the sensor is located behind the diffuser surface and on the axis of the laser source (angular orientation 0°). In this case, the coefficient of determination of the measured displacement, R2, was very high (>0.99) with a relative error of less than 1.29%. Increasing the distance between the surface and the sensor also increased the sensitivity which increases linearly, R2 = 0.99. Finally, this measurement setup was proposed to measure very low frequency mechanical oscillations applied to the laser device, up to 0.01 Hz in this work. The results have shown that increasing the distance between the surface and the optical flow sensor also increases the sensitivity and the measurement range. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Figures

Open AccessArticle Development and Evaluation of a Miniaturized Taste Sensor Chip
Sensors 2011, 11(10), 9878-9886; doi:10.3390/s111009878
Received: 22 September 2011 / Revised: 17 October 2011 / Accepted: 18 October 2011 / Published: 20 October 2011
Cited by 13 | PDF Full-text (847 KB) | HTML Full-text | XML Full-text
Abstract
A miniaturized taste sensor chip was designed for use in a portable-type taste sensing system. The fabricated sensor chip (40 mm × 26 mm × 2.2 mm) has multiple taste-sensing sites consisting of a poly(hydroxyethyl methacrylate) hydrogel with KCl as the electrolyte layer
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A miniaturized taste sensor chip was designed for use in a portable-type taste sensing system. The fabricated sensor chip (40 mm × 26 mm × 2.2 mm) has multiple taste-sensing sites consisting of a poly(hydroxyethyl methacrylate) hydrogel with KCl as the electrolyte layer for stability of the membrane potential and artificial lipid membranes as the taste sensing elements. The sensor responses to the standard taste substances showed high accuracy and good reproducibility, which is comparable with the performance of the sensor probe of the commercialized taste sensing system. Thus, the fabricated taste sensor chip could be used as a key element for the realization of a portable-type taste sensing system. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessArticle A Monolithically-Integrated μGC Chemical Sensor System
Sensors 2011, 11(7), 6517-6532; doi:10.3390/s110706517
Received: 3 May 2011 / Revised: 3 June 2011 / Accepted: 20 June 2011 / Published: 24 June 2011
Cited by 34 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
Gas chromatography (GC) is used for organic and inorganic gas detection with a range of applications including screening for chemical warfare agents (CWA), breath analysis for diagnostics or law enforcement purposes, and air pollutants/indoor air quality monitoring of homes and commercial buildings. A
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Gas chromatography (GC) is used for organic and inorganic gas detection with a range of applications including screening for chemical warfare agents (CWA), breath analysis for diagnostics or law enforcement purposes, and air pollutants/indoor air quality monitoring of homes and commercial buildings. A field-portable, light weight, low power, rapid response, micro-gas chromatography (μGC) system is essential for such applications. We describe the design, fabrication and packaging of mGC on monolithically-integrated Si dies, comprised of a preconcentrator (PC), μGC column, detector and coatings for each of these components. An important feature of our system is that the same mechanical micro resonator design is used for the PC and detector. We demonstrate system performance by detecting four different CWA simulants within 2 min. We present theoretical analyses for cost/power comparisons of monolithic versus hybrid μGC systems. We discuss thermal isolation in monolithic systems to improve overall performance. Our monolithically-integrated μGC, relative to its hybrid cousin, will afford equal or slightly lower cost, a footprint that is 1/2 to 1/3 the size and an improved resolution of 4 to 25%. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Review

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Open AccessReview Development and Application of Integrated Optical Sensors for Intense E-Field Measurement
Sensors 2012, 12(8), 11406-11434; doi:10.3390/s120811406
Received: 22 June 2012 / Revised: 25 July 2012 / Accepted: 31 July 2012 / Published: 21 August 2012
Cited by 17 | PDF Full-text (819 KB) | HTML Full-text | XML Full-text
Abstract
The measurement of intense E-fields is a fundamental need in various research areas. Integrated optical E-field sensors (IOESs) have important advantages and are potentially suitable for intense E-field detection. This paper comprehensively reviews the development and applications of several types of IOESs over
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The measurement of intense E-fields is a fundamental need in various research areas. Integrated optical E-field sensors (IOESs) have important advantages and are potentially suitable for intense E-field detection. This paper comprehensively reviews the development and applications of several types of IOESs over the last 30 years, including the Mach-Zehnder interferometer (MZI), coupler interferometer (CI) and common path interferometer (CPI). The features of the different types of IOESs are compared, showing that the MZI has higher sensitivity, the CI has a controllable optical bias, and the CPI has better temperature stability. More specifically, the improvement work of applying IOESs to intense E-field measurement is illustrated. Finally, typical uses of IOESs in the measurement of intense E-fields are demonstrated, including application areas such as E-fields with different frequency ranges in high-voltage engineering, simulated nuclear electromagnetic pulse in high-power electromagnetic pulses, and ion-accelerating field in high-energy physics. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessReview In-Line Fiber Optic Interferometric Sensors in Single-Mode Fibers
Sensors 2012, 12(8), 10430-10449; doi:10.3390/s120810430
Received: 14 May 2012 / Revised: 5 June 2012 / Accepted: 30 July 2012 / Published: 2 August 2012
Cited by 43 | PDF Full-text (1126 KB) | HTML Full-text | XML Full-text
Abstract
In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It’s known that the in-line fiber optic
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In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It’s known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
Open AccessReview Microfiber-Based Bragg Gratings for Sensing Applications: A Review
Sensors 2012, 12(7), 8861-8876; doi:10.3390/s120708861
Received: 27 April 2012 / Revised: 24 May 2012 / Accepted: 15 June 2012 / Published: 27 June 2012
Cited by 42 | PDF Full-text (1522 KB) | HTML Full-text | XML Full-text
Abstract
Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of
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Microfiber-based Bragg gratings (MFBGs) are an emerging concept in ultra-small optical fiber sensors. They have attracted great attention among researchers in the fiber sensing area because of their large evanescent field and compactness. In this review, the basic techniques for the fabrication of MFBGs are introduced first. Then, the sensing properties and applications of MFBGs are discussed, including measurement of refractive index (RI), temperature, and strain/force. Finally a summary of selected MFBG sensing elements from previous literature are tabulated. Full article
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)

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