scholarly journals Recent Progress in Microfiber-Optic Sensors

2021 ◽  
Vol 11 (1) ◽  
pp. 45-68
Author(s):  
Wei Luo ◽  
Ye Chen ◽  
Fei Xu
Keyword(s):  
Fiber Optics ◽  
Recent Progress ◽  
Response Times ◽  
Functional Materials ◽  
High Sensitivity ◽  
Fast Response ◽  
Basic Principles ◽  
Area Of Interest ◽  
Compact Size ◽  
Optical Microfiber

AbstractRecently, microfiber-optic sensors with high sensitivity, fast response times, and a compact size have become an area of interest that integrates fiber optics and nanotechnology. Distinct advantages of optical microfiber, such as large accessible evanescent fields and convenient configurability, provide attractive benefits for micro- and nano-scale optical sensing. Here, we review the basic principles of microfiber-optic sensors based on a broad range of microstructures, nanostructures, and functional materials. We also introduce the recent progress and state-of-the-art in this field and discuss the limitations and opportunities for future development.

Recent progress of dissolved carbon dioxide measurement technologies based on optical methods

2018 ◽  
Vol 41 (8) ◽  
pp. 2374-2385
Author(s):  
Xiang Li ◽  
Qi Wang
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Effect ◽  
Recent Progress ◽  
High Sensitivity ◽  
Fast Response ◽  
Field Method ◽  
Optical Methods ◽  
Dissolved Carbon ◽  
Carbon Dioxide Measurement ◽  
Dissolved Carbon Dioxide

This paper sums up the developments and achievements of optical methods in the field of dissolved carbon dioxide measurement based on past work. The dissolved CO2 measurement in optical methods is highly applied owing to high sensitivity, fast response and greater versatility with more attention people paid to greenhouse effect. In this article, the measuring is mainly partitioned into fluorescent methods, spectrometric methods and specific optical methods like evanescent field method. Principles, characteristics and structures in previous research are described in detail and our own ideas and perspectives in tendency of dissolved carbon dioxide sensing are emphasized lastly.

Speed of Sound Measurement in Solids Using Polyvinylidene Fluoride (PVDF) Sensors

2013 ◽  
Author(s):  
Leon M. Headings ◽  
Kunal Kotian ◽  
Marcelo J. Dapino
Keyword(s):  
Finite Element ◽  
Stress Wave ◽  
Speed Of Sound ◽  
Polyvinylidene Fluoride ◽  
Response Times ◽  
High Sensitivity ◽  
Fast Response ◽  
Load Path ◽  
Straightforward Method ◽  
The Impact

Piezoelectric film sensors such as polyvinylidene flouride (PVDF) generate an electrical voltage in response to an applied mechanical stress with a remarkably high sensitivity. They provide very fast response times and do not require extensive signal conditioning. This paper presents a straightforward method of measuring the speed of sound in solid materials and structures using commercial PVDF sensors. PVDF sensors are most commonly used to measure stresses applied in the sensors’ thickness direction. However, this requires that the sensors be located in the load path, which may result in damage to the sensor or affect the response of the system. In this paper, two PVDF sensors are bonded to the side of a structure and a small impact is applied to one end. The sensors are used to measure the time for the impact-induced plane stress wave to travel between the sensors. The observed speed of the propagating stress wave is shown to be in good agreement with the theoretical speed of sound for the material and finite element calculations. In addition, the finite element simulations confirm the validity of the plane wave assumption for non-ideal and non-uniform impact inputs.

A Self-Locking Technique With Fast Response and High Sensitivity for Micro-Cantilever Based Sensing of Analytes

2002 ◽  
Vol 723 ◽  
Author(s):  
A. Mehta ◽  
G. Muralidharan ◽  
A. Passian ◽  
S. Cherian ◽  
T.L. Ferrell ◽  
...  
Keyword(s):  
Response Times ◽  
High Sensitivity ◽  
Fast Response ◽  
Q Factor ◽  
Ambient Conditions ◽  
Sensor Applications ◽  
Feedback Scheme ◽  
Micro Cantilever ◽  
Lock In ◽  
Thermal Oscillations

AbstractMEMS based microcantilevers have been employed as sensors in both liquid and ambient conditions. One scheme for detection is based upon monitoring the change in microcantilever resonant frequency as a function of the adsorbed analyte concentration. However, the sensitivity is limited by the accuracy of the frequency measurements, which is a function of the Q-factor of the vibrating element and the measurement bandwidth. In this paper, we present a feedback scheme for self-locking amplification of the small-amplitude thermal oscillations of the microcantilever. Using this approach, we demonstrate an improvement in the Q-factor by two to three orders of magnitude as compared to that of the undriven microcantilever. Use of this technique eliminates the need for lock-in detection and results in improved response times for sensor applications. Experiments using the proposed feedback amplification technique show improved sensitivity for the detection of biological molecules in liquids, and for adsorbed vapors under ambient conditions.

scholarly journals Optical Microfiber Sensor : A Review

2021 ◽  
Vol 2075 (1) ◽  
pp. 012021
Author(s):  
Mohd Hafiz Jali ◽  
Hazli Rafis Abdul Rahim ◽  
Md Ashadi Md Johari ◽  
Mohamad Faizal Baharom ◽  
Aminah Ahmad ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Environmental Control ◽  
High Sensitivity ◽  
Low Noise ◽  
Detection Range ◽  
Sensing Applications ◽  
Manufacturing Process Control ◽  
Compact Size ◽  
Temperature Levels ◽  
Optical Microfiber

Abstract Due to numerous benefits such as geometrical simplicity, compact size, high sensitivity, broad detection range, low noise, and high accuracy, optical devices have attracted a lot of interest for sensing applications. It is critical in a variety of sectors, including cultural relic preservation, warehouse products maintenance, manufacturing process control, semiconductor, agriculture, food production storage, environmental control, health industries, chemical and home improvement. It outperforms its electronic equivalent owing to its capacity to function in tough and demanding situations such as combustible surroundings, greater pressure and temperature levels, and the ability to send signals over long distances without electromagnetic interference. Optical fiber sensors are classified based on their operating principles such as interferometers, fiber Bragg gratings (FBG), resonators and whispering galleries modes (WGM). This paper presents a comprehensive review related to the optical microfiber sensor such as its properties, fabrication techniques, evanescent wave, optical micro resonators and recent study on the application of microfiber towards humidity sensing. This review could be beneficial to help other researchers to gain greater view in the field of optical microfiber sensor.

Electrospun Electroactive Polymer and Metal Oxide Nanofibers for Chemical Sensor Applications

2010 ◽  
Author(s):  
Jonas Flueckiger ◽  
Frank K. Ko ◽  
Karen C. Cheung
Keyword(s):  
Metal Oxide ◽  
Chemical Sensor ◽  
Response Times ◽  
Electrical Characterization ◽  
Volume Ratio ◽  
High Sensitivity ◽  
Fast Response ◽  
Sensor Applications ◽  
Tio2 Nanofiber ◽  
Good Signal

We present the fabrication of a polymer blend PANi/PEO nanofiber based sensor as well as a metal oxide TiO2 nanofiber based sensor. Electrospinning was used for the fabrication of the electroactive nanofibers. The conductivity of those fibers is highly sensitive to the chemical environment and is modified through the adsorption of different species. Used as a chemiresistor the nanofibers offer a higher sensitivity than thin films due to the increased surface to volume ratio. Impedance spectroscopy was used for electrical characterization of the fibers showing high sensitivity. Preliminary measurements of the sensors dynamic response when exposed to alternating chemical environments showed fast response times and good signal stability.

Nanostructure of semiconductor quantum dots in a borosilicate glass matrix by complementary use of HREM and AEM

1990 ◽  
Vol 48 (4) ◽  
pp. 728-729
Author(s):  
M.J. Kim ◽  
L.C. Liu ◽  
S.H. Risbud ◽  
R.W. Carpenter
Keyword(s):  
Quantum Dots ◽  
Borosilicate Glass ◽  
Glass Matrix ◽  
Optical Switching ◽  
Response Times ◽  
Fast Response ◽  
Processing Technique ◽  
Internal Stresses ◽  
Electron Hole ◽  
Spatial Dimensions

When the size of a semiconductor is reduced by an appropriate materials processing technique to a dimension less than about twice the radius of an exciton in the bulk crystal, the band like structure of the semiconductor gives way to discrete molecular orbital electronic states. Clusters of semiconductors in a size regime lower than 2R {where R is the exciton Bohr radius; e.g. 3 nm for CdS and 7.3 nm for CdTe) are called Quantum Dots (QD) because they confine optically excited electron- hole pairs (excitons) in all three spatial dimensions. Structures based on QD are of great interest because of fast response times and non-linearity in optical switching applications.In this paper we report the first HREM analysis of the size and structure of CdTe and CdS QD formed by precipitation from a modified borosilicate glass matrix. The glass melts were quenched by pouring on brass plates, and then annealed to relieve internal stresses. QD precipitate particles were formed during subsequent "striking" heat treatments above the glass crystallization temperature, which was determined by differential thermal analysis.

Compact and efficient gas diffusion electrodes based on nanoporous alumina membranes for microfuel cells and gas sensors

The Analyst ◽  
2020 ◽  
Vol 145 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Wanda V. Fernandez ◽  
Rocío T. Tosello ◽  
José L. Fernández
Keyword(s):  
Response Times ◽  
Hydrogen Oxidation ◽  
Fast Response ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Gas Diffusion Electrodes ◽  
Nanoporous Alumina ◽  
Alumina Membranes ◽  
Current Densities ◽  
Microfuel Cells

Gas diffusion electrodes based on nanoporous alumina membranes electrocatalyze hydrogen oxidation at high diffusion-limiting current densities with fast response times.

scholarly journals Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 648
Author(s):  
Aijie Liang ◽  
Jingyuan Ming ◽  
Wenguo Zhu ◽  
Heyuan Guan ◽  
Xinyang Han ◽  
...  
Keyword(s):  
Humidity Sensor ◽  
Small Diameter ◽  
High Sensitivity ◽  
Large Change ◽  
Small Variation ◽  
Response Speed ◽  
Fast Response ◽  
Tin Disulfide ◽  
Recovery Times ◽  
Response And Recovery

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by coating tin disulfide (SnS2) nanosheets onto the surface of MF. The small diameter (~8 μm) and the long length (~5 mm) of the MF promise strong interaction between guiding light and SnS2. Thus, a small variation in the relative humidity (RH) will lead to a large change in optical transmitted power. A high RH sensitivity of 0.57 dB/%RH is therefore achieved. The response and recovery times are estimated to be 0.08 and 0.28 s, respectively. The high sensitivity and fast response speed enable our SnS2-MF sensor to monitor human breath in real time.

Remote, Long-Pathlength Cell for High-Sensitivity Raman Spectroscopy

1987 ◽  
Vol 41 (1) ◽  
pp. 126-130 ◽  
Author(s):  
Scott D. Schwab ◽  
Richard L. McCreery
Keyword(s):  
Fiber Optics ◽  
Laser Light ◽  
Capillary Tube ◽  
High Sensitivity ◽  
Sample Tube ◽  
Increased Sensitivity ◽  
Sampling Systems ◽  
Power Densities ◽  
Objective Being ◽  
Focused Beam

Fiber optics were used to interface a Raman spectrometer to a long (1 m) sample tube, with the objective being increased sensitivity. Internal reflection of the laser light and the Raman scatter within the sample tube permitted a long solution length to be sampled, increasing the Raman sensitivity by factors of 30–50 over conventional capillary tube sampling systems. In addition, the sample was subjected to much lower power densities than with systems employing a focused beam, thus minimizing radiation damage. Detection limits of 10−9 to 10−8 M were achieved for resonance Raman scatterers, and normal Raman scatterers could be detected at the 1 × 10−5 M level.

scholarly journals A Full-Range Flexible and Printed Humidity Sensor Based on a Solution-Processed P(VDF-TrFE)/Graphene-Flower Composite

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1915
Author(s):  
Shenawar Ali Khan ◽  
Muhammad Saqib ◽  
Muhammad Muqeet Rehman ◽  
Hafiz Mohammad Mutee Ur Rehman ◽  
Sheik Abdur Rahman ◽  
...  
Keyword(s):  
Active Layer ◽  
Humidity Sensor ◽  
High Reliability ◽  
Full Range ◽  
High Sensitivity ◽  
Fast Response ◽  
Considerable Change ◽  
Relative Humidity Range ◽  
Response And Recovery ◽  
Proportional Relationship

A novel composite based on a polymer (P(VDF-TrFE)) and a two-dimensional material (graphene flower) was proposed as the active layer of an interdigitated electrode (IDEs) based humidity sensor. Silver (Ag) IDEs were screen printed on a flexible polyethylene terephthalate (PET) substrate followed by spin coating the active layer of P(VDF-TrFE)/graphene flower on its surface. It was observed that this sensor responds to a wide relative humidity range (RH%) of 8–98% with a fast response and recovery time of 0.8 s and 2.5 s for the capacitance, respectively. The fabricated sensor displayed an inversely proportional response between capacitance and RH%, while a directly proportional relationship was observed between its impedance and RH%. P(VDF-TrFE)/graphene flower-based flexible humidity sensor exhibited high sensitivity with an average change of capacitance as 0.0558 pF/RH%. Stability of obtained results was monitored for two weeks without any considerable change in the original values, signifying its high reliability. Various chemical, morphological, and electrical characterizations were performed to comprehensively study the humidity-sensing behavior of this advanced composite. The fabricated sensor was successfully used for the applications of health monitoring and measuring the water content in the environment.

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