scholarly journals Relative Humidity Sensors Based on Microfiber Knot Resonators—A Review

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5196 ◽  
Author(s):  
Young-Geun Han
Keyword(s):  
Relative Humidity ◽  
High Sensitivity ◽  
Physical Parameters ◽  
Humidity Sensors ◽  
Coating Materials ◽  
High Q ◽  
Sensing Applications ◽  
Compact Size ◽  
The Many ◽  
Humidity Sensitivity

Recent research and development progress of relative humidity sensors using microfiber knot resonators (MKRs) are reviewed by considering the physical parameters of the MKR and coating materials sensitive to improve the relative humidity sensitivity. The fabrication method of the MKR based on silica or polymer is briefly described. The many advantages of the MKR such as strong evanescent field, a high Q-factor, compact size, and high sensitivity can provide a great diversity of sensing applications. The relative humidity sensitivity of the MKR is enhanced by concerning the physical parameters of the MKR, including the waist or knot diameter, sensitive materials, and Vernier effect. Many techniques for depositing the sensitive materials on the MKR surface are discussed. The adsorption effects of water vapor molecules on variations in the resonant wavelength and the transmission output of the MKR are described regarding the materials sensitive to relative humidity. The sensing performance of the MKR-based relative humidity sensors is discussed, including sensitivity, resolution, and response time.

scholarly journals A Compact Double-Folded Substrate Integrated Waveguide Re-Entrant Cavity for Highly Sensitive Humidity Sensing

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3308 ◽  
Author(s):  
Zhihua Wei ◽  
Jie Huang ◽  
Jing Li ◽  
Junshan Li ◽  
Xuyang Liu ◽  
...  
Keyword(s):  
Humidity Sensor ◽  
High Sensitivity ◽  
Substrate Integrated Waveguide ◽  
Humidity Sensing ◽  
Food Industries ◽  
High Q ◽  
Sensing Applications ◽  
Compact Size ◽  
Highly Sensitive ◽  
Humidity Chamber

In this study, an ultra-compact humidity sensor based on a double-folded substrate integrated waveguide (SIW) re-entrant cavity was proposed and analyzed. By folding a circular re-entrant cavity twice along its two orthogonally symmetric planes, the designed structure achieved a remarkable size reduction (up to 85.9%) in comparison with a conventional TM010-mode circular SIW cavity. The operating principle of the humidity sensor is based on the resonant method, in other words, it utilizes the resonant properties of the sensor as signatures to detect the humidity condition of the ambient environment. To this end, a mathematical model quantitatively relating the resonant frequency of the sensor and the relative humidity (RH) level was established according to the cavity perturbation theory. The sensing performance of the sensor was experimentally validated in a RH range of 30%–80% by using a humidity chamber. The measured absolute sensitivity of the sensor was calculated to be 135.6 kHz/%RH, and the corresponding normalized sensitivity was 0.00627%/%RH. It was demonstrated that our proposed sensor not only has the merits of compact size and high sensitivity, but also benefits from a high Q-factor and ease of fabrication and integration. These advantages make it an excellent candidate for humidity sensing applications in various fields such as the agricultural, pharmaceutical, and food industries.

Highly chemoresistive humidity sensing using poly(ionic liquid)s

2016 ◽  
Vol 52 (54) ◽  
pp. 8417-8419 ◽  
Author(s):  
Lingling Wang ◽  
Xiaochuan Duan ◽  
Wuyuan Xie ◽  
Qiuhong Li ◽  
Taihong Wang
Keyword(s):  
Ionic Liquid ◽  
Relative Humidity ◽  
High Performance ◽  
Humidity Sensor ◽  
High Sensitivity ◽  
Fast Response ◽  
Humidity Sensors ◽  
Humidity Sensing ◽  
Good Repeatability ◽  
Poly Ionic Liquid

A novel resistance type humidity sensor was fabricated using poly(ionic liquid)s, which exhibited high sensitivity, fast response, small hysteresis and good repeatability at a relative humidity (RH) in the range of 11–98%, making poly(ionic liquid)s as promising sensing materials for high-performance humidity sensors.

scholarly journals Porous Nanostructured Gadolinium Aluminate for High-Sensitivity Humidity Sensors

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7102
Author(s):  
Corneliu Doroftei ◽  
Liviu Leontie
Keyword(s):  
Relative Humidity ◽  
Significant Influence ◽  
Humidity Sensor ◽  
Sol Gel ◽  
High Sensitivity ◽  
Combustion Method ◽  
Humidity Sensors ◽  
Oxide Compound ◽  
P Type ◽  
Highly Porous

This paper presents the synthesis of gadolinium aluminate (GdAlO3), an oxide compound with a perovskite structure, for applications as a capacitive and/or resistive humidity sensor. Gadolinium aluminate was synthesized by the sol-gel self-combustion method. This method allowed us to obtain a highly porous structure in which open pores prevail, a structure favorable to humidity sensors. Most of the materials studied as capacitive/resistive humidity sensors have significant sensitivities only with respect to one of these types of sensors. In the case of the studied gadolinium aluminate with p-type electric conductivity, the relative humidity of the air has a significant influence on both capacitive and resistive types of electric humidity sensors. The capacity increases about 10,000 times, and the resistance decreases about 8000 times as the relative humidity increases from 0 to 98%. The investigated gadolinium aluminate can be used successfully to obtain high-sensitivity capacitive and/or resistive humidity sensors.

scholarly journals State-of-the-Art Optical Devices for Biomedical Sensing Applications—A Review

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 973
Author(s):  
N. L. Kazanskiy ◽  
S. N. Khonina ◽  
M. A. Butt ◽  
A. Kaźmierczak ◽  
R. Piramidowicz
Keyword(s):  
Optical Sensors ◽  
Low Cost ◽  
High Sensitivity ◽  
Sensor Technology ◽  
Biomedical Sensors ◽  
Plasmonic Sensors ◽  
Biomedical Sensing ◽  
Sensing Applications ◽  
Compact Size ◽  
Pros And Cons

Optical sensors for biomedical applications have gained prominence in recent decades due to their compact size, high sensitivity, reliability, portability, and low cost. In this review, we summarized and discussed a few selected techniques and corresponding technological platforms enabling the manufacturing of optical biomedical sensors of different types. We discussed integrated optical biosensors, vertical grating couplers, plasmonic sensors, surface plasmon resonance optical fiber biosensors, and metasurface biosensors, Photonic crystal-based biosensors, thin metal films biosensors, and fiber Bragg grating biosensors as the most representative cases. All of these might enable the identification of symptoms of deadly illnesses in their early stages; thus, potentially saving a patient’s life. The aim of this paper was not to render a definitive judgment in favor of one sensor technology over another. We presented the pros and cons of all the major sensor systems enabling the readers to choose the solution tailored to their needs and demands.

scholarly journals Development of Enhanced Range, High Q, Passive, Chipless RFID Tags for Continuous Monitoring and Sensing Applications

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 127
Author(s):  
Aiswarya S ◽  
Sreedevi K. Menon ◽  
Massimo Donelli
Keyword(s):  
Continuous Monitoring ◽  
Analytical Formula ◽  
High Sensitivity ◽  
Proof Of Concept ◽  
Rfid Tag ◽  
High Q ◽  
Dielectric Substrates ◽  
Sensing Applications ◽  
Chipless Rfid ◽  
System Prototype

A high Q planar chipless RFID tag with high sensitivity is proposed for communication applications. In particular, the tag structure is composed of a complementary spiral structure (CSS) that is able to provide high sensitivity and compactness. A semi analytical formula for the design of a single bit tag is derived, and the behaviour of the CSS is analysed for different dielectric substrates. Different tags, composed of up to a set of eight resonators, have been numerically and experimentally assessed. In particular, a system prototype composed of a reader and a set of tags are fabricated and experimentally assessed as a proof of concept. The system provided an operative range of tens of centimetres (a maximum operative range of 65 cm). The obtained results are quite promising and the agreement between simulated and measured results are found to be good.

scholarly journals Overview of Quartz Crystal Microbalance Behavior Analysis and Measurement

Chemosensors ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 350
Author(s):  
Sawit Na Songkhla ◽  
Takamichi Nakamoto
Keyword(s):  
Equivalent Circuit ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
High Sensitivity ◽  
Theoretical Models ◽  
Coating Materials ◽  
Sensor Applications ◽  
Acoustic Transducer ◽  
Electronic Measurement ◽  
The Many

Quartz Crystal Microbalance (QCM) is one of the many acoustic transducers. It is the most popular and widely used acoustic transducer for sensor applications. It has found wide applications in chemical and biosensing fields owing to its high sensitivity, robustness, small sized-design, and ease of integration with electronic measurement systems. However, it is necessary to coat QCM with a sensing film. Without coating materials, its selectivity and sensitivity are not obtained. At present, this is not an issue, mainly due to the advancement of oscillator circuits and dedicated measurement circuits. Since a new researcher may seek to understand QCM sensors, we provide an overview of QCM from its fundamental knowledge. Then, we explain some of the recent QCM applications both in gas-phase and liquid-phase. Next, the theory of QCM is introduced by using piezoelectric stress equations and the Mason equivalent circuit, which explains how the QCM behavior is obtained. Then, the conventional equations that govern QCM behaviors in terms of resonant frequency and resistance are described. We show the behavior of QCM with a viscous film based on the acoustic wave equation and Mason equivalent circuit. Then, we present various existing QCM electronic measurement methods. Furthermore, we describe the experiment on QCM with viscous loading and its interpretation based on the Mason equivalent circuit. Lastly, we review some theoretical models to describe QCM behavior with various models.

scholarly journals Study on the Nanosensor Based on a MIM Waveguide with a Stub Coupled with a Horizontal B-Type Cavity

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 125
Author(s):  
Shubin Yan ◽  
Haoran Shi ◽  
Xiaoyu Yang ◽  
Jing Guo ◽  
Wenchang Wu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Spectral Characteristics ◽  
High Sensitivity ◽  
Refractive Index Sensor ◽  
Plasmonic Sensors ◽  
Sensing Applications ◽  
Compact Size ◽  
Metal Insulator Metal ◽  
The Difference ◽  
Mim Waveguide

Due to their compact size and high sensitivity, plasmonic sensors have become a hot topic in the sensing field. A nanosensor structure, comprising the metal–insulator–metal (MIM) waveguide with a stub and a horizontal B-Type cavity, is designed as a refractive index sensor. The spectral characteristics of proposed structure are analyzed via the finite element method (FEM). The results show that there is a sharp Fano resonance profile, which is excited by a coupling between the MIM waveguide and the horizontal B-Type cavity. The normalized HZ field is affected by the difference value between the outer radii R1 and R2 of the semi-circle of the horizontal B-Type cavity greatly. The influence of every element of the whole system on sensing properties is discussed in depth. The sensitivity of the proposed structure can obtain 1548 nm/RIU (refractive index unit) with a figure of merit of 59. The proposed structure has potential in nanophotonic sensing applications.

Compliant and Low-Cost Humidity Sensors Using Nano-Porous Polymer Membranes

2004 ◽  
Author(s):  
Bozhi Yang ◽  
Burak Aksak ◽  
Shan Liu ◽  
Qiao Lin ◽  
Metin Sitti
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Capillary Condensation ◽  
Low Cost ◽  
Polymer Membranes ◽  
High Sensitivity ◽  
Porous Polymer ◽  
Humidity Sensors ◽  
Water Leakage Detection

This paper proposes non-fragile compliant humidity sensors that can be fabricated inexpensively on various types of nano-porous polymer membranes such as polycarbonate, cellulose acetate, and nylon membranes. The sensor contains a pair of interdigitated electrodes deposited on the nano-porous polymer membranes. The resistance and/or capacitance between these electrodes vary at different humidity levels with a very high sensitivity due to the water adsorption (capillary condensation) inside the nano-pores. The proposed sensors are low-cost in both material and fabrication. Due to its compliance, the sensors can be suitable for certain applications such as in-situ water leakage detection on roofs, where people can walk on top of them. Testing results demonstrated that the sensor changes resistance within large range of humidity values. For most sensors, the resistance changes from 0.1 GΩ to 2000 GΩ when the relative humidity changes from 39% to 100% at room temperature. It takes about 4–8 minutes for the resistance to reach steady state when the sensor was taken from 100% to 39% relative humidity at the room temperature.

scholarly journals Effects of Tungsten Disulphide Coating on Tapered Microfiber for Relative Humidity Sensing Applications

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7132
Author(s):  
Norazida Ali ◽  
Saaidal Razalli Azzuhri ◽  
Md Ashadi Md Johari ◽  
Haroon Rashid ◽  
Muhammad Imran Mustafa Abdul Khudus ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Humidity Sensor ◽  
Near Field ◽  
High Sensitivity ◽  
Evanescent Field ◽  
Transition Metal Dichalcogenide ◽  
Casting Technique ◽  
Tungsten Disulphide ◽  
Sensing Applications ◽  
Tapered Region

Tungsten disulphide (WS2) is a two-dimensional transition-metal dichalcogenide material that can be used to improve the sensitivity of a variety of sensing applications. This study investigated the effect of WS2 coating on tapered region microfiber (MF) for relative humidity (RH) sensing applications. The flame brushing technique was used to taper the standard single-mode fiber (SMF) into three different waist diameter sizes of MF 2, 5, and 10 µm, respectively. The MFs were then coated with WS2 via a facile deposition method called the drop-casting technique. Since the MF had a strong evanescent field that allowed fast near-field interaction between the guided light and the environment, depositing WS2 onto the tapered region produced high humidity sensor sensitivity. The experiments were repeated three times to measure the average transmitted power, presenting repeatability and sensing stability. Each MF sample size was tested with varying humidity levels. Furthermore, the coated and non-coated MF performances were compared in the RH range of 45–90% RH at room temperature. It was found that the WS2 coating on 2 µm MF had a high sensitivity of 0.0861 dB/% RH with linearity over 99%. Thus, MF coated with WS2 encourages enhancement in the evanescent field effect in optical fiber humidity sensor applications.

scholarly journals Humidity Sensor Based on Multi-Walled Carbon Nanotube Thin Films

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
C. L. Cao ◽  
C. G. Hu ◽  
L. Fang ◽  
S. X. Wang ◽  
Y. S. Tian ◽  
...  
Keyword(s):  
Thin Films ◽  
Carbon Nanotube ◽  
Relative Humidity ◽  
Humidity Sensor ◽  
Sensitive Material ◽  
Humidity Sensors ◽  
Multi Walled Carbon Nanotube ◽  
Chemically Treated ◽  
Humidity Sensitivity ◽  
Higher Sensitivity

The properties of the humidity sensors made of chemically treated and untreated multi-walled carbon nanotube (MWCNT) thin films are investigated systematically. It shows that both the chemically treated and untreated MWCNT thin films demonstrate humidity sensitive properties, but the former have stronger sensitivity than the latter. In the range of 11%–98% relative humidity (RH), the resistances of the chemically treated and untreated MWCNT humidity sensors increase 120% and 28%, respectively. Moreover, the treated humidity sensors showed higher sensitivity and better stability. In addition, the response and recover properties, and stabilization of the humidity sensors are measured, and the humidity sensitive mechanisms of the sensors are analyzed. The humidity sensitivity of carbon nanotube thin films indicates it promise as a kind of humidity sensitive material.

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