Humidity Sensor Applications Research Articles

Miniature and high-performance optical fiber relative humidity sensor based on Fabry-Perot structure interacting with hydroxyethyl cellulose

A miniature Fabry-Perot fiber-optic sensor is demonstrated for high-performance relative humidity (RH) detection. This sensor is constructed by fusing a single-mode fiber to a small section of capillary coating the end with a hydroxyethyl cellulose film (HEC). The effects of capillary length and hydroxyethyl cellulose concentration on the RH response are investigated to obtain the preferential condition with capillary length of 102 μm and HEC concentration of 0.03 g/ml. A testing RH sensitivity of 1.24 nm/%RH can be achieved in the range of 48%RH to 60%RH. Simultaneously, small hysteresis errors are demonstrated in the tests with increasing and decreasing RH values. The dynamic measurements reveal a response time of 1.61 s and a recovery time of 2.1 s. The high sensitivity, good stability and simple fabrication process of the sensor make it promising for practical applications of relative humidity sensors.

Humidity Sensor Performance Based ZnO/SnO<sub>2</sub> Nanorods Structure Using Different ZnO Seed Layer

This paper investigates performance of ZnO/SnO2 nanorods structure thin film deposited at two different ZnO seed layer (ZnO seed A and ZnO seed B) for humidity sensor application. ZnO seed A and ZnO seed B were deposited using two different method which were sputtering method and spin coating method respectively. ZnO/SnO2 nanorods structure thin film that has been prepared on ZnO seed A and ZnO seed B using thermal chemical vapor deposition (CVD). The structural properties have been characterized using field emission scanning electron microscopy (FESEM) (JEOL JSM 6701F). Base on the FESEM image the size of ZnO seed A and ZnO seed B were ranging around 75 to 85 nm and 17 to 21 nm respectively. The results analyzed were for ZnO/SnO2 composite nanorods structure size on ZnO seed A and ZnO seed B were averagely around 18 nm to 29 nm. The sensor properties were characterized by using current-voltage (I-V) measurement (Keithley 2400). ZnO/SnO2 nanorods structure thin film deposited on ZnO Seed A performed highest sensitivity with 265 ratio compare to ZnO/SnO2 nanorods structure thin film deposited on ZnO Seed B with 75 ratio of sensitivity.

Frequency Sensitivity Analysis of Coil-IDE Resonance Topology Circuit and Its Humidity Sensor Applications

In this paper, the frequency sensitivity of Coil-IDE (interdigital electrode) sensor in different integrated topology is studied. In particular, the expression of resonance frequency of the Coil-IDE sensor both in series and parallel topological structure is derived. The sensitivity of frequency to IDE capacitance was analyzed, and two new results can be found: (i) Due to the existence of coil winding capacitance and grounding capacitance, Coil-IDE topology circuit has been changed which cause the Coil-IDE parallel topology structure has the higher frequency sensitivity than series; (ii) Not only the topology structure but also the parameters such as coil inductance and IDE capacitance have the regulatory effect on the frequency sensitivity. After analysis, an experiment of Coil-IDE humidity sensor was applied to verify the presented results. The parallel frequency of the Coil-IDE parallel structure has the higher sensitivity was confirmed. The error of the proposed formula predicting the regulatory effect of parameters on frequency sensitivity was discussed. The error is as low as 7.57%, which shows the beneficial to the integrated design of Coil-IDE sensor both in topological structure and parameters.

Environment friendly lead-free Cs3Sb2Br9 perovskite: Wide measure range, high sensitivity, and rapid sensing response for high-performance humidity sensor

Due to the superiority of easy manufacture, low cost, coupled with super optoelectronic attributes, the metal halide perovskites have appeared as an emerging class of semiconductors owning their considerable potential for assorted utilization in humidity sensors. Nevertheless, the toxicity problem along with inherent instability of lead (Pb) halide perovskites is grimly impeding the large-scale manufacturing as well as commercialization. Herein, lead-free Cs3Sb2Br9 perovskites were successfully synthesized using a modified ligand-assisted reprecipitation approach and the humidity sensing properties relevant for humidity sensor applications were investigated. The as-fabricated Cs3Sb2Br9 humidity sensors display a super-high impedance variation of more than 105, and the testing range can be extended to a very low humidity (2% relative humidity, RH). The value of hysteresis is as low as 2.9%, and the response/recovery time is discovered to reach ∼0.9/3 s from 11% to 95% RH, which owns a large potential in the detection of the real-time moisture. Moreover, the Cs3Sb2Br9 humidity sensor boasts good reversibility and a remarkable level of stability. Our results demonstrate the potential for lead-free Cs3Sb2Br9 perovskites in a real-time and high-performance humidity sensor.

Synthesis and structural, microstructural and humidity sensing behavior of (x)rGo+(1-x)CoCr2O4 composite for humidity sensor applications

Immediate research is needed to determine why monolayer carbon atom (rGO) composites function so poorly as humidity sensors. Here, an attempt is made on (x)rGo+(1-x)CoCr2O4(x = 0,0.1,0.2 and 0.3) composite for humidity sensor. The method is straightforward, cheap, and basic, making it ideal for mass-producing (x)rGo+(1-x)CoCr2O4 composite. In this research, we investigate whether or not the (x)rGo+(1-x)CoCr2O4 composite can be used to improve the responsiveness of humidity sensors at ambient temperature. The use of X-ray diffraction allows for the investigation of crystallinity, phase, and structure (XRD). Crystallite size were estimated and found 9–11 nm. Morphology of the samples were seen ultrathin, wrinkled, paper-like, spherical type image. Samples were subjected to study the humidity sensing behavior. Within the range of 11%–97% RH, CCR-most rGO's impressive sensing response was 92%. The compound's stability was evaluated over the course of three months, and its response time was found to be between 32 and 36 s. To illustrate the mechanism of humidity sensing, we will use the stages of an adsorption process. For x = 0.3 concentration we observed high sensing response.

Noncontact sensing for water area scanning identification based on Ho2O3/GO humidity sensor

With the advent of the era of intelligent perception and artificial intelligence, higher requirements on the response/recovery speed of humidity sensitive materials and the expansion of new applications of humidity sensors have been put forward. In this study, Ho2O3/GO composites were obtained by ultrasonic stirring of the GO solution with the synthesized Ho2O3 material. Benefiting from the presence of adsorbed hydroxyl oxygen on the surface and the regular arrangement of the nanosheets, the humidity response of Ho2O3/GO sensor has nearly doubled from 1102 to 2136, and the recovery time was reduced by more than half from 6 s to 1 s. Based on excellent humidity sensitive properties, the sensor was used for non-contact scanning to identify water zones of different shapes, thus presenting information on the distribution of water beneath the sensor. This research opens up further possibilities for the expansion of humidity sensors in emerging applications such as smart sensing.

TiO2-SnS2 Nanoheterostructures for High-Performance Humidity Sensor

The larger surface-to-volume ratio of the hierarchical nanostructure means it has attracted considerable interest as a prototype gas sensor. Both TiO2 and SnS2 can be used as sensitive materials for humidity sensing with excellent performance. However, TiO2-SnS2 nanocomposites are rarely used in humidity detection. Therefore, in this work, a new humidity sensor was prepared by a simple one-step synthesis process based on nano-heterostructures, and the humidity sensing performance of the device was systematically characterized by much faster response/recovery behavior, better linearity and greater sensitivity compared to pure TiO2 or SnS2 nanofibers. The enhanced sensitivity of the nanoheterostructure should be attributed to its special hierarchical structure and TiO2-SnS2 heterojunction, which ultimately leads to a significant change in resistance upon water molecule exposure. In consideration of its non-complicated, cost-effective fabrication process and environmental friendliness, the TiO2-SnS2 nanoheterostructure is a hopeful candidate for humidity sensor applications.

Reduced Graphene Oxide/Polyelectrolyte Multilayers for Fast Resistive Humidity Sensing.

Fast humidity sensors are of interest due to their potential application in new sensing technologies such as wearable personal healthcare and environment sensing devices. However, the realization of rapid response/recovery humidity sensors remains challenging primarily due to the sluggish adsorption/desorption of water molecules, which particularly impacts the response/recovery times. Moreover, another key factor for fast humidity sensing, namely the attainment of equal response and recovery times, has often been neglected. Herein, the layer-by-layer (LbL) assembly of a reduced graphene oxide (rGO)/polyelectrolyte is demonstrated for application in fast humidity sensors. The resulting sensors exhibit fast response and recovery times of 0.75 and 0.85 s (corresponding to times per RH range of 0.24 and 0.27 s RH-1, respectively), providing a difference of only 0.1 s (corresponding to 0.03 s RH-1). This performance exceeds that of the majority of previously reported graphene oxide (GO)- or rGO-based humidity sensors. In addition, the polyelectrolyte deposition time is shown to be key to controlling the humidity sensing kinetics. The as-developed rapid sensing system is expected to provide useful guidance for the tailorable design of fast humidity sensors.

Structural, morphological, and impedance spectroscopy of Tin oxide -Titania based electronic material

A ceramic composite electronic sample (Sn0·6Ti0.4)O2 is processed through solid-state reaction approach. Crystallographic, morphological, and different temperature-frequency-dependent electrical characteristics have been examined. The formation of a crystallographic polycrystalline tetragonal structure has been ensured through X-Ray Diffraction. The hydrophilic porous nature with uniform distribution of grains is ascertained through SEM. The electrical parameters are evaluated across broad temperatures and frequency ranges of 35 °C–450 °C and 1 kHz - 1 MHz respectively. A superior dielectric permittivity (εr: 44,730), low loss tangent (tanδ: 11.074) (for 400 °C, frequency 1 kHz) with enhanced capacitive behaviour are depicted. The conductivity spectrum reveals the nature and mechanism of conduction. The impedance analyzer divulges the realization of the grain and grain boundary effect on the electrical characteristics. The Non-Debye relaxation behaviour is substantiated by an electric modulus analysis. The comprehensive investigations illustrate this component as a capacitive electronic element for humidity sensor applications.

Synthesis and study of transition metal(Co, Cu, and Ni) substituted ferrites for humidity sensor applications

Synthesis and study of transition metal(Co, Cu, and Ni) substituted ferrites for humidity sensor applications

NiFe2O4 and ZnFe2O4 nanoparticles synthesis by sol-gel auto-combustion for humidity sensor applications

NiFe2O4 and ZnFe2O4 nanoparticles synthesis by sol-gel auto-combustion for humidity sensor applications

IOT-BASED SMART GARDENING SYSTEM USING ARDUINO UNO

Abstract—Environmental awareness is one of the most important factors for environmental sustainability. This paper describes a Smart gardening system using an IoT platform. The main purpose of this automation is to make home gardening more convenient by eliminating manual work. The Soil Moisture Sensor has many applications in agricultural research, everyday gardening, and humidity and temperature sensors. By tracking the amount of water in your soil, you can ensure your valuable crops stay hydrated and know how they’re doing before planting. Our project uses a soil moisture meter and a humidity and temperature sensor using the ESP8266 to alert the user when plants need to be watered. Next, we built an automatic irrigation system using the IoT board. Our system also includes an OLED display and uses an IoT cloud, so you can monitor and control the system over the internet. PIR sensors are built into the system to help prevent pests from getting closer to your plants or destroy plants. Additionally, after much research, our project includes a purple LED light to stimulate plant growth. Index Terms—IoT, ESP8266 micro controller, soil moisture sensor, humidity sensor and temperature sensor, PIR sensor, purple LED lights

Combustion-Synthesized CoFe2O4 Nanoparticles: Structure and electrical conductivity Studies

Nanocrystalline ferrites MFe2O4 (M = Ni, Co, Cu, Zn, Mn, Mg, etc.) are attracting the attention of researchers due to their utility in recording media, magneto-optics, spintronics, Ferrofluids, microwave devices, and so on. Ferrites are also utilized in gas and humidity sensors applications, anode material for a Li/Na-ion battery and electronic & magnetic applications. Combustion successfully generated cobalt ferrite (CoFe2O4) nanoparticles. X-ray diffraction (XRD) and infrared spectroscopy (FT-IR) were used to study the structural information. The crystallite size calculated by Scherer's formula is 14 nm based on XRD patterns. FTIR spectra indicate ferrite atoms in tetrahedral and octahedral positions, confirming the spinel phase. The electrical conductivity of CoFe2O4 nanoparticles at room temperature is 4.6 × 10-5 S cm−1.

NiFe2O4 nanoparticles prepared using the sol-gel process: Structural and impedance investigations

The versatile properties of nano-crystalline ferrites (MFe2O4) are attracting the attention of researchers due to their utility in various fields, including recording media, magneto-optics, spintronics, ferro fluids, microwave devices, and more. Ferrites are also utilized in gas and humidity sensors applications, anode material for a Li/Na-ion battery, and electronic and magnetic applications. The sol–gel approach has successfully produced nickel ferrite (NiFe2O4) nanoparticles. After manufacturing, XRD and Infrared spectroscopy (FT-IR) were used to learn about the powders structural properties. Scherer's formula estimates the crystallite size to be 18 nm, and an examination of the XRD patterns supports the single-phase cubic spinel structure. FTIR spectra verify the spinel phase is maintained by the distinctive vibration of ferrite atoms at tetrahedral and octahedral positions. Variations in temperature and frequency were used to conduct the impedance tests. The electrical conductivity of NiFe2O4 nanoparticles at room temperature is 5.2 × 10-6 S cm−1.

Amorphous carbon material of daily carbon ink: emerging applications in pressure, strain, and humidity sensors

In this review, the state-of-the-art advances in amorphous carbon materials of the daily carbon ink for pressure, strain, and humidity sensors are presented and discussed.

GO: Ag Composites Materials for Dynamic Humidity Sensing Applications

Silver crystallite-graphene oxide (Ag-Nps/GO) composites are widely used for various applications and are an attractive material for next-generation nano-electronic devices, and we demonstrate their use in humidity sensors. Silver crystallite (Ag-Nps) is prepared through a single step by reduction method at room temperature. The resulting crystallite is a pure phase as confirmed through X-ray diffraction (XRD) without any traces of oxides or secondary impurities. The crystallite size is around 1 μm. These crystallites are blended with synthesized graphene oxide in a different weight ratio to make the composite. Various characterization techniques like scanning electron microscopy (SEM), UV spectroscopy, and XRD are used to understand structures and surface morphology. The composite is dropped on Al printed sensor (IDE). The humidity is varied from 5% to 55%, the conductivity decreases with an increase in humidity. The sensor has a fast response/recovery time reproducible. In conclusion, the present work describes a low-cost, novel strategy for synthesizing humidity sensor applications. The sensors can be used in applications like biomedical, food processing, agriculture, pharmaceutical, and microelectronics.

Synthesis and characterization of PVDF/PMMA/ZnO hybrid nanocomposite thin films for humidity sensor application

This work aimed PVDF/PMMA thin films in a range of ZnO NPs weight ratios that were successfully manufactured via spin coating as high-performance humidity sensors. The films have been characterized to calculate the structure, functional groups, transmittance and optical energy band gap. X-ray diffraction (XRD) structural studies reveal that the prepared films are polycrystalline with hexagonal crystal structures. It was found that the grain size of these films decreases with the increasing weight ratios of zinc oxide nanoparticles. Field emission scanning electron microscopy reveals the homogeneous distribution of zinc oxide nanoparticles in the PMMA/PVDF matrix. EDX was used to investigate the chemical composition of the PVDF/PMMA/ZnO nanocomposite. FTIR test was performed to identify the functional groups in the prepared samples as well as the detection of doping which is added to the samples. The optical energy band gap values were calculated and types of optical transmission and absorption of the films were determined from the optical transmittance spectra. The optical absorption studies in the wavelength range (200−700) nm show that energy band gap values of the prepared films decrease from (4.98–4.28) eV with increasing the ZnO NPs weight ratio. A sensor for relative humidity within the range (31−100) % RH was manufactured by studying the change of electrical properties (capacitive, resistance) and simulating them theoretically. It was found that the PVDF/PMMA/ZnO NPs nanocomposite is highly sensitive to humidity due to the high porosity of the material. The parameters of the sensors, such as response time and retrieval time, were also studied, and it was found that the manufactured sensors have acceptable values for these parameters.

Elucidation of rGO Incorporation on Structural, Morphological and Optical Properties of rGO/ZnO Nanocomposites for Flexible Humidity Sensor Applications

The effect on structural, morphological and optical characteristics towards humidity sensing capability was elucidated as humidity-sensitive sensing material that is made by composting zinc oxide nanostructured powder (ZN) nanoparticles with varying capacities of reduced graphene oxide (rGO). The ZN was successfully synthesized through the ultrasonicated solution immersion technique and the rGO/ZN (rZN) nanocomposite sensing material was spread on cellulose substrates employing a simple brush printing technique. XRD, FESEM and UV–Vis Diffuse Reflectance Spectroscopy were utilized to examine the morphological and optical properties of the pristine ZN and rZN nanocomposites. As per the FESEM assessment, ZN nanoparticles with variable sizes were evenly distributed, adhered to, and irregularly positioned on filter paper cellulose fibres. The average reflectance in the visible region declined substantially as the rGO content increased. According to the estimated Urbach energy, the defects in the sensing materials increased as the rGO content increased. The humidity response capability of the nanocomposites exhibits a significant reliance on the quantity of rGO integrated, with the maximum humidity sensitivity achieved for the 1.0 wt.% rGO dosage. At a high operating temperature (85 °C), the humidity sensor based on rZN-1.0% nanocomposite exhibits an amplified humidity sensing response current value. These outcomes indicate that rZN nanocomposites have the potential to operate as a humidity-sensitive sensing material with great sensitivity.

Structural, Magnetic Evaluation of Neodymium Doped Nickel-Zinc-Iron Soft Spinel Metal Oxides for Humidity Sensor Applications

A series of combustion assisted low-temperature neodymium substituted Ni–Zn–Fe (NZF) nanoparticles were synthesized to unravel the impact on functional behavior of NZF due to the presence of larger Nd ions. The nanopowders were structurally evaluated with X-ray diffraction and infrared spectroscopy measurements without further heat treatment. X-ray diffraction clearly evident the monophasic nature of all the samples and solubility of Nd ions in the spinel unit cell. The average crystallite size from Scherrer and Williamson–Hall method are found below 30 and 20 nm for all the samples, respectively. A distinct shift was observed in most intense peak (3 1 1) suggesting the adjustment among interionic distances to accommodate larger ions. The microstructure, morphology was evaluated from SEM measurements. Magnetic measurements at room temperature show a dramatic change in magnetization, improvement in soft-magnetic nature with low coercivity behavior with Nd substitution. The variation of resistance with respect to humidity conditions suggested that these materials are potentially suitable for resistive humidity sensor applications.

Optical fiber humidity sensor with C60-THAM as molecule receptors

This study proposed a high sensitivity optical fiber relative humidity sensor (OFHS). Besides, a fullerene derivative, C 60 -THAM, was synthesized and firstly reported as a molecule receptor in the OFHS. Compared with the widely researched carbon-based materials in OFHS, the C 60 -THAM film has abundant amino dangling bonds, hence emerges naturally as excellent receptors for water molecules. Besides, a cascaded Fabry-Perot interferometer (FPI) was fabricated in the core of single-mode fiber (SMF) without surface damage by femtosecond laser. In the OFHS, the relative humidity (RH) was measured by the Vernier effect. The working principle of the OFHS was analyzed through calculation and simulation. In the experiment, C 60 -THAM was coated on the plant fiber end. The sensitivity of the sensor is about 0.42 nm/RH as the relative humidity change from 30% to 65% while the optical-matter reaction length is only about 150 nm. Moreover, the sensor exhibited a stable performance as the RH was decreasing from 65% to 30%. The OFHS in this work is fast response and the response time for the rising and decay process was about 2.2 s and 3.2 s respectively. • A fullerene derivative, C 60 -THAM, was synthesized and its application in the fiber humidity sensor was researched. • The humidity sensor is fast response and the rising and decay time is about 2.2 s and 3.2 s respecitively. • The sensitivity is 0.42 nm/RH as the humidity change from 30% to 65% while the optical-matter reaction length is 150 nm.