Performance Of Humidity Sensor Research Articles

Improving humidity sensor performance through phenylphosphonic acid-intercalated layered double hydroxide

This work delineates the development of humidity sensors utilizing layered double hydroxides (LDH) intercalated with phenylphosphonic acid (PPA), characterized by strong coordination and hydrophilicity. Following the meticulous synthesis of pristine LDH and PPA-LDH, sensor fabrication and comprehensive performance evaluation were conducted. Morphological analysis through SEM and TEM revealed a layered, thin PPA-LDH structure, augmenting the surface area for interaction with water. Density functional theory (DFT) computations elucidated the enhanced sensing mechanism, demonstrating that PPA intercalation significantly amplifies the adsorption energy of water molecules at metal sites, thereby facilitating proton and charge transfer. At 85 % relative humidity, the PPA-LDH sensor manifested an astonishing response of 4392.3 %, showcasing exceptional cyclic stability and rapid response/recovery times of 23 and 10 s, respectively. Comparative analysis with existing technologies underscored the superior sensitivity and response characteristics of the PPA-LDH sensor. The study concludes that PPA-intercalated LDH notably enhances humidity sensing capabilities, furnishing a material with heightened sensitivity and stability for the forthcoming generation of humidity sensors.

Impact of Compositional Engineering on PTB7-Th:PC71BM Capacitive Humidity Sensor Performance

Impact of Compositional Engineering on PTB7-Th:PC71BM Capacitive Humidity Sensor Performance

Preparation and Mechanism Analysis of High-Performance Humidity Sensor Based on Eu-Doped TiO2.

TiO2 is a typical semiconductor material, and it has attracted much attention in the field of humidity sensors. Doping is an efficient way to enhance the humidity response of TiO2. Eu-doped TiO2 material was investigated in both theoretical simulations and experiments. In a simulation based on density functional theory, a doped Eu atom can increase the performance of humidity sensors by producing more oxygen vacancies than undoped TiO2. In these experiments, Eu-doped TiO2 nanorods were prepared by hydrothermal synthesis, and the results also confirm the theoretical prediction. When the doping mole ratio is 5 mol%, the response of the humidity sensor reaches 23,997.0, the wet hysteresis is 2.3% and the response/recovery time is 3/13.1 s. This study not only improves the basis for preparation of high-performance TiO2 humidity sensors, but also fills the research gap on rare earth Eu-doped TiO2 as a humidity-sensitive material.

Flexible Humidity Sensor Based on a Graphene Oxide-Carbon Nanotube-Modified Co3O4 Nanoparticle-Embedded Laser-Induced Graphene Electrode.

To meet evolving humidity monitoring needs, the development of flexible, high-performance humidity sensors is crucial. This study introduces an innovative flexible humidity sensor using a single-step laser scribing technique to fabricate a flexible in situ Co3O4 nanoparticle-embedded laser-induced graphene (Co3O4-LIG) composite electrode. Compared to conventional LIG electrodes, the Co3O4-LIG electrode exhibits improved conductivity and hydrophilicity, enhancing charge transfer and water molecule affinity. The unique two-dimensional structure and exceptional water permeability of graphene oxide (GO) combine with the rapid water response and high specific surface area of carboxylated multiwalled carbon nanotubes (MWCNTs), thereby assuming a crucial function in the modification and optimization of the performance of humidity sensors. Through the application of a homogenously blended aqueous solution comprising GO and MWCNTs in precise proportions onto the Co3O4-LIG composite electrode, an excellent humidity-responsive layer is established, culminating in the realization of a cutting-edge GO-MWCNTs@Co3O4-LIG flexible humidity sensor. Noteworthy attributes of this sensor include a heightened sensitivity [959.1% (ΔR/R0)], rapid response and recovery times (within 5 and 26 s, respectively), and a noteworthy linearity (R2 = 0.994) across a relative humidity range of 14 to 95%. The findings presented herein offer valuable insights and a practical blueprint for the design and production of flexible humidity sensors.

Ultrafast and low-hysteresis humidity sensors based on mesoporous LaFe0.925Ti0.075O3 perovskite

Humidity sensors are omnipresent. Thus, significant efforts have been undertaken to advance their performance, for example, to have a fast detection time, negligible hysteresis, and excellent stability. Despite numerous active research endeavors, establishing a sensor that excels in all these key performances is still challenging. Here, we address this challenge by designing a capacitive-based humidity sensor employing porous LaFeO3 perovskite. Integrating Ti into the perovskite using a sol-gel method, i.e., LaFe0.925Ti0.075O3, results in a 400% increase in specific surface area achieved through pore formation, translating to a 2094% response parameter. Furthermore, due to the rapid equilibrium between adsorption and desorption processes, the sensor achieves ultrafast 4.4 s response time and 1.4 s recovery time, with <1% hysteresis and excellent stability over 28 days, when assessed at 300 K. Our work significantly advances current humidity sensor performance and, in a broader context, emphasizes the efficacy of porous (perovskite) materials for high performance gas detection.

Influence of Anodic Aluminum Oxide Nanostructures on Resistive Humidity Sensing

Humidity nanosensors play a vital role in modern technology industries, including weather forecasts, industrial manufacturing, agriculture, food and chemistry storage. In recent years, research on humidity sensors has focused on different materials such as ceramics, polymers, carbon-based materials, semiconductors, MXenes or triboelectric nanogenerators, each with their own advantages and disadvantages. Among them, anodic aluminum oxide (AAO) is a well-known ceramic humidity sensor material with a long history of research and development. AAO humidity sensors offer advantages such as simple manufacturing processes, controllable nanostructures, high thermal stability and biocompatibility. However, traditional AAO fabrication still has disadvantages like high costs and longer process times. Hence, finding a low-cost and efficient method to fabricate AAO for controlling different nanostructures to meet the requirements is consistently a major research topic. From our previous studies, we have studied the relationship between the AAO capacitive humidity sensor and its nanostructures. In this paper, we explore the effect of an AAO nanoporous structure controlled by an anodization voltage of 20–40 V on the resistive-type humidity sensor performance instead of a capacitive one. We efficiently apply one-step hybrid pulse anodization at 25 °C to significantly reduce the processing time compared to the traditional two-step process under 0–10 °C. The AAO nanostructures and their impact on sensor measurements of humidity at 20–80 RH% will be discussed in detail. An electrical resistive sensing mechanism is established for further performance improvement by controlling anodization voltage.

Enhancing Urban Waste Management: Development and Application of Smart Garbage Bin Technologies

With urbanization and population growth, the volume of waste generated is also increasing. Traditional waste management methods may become insufficiently efficient, necessitating more intelligent and sustainable solutions to meet this challenge. In traditional waste management systems, garbage trucks often collect waste according to a fixed schedule without considering the actual fill level of the garbage bins. This can lead to resource wastage and unnecessary carbon emissions. The research background of smart garbage bins is also closely related to environmental protection. By managing waste more effectively, reducing pollution to land and water sources is possible, contributing to achieving sustainable development goals. This study investigates the application of smart waste bin technology in urbanization, focusing on its potential in waste classification and environmental protection. The research encompasses three main stages: system design, prototype construction, and functional testing. In the system design phase, key components such as LED displays, ultrasonic sensors, and servo motors were selected based on functional requirements, and intelligent control was implemented using Arduino boards and the U8g2lib library. During the prototype construction phase, 3D printing and precise assembly were employed to ensure the effective layout of electronic components. The testing phase involved evaluating the performance of humidity sensors, ultrasonic sensors, and voice modules. The test indicates that the smart waste bins perform well in terms of sorting accuracy and ease of operation, but improvements are needed in real-time monitoring and user interaction. Overall, this study provides significant insights into the technological development of smart waste bins and their application in urban environments.

Rapid dielectrophoresis-assisted deposition of highly concentrated ZnO nanowires for enhanced performance of humidity sensors

Fabrication of devices containing a high density of aligned nanowires (NWs) between planar electrodes is very promising for numerous sensing applications. In this work, we demonstrate that a high concentration of ZnO NWs can be assembled between the planar electrodes by employing dielectrophoresis. ZnO NWs with an average length of 12 µm were synthesized via a hydrothermal method. The synthesized NWs were suspended in different solvents and the suspension was subsequently dried on top of the planar electrodes in the presence of an AC electric field. The electric field pattern between the electrodes was simulated using COMSOL Multiphysics. The simulation results showed that the real part of the Clausius-Mossotti factor, and consequently, the dielectrophoretic force, is highest for NWs dispersed in acetone. The deposition experiments also verified that the NWs suspended in acetone provide the highest concentration of aligned NWs between the electrodes. Moreover, in this case, the bridging of the electrode gap by NWs can be achieved within one min of deposition time. The fabricated device was employed for humidity sensing. Owing to the high NW density which provided ample adsorption sites for water molecules, the device demonstrated excellent humidity sensing capability. The sensor showed a response time of 17 s and a recovery time of 9 s. Moreover, the bulk resistance changed from 40 MΩ to 8 MΩ with a change in humidity from 11% to 97%. The sensor also showed an excellent response of 27. These results confirmed that dielectrophoresis is an effective technique for the fabrication of a sensitive humidity-sensing device.

Eco-Friendly, High-Performance Humidity Sensor Using Purple Sweet-Potato Peel for Multipurpose Applications

Biomaterials offer great potential for enhancing the performance of humidity sensors, which play a critical role in controlling moisture levels across different applications. By utilizing environmentally friendly, sustainable, and cost-effective biomaterials, we can improve the manufacturing process of these sensors while reducing our environmental impact. In this study, we present a high-performance humidity sensor that utilizes purple sweet potato peel (PSPP) as both the substrate and sensing layer. The PSPP is chosen for its polar hydrophilic functional groups, as well as its environmentally friendly nature, sustainability, and cost-effectiveness. Remarkably, this humidity sensor does not require an external substrate. It exhibits a wide detection range of 0 to 85% relative humidity at various operating frequencies (100 Hz, 1 kHz, and 10 kHz) in ambient temperature, demonstrating its effectiveness in responding to different humidity levels. The sensor achieves a high sensitivity value of 183.23 pF/%RH and minimal hysteresis of only 5% at 10 kHz under ambient conditions. It also boasts rapid response and recovery times of 1 and 2 s, respectively, making it suitable for use in high-end electronic devices. Moreover, the sensor’s applications extend beyond environmental monitoring. It has proven effective in monitoring mouth and nasal breathing, indicating its potential for respiratory monitoring and noncontact proximity response. These findings suggest that sweet potato peel material holds great promise as a highly stable, non-toxic, biodegradable, cost-effective, and environmentally friendly option for various domains, including healthcare monitoring.

Humidity Sensor Composed of Laser-Induced Graphene Electrode and Graphene Oxide for Monitoring Respiration and Skin Moisture.

Respiratory rate and skin humidity are important physiological signals and have become an important basis for disease diagnosis, and they can be monitored by humidity sensors. However, it is difficult to employ high-quality humidity sensors on a broad scale due to their high cost and complex fabrication. Here, we propose a reliable, convenient, and efficient method to mass-produce humidity sensors. A capacitive humidity sensor is obtained by ablating a polyimide (PI) film with a picosecond laser to produce an interdigital electrode (IDE), followed by drop-casting graphene oxide (GO) as a moisture-sensitive material on the electrode. The sensor has long-time stability, a wide relative humidity (RH) detection range from 10% to 90%, and high sensitivity (3862 pF/%RH). In comparison to previous methods, the technology avoids the complex procedures and expensive costs of conventional interdigital electrode preparation. Furthermore, we discuss the effects of the electrode gap size and the amount of graphene oxide on humidity sensor performance, analyze the humidity sensing mechanism by impedance spectrum, and finally perform the monitoring of human respiratory rate and skin humidity change in a non-contact manner.

Construction of Dual-Channel Water Transport in Mesoporous Silica Low Humidity Sensors to Achieve High Sensitivity.

In this paper, strong hydrophilic poly(ionic liquid)s (PILs) are selectively grafted on different positions (mesoporous channels and outer surface) of mesoporous silica via thiol-ene click chemical reaction. The purposes of selective grafting are on the one hand, to explore the differences of adsorption and transportation of water molecules in mesoporous channels and on the outer surface, and on the other hand, to combine the two approaches (intra-pore grafting and external surface grafting) to reasonably design SiO2 @PILs low humidity sensing film with synergetic function to achieve high sensitivity. The results of low relativehumidity （RH）sensing test show that the sensing performance of humidity sensor based on mesoporous silica grafted with PILs in the channels is better than that of humidity sensor based on mesoporous silica grafted with PILs on the outer surface. Compared with water molecules transport single channel, the construction of dual-channel water transport significantly improves the sensitivity of the low humidity sensor, and the response of the sensor is up to 4112% in the range of 7-33% RH. Moreover, the existence of micropores and the formation of dual-channel water transport affect the adsorption/desorption behaviors of the sensor under different humidity ranges, especially below 11% RH.

Effect of dipping number of polyvinyl alcohol (PVA) -coated on optical Fiber for Humidity Sensor

Optical Fiber Humidity Sensors (OFHSs) have attracted significant research interest due to their several advantages including small size, high durability and can withstand the extreme environment regardless of high temperature, high pressure and high electromagnetic radiation. In this study, the proposed sensors were built from standard single-mode silica fibers working at telecommunication wavelengths and exhibited very good humidity sensing characteristics. Single-mode optical fibers were coated with different dipping numbers (2, 4, 6 8, and 10 times) of polyvinyl alcohol (PVA) solution using a dip coating method. The sensing performance of uncoated and PVA-coated optical fiber sensors in terms of its sensitivity for various relative humidity (RH) percentages ranging from 40 to 90 % RH was monitored using Ocean Optics spectrometer. The intensity peaks of PVA-coated optical fibers were increased linearly with dipping numbers. The optimum sensing performance was observed for 10 times dipping number of PVA solution with the highest intensity of 4100 counts at 60 % RH and exhibits good repeatability with precision error values in the range of 0 to 2 %. Furthermore, the gap difference between intensity counts due to % RH changes could be clearly observed for 10 times dipping numbers. These reported results are important to enhance the performance of humidity sensor for sensing and monitoring purposes.

Ultrafast response of self-powered humidity sensor of flexible graphene oxide film

Next-generation humidity sensor, as one of the smart devices in artificial skin or flexible electronics, will need to be self-powered, flexible, fast and accurately detecting in the microenvironment. Although various flexible humidity sensors have already been demonstrated, most of them rely on large external power sources to operate, and still suffer from slow response, poor selectivity in environmental stimuli, and expensive and complicated procedures. Here, we realize a self-powered humidity sensor with ultrafast response and recovery time of less than 0.3 s by flexible GO film. Importantly, of all state-of-the-art humidity sensors, this is the fastest response for humidity sensor. Moreover, the sensor has a high sensitivity within a wide range of RH from 33% to 98%, and an excellent selective response to humidity under multiple environmental stimuli, due to its moist-induced generator. Theoretical computations reveal that protons generated spontaneously from oxygen-containing groups and water molecules, have a fast diffusion behavior as Grotthuss hopping. In particular, we build four real-time measurement systems capable of respiration monitoring of human, smart leaf surface humidity sensor, and energy harvesting. Our work provides a simple way to fabricate next-generation self-powered sensor using GO film with outstanding humidity sensor performance.

Fabrication a sensor based on sulfonate-based COF for humidity sensing

• ►Humidity sensor based on sulfonate-based COF is fabricated. • ►2D sulfonate-based COF possesses superior water adsorption capacity (∼396 mg/g). • ►COF’s 1D pore can provide continuous proton/ions conducting channel. Sensing material is crucial to the performance of humidity sensors. Porous material is widely used for humidity sensing but suffers from the narrow detecting range and slow response speed. Herein, the porous TpBDSA-Na COF with a large pore size (∼1.7 nm) and high density of hydrophilic active sites is used as sensing material for humidity detector. The superior adsorption capacity of water molecules (∼396 mg/g) in TpBDSA-Na COF makes the humidity detector exhibit fast response speed (18/9 s), small hysteresis (∼3% RH) and long-term stability (∼20 days) in 11%-95% RH range. Moreover, the sensing mechanism of TpBDSA-Na sensor is also discussed in detail. This research indicates the 2D COF with a hydrophilic channel can be used as a promising material for humidity sensing.

Evaluating Different TiO2 Nanoflower-Based Composites for Humidity Detection.

Unique three-dimensional (3D) titanium dioxide (TiO2) nanoflowers (TFNA) have shown great potential for humidity sensing applications, due to their large surface area-to-volume ratio and high hydrophilicity. The formation of a composite with other materials could further enhance the performance of this material. In this work, the effect of different types of composites on the performance of a TNFA-based humidity sensor was examined. NiO, ZnO, rGO, and PVDF have been explored as possible composite pairing candidates with TiO2 nanoflowers, which were prepared via a modified solution immersion method. The properties of the composites were examined using field emission electron spectroscopy (FESEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) analysis, Hall effect measurement, and contact angle measurement. The performance of the humidity sensor was assessed using a humidity sensor measurement system inside a humidity-controlled chamber. Based on the result, the combination of TiO2 with rGO produced the highest sensor response at 39,590%. The achievement is attributed to the increase in the electrical conductivity, hydrophilicity, and specific surface area of the composite.

High Sensitivity Humidity Sensors Based on Zn1−xSnxO Nanostructures and Plausible Sensing Mechanism

Four kinds of Zn1−xSnxO (X = 0%, 1%, 3%, 5%) nanowires with different concentrations are synthesized by a hydrothermal method. The samples are characterized and measured by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐Ray photoelectron spectroscopy (XPS). Then, the nanostructures are arranged on predesigned Ti/Au electrodes through the dielectrophoresis (DEP) nanomanipulation technique to fabricate four humidity sensors and investigate the humidity sensing properties. The results demonstrate that the Sn doping process can regulate the surface oxygen vacancy concentration and improve the performance of humidity sensors. In particular, the 3% Sn‐doped ZnO humidity sensor exhibits higher sensitivity with a response/recovery time of 4s/2s, lower hysteresis, and better repeatability. In addition, the sensing mechanisms are discussed in depth by combining complex impedance spectroscopy and multilayer adsorption theory. The obtained results indicate that a certain amount of Sn doping can introduce oxygen vacancies, adjust the lattice and surface state, and hence modulate the sensing properties of ZnO nanosensors.

Renewable and fast response humidity sensors based on multiple construction of water graftable molecules highly sensitive surface

It is a challenge to solve the performance regeneration and reuse of humidity sensor. This paper presents a new strategy to effectively solve the performance regeneration of humidity sensors. A humidity sensor featuring high sensitivity and fast response is obtained by adsorption of the bipyridyl ruthenium molecule (N3) on the TiO2 film on the surface of interdigital electrode (IDE) to form a humidity-enhanced sensing material. At 11% to 97% RH, the impedance value is changed by over 2 orders of magnitude, with a fast response time of 5 s and a recovery time of 8 s as well as relatively small hysteresis (2.09%). Meanwhile, through continuous multiple erase/re-sensing techniques, the humidity sensor performance is regenerated up to 30 cycles with no significant change in sensor performance. The humidity sensing mechanism of this sensor is investigated utilizing impedance spectroscopy, which reveals the unique humidity sensing mechanism of TiO2/N3 humidity sensor. Compared with general sensors, the biggest advantage of the humidity sensor designed in this paper is that it can regenerate the performance of the sensor and the idea and technology of this work can also be applied to other sensor fields.

Composite Effect on Zinc Oxide based Resistive Type Humidity Sensor Performance: A Preliminary Assessment

Composite Effect on Zinc Oxide based Resistive Type Humidity Sensor Performance: A Preliminary Assessment

A Facile and Flexible Humidity Sensor Based on Porous PDMS/AgNWs and GO for Environmental Humidity and Respiratory Detection

AbstractHumidity sensors, benefit from their superior humidity‐sensitive components, are able to respond to the environment moisture changes. Based on this feature, the humidity sensor plays an increasingly vital role in biological detection. To improve the performance of humidity sensors, a large number of optimizations have been made from several aspects, such as material synthesis and structural design. In this study, a novel humidity sensor is designed to increase its specific surface area to carry more humidity‐sensitive and conductive materials. A porous polydimethylsiloxane (PDMS) substrate is prepared in an economical friendly approach by using the thermal decomposition of sodium bicarbonate (NaHCO3). Meanwhile, high‐quality nano silvers (AgNWs) are applied as the intermediate conductive layer connecting the substrate and detective layer. graphene oxide (GO) is used as the humidity sensitive material in the sensor. It is remarkable that this sensor can detect the humidity with a wide range of 8.6 RH% to 93 RH% in a quick response with high sensitivity. Since this humidity sensor showed powerful functions, such as monitoring respiration and detecting environmental humidity, it will have broad potentials for real‐time clinical and domestic healthcare.

Enhanced performance of humidity sensor based on Gr/hollow sphere ZrO2 nanocomposites

In the particular research work, a unique humidity sensor based on graphene doped with hollow spheres of zirconium dioxide (Gr/HS-ZrO2) nanocomposite material was prepared using the hydrothermal method with various weight percentages of graphene for use in humidity sensors. The surface morphologies and structural of the Gr/HS-ZrO2nanocomposite have been characterized by Raman spectroscopy, TEM, EDX, and XRD; the electrical properties were analyzed based on the humidity variation on Gr/HS-ZrO2nanocomposite. The experimental results exhibited that with 1 wt% Gr/HS-ZrO2nanocomposite has excellent humidity sensing properties such as high sensing response (S = 1740), the rapid response was 11 s and recovery times was 30 s, indicating that Gr/HS-ZrO2 nano-composite will have great potential application in monitoring atmospheric humidity. Besides, the mechanism of humidity sensing of Gr/HS-ZrO2 nanocomposite has been explored in this paper.