Humidity Monitoring Research Articles

$\mu$WSense: A Self-Sustainable Microwave-Powered Battery-Less Wireless Sensor Node for Temperature and Humidity Monitoring

$\mu$WSense: A Self-Sustainable Microwave-Powered Battery-Less Wireless Sensor Node for Temperature and Humidity Monitoring

Simultaneous monitoring of humidity and temperature by polarization volume gratings utilizing responsive cholesteric liquid crystals

Optical sensing devices are utilized for noncontact operation in harsh environments due to their advantage of local separation between the measurement and detector systems. Cholesteric liquid crystals (CLCs) with vivid structural colors are integrated into optical sensors, attracting significant interest for naked-eye detection. To enable vision-based, real-time remote monitoring, we propose a cost-effective method to convert the stimuli-responsive reflection change of CLCs into recordable diffraction patterns using polarization volume gratings (PVGs). This enables real-time remote readout of environmental parameters. PVGs are constructed through holographic polarization interference and photoalignment technologies. The diffraction efficiency of PVGs varies with relative humidity (RH). To improve sensing accuracy and extend the monitoring range of RH, we employ two methods: an orthogonal grating structure and dual-wavelength detection optical path. In addition, we demonstrate the simultaneous measurement of humidity and temperature by cascading independently responding PVGs. We believe that this work will provide a broader perspective and expand the application of light dimensions in LC-based optical sensing.

A bio-based, self-healable, conductive rubber film with oxidized cellulose nanofiber segregated network

Rubber composites are indispensable in all areas of our daily lives. However, the formation of permanent crosslinked networks in rubber materials makes it difficult to recycle, resulting in a non-negligible waste of resources. In this paper, a vulcanization-free, fully bio-sourced rubber composite was prepared by using oxidized natural rubber (oNR) and oxidized cellulose nanofibers (TOCFs). TOCFs are selectively dispersed between the latex particles to form a segregated network. Meanwhile, the formation of hydrogen-bonding between oxygenated polar groups of oNR and abundant hydroxyl and carboxyl groups of TOCFs improves their interfacial interactions. This special structure promotes strain-induced crystallization (SIC) behavior of oNR matrix, giving its tensile strength up to 14.7 MPa. Furthermore, the oNR/TOCFs film shows excellent self-healing efficiency (96 %) at 40 °C for 5 h. The hygroscopicity of the TOCFs segregated network can turn the oNR/TOCFs film to be a conductive film by regulating the absorbed water content. The film has high conductivity (0.05 S/m) at a water content of 8.99 wt%, and the resistance change (RV/R0) can be varied between 1–5.9 × 10−6 at a water content range of 0–8.99 wt%, which makes it have potential for a wide range of humidity monitoring applications.

Interfacially Fabricated Covalent Organic Framework Membranes for Film‐Based Fluorescence Humidity Sensors and Moisture Driven Actuators

AbstractRapid, on‐site measurement of ppm‐level humidity in real time remains a challenge. In this work, we fabricated a few micrometer thick, β‐ketoenamine‐linked covalent organic framework (COF) membrane via interfacially confined condensation of 1,3,5‐tris‐(4‐aminophenyl)triazine (TTA) with 1,3,5‐tri‐formylphloroglucinol (TP). Based on the super‐sensitive and reversible response of the COF membrane to water vapor, we developed a high‐performance film‐based fluorescence humidity sensor, depicting unprecedented detection limit of 0.005 ppm, fast response/recovery (2.2 s/2.0 s), and a detection range from 0.005 to 100 ppm. Remarkably, more than 7,000‐time continuous tests showed no observable change in the performance of the sensor. The applicability of the sensor was verified by on‐site and real‐time monitoring of humidity in a glovebox. The superior performance of the sensor was ascribed to the highly porous structure and unique affinity of the COF membrane to water molecules as they enable fast mass transfer and efficient utilization of the water binding sites. Moreover, based on the remarkable moisture driven deformation of the COF membrane and its composition with the known polyimide films, some conceptual actuators were created. This study brings new ideas to the design of ultra‐sensitive film‐based fluorescent sensors (FFSs) and high‐performance actuators.

Interfacially Fabricated Covalent Organic Framework Membranes for Film-Based Fluorescence Humidity Sensors and Moisture Driven Actuators.

Rapid, on-site measurement of ppm-level humidity in real time remains a challenge. In this work, we fabricated a few micrometer thick, β-ketoenamine-linked covalent organic framework (COF) membrane via interfacially confined condensation of 1,3,5-tris-(4-aminophenyl)triazine (TTA) with 1,3,5-tri-formylphloroglucinol (TP). Based on the super-sensitive and reversible response of the COF membrane to water vapor, we developed a high-performance film-based fluorescence humidity sensor, depicting unprecedented detection limit of 0.005 ppm, fast response/recovery (2.2 s/2.0 s), and a detection range from 0.005 to 100 ppm. Remarkably, more than 7,000-time continuous tests showed no observable change in the performance of the sensor. The applicability of the sensor was verified by on-site and real-time monitoring of humidity in a glovebox. The superior performance of the sensor was ascribed to the highly porous structure and unique affinity of the COF membrane to water molecules as they enable fast mass transfer and efficient utilization of the water binding sites. Moreover, based on the remarkable moisture driven deformation of the COF membrane and its composition with the known polyimide films, some conceptual actuators were created. This study brings new ideas to the design of ultra-sensitive film-based fluorescent sensors (FFSs) and high-performance actuators.

Colorimetric Fabry-Pérot Sensor with Hetero-Structured Dielectric for Humidity Monitoring.

A full-color colorimetric humidity sensor with high brightness is proposed by using a hetero-structured dielectric film in a metal-insulator-metal (MIM) resonator. A humidity-responsive polymer is designed to graft on top of a metal-organic frameworks (MOFs) thin film (MOFs-Polymer) as insulator layer in the resonator. Programmable tuning of reflected color is achieved by controlling the polymer thicknesses, and finite difference time domain simulation of light-matter interactions at subwavelength scales proves the dependence of the reflected wavelength on dielectric layer thickness of the resonator. Vivid full-color changing is realized during tracking humidity process due to swelling of the stimuli-responsive polymer. Ultrafast response (≈0.75 s) is achieved for tracking trace H2O from H2O/methanol mixture, which is ≈104 faster than that of the pure polymer-based MIM resonator. Meanwhile, the study observes significant spectral redshift because the porous MOFs film facilitates the preconcentration of external stimulus and improves the detection sensitivity of the resonator. Further, double-channel anti-counterfeiting multiplexing imaging is devised on the MIM resonator by photomask technology. Patterned encoding for security label is achieved on the MIM resonator by engineering humidity-tunable pixels of Au/MOFs-Polymer/Au and humidity-invalid pixels of Au/MOFs/Au.

Sensitivity-enhanced optical fiber probe-type humidity sensor based on CaAlg film

Optical fiber probe-type humidity sensors based on calcium alginate (CaAlg) hydrogel films are proposed. The sensor is based on the Michelson interferometer (MI) and constructed by splicing a tapered multimode fiber (MMF) in the middle of two single-mode fibers (SMFs). One of the 1.5 cm long SMFs is coated with CaAlg hydrogel film and can be regarded as the sensor probe. The sensitivity of the sensor is 0.31015 nm/%RH. The high sensitivity, low temperature crosstalk, compact probe structure, and stability of the sensor allow it to be used for humidity monitoring in a variety of complex environments.

Impact of the WELLBASED urban programs on health, well-being, and energy poverty

Abstract Background The WELLBASED project developed and implemented urban programs across six pilot sites to tackle energy poverty. This study aimed to evaluate these programs’ effectiveness on a broad range of health, well-being, and energy poverty indicators. Methods a controlled study was performed in six European pilot sites. Participants in the intervention condition receive the 12-month WELLBASED urban program. Participants were recruited via different methods and provided informed consent to participate in the 18-month study. Self-report questionnaires were completed at baseline, 6-, 12 and 18 months in both research conditions. In the intervention group, monthly health monitoring of e.g. heart rate and blood pressure, and continuous monitoring of indoor CO2, temperature and humidity were performed. Descriptive statistics and regression analyses are performed to assess the impact of the urban programs on health, well-being and energy poverty-indicators Results In the baseline sample (n = 1350; n = 661 intervention group, n = 689 control group) the mean age was 49 years (SD 16), 15.6% was >65 years, 65% were women, and 42% was married. At baseline people reported not feeling comfortable warm in winter (58%) or cool in summer (70%), 43% reported damp or leak. Preliminary findings at 6-month follow-up indicate changes in HR-QoL, subjective well-being and depression/anxiety differ strongly per pilot site location (p < 0.01). In summer 2024 all data will be available for analysis. Conclusions the comprehensive urban programs developed in the WELLBASED project may support public health to tackle energy and improve health and well-being of vulnerable citizens.

Heat and mass transfer during conductive drying of washing phosphate sludge

This study investigates the influence of drying temperature on the conductive drying behavior of washing phosphate sludge. A mathematical model, based on Fourier's Fick diffusion law and the heat transfer equation, was developed to simulate coupled heat and mass transfer during the drying process, incorporating the shrinkage effect. The sludge samples, obtained from the Khouribga phosphate plant in Morocco, were subjected to drying at temperatures of 70°C and 95°C. The experimental setup included continuous monitoring of temperature, humidity, and mass loss throughout the process. COMSOL Multiphysics software was used to solve the nonlinear equations governing heat and mass transfer. Results indicate that increasing the drying temperature significantly accelerates the drying rate. The model successfully predicts the moisture content and temperature distribution over time, aligning well with experimental data. Statistical validation, using the determination coefficient (R²) and root mean square error (RMSE), confirms that the model accurately describes the drying behavior, with R² values of 0.9957 and 0.9967 at 70°C and 95°C, respectively. The inclusion of the shrinkage effect enhances the model's precision in describing the drying kinetics under varying conditions.

Climate-induced risk assessment of the quarantine room in a University Library

Microclimate conditions in conservation spaces such as museums, galleries, storages, archives, and libraries significantly impact the preservation of cultural materials, potentially leading to permanent damage. This study focuses on quarantine rooms, essential for isolating and inspecting incoming collections for infestations or contamination. Despite their importance, systematic microclimate investigations in such spaces have not been conducted until now. In this research, temperature and relative humidity monitoring has been conducted over the past 3 years (i.e., 2021-2022-2023) within the quarantine room of the Norwegian University of Science and Technology (NTNU) University Library (located within the DORA I concrete bunker, Trondheim, Norway). Data analysis revealed stable indoor conditions due to the buffering capacity of the massive building envelope together with climate control system. Specific metrics for the estimation of climate-induced chemical and biological risks on vulnerable artifacts were applied to compute the percentage of time for which thermohygrometric conditions could favour cellulose hydrolysis and biodeteriogens proliferation on a yearly basis. In this way, the study provided a decision-making tool useful to evaluate the best time (in terms of safest temperature and relative humidity conditions) when to introduce incoming collections into the quarantine room, depending on the material they are made of and on the timeframe selected for their isolation.

Design of low-cost humidity sensor based on chipless RFID

It is of great significance to design a low-cost chipless radio frequency identification(RFID) sensor for environmental humidity monitoring. To this end, polyvinyl alcohol (PVA) film is used as a humidity sensitive material, and the overall size of the rectangular substrate is 18 mm × 18 mm ×0.5 mm. Through the humidity sensing principle and simulation analysis, the change of environmental humidity causes the change of the dielectric constant of the humidity sensitive material PVA, which in turn affects the resonant frequency offset of the entire sensor. The simulation results show that the relative humidity working range of the designed humidity sensor is 21.9% ∼ 52.5%, the corresponding sensor resonant frequency range is 2.76 ∼ 2.51GHz, the total offset reaches 250 MHz, and the average sensitivity at the maximum relative humidity is 23.08MHz/% . The designed humidity sensor has the advantages of miniaturization, simple structure and low cost, and can be used for humidity monitoring in various target environments. Keywords.low cost; chipless RFID humidity sensor; polyvinyl alcohol; humidity monitoring; humidity sensitive material.

Energy-efficient and location-aware IoT and WSN-based precision agricultural frameworks

Precision agriculture has emerged as a promising approach to enhance crop yield, reduce environmental impact, and optimize resource utilization through advanced sensing and automation technologies. This paper proposes an energy-efficient and location-aware framework for Internet of Things (IoT) and Wireless Sensor Networks (WSN)-based precision agriculture systems. The framework leverages low-power wireless communication protocols, adaptive sensor scheduling, and location-based clustering algorithms to minimize energy consumption and prolong the network lifetime. Key features include real-time monitoring of soil moisture, temperature, humidity, and crop health through geographically distributed sensors, with automated decision-making for irrigation, fertilization, and pest control. The proposed framework also integrates machine learning models for predictive analysis and anomaly detection, enabling early identification of potential issues that could adversely affect crop productivity. Simulation results demonstrate a significant reduction in energy consumption and communication overhead, while maintaining high accuracy in environmental parameter monitoring and resource allocation. This framework offers a scalable and robust solution for implementing sustainable precision agriculture practices, particularly in remote and resource-constrained areas

Fast detection of humidity sensor with a weakly coupled fiber coated with carbomer

Humidity, as one of the basic environmental physical quantities, is essential in medical monitoring, food production and pharmaceutical industries.Fast and highly sensitive humidity sensing technology has become an urgent need in areas such as medical monitoring. We proposed and realized a novel coupled fiber-optic humidity sensor based on double tapered fiber twisted weakly coupled structure coated with carbomer film. The sensor adopts 2 × 2 coupler structure with waist diameter of 10 μm. The Carbomer film is coated in the weakly coupled area to improve the sensitivity of the sensor, and the thickness of this coating is about 79.2 nm. The sensor provides linear sensing over a relative humidity range of 40%–65% RH, with a dynamic response time of 208 ms and a recovery time of 464 ms. The sensitivity of the sensor is up to −0.28 dB/%RH and the linearity of the sensor is as high as 99.89%. Moreover, the sensor has good stability, reversibility, and low temperature crosstalk. Based on these characteristics, it can be expected that the sensor will bring a great breakthrough in applications where sensitive monitoring of humidity is required.

Strategies to control humidity sensitivity of azobenzene isomerisation kinetics in polymer thin films

Azobenzenes are versatile photoswitches that garner interest in applications ranging from photobiology to energy storage. Despite their great potential, transforming azobenzene-based discoveries and proof-of-concept demonstrations from the lab to the market is highly challenging. Herein we give an overview of a journey that started from a discovery of hydroxyazobenzene’s humidity sensitive isomerisation kinetics, developed into commercialization efforts of azobenzene-containing thin film sensors for optical monitoring of the relative humidity of air, and arrives to the present work aiming for better design of such sensors by understanding the different factors affecting the humidity sensitivity. Our concept is based on thermal isomerisation kinetics of tautomerizable azobenzenes in polymer matrices which, using pre-defined calibration curves, can be converted to relative humidity at known temperature. We present a small library of tautomerizable azobenzenes exhibiting humidity sensitive isomerisation kinetics in hygroscopic polymer films. We also investigate how water absorption properties of the polymer used, and the isomerisation kinetics are linked and how the azobenzene content in the thin film affects both properties. Based on our findings we propose simple strategies for further development of azobenzene-based optical humidity sensors.

Centrifugation-modulated uniform antibacterial paper with well-interconnected hierarchical pores for flexible high-sensitivity humidity monitoring

Humidity-sensitive electrode architecture with high uniformity and enriched open pores is essential and crucial to the high-performance humidity monitoring. However, challenges remain pertaining to manufacturing consistency, remarkable water trapping and superior electrical conductivity. Herein, we demonstrated a facile and controllable centrifugal casting strategy for consistently constructing flexible antibacterial graphene oxide (GO)-silver nanowire (AgNW) humidity sensor, with ample well-interconnected hierarchical pores built by uniformly-distributed AgNWs and orientated GO nanosheets. The unique architectural features facilitated highly efficient transport and high-level trapping of water molecules, and meanwhile guaranteed continuous conductive network for accelerating electrochemical reactions of water molecules trapped inside the device, thereby boasting impressive humidity-sensing capability with a wide sensing range (7.6–95.6 % relative humidity (RH)), a low detection limit (3.8 % RH), good long-time stability (more than 100 days), exceptional folding durability (up to 1000 times), superior selectivity and sensitive monitoring in actual scenes. This work opens a promising route for architecting advanced humidity sensor with prominent monitoring ability toward future uses.

Synthesis of copper-containing metal–polymer nanocomposites and their use as a humidity sensor

Recently, the synthesis of new gas-sensitive materials for use in resistive humidity sensors has attracted considerable interest. In the study, copper-containing metal–polymer nanocomposites were obtained by thermolysis of copper fumarate (I) and its complexes with 2,2′-dipyridyl (II) and 1,10-phenanthroline (III). The nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy, elemental analysis, energy-dispersive X-ray (EDX) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The most common particle sizes of the thermolysis products of compounds I, II, and III were 18.7, 8.3, and 20.7 nm, respectively. The manufactured sensor samples exhibited good sensitivity to the relative humidity (RH) of air: 2.48%/%RH, 3.77%/%RH, and 3.11%/%RH for the thermolysis products of compounds I, II, and III, respectively. Because of the high porosity and moisture absorption of the film, the maximum sensitivity was approximately 0.005 MΩ/%RH, which indicates fairly effective behavior of the film with respect to humidity. The response and recovery times were 23.7, and 37.3 s; 24.7, and 35.8 s; 32.4, and 58.4 s, respectively. The experiment had 88%–97% reproducibility. The fabricated sensors have great potential as humidity-sensing elements for humidity monitoring.

CLIMATE PULSE INDIA –AN APPLICATION TO PREDICT THE CLIMATE CHANGES

Climate Pulse India is a comprehensive web platform that helps users monitor and predict weather conditions in any city, focusing on essential factors such as temperature, humidity, and wind speed. By analyzing these elements, the application classifies cities into three safety zones: red (high danger), orange (moderate risk), and green (safe). The application is powered by the ClimatePulse - API, which delivers real-time weather data that fuels its prediction and forecasting capabilities. Designed with user accessibility in mind, Climate Pulse India provides weather insights, allowing users to assess the conditions of their hometown or any travel destination. With this information, users can make informed decisions regarding safety and travel. The predictions are presented on the website in a straightforward and easy- to-understand format. This paper demonstrates about providing accurate weather predictions for any location across India. Once predictions are made, the results are displayed directly on the webpage for the user. KEYWORDS: Weather forecasting, Safety zone classifications, Wind speed analysis, Risk assessment, Temperature prediction, Humidity monitoring

Development of the architecture of the remote access system to educational laboratory equipment using automated solutions

The subject of the study is remote access to Raspberry Pi-based training equipment and remote desktop software. The purpose of the work is to analyze the means of remote control of equipment and develop the architecture of the system of remote access of students to laboratory equipment for the implementation of distance learning. The following tasks are solved in the article: the branches in which application of means of remote access is the most critical are analyzed, among which the special place is occupied by the educational branch; analysis of existing methods of organization of remote access to training equipment was carried out, advantages and disadvantages of each method were allocated; justification is being made for choosing a Raspberry Pi minicomputer as a hardware platform for building remote access systems; describes the architecture of a complex of technical solutions based on Raspberry Pi for remote control of educational laboratory equipment; implementation of applied system of temperature and humidity monitoring using developed approach is described. Research methods include comparative analysis of existing remote control technologies, prototyping and experimental testing of the developed system. The following results were obtained: the feasibility of using the remote desktop approach and AnyDesk software for organizing access was substantiated, a system based on the Raspberry Pi minicomputer for managing equipment and visualizing data was developed, an applied system for monitoring temperature and humidity using Raspberry Pi and AnyDesk was implemented. Conclusions: The proposed approach of using Raspberry Pi and remote desktop software allows students to effectively organize remote access to laboratory equipment from engineering disciplines during distance learning. This solution combines ease of implementation, interaction with real physical equipment and low cost compared to the use of industrial PLCs.

Crosstalk-free hybrid integrated multimodal sensor for human temperature, humidity, and pressure monitoring

Crosstalk-free hybrid integrated multimodal sensor for human temperature, humidity, and pressure monitoring

Smart filtering facepiece respirator with self-adaptive fit and wireless humidity monitoring

The widespread emergence of airborne diseases has transformed our lifestyle, and respirators have become an essential part of daily life. Nevertheless, finding respirators that fit well can be challenging due to the variety of human facial sizes and shapes, potentially compromising protection. In addition, the current respirators do not inform the user of the air quality in case of continuous long-term use. Here, we introduce a smart filtering facepiece respirator incorporating a humidity sensor and pressure sensory feedback for self-fit adjusting and maintaining an adequate fit. The humidity detection sensor uses laser-induced graphene, and the pressure sensor array based on the dielectric elastomeric sponge monitors the respirator contact on the user's face, providing real-time closed-loop feedback and the wearer's fitting status. Those membrane sensors show outstanding performance, such as a low humidity hysteresis of 0.131 % and a precise pressure detection limit of 0.23 ± 0.02 kPa. As a result of the self-fit adjusting mode, the overall fit factor is increased by 10 % on average compared to the commercial respirator. This significant improvement in fit factor, coupled with the innovative design, has the potential to develop next-generation facepiece respirators as essential personal protective equipment.