Journal articles: 'RH Sensing'

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Mishra, Surabhi, Pooja Lohia, Priyanka Chaudhary, B. C. Yadav, D. K. Dwivedi, Hassan Fouad, and M. S. Akhtar. "High-Performance Humidity Sensing of Arsenic Based Chalcogenide Thin Films at Different Frequencies." Science of Advanced Materials 13, no. 10 (October 1, 2021): 2033–42. http://dx.doi.org/10.1166/sam.2021.4153.

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Present paper consists of the study of arsenic-based chalcogenide thin film for sensing elements for humidity sensors. The chemical composition of the prepared sensing element makes it more sensitive towards water molecule absorption and hence affects sensitivity. The bulk samples of Ge–Se–Te–As composition were prepared using the conventional melt-quench technique and the thin films were obtained using the thermal evaporation method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the structural characteristics of the prepared sensing element. Tauc’s plot, using UV-Vis spectrophotometer data, was used to determine the optical bandgap of the sensing materials. The relative humidity (RH) variation of the prepared sensing element was recorded in the range of 10%–90%. The sensitivity of the prepared sensing membrane was obtained as 8.54 MΩ/%RH, 9.724 MΩ/%RH, 10.257 MΩ/%RH for x = 10, 20, 30 respectively. The repeatability of the prepared samples was also reported to increase with Arsenic concentration.

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Shi, Zhen, and Sheng-Yuan Xia. "First-Principle Study of Rh-Doped Nitrogen Vacancy Boron Nitride Monolayer for Scavenging and Detecting SF6 Decomposition Products." Polymers 13, no. 20 (October 13, 2021): 3507. http://dx.doi.org/10.3390/polym13203507.

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The scavenging and detection of sulfur hexafluoride (SF6) decomposition products (SO2, H2S, SO2F2, SOF2) critically matters to the stable and safe operation of gas-insulated switchgear (GIS) equipment. In this paper, the Rh-doped nitrogen vacancy boron nitride monolayer (Rh-VNBN) is proposed as a gas scavenger and sensor for the above products. The computational processes are applied to investigate the configurations, adsorption and sensing processes, and electronic properties in the gas/Rh-VNBN systems based on the first-principle calculations. The binding energy (Eb) of the Rh-VNBN reaches −8.437 eV, while the adsorption energy (Ead) and band gap (BG) indicate that Rh-VNBN exhibits outstanding adsorption and sensing capabilities. The density of state (DOS) analysis further explains the mechanisms of adsorption and sensing, demonstrating the potential use of Rh-VNBN in sensors and scavengers of SF6 decomposition products. This study is meaningful as it explores new gas scavengers and sensors of SF6 decomposition products to allow the operational status assessment of GIS equipment.

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Shi, Zhen, and Sheng-Yuan Xia. "First-Principle Study of Rh-Doped Nitrogen Vacancy Boron Nitride Monolayer for Scavenging and Detecting SF6 Decomposition Products." Polymers 13, no. 20 (October 13, 2021): 3507. http://dx.doi.org/10.3390/polym13203507.

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The scavenging and detection of sulfur hexafluoride (SF6) decomposition products (SO2, H2S, SO2F2, SOF2) critically matters to the stable and safe operation of gas-insulated switchgear (GIS) equipment. In this paper, the Rh-doped nitrogen vacancy boron nitride monolayer (Rh-VNBN) is proposed as a gas scavenger and sensor for the above products. The computational processes are applied to investigate the configurations, adsorption and sensing processes, and electronic properties in the gas/Rh-VNBN systems based on the first-principle calculations. The binding energy (Eb) of the Rh-VNBN reaches −8.437 eV, while the adsorption energy (Ead) and band gap (BG) indicate that Rh-VNBN exhibits outstanding adsorption and sensing capabilities. The density of state (DOS) analysis further explains the mechanisms of adsorption and sensing, demonstrating the potential use of Rh-VNBN in sensors and scavengers of SF6 decomposition products. This study is meaningful as it explores new gas scavengers and sensors of SF6 decomposition products to allow the operational status assessment of GIS equipment.

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Ngoune, Bernard Bobby, Hamida Hallil, Bérengère Lebental, Guillaume Perrin, Shekhar Shinde, Eric Cloutet, Julien George, Stéphane Bila, Dominique Baillargeat, and Corinne Dejous. "Selective Outdoor Humidity Monitoring Using Epoxybutane Polyethyleneimine in a Flexible Microwave Sensor." Chemosensors 11, no. 1 (December 23, 2022): 16. http://dx.doi.org/10.3390/chemosensors11010016.

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The rise of gas-sensing applications and markets has led to microwave sensors associated to polymer-based sensitive materials gaining a lot of attention, as they offer the possibility to target a large variety of gases (as polymers can be easily functionalised) at ultra-low power and wirelessly (which is a major concern in the Internet of Things). A two-channel microstrip sensor with one resonator coated with 1,2 epoxybutane-functionalised poly(ethyleneimine) (EB-PEI) and the other left bare was designed and fabricated for humidity sensing. The sensor, characterised under controlled laboratory conditions, showed exponential response to RH between 0 and 100%, which is approximated to −1.88 MHz/RH% (−0.03 dB/RH%) and −8.24 MHz/RH% (−0.171 dB/RH%) in the RH ranges of 30–80% and 80–100%, respectively. This is the first reported use of EB-PEI for humidity sensing, and performances, especially at high humidity level (RH > 80%), as compared with transducer working frequencies, are better than the state of the art. When further tested in real outdoor conditions, the sensor shows satisfying performances, with 4.2 %RH mean absolute error. Most importantly, we demonstrate that the sensor is selective to relative humidity alone, irrespective of the other environmental variables acquired during the campaign (O3, NO, NO2, CO, CO2, and Temperature). The sensitivities obtained outdoors in the ranges of 50–70% and 70–100% RH (−0.61 MHz/%RH and −3.68 MHz/%RH, respectively) were close to lab results (−0.95 MHz/%RH and −3.51 MHz/%RH, respectively).

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Ye, Lun, Xiao Liu, Danyang Pei, Jing Peng, Shuchang Liu, Kai Guo, Xiaogang Li, Xuanyu Chen, Xuan Zhang, and Daquan Yang. "Simultaneous Detection of Relative Humidity and Temperature Based on Silicon On-Chip Cascaded Photonic Crystal Nanobeam Cavities." Crystals 11, no. 12 (December 14, 2021): 1559. http://dx.doi.org/10.3390/cryst11121559.

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In this paper, we propose and numerically demonstrate a novel cascaded silicon-on-insulator (SOI) photonic crystal nanobeam cavity (PCNC) dual-parameter sensor for the simultaneous detection of relative humidity (RH) and temperature. The structure consists of two independent PCNCs supporting two different resonant modes: a dielectric-mode and an air-mode, respectively. The dielectric-mode nanobeam cavities (cav1) are covered with SU-8 cladding to increase the sensitivity ratio contrast between RH sensing and temperature sensing. The air-mode nanobeam cavities (cav2) are coated with a water-absorbing polyvinyl-alcohol (PVA) layer that converts the change in RH into a change in refractive index (RI) under different ambient RH levels, thereby inducing a wavelength shift. Due to the positive thermo-optic (TO) coefficient of silicon and the negative TO coefficient of SU-8 cladding, the wavelength responses take the form of a red shift for cav2 and a blue shift for cav1 as the ambient temperature increases. By using 3D finite-difference time-domain (3D-FDTD) simulations, we prove the feasibility of simultaneous sensing by monitoring a single output transmission spectrum and applying the sensor matrix. For cav1, the RH and temperature sensitivities are 0 pm/%RH and −37.9 pm/K, while those of cav2 are −389.2 pm/%RH and 58.6 pm/K. The sensitivity ratios of temperature and RH are −1.5 and 0, respectively, which is the reason for designing two different resonant modes and also implies great potential for realizing dual-parameter sensing detection. In particular, it is also noteworthy that we demonstrate the ability of the dual-parameter sensor to resist external interference by using the dual wavelength matrix method. The maximum RH and temperature detection errors caused by the deviation of resonance wavelength 1 pm are only 0.006% RH and 0.026 K, which indicates that it achieves an excellent anti-interference ability. Furthermore, the structure is very compact, occupying only 32 μm × 4 μm (length × width). Hence, the proposed sensor shows promising prospects for compact lab-on-chip integrated sensor arrays and sensing with multiple parameters.

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Fort, Ada, Anna Lo Grasso, Marco Mugnaini, Enza Panzardi, Lorenzo Parri, Valerio Vignoli, Cecilia Viti, Ammar Al-Hamry, and Olfa Kanoun. "QCM Measurements of RH with Nanostructured Carbon-Based Materials: Part 2-Experimental Characterization." Chemosensors 10, no. 8 (August 10, 2022): 320. http://dx.doi.org/10.3390/chemosensors10080320.

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In this series of two papers, the humidity sensing of a carbon nanotube (CNT) network-based material is transduced and studied through quartz crystal microbalance (QCM) measurements. To this aim, quartzes functionalized with different amounts of sensing material were realized, exposed to different humidity levels, and characterized. In this second paper, the experimental results are presented and discussed. The sensing mechanisms are elucidated exploiting the theory presented in the first paper of this series. The presented results show that the investigated material functionalization induces a large response of QCM to humidity in terms of resonant frequency even at low RH levels, with a sensitivity of about 12 Hz/%RH (at RH < 30% and room temperature and 10 ug of deposited SWCNT solution) and an increase in sensitivity in the high RH range typical of nanostructured film. Regarding the response in terms of motional resistance, a large response is obtained only at intermediate and high humidity levels, confirming that condensation of water in the film plays an important role in the sensing mechanism of nanostructured materials.

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Șerban, Bogdan Cătălin, Octavian Buiu, Cornel Cobianu, Viorel Avramescu, Nicolae Dumbrăvescu, Mihai Brezeanu, Marius Bumbac, Cristina Mihaela Nicolescu, and Roxana Marinescu. "Ternary Carbon-Based Nanocomposite as Sensing Layer for Resistive Humidity Sensor." Proceedings 29, no. 1 (October 18, 2019): 114. http://dx.doi.org/10.3390/proceedings2019029114.

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Kaňok, Roman, Petr Hlubina, Lucie Gembalová, and Dalibor Ciprian. "Efficient Optical Sensing Based on Phase Shift of Waves Supported by a One-Dimensional Photonic Crystal." Sensors 21, no. 19 (September 30, 2021): 6535. http://dx.doi.org/10.3390/s21196535.

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Interferometric methods of optical sensing based on the phase shift of the Bloch surface waves (BSWs) and guided waves (GWs) supported by a one-dimensional photonic crystal are presented. The photonic crystal, composed of six SiO2/TiO2 bilayers with a termination layer of TiO2, is employed in the Kretschmann configuration. Under resonance condition, an abrupt phase change is revealed, and the corresponding phase shift is measured by interferometric techniques applied in both the spectral and spatial domains. The spectral interferometric technique employing a birefringent quartz crystal is used to obtain interference of projections of p- and s-polarized light waves reflected from the photonic crystal. The phase shifts are retrieved by processing the spectral interferograms recorded for various values of relative humidity (RH) of air, giving the sensitivity to the RH as high as 0.029 rad/%RH and 0.012 rad/%RH for the BSW and GW, respectively. The spatial interferometric technique employs a Wollaston prism and an analyzer to generate an interference pattern, which is processed to retrieve the phase difference, and results are in good agreement with those obtained by sensing the phase shift in the spectral domain. In addition, from the derivative of the spectral phase shifts, the peak positions are obtained, and their changes with the RH give the sensitivities of 0.094 nm/%RH and 0.061 nm/%RH for the BSW and GW, respectively. These experimental results demonstrate an efficient optical sensing with a lot of applications in various research areas.

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Dias, Bernardo, João Carvalho, João P. Mendes, José M. M. M. Almeida, and Luís C. C. Coelho. "Analysis of the Relative Humidity Response of Hydrophilic Polymers for Optical Fiber Sensing." Polymers 14, no. 3 (January 22, 2022): 439. http://dx.doi.org/10.3390/polym14030439.

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Relative humidity (RH) monitorization is of extreme importance on scientific and industrial applications, and optical fiber sensors (OFS) may provide adequate solutions. Typically, these kinds of sensors depend on the usage of humidity responsive polymers, thus creating the need for the characterization of the optical and expansion properties of these materials. Four different polymers, namely poly(vinyl alcohol), poly(ethylene glycol), Hydromed™ D4 and microbiology agar were characterized and tested using two types of optical sensors. First, optical fiber Fabry–Perot (FP) tips were made, which allow the dynamical measurement of the polymers’ response to RH variations, in particular of refractive index, film thickness, and critical deliquescence RH. Using both FP tips and Long-Period fiber gratings, the polymers were then tested as RH sensors, allowing a comparison between the different polymers and the different OFS. For the case of the FP sensors, the PEG tips displayed excellent sensitivity above 80%RH, outperforming the other polymers. In the case of LPFGs, the 10% (wt/wt) PVA one displayed excellent sensitivity in a larger working range (60 to 100%RH), showing a valid alternative to lower RH environment sensing.

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Maciak, Erwin. "Low-Coherence Interferometric Fiber Optic Sensor for Humidity Monitoring Based on Nafion® Thin Film." Sensors 19, no. 3 (February 2, 2019): 629. http://dx.doi.org/10.3390/s19030629.

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The main aim of this work was the design and development simple fiber optic Fabry-Perot interferometer (FPI) sensor devices for relative humidity (RH) sensing with emphasis on high sensitivity and good stability. The RH fiber FPI sensor is fabricated by coating the end of a cleaved standard multi-mode (MM) fiber with hydrophilic Nafion® sensing film. The Nafion® thin film acts as an active resonance cavity of the low-coherence interferometric sensing structure. The fringe pattern, which is caused by interfering light beam in the Nafion® thin film will shift as the RH changes because the water molecules will swell the Nafion® film and thus change optical pathlength of the sensing structure. The operating principle of a FPI sensor based on the adsorption and desorption of water vapour in the Nafion® and the limitations of this sensor type are discussed in this work. The fiber optic hygrometer was tested in the visible (400–900 nm) region of spectra for measurement of relative humidity (RH) in the range of 5.5–80% at room temperature (RT) in air. The fiber optic humidity sensor has a very short response time (t90 = 5–80 s) and a fast regeneration time (t10 = 5–12 s) as good as commercial sensors.

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Hashtroudi, Hanie, Aimin Yu, Saulius Juodkazis, and Mahnaz Shafiei. "Two-Dimensional Dy2O3-Pd-PDA/rGO Heterojunction Nanocomposite: Synergistic Effects of Hybridisation, UV Illumination and Relative Humidity on Hydrogen Gas Sensing." Chemosensors 10, no. 2 (February 14, 2022): 78. http://dx.doi.org/10.3390/chemosensors10020078.

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A two-dimensional (2D) Dy2O3-Pd-PDA/rGO heterojunction nanocomposite has been synthesised and tested for hydrogen (H2) gas sensing under various functioning conditions, including different H2 concentrations (50 ppm up to 6000 ppm), relative humidity (up to 25 %RH) and working temperature (up to 200 °C). The material characterisation of Dy2O3-Pd-PDA/rGO nanocomposite performed using various techniques confirms uniform distribution of Pd NPs and 2D Dy2O3 nanostructures on multi-layered porous structure of PDA/rGO nanosheets (NSs) while forming a nanocomposite. Moreover, fundamental hydrogen sensing mechanisms, including the effect of UV illumination and relative humidity (%RH), are investigated. It is observed that the sensing performance is improved as the operating temperature increases from room temperature (RT = 30 °C) to the optimum temperature of 150 °C. The humidity effect investigation revealed a drastic enhancement in sensing parameters as the %RH increased up to 20%. The highest response was found to be 145.2% towards 5000 ppm H2 at 150 °C and 20 %RH under UV illumination (365 nm). This work offers a highly sensitive and selective hydrogen sensor based on a novel 2D nanocomposite using an environmentally friendly and energy-saving synthesis approach, enabling us to detect hydrogen molecules experimentally down to 50 ppm.

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Taylor, R. A., R. S. Brown, and L. C. Godbey. "Reducing HVI Strength Variability by Sensing Humidity." Textile Research Journal 62, no. 2 (February 1992): 80–86. http://dx.doi.org/10.1177/004051759206200204.

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Short-term exposure of small cotton specimens to nonstandard atmospheric conditions can cause errors in their strength measurements. Experiments were conducted to evaluate the effect of local humidity changes on strength measurements. Two production model high volume instruments were equipped with humidity sensors near their specimen brushing stations. The system from one vendor was more sensitive to short-term humidity cycles (1.15 compared to 0.6 %gf/tex/%RH), while the other system was more sensitive to humidity changes including sample conditioning (1.81 compared to 1.42 %gf/tex/%RH). Both instruments showed a wide range of strength-humidity sensitivities for the 57 cottons surveyed.

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Kosuru, Lakshmoji, Adam Bouchaala, Nizar Jaber, and Mohammad I. Younis. "Humidity Detection Using Metal Organic Framework Coated on QCM." Journal of Sensors 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/4902790.

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Quartz crystal microbalance (QCM) coated with poly-4-vinylpyridine (PVP) and metal organic framework HKUST-1 are investigated and compared for humidity sensing. Drop casting method is employed to coat the PVP and HKUST-1 solutions onto the surface of a quartz crystal microbalance. The resonance frequencies of these sensors with varying relative humidity (RH) from 22% RH to 69% RH are measured using impedance analysis method. The sensitivity, humidity hysteresis, response, and recovery times of these sensors are studied. The sensitivities of uncoated, PVP, and HKUST-1 coated QCM sensors are 7 Hz, 48 Hz, and 720 Hz, respectively, in the range of 22% RH–69% RH. The extraction of desorption rate and adsorption energy associated with the adsorption and desorption of water molecules on these surfaces reveals that HKUST-1 has better sensing properties than PVP and uncoated QCM sensors. In this work, the HKUST-1 coated QCM is shown to be a promising material for moisture detection.

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Yi, Ruobing, Bingquan Peng, Yimin Zhao, Dexi Nie, Liang Chen, and Lei Zhang. "Quartz Crystal Microbalance Humidity Sensors Based on Structured Graphene Oxide Membranes with Magnesium Ions: Design, Mechanism and Performance." Membranes 12, no. 2 (January 21, 2022): 125. http://dx.doi.org/10.3390/membranes12020125.

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The application of graphene oxide (GO)-based membranes combined with a quartz crystal microbalance (QCM) as a humidity sensor has attracted great interest over the past few years. Understanding the influence of the structure of the GO membrane (GOM) on the adsorption/desorption of water molecules and the transport mechanism of water molecules in the membrane is crucial for development of applications using GOM-based humidity sensors. In this paper, by investigating the effects of oxygen-containing groups, flake size and interlayer spacing on the performance of humidity sensing, it was found that humidity-sensing performance could be improved by rational membrane-structure design and the introduction of magnesium ions, which can expand the interlayer spacing. Therefore, a novel HGO&GO&Mg2+ structure prepared by uniformly doping magnesium ions into GO&HGO thin composite membranes was designed for humidity sensing from 11.3% RH to 97.3% RH. The corresponding sensor exhibits a greatly improved humidity sensitivity (~34.3 Hz/%RH) compared with the original pure GO-based QCM sensor (~4.0 Hz/%RH). In addition, the sensor exhibits rapid response/recovery times (7 s/6 s), low hysteresis (~3.2%), excellent repeatability and good stability. This research is conducive to understanding the mechanism of GOM-based humidity sensors. Owing to its good humidity-sensing properties, the HGO&GO&Mg2+ membrane-based QCM humidity sensor is a good candidate for humidity sensing.

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Barmpakos, Dimitris, Apostolos Segkos, Christos Tsamis, and Grigoris Kaltsas. "A Disposable Inkjet-Printed Humidity and Temperature Sensor Fabricated on Paper." Proceedings 2, no. 13 (December 10, 2018): 977. http://dx.doi.org/10.3390/proceedings2130977.

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In this work we present the development of a low-cost humidity and temperature sensing platform on paper by inkjet printing, using a commercial AgNPs conductive ink. The humidity sensing module was capable of measuring relative humidity in the range of 0–90%rH, exhibiting linear response with minimal memory effect when returning to 0%rH baseline signal while the temperature sensor performed linearly as well in the range of 25–75°C. Process repeatability has been verified by electrical and optical characterization. Mechanical bending results highlight the platform’s capability to serve as an easy to install, flexible multi-parametric sensing platform.

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Chen, Chang-Ming, and Jun Xu. "A miniaturized evanescent mode HMSIW humidity sensor." International Journal of Microwave and Wireless Technologies 10, no. 1 (November 21, 2017): 87–91. http://dx.doi.org/10.1017/s175907871700126x.

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A passive evanescent mode half-mode substrate integrated waveguide (HMSIW) resonator loaded with a complementary split ring resonator (CSRR) is designed and fabricated for humidity sensing applications. The use of the CSRR which is etched on the top plane of the HMSIW can significantly reduce the size of the device. Without any sensing material, the sensor which has a compact size of 0.17λg × 0.17λg can provide high humidity sensitivity up to 5.82 MHz/%relative humidity (RH) at high RH region (>84.3%). The results indicate that the proposed structure is a promising candidate for radio and microwave humidity sensing applications.

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Zhang, Xinpu, Xihua Zou, Bin Luo, Wei Pan, Lianshan Yan, and Wei Peng. "Optically functionalized microfiber Bragg grating for RH sensing." Optics Letters 44, no. 19 (September 18, 2019): 4646. http://dx.doi.org/10.1364/ol.44.004646.

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Timár-Horváth, Veronika, László Juhász, András Vass-Várnai, and Gergely Perlaky. "Usage of porous Al2O3 layers for RH sensing." Microsystem Technologies 14, no. 7 (November 22, 2007): 1081–86. http://dx.doi.org/10.1007/s00542-007-0466-2.

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Guermat, N., A. Bellel, Salah Sahli, Yvan Segui, and Patrice Raynaud. "Plasma Polymerization of Hexamethyldisiloxane and Tetraethoxysilane Thin Films for Humidity Sensing Application." Defect and Diffusion Forum 354 (June 2014): 41–47. http://dx.doi.org/10.4028/www.scientific.net/ddf.354.41.

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Humidity sensitive layers elaborated from pure HMDSO and TEOS by PECVD technique have been studied. Humidity sensing properties including impedance relative humidity (RH) and current RH characteristics were investigated. TEOS films show higher sensitivity and excellent linearity over the explored range of humidity (20–95% RH). However, HMDSO films exhibits a small response and recovery of about 8 and 34 s for humidification and desiccation, respectively, in addition to very low hysteresis (2%). Structural analyses of sensitive layers were characterized by Fourier transform infrared spectroscopy (FTIR).

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Liu, Yin, Xiaowei Li, Yufeng Chen, Guangzhou Geng, Junjie Li, Yongtian Wang, and Lingling Huang. "Imaging-based optical barcoding for relative humidity sensing based on meta-tip." Nanophotonics 11, no. 1 (November 2, 2021): 111–18. http://dx.doi.org/10.1515/nanoph-2021-0529.

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Abstract In a wide range of applications such as healthcare treatment, environmental monitoring, food processing and storage, and semiconductor chip manufacturing, relative humidity (RH) sensing is required. However, traditional fiber-optic humidity sensors face the challenges of miniaturization and indirectly obtaining humidity values. Here, we propose and demonstrate an optical barcode technique by cooperating with RH meta-tip, which can predict the humidity values directly. Such RH meta-tip is composed of fiber-optic sensor based on surface plasmon resonance (SPR) effect and graphene oxide film as humidity sensitizer. While SPR sensor is composed of multimode fiber (MMF) integrated with metallic metasurface. Dynamic time warping (DTW) algorithm is used to obtain the warp path distance (WPD) sequence between the measured reflection spectrum and the spectra of the precalibrated database. The distance sequence is transformed into a pseudo-color barcode, and the humidity value is corresponded to the lowest distance, which can be read by human eyes. The RH measurement depends on the collective changes of the reflection spectrum rather than tracking a single specific resonance peak/dip. This work can open up new doors to the development of a humidity sensor with direct RH recognition by human eyes.

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Adhyapak, Parag V., Aishwarya M. Kasabe, Amruta D. Bang, Jalindar Ambekar, and Sulabha K. Kulkarni. "Highly sensitive, room temperature operated gold nanowire-based humidity sensor: adoptable for breath sensing." RSC Advances 12, no. 2 (2022): 1157–64. http://dx.doi.org/10.1039/d1ra07510a.

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Buhrke, Thorsten, Boris Bleijlevens, Simon P. J. Albracht, and Bärbel Friedrich. "Involvement of hyp Gene Products in Maturation of the H2-Sensing [NiFe] Hydrogenase ofRalstonia eutropha." Journal of Bacteriology 183, no. 24 (December 15, 2001): 7087–93. http://dx.doi.org/10.1128/jb.183.24.7087-7093.2001.

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ABSTRACT The biosynthesis of [NiFe] hydrogenases is a complex process that requires the function of the Hyp proteins HypA, HypB, HypC, HypD, HypE, HypF, and HypX for assembly of the H2-activating [NiFe] site. In this study we examined the maturation of the regulatory hydrogenase (RH) of Ralstonia eutropha. The RH is a H2-sensing [NiFe] hydrogenase and is required as a constituent of a signal transduction chain for the expression of two energy-linked [NiFe] hydrogenases. Here we demonstrate that the RH regulatory activity was barely affected by mutations inhypA, hypB, hypC, andhypX and was not substantially diminished inhypD- and hypE-deficient strains. The lack of HypF, however, resulted in a 90% decrease of the RH regulatory activity. Fourier transform infrared spectroscopy and the incorporation of 63Ni into the RH from overproducing cells revealed that the assembly of the [NiFe] active site is dependent on all Hyp functions, with the exception of HypX. We conclude that the entire Hyp apparatus (HypA, HypB, HypC, HypD, HypE, and HypF) is involved in an efficient incorporation of the [NiFe] center into the RH.

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Yang, Chih Chin, Ting Hao Liu, and Shun Hsyung Chang. "Relative humidity sensing properties of indium nitride compound with oxygen doping on silicon and AAO substrates." Modern Physics Letters B 33, no. 14n15 (May 28, 2019): 1940044. http://dx.doi.org/10.1142/s021798491940044x.

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The research used a DC sputtering system to grow indium nitride compound doped oxygen sensing film, which could be applied in the fabrication of relative humidity sensor. In this study, the design of two specific substrates, including silicon substrate and anodic aluminum oxide (AAO) substrate, were of some uses for relative humidity sensor fabrication to enhance the sensitivity. Besides, the influence of different substrates on responsivity was also explored to verify the sensing performances of indium nitride compound doped oxygen element in relative humidity sensor. The resistance response of InN:O sensing device using silicon substrate was better than that using AAO substrate. The RH adsorption and desorption time of InN:O sensing device using silicon substrate were 94 s and 35 s, respectively. The capacitance response of InN:O sensing device using AAO substrate was better than that using silicon substrate. The RH adsorption and desorption times of InN:O sensing device using AAO substrate were 289 s and 286 s respectively.

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Cappelli, Irene, Ada Fort, Anna Lo Grasso, Enza Panzardi, Marco Mugnaini, and Valerio Vignoli. "RH Sensing by Means of TiO2 Nanoparticles: A Comparison among Different Sensing Techniques Based on Modeling and Chemical/Physical Interpretation." Chemosensors 8, no. 4 (September 25, 2020): 89. http://dx.doi.org/10.3390/chemosensors8040089.

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TiO2 nanoparticles coating has been proven to be an extremely performing sensing material for relative humidity (RH) measurements. The chemical activity of TiO2 toward water vapor adsorption and the very large surface to volume ratio typical of nanostructures are ideal characteristics for the development of RH fast and sensitive sensors. Different sensor technologies can be used in conjunction with this material to realize devices with satisfactory performance. In this paper, the authors aim to describe and discuss the main different possible choices and highlight the advantages and disadvantages, and linking them both to the underlying mechanism of water adsorption on the TiO2 sensing layer and to the modification of the electrical behavior due to the water adsorption. In particular, the authors start from results obtained by depositing TiO2 nanoparticles on a novel MEMS microbalance operating at low frequency, which allows to sense only the adsorbed water mass, and they exploit the sensor output to obtain a dynamic model of the water adsorption. They also link these results to those obtained with a Quartz Crystal Microbalance (QCM) functionalized with the same material operating at 10 MHz as a part of an oscillator. Finally, they establish a link with the results obtained by an RH impedance sensor, which exploits the same active material and the same deposition technique. With this sensor technology, the conductive and electrical behavior of the sensing and adsorbed films play a role. The whole work tries to unravel the different phenomena that contribute to the response of RH sensors not only based on TiO2 nanoparticles but also, more generally, based on nanostructured metal oxide materials.

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Lazarova, Katerina, Silvia Bozhilova, Christo Novakov, Darinka Christova, and Tsvetanka Babeva. "Amphiphilic Poly(vinyl Alcohol) Copolymers Designed for Optical Sensor Applications—Synthesis and Properties." Coatings 10, no. 5 (May 9, 2020): 460. http://dx.doi.org/10.3390/coatings10050460.

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A possible approach for enhancement of Poly(vinyl alcohol) (PVA) humidity-sensing performance using hydrophobically modified PVA copolymers is studied. Series of poly(vinylalcohol-co-vinylacetal)s (PVA–Ac) of acetal content in the range 18%–28% are synthesized by partial acetalization of hydroxyl groups of PVA with acetaldehyde and thin films are deposited by spin-coating using silicon substrates and glass substrates covered with Au–Pd thin film with thickness of 30 nm. Sensing properties are probed through reflectance measurements at relative humidity (RH) in the range 5%–95% RH. The influence of film thickness, post-deposition annealing temperature, and substrate type/configuration on hysteresis, sensitivity, and accuracy/resolution of humidity sensing is studied for partially acetalized PVA copolymer films, and comparison with neat PVA is made. Enhancement of sensing behavior through preparation of polymer–silica hybrids is demonstrated. The possibility of color sensing is discussed.

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Qiao, Siqi, Xiaoyan Peng, Lidan Wang, Shukai Duan, Jin Chu, and Pengfei Jia. "Highly Sensitive Humidity Sensor Based on Oblique Carbon Nanoplumes." Sensors 18, no. 10 (October 11, 2018): 3407. http://dx.doi.org/10.3390/s18103407.

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In this work, we fabricated three carbon nanoplume structured samples under different temperatures using a simple hot filament physical vapor deposition (HFPVD) process, and investigated the role of surface morphology, defects, and graphitic content on relative humidity (RH) sensing performances. The Van der Drift growth model and oblique angle deposition (OAD) technique of growing a large area of uniformly aligned and inclined oblique arrays of carbon nanoplumes (CNPs) on a catalyst-free silicon substrate was demonstrated. The optimal growing temperature of 800 °C was suitable for the formation of nanoplumes with larger surface area, more defect sites, and less graphitic content, compared to the other samples that were prepared. As expected, a low detection limit, high response, capability of reversible behavior, and rapid response/recovery speed with respect to RH variation, was achieved without additional surface modification or chemical functionalization. The holes’ depletion has been described as a RH sensing mechanism that leads to the increase of the conduction of the CNPs with increasing RH levels.

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27

Ali, Norazida, Saaidal Razalli Azzuhri, Md Ashadi Md Johari, Haroon Rashid, Muhammad Imran Mustafa Abdul Khudus, Mohd Zulhakimi Ab Razak, Zhe Chen, Norbahiah Misran, and Norhana Arsad. "Effects of Tungsten Disulphide Coating on Tapered Microfiber for Relative Humidity Sensing Applications." Sensors 21, no. 21 (October 27, 2021): 7132. http://dx.doi.org/10.3390/s21217132.

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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.

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Poonia, Ekta, Prashant Kumar Mishra, Vijay Kiran, Jasbir Sangwan, Rakesh Kumar, Pramod Kumar Rai, Ritu Malik, Vijay K. Tomer, Rajeev Ahuja, and Yogendra Kumar Mishra. "Aero-gel based CeO2 nanoparticles: synthesis, structural properties and detailed humidity sensing response." Journal of Materials Chemistry C 7, no. 18 (2019): 5477–87. http://dx.doi.org/10.1039/c9tc01081e.

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Ashok, Gadkari B., Shinde J. Tukaram, and Vasambekar N. Pramod. "Role of Sm³⁺ Addition on Humidity Sensing of Nanocrystallite Mg-Cd Ferrites." Advanced Materials Research 645 (January 2013): 160–63. http://dx.doi.org/10.4028/www.scientific.net/amr.645.160.

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Nanocrystallite powders of 5 wt% Sm3+ added Mg-Cd ferrite samples were prepared by oxalate co-precipitation method. XRD, SEM and FT-IR techniques were used for characterization of the samples. The XRD reveals cubic spinel nature with secondary phase (SmFeO3). The crystallite size lies in the range of 28.69 to 32.66 nm. All the Sm3+ ions added samples are humidity sensitive at low humidity range 40 to70 %RH. The electrical resistivity of Sm3+ ions added samples decreased by four orders of magnitude, when %RH increased from 40%RH to 90 %RH. The response and recovery time of all the samples are 160-290 sec. The shorter response time was observed for Sm3+ added Cd ferrite sensor.

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30

Guo, Liang, Xuefeng Chu, Xiaohong Gao, Chao Wang, Yaodan Chi, and Xiaotian Yang. "AC Humidity Sensing Properties of Mesoporous K2CO3-SiO2Composite Materials." Journal of Chemistry 2016 (2016): 1–6. http://dx.doi.org/10.1155/2016/3508307.

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The mesoporous silica SBA-15 and mesoporous K2CO3-SiO2composite material were synthesized. Characterization of microstructure and morphology of materials indicated that the composite material had saved the porous framework of mesoporous silica SBA-15. Humidity sensing properties of different inverse proportion K2CO3-SiO2composite material were studied and we found that the sample with 0.16 g/g K2CO3exhibited excellent linearity in the wide humidity range. The complex impedance changed five orders of magnitude from 11% RH to 95% RH. The rapid response and recovery time were 10 s and 38 s, respectively. Finally a feasible ion transfer mechanism was brought forward to explain the sensing mechanism.

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Serban, Bogdan-Catalin, Cornel Cobianu, Octavian Buiu, Marius Bumbac, Niculae Dumbravescu, Viorel Avramescu, Cristina Mihaela Nicolescu, et al. "Ternary Nanocomposites Based on Oxidized Carbon Nanohorns as Sensing Layers for Room Temperature Resistive Humidity Sensing." Materials 14, no. 11 (May 21, 2021): 2705. http://dx.doi.org/10.3390/ma14112705.

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This paper presents the relative humidity (RH) sensing response of a resistive sensor employing sensing layers based on a ternary nanocomposite comprising graphene oxide-oxidized carbon nanohorns-polyvinylpyrrolidone (GO-CNHox–PVP), at 1/1/1, 1/2/1, and 1/3/1 w/w/w mass ratios. The sensing structure is composed of a silicon substrate, a SiO2 layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The morphology and the composition of the sensing layers are investigated through scanning electron microscopy (SEM) and RAMAN spectroscopy. The RH sensing capability of each carbonaceous nanocomposite-based thin film was analyzed by applying a current between the two electrodes and by measuring the voltage difference when varying the RH from 0% to 100% in humid nitrogen. The sensors have a room temperature response comparable to that of a commercial humidity sensor and are characterized by a rapid response, excellent linearity, good sensitivity, and recovery time. The manufactured sensing devices’ transfer functions were established, and we extracted the response and recovery times. While the structures with GO/CNHox/PVP at 1/1/1 ratio (w/w/w) had the best performance in terms of relative sensibility, response time, and recovery time, the sensors employing the GO/CNHox/PVP nanocomposite at the 1/2/1 ratio (w/w/w) had the best linearity. Moreover, the ternary mixture proved to have much better sensing properties compared to CNHox and CNHox-PVP-based sensing layers in terms of sensitivity and linearity. Each component of the ternary nanocomposites’ functional role is explained based on their physical and chemical properties. We analyzed the potential mechanism associated with the sensors’ response; among these, the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of the PVP, was dominant and led to increased resistance of the sensing layer.

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Mandić, Vilko, Arijeta Bafti, Luka Pavić, Ivana Panžić, Stanislav Kurajica, Jakov-Stjepan Pavelić, Zhen Shi, Katarina Mužina, and Ivana Katarina Ivković. "Humidity Sensing Ceria Thin-Films." Nanomaterials 12, no. 3 (February 2, 2022): 521. http://dx.doi.org/10.3390/nano12030521.

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Lowering the constitutive domains of semiconducting oxides to the nano-range has recently opened up the possibility of added benefit in the research area of sensing materials, in terms both of greater specific surface area and pore volume. Among such nanomaterials, ceria has attracted much attention; therefore, we chemically derived homogeneous ceria nanoparticle slurries. One set of samples was tape-casted onto a conducting glass substrate to form thin-films of various thicknesses, thereby avoiding demanding reaction conditions typical of physical depositions, while the other was pressed into pellets. Structural and microstructural features, along with electrical properties and derivative humidity-sensing performance of ceria thin-films and powders pressed into pellets, were studied in detail. Particular attention was given to solid-state impedance spectroscopy (SS-IS), under controlled relative humidity (RH) from 30%–85%, in a wide temperature and frequency range. Moreover, for the thin-film setup, measurements were performed in surface-mode and cross-section-mode. From the results, we extrapolated the influence of composition on relative humidity, the role of configuration and thin-film thickness on electrical properties, and derivative humidity-sensing performance. The structural analysis and depth profiling both point to monophasic crystalline ceria. Microstructure analysis reveals slightly agglomerated spherical particles and thin-films with low surface roughness. Under controlled humidity, the shape of the conductivity spectrum stays the same along with an increase in RH, and a notable shift to higher conductivity values. The relaxation is slow, as the thickness of the pellet slows the return of conductivity values. The increase in humidity has a positive effect on the overall DC conductivity, similar to the temperature effect for semiconducting behavior. As for the surface measurement setup, the thin-film thickness impacts the shape of the spectra and electrical processes. The surface measurement setup turns out to be more sensitive to relative humidity changes, emphasized with higher RH, along with an increase in thin-film thickness. The moisture directly affects the conductivity spectra in the dispersion part, i.e., on the localized short-range charge carriers. Moisture sensitivity is a reversible process for thin-film samples, in contrast to pellet form samples.

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He, Chenyang, Serhiy Korposh, Francisco Ulises Hernandez, Liangliang Liu, Ricardo Correia, Barrie R. Hayes-Gill, and Stephen P. Morgan. "Real-Time Humidity Measurement during Sports Activity using Optical Fibre Sensing." Sensors 20, no. 7 (March 30, 2020): 1904. http://dx.doi.org/10.3390/s20071904.

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An optical fibre sensor for monitoring relative humidity (RH) changes during exercise is demonstrated. The humidity sensor comprises a tip coating of poly (allylamine hydrochloride) (PAH)/silica nanoparticles (SiO2 NPs) deposited using the layer-by-layer technique. An uncoated fibre is employed to compensate for bending losses that are likely to occur during movement. A linear fit to the response of the sensing system to RH demonstrates a sensitivity of 3.02 mV/% (R2 = 0.96), hysteresis ± 1.17% RH when 11 bilayers of PAH/SiO2 NPs are coated on the tip of the fibre. The performance of two different textiles (100% cotton and 100% polyester) were tested in real-time relative humidity measurement for 10 healthy volunteers. The results demonstrate the moisture wicking properties of polyester in that the relative humidity dropped more rapidly after cessation of exercise compared to cotton. The approach has the potential to be used to monitor sports performance and by clothing developers for characterising different garment designs.

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Stajanca, Pavol, Konstantin Hicke, and Katerina Krebber. "Distributed Fiberoptic Sensor for Simultaneous Humidity and Temperature Monitoring Based on Polyimide-Coated Optical Fibers." Sensors 19, no. 23 (November 30, 2019): 5279. http://dx.doi.org/10.3390/s19235279.

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Along temperature, humidity is one of the principal environmental factors that plays an important role in various application areas. Presented work investigates possibility of distributed fiberoptic humidity monitoring based on humidity-induced strain measurement in polyimide (PI)-coated optical fibers. Characterization of relative humidity (RH) and temperature response of four different commercial PI- and one acrylate-coated fiber was performed using optical backscattering reflectometry (OBR). The study addresses issues of temperature-humidity cross-sensitivity, fiber response stability, repeatability, and the influence of annealing. Acrylate-coated fiber exhibited rather unfavorable nonlinear RH response with strong temperature dependence, which makes it unsuitable for humidity sensing applications. On the other hand, humidity response of PI-coated fibers showed good linearity with fiber sensitivity slightly decreasing at rising temperatures. In the tested range, temperature sensitivity of the fibers remained humidity independent. Thermal annealing was shown to considerably improve and stabilize fiber RH response. Based on performed analysis, a 20 m sensor using the optimal PI-coated fibers was proposed and constructed. The sensor uses dual sensing fiber configuration for mutual decoupling and simultaneous measurement of temperature and RH variations. Using OBR, distributed dual temperature-RH monitoring with cm spatial resolution was demonstrated for the first time.

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35

Meng, Fanting, Zhuang Zhuang, Yurong Zhang, and Hui Na. "Investigations of the humidity sensing properties of side-chain-type sulfonated poly (arylene ether ketone)s." High Performance Polymers 31, no. 9-10 (April 29, 2019): 1248–58. http://dx.doi.org/10.1177/0954008319846221.

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Side-chain-type sulfonated poly (arylene ether ketone)s containing naphthalene moieties with a degree of sulfonation (Ds) from 0.2 to 1.9 were synthesized. Humidity sensors were fabricated by cast coating on silver–palladium interdigital microelectrodes. The properties of this series of materials in terms of water absorption, glass transition temperature, and humidity sensing were characterized in detail. The investigations on the humidity sensing performance showed that with the increase in the Ds, the hysteresis of our materials exhibits an increasing trend first, followed by a decrease. This special phenomenon has not been reported before and caught our attention. From the results of humidity sensing properties, among the materials, the one with 0.2 Ds is promising for applications in humidity sensing due to its small hysteresis and fast response to varied relative humidity (RH). For a better understanding of the humidity sensing behavior of the sensor, complex impedance spectra were also measured. In the long-term stability measurement, the deviation of the measured impedance of the sensor at 97% RH is not obvious, proving good stability in a humid environment.

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Hou, Zhaonan, Zhiyan Ma, Xin Guan, Hongran Zhao, Sen Liu, Teng Fei, and Tong Zhang. "A Cellulose Nanofiber Capacitive Humidity Sensor with High Sensitivity and Fast Recovery Characteristics." Chemosensors 10, no. 11 (November 8, 2022): 464. http://dx.doi.org/10.3390/chemosensors10110464.

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Humidity sensors with high sensitivity and fast response characteristics are of great interest for researchers. In this work, capacitive humidity sensors were fabricated using ionic liquid/cellulose nanofibers (CNFs) as the composited sensing film. The porous CNFs are beneficial for preparing sensing films via a solution process, and the ionic liquid could be uniformly dispersed in the films. The humidity-sensing performance of the as-prepared sensors was investigated. The optimized sensor showed a high response (27.95 pF/% RH) in a wide humidity range (11–95% RH) and a fast response speed in the adsorption process (the recovery time was only ~1 s). The high response of the sensors was attributed to the polarization at the interface between the electrolyte and the metal electrode, while the fast recovery was due to the rapid desorption of water molecules on the sensing films. Finally, the application of the obtained sensors in human breath monitoring was explored.

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37

Ahmad, Waqas, Bushra Jabbar, Imtiaz Ahmad, Badrul Mohamed Jan, Minas M. Stylianakis, George Kenanakis, and Rabia Ikram. "Highly Sensitive Humidity Sensors Based on Polyethylene Oxide/CuO/Multi Walled Carbon Nanotubes Composite Nanofibers." Materials 14, no. 4 (February 22, 2021): 1037. http://dx.doi.org/10.3390/ma14041037.

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Polymer composites are favorite materials for sensing applications due to their low cost and easy fabrication. In the current study, composite nanofibers consisting of polyethylene oxide (PEO), oxidized multi-walled carbon nanotubes (MWCNT) and copper oxide (CuO) nanoparticles with 1% and 3% of fillers (i.e., PEO–CuO–MWCNT: 1%, and PEO–CuO–MWCNT: 3%) were successfully developed through electrospinning for humidity sensing applications. The composite nanofibers were characterized by FTIR, XRD, SEM and EDX analysis. Firstly, they were loaded on an interdigitated electrode (IDE), and then the humidity sensing efficiency was investigated through a digital LCR meter (E4980) at different frequencies (100 Hz–1 MHz), as well as the percentage of relative humidity (RH). The results indicated that the composite nanofibers containing 1% and 3% MWCNT, combined with CuO in PEO polymer matrix, showed potent resistive and capacitive response along with high sensitivity to humidity at room temperature in an RH range of 30–90%. More specifically, the PEO–CuO–MWCNT: 1% nanocomposite displayed a resistive rapid response time within 3 s and a long recovery time of 22 s, while the PEO–CuO–MWCNT: 3% one exhibited 20 s and 11 s between the same RH range, respectively.

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Qi, Qi, Qi Wang, Nanliu Liu, Xiaoping Zheng, Xiongjie Ding, Zhiwen Liang, Qing Wang, and Guoyi Zhang. "A Flexible Humidity Sensor Based on Co3O4 Nanoneedles with High Sensitivity and Quick Response." Journal of Nanoelectronics and Optoelectronics 15, no. 7 (July 1, 2020): 870–74. http://dx.doi.org/10.1166/jno.2020.2788.

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A flexible humidity sensor has been realized based on Co3O4 nanoneedles via a deposition technique. High humidity sensing and excellent flexible properties are observed in the tests. The impedance of the as-prepared sensor decreases by nearly three orders of magnitude with increasing relative humidity (RH) from 11% to 95% on a semilogarithmic scale. The response and recovery times are about 3 and 6 s respectively. The maximum hysteresis is less than 4% under 80% RH. No obvious changes for the sensing performance can be obtained after 100 bending/extending cycles and bending tests. These performances make the current sensor a good candidate for flexible humidity detection.

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Tousi, Maryam Mesgarpour, Yujing Zhang, Shaowei Wan, Li Yu, Chong Hou, Ning Yan, Yoel Fink, Anbo Wang, and Xiaoting Jia. "Scalable Fabrication of Highly Flexible Porous Polymer-Based Capacitive Humidity Sensor Using Convergence Fiber Drawing." Polymers 11, no. 12 (December 2, 2019): 1985. http://dx.doi.org/10.3390/polym11121985.

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In this study, we fabricated a highly flexible fiber-based capacitive humidity sensor using a scalable convergence fiber drawing approach. The sensor’s sensing layer is made of porous polyetherimide (PEI) with its porosity produced in situ during fiber drawing, whereas its electrodes are made of copper wires. The porosity induces capillary condensation starting at a low relative humidity (RH) level (here, 70%), resulting in a significant increase in the response of the sensor at RH levels ranging from 70% to 80%. The proposed humidity sensor shows a good sensitivity of 0.39 pF/% RH in the range of 70%–80% RH, a maximum hysteresis of 9.08% RH at 70% RH, a small temperature dependence, and a good stability over a 48 h period. This work demonstrates the first fiber-based humidity sensor fabricated using convergence fiber drawing.

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Jalkanen, Tero, Anni Määttänen, Ermei Mäkilä, Jaani Tuura, Martti Kaasalainen, Vesa-Pekka Lehto, Petri Ihalainen, Jouko Peltonen, and Jarno Salonen. "Fabrication of Porous Silicon Based Humidity Sensing Elements on Paper." Journal of Sensors 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/927396.

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A roll-to-roll compatible fabrication process of porous silicon (pSi) based sensing elements for a real-time humidity monitoring is described. The sensing elements, consisting of printed interdigitated silver electrodes and a spray-coated pSi layer, were fabricated on a coated paper substrate by a two-step process. Capacitive and resistive responses of the sensing elements were examined under different concentrations of humidity. More than a three orders of magnitude reproducible decrease in resistance was measured when the relative humidity (RH) was increased from 0% to 90%. A relatively fast recovery without the need of any refreshing methods was observed with a change in RH. Humidity background signal and hysteresis arising from the paper substrate were dependent on the thickness of sensing pSi layer. Hysteresis in most optimal sensing element setup (a thick pSi layer) was still noticeable but not detrimental for the sensing. In addition to electrical characterization of sensing elements, thermal degradation and moisture adsorption properties of the paper substrate were examined in connection to the fabrication process of the silver electrodes and the moisture sensitivity of the paper. The results pave the way towards the development of low-cost humidity sensors which could be utilized, for example, in smart packaging applications or in smart cities to monitor the environment.

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Dias, Bernardo, José Almeida, and Luís Coelho. "Long-Period Fiber Gratings Coated with Poly(ethylene glycol) as Relative Humidity Sensors." U.Porto Journal of Engineering 8, no. 3 (May 30, 2022): 2–6. http://dx.doi.org/10.24840/2183-6493_008.003_0002.

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Relative humidity is an important parameter in controlled environments and is typically monitored using low-cost electrochemical sensors with low resolution and accuracy. This kind of sensors cannot not be implemented in harsh or explosive environments (as in pyrotechnic facilities) due to electrical discharges, or in marine structures where the oxidation of the sensing probe materials changes the sensing response). In these cases, fiber optic sensors can provide solutions due to their intrinsic properties, such as immunity to electromagnetic interference and resistance in harsh environments. This work presents preliminary results regarding the steps of the fabrication of Long-Period Fiber Gratings, the coating processes with a thin layer of poly(ethylene glycol) (PEG) and its sensing performance to relative humidity, displaying a from 60 to 100%sensitivity of 0.6 nm/%RH in the range of 80 to 100%RH.

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Liang, Aijie, Jingyuan Ming, Wenguo Zhu, Heyuan Guan, Xinyang Han, Shuo Zhang, Yuxin Lin, et al. "Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity." Crystals 11, no. 6 (June 8, 2021): 648. http://dx.doi.org/10.3390/cryst11060648.

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

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Alam, Noor, and S. S. Islam. "Development of Y-Shaped Porous Anodic Alumina Humidity Sensor to Enhance Lower Detection Limit and Sensitivity." ECS Transactions 107, no. 1 (April 24, 2022): 11991–2000. http://dx.doi.org/10.1149/10701.11991ecst.

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The amount of water vapours in the air can affect the productivity and safety of many manufacturing processes, such as agriculture, pharmaceuticals, and semiconductor industries, as well as human comfort. The humidity sensors based on porous materials, such as Porous Anodic Alumina (PAA), have persuaded much attention because of their high porosity and tuneable structure. In this work, we have developed a PAA capacitive sensor using phosphoric acid electrolyte by the Differential Pulse Voltammetry method of anodization. The PAA-based humidity sensor shows ultra-high sensitivity, fast response, and a wide detection range of relative humidity (RH). Response and recovery time of the sensor are ~ 16 s and ~ 4 s, respectively at 64 RH%, and the sensor is capable of sensing 1-100 RH%. These results advocate that PAA is a propitious applicant for various humidity sensing applications, especially where low humidity detection is required i.e., paper, lithium-ion battery, tea industries, etc.

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Paul, Jiss, and Jacob Philip. "Design optimization and stability enhancement of modified inter-digital capacitive humidity transducer with cobalt ferrite nanoparticles as dielectric." Transactions of the Institute of Measurement and Control 42, no. 4 (December 1, 2019): 917–23. http://dx.doi.org/10.1177/0142331219889485.

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A modified inter-digital capacitive (IDC) transducer for relative humidity (RH) measurement is fabricated by coating a thick film of polyvinyl alcohol (PVA) on the structure. The effective capacitance of the sensor, measured at 1MHz, increases with RH at room temperature. The RH sensing characteristics of PVA coated IDC transducer are analysed in terms of its sensitivity, dynamic range, frequency response, repeatability and recovery time. It is found that the stability of such a PVA based RH transducer improves remarkably by diffusing nanoparticles of CoFe2O4 in the PVA layer. A standard deviation of ± 0.05 and ± 0.01 for a sensitive layer with pure PVA and PVA-CoFe2O4 combination respectively results in a measurement error of ± 0.005 and ± 0.003.

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Choi, Kwon-Il, Su-Jin Hwang, Zhengfei Dai, Yun Chan Kang, and Jong-Heun Lee. "Rh-catalyzed WO3 with anomalous humidity dependence of gas sensing characteristics." RSC Adv. 4, no. 95 (2014): 53130–36. http://dx.doi.org/10.1039/c4ra06654e.

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Pandey, N. K., A. Tripathi, Dr Karunesh Tiwari, and Akash Roy. "Relative Humidity Sensing Studies of WO₃-ZnO Nanocomposite." Advanced Materials Research 79-82 (August 2009): 365–68. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.365.

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Paper reports morphological and humidity sensing studies of WO3 and WO3-ZnO nanocomposite pellets prepared in the weight % ratio of 10:1, 4:1 and 2:1 by solid-state reaction route. The pellets have been annealed at temperatures of 300-500°C. XRD pattern shows peaks of ZnWO4 formed due to solid state reaction between WO3 and ZnO. SEM micrographs show that the sensing elements manifest porous structure. Granulation and tendency to agglomerate seen in the SEM micrograph are due to the presence of zinc ions in ZnWO4. Nanoparticles are having their sizes in the range 37-182 nm. The average Kelvin radius at 20°C room temperature is 27 Ả. Humidity sensing application of the pellets has been studied in a humidity control cabinet. It is observed that as relative humidity increases, there is decrease in the resistance of pellets in the range 10-85% RH. Sensing element of WO3-ZnO in 2:1 weight % ratio shows best results in 10-85 % relative humidity range. The average sensitivity of this sample is 1.20 MΩ/%RH. This sensing element shows good reproducibility, low hysteresis and less effect of aging.

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Zeeshan, Afaque Manzoor Soomro, and Sungbo Cho. "Design and Fabrication of a Robust Chitosan/Polyvinyl Alcohol-Based Humidity Sensor energized by a Piezoelectric Generator." Energies 15, no. 20 (October 15, 2022): 7609. http://dx.doi.org/10.3390/en15207609.

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Due to their rapid growth in industrial and environmental applications, there is a need to develop self-powered humidity sensor systems with improved sensitivity, a wide detection range, and an eco-friendly nature. In this study, an aqueous solution of chitosan (CS) and polyvinyl alcohol (PVA) was blended to yield a composite film material with enhanced humidity detection properties. Meanwhile, a polyvinylidene difluoride (PVDF)-loaded chitosan composite film was developed and employed as a piezoelectric generator. Moreover, the developed composite materials for both devices (the piezoelectric generator and the humidity sensor) were optimized based on output performance. The piezoelectric generator generates a maximum of 16.2 V when a force of 10 N is applied and works as a power source for the humidity-sensing film. The sensing film swells in response to changes in relative humidity, which affects film resistance. This change in resistance causes a change in voltage through the piezoelectric generator and allows the precise measurement of relative humidity (RH). The fabricated sensor showed a linear response (R2 = 0.981) with a reasonable sensitivity (0.23 V/% RH) in an environment with an RH range of 21–89%. In addition, the device requires no external power, and therefore, it has numerous sensing applications in various fields.

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Ali, Salman, Mohammed A. Jameel, Christopher J. Harrison, Akhil Gupta, Richard A. Evans, Mahnaz Shafiei, and Steven J. Langford. "Enhanced Capacitive Humidity Sensing Performance at Room Temperature via Hydrogen Bonding of Cyanopyridone-Based Oligothiophene Donor." Chemosensors 9, no. 11 (November 15, 2021): 320. http://dx.doi.org/10.3390/chemosensors9110320.

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Cyanopyridone-based oligothiophene donors with both hydrophobic and hydrophilic characters have been evaluated as active layers within simple capacitive devices for humidity sensing at room temperature. Surface studies using atomic force microscopy revealed a self-assembled nanofibrous network with a thin needle-like structure for the terminal hydroxy example (CP6), devoid in the methyl example (CP1). The sensing performance of each sensor was investigated over a broad range of relative humidity levels as a function of capacitance at room temperature. The sensor CP6 demonstrated favourable features such as high sensitivity (12.2 pF/%RH), quick response/recovery (13 s/20.7 s), wide working range of relative humidity (10%–95% RH), low hysteresis (0.57%), outstanding recyclability, and excellent long-term stability. From the results obtained, hydrophilicity and hydrogen bonding appear to play a vital role in enhancing humidity sensing performance, leading to possible new design directions for simple organic semiconductor-based sensors.

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Urbancova, Petra, Jakub Chylek, Petr Hlubina, and Dusan Pudis. "Guided-Mode Resonance-Based Relative Humidity Sensing Employing a Planar Waveguide Structure." Sensors 20, no. 23 (November 27, 2020): 6788. http://dx.doi.org/10.3390/s20236788.

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In this paper, we present a new type of guided-mode resonance (GMR)-based sensor that utilizes a planar waveguide structure (PWS). We employed a PWS with an asymmetric three-layer waveguide structure consisting of substrate/Au/photoresist. The ellipsometric characterization of the structure layers, the simulated reflectance spectra, and optical field distributions under GMR conditions showed that multiple waveguide modes can be excited in the PWS. These modes can be used for refractive index sensing, and the theoretical analysis of the designed PWS showed a sensitivity to the refractive index up to 6600 nm per refractive index unit (RIU) and a figure of merit (FOM) up to 224 RIU−1. In response to these promising theoretical results, the PWS was used to measure the relative humidity (RH) of moist air with a sensitivity up to 0.141 nm/%RH and a FOM reaching 3.7 × 10−3%RH−1. The results demonstrate that this highly-sensitive and hysteresis-free sensor based on GMR has the potential to be used in a wide range of applications.

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Hashtroudi, Hanie, Aimin Yu, Saulius Juodkazis, and Mahnaz Shafiei. "Ultra-Sensitive Photo-Induced Hydrogen Gas Sensor Based on Two-Dimensional CeO2-Pd-PDA/rGO Heterojunction Nanocomposite." Nanomaterials 12, no. 10 (May 10, 2022): 1628. http://dx.doi.org/10.3390/nano12101628.

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A two-dimensional (2D) CeO2-Pd-PDA/rGO heterojunction nanocomposite has been synthesised via an environmentally friendly, energy efficient, and facile wet chemical procedure and examined for hydrogen (H2) gas sensing application for the first time. The H2 gas sensing performance of the developed conductometric sensor has been extensively investigated under different operational conditions, including working temperature up to 200 °C, UV illumination, H2 concentrations from 50–6000 ppm, and relative humidity up to 30% RH. The developed ceria-based nanocomposite sensor was functional at a relatively low working temperature (100 °C), and its sensing properties were improved under UV illumination (365 nm). The sensor’s response towards 6000 ppm H2 was drastically enhanced in a humid environment (15% RH), from 172% to 416%. Under optimised conditions, this highly sensitive and selective H2 sensor enabled the detection of H2 molecules down to 50 ppm experimentally. The sensing enhancement mechanisms of the developed sensor were explained in detail. The available 4f electrons and oxygen vacancies on the ceria surface make it a promising material for H2 sensing applications. Moreover, based on the material characterisation results, highly reactive oxidant species on the sensor surface formed the electron–hole pairs, facilitated oxygen mobility, and enhanced the H2 sensing performance.

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Journal articles on the topic 'RH Sensing'

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