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The natural polymer cellulose exhibits significant potential for various applications due to its unique optical, electronic, and chemical properties. However, the use of cellulose materials in luminescent applications has been relatively limited. This study aims to develop a simple and efficient method to enhance the fluorescence of cellulose materials by incorporating rare earth elements, thereby expanding their range of applications. In this work, we synthesized hybrid cellulose materials by grafting Eu‐bpy (H2bpydc=2,2‐bipyridine‐5,5‐dicarboxylic acid) onto the surface of cellulose fibers through a straightforward post‐processing procedure, resulting in materials with excellent fluorescence properties. By leveraging the abundant hydroxyl groups on the surface of cellulose fibers, Eu‐bpy@CF exhibits high luminescence in response to relative humidity and pH changes, with a noticeable color shift from light red to red visible to the naked eye. Consequently, these materials were further applied in the construction of smart fluorescent switches for the highly accurate and selective detection of phenylenediamine. Our research provides a simple approach to creating environmentally responsive handheld fluorescent papers and expands the diversity of rare‐earth cellulose fibers for developing new fluorescent materials with smart functions. [ABSTRACT FROM AUTHOR]

Flexible optoelectronic devices have attracted enormous attention as an essential component in next‐generation wearable devices. To meet the trend of biocompatibility, flexibility and low cost, paper‐based optoelectronic devices have become compelling candidates. Moreover, 2D organic–inorganic metal halide perovskites have been extensively studied for the application in flexible optoelectronic devices owing to their long‐term moisture stability, optoelectronic tunability, and multiple quantum well (MQW) structures. Herein, the paper‐based flexible optoelectronic devices are designed by spin‐coating PEDOT:PSS and (iso‐BA)2MAn‐1PbnI3n+1 (n ≥ 1) on regular filter paper with responsivity of 2.62 mA W−1 and response time (τrise/τdecay) of 0.81/0.18 s at 35% relative humidity (RH). Furthermore, the responsivity may be increased by 250% within the humidity range from 35% to 90%, and remains above 92% of the initial value after measured for 1800 s at 60% RH. This work can pave the way for further studies about the humidity effect on perovskites for next‐generation green wearable electronics. [ABSTRACT FROM AUTHOR]

Herein we report the development of bilayer‐coated‐paper with corn starch as the bottom layer and zein protein as the top layer. Two different methods were used for preparation of the coated paper, namely rod‐coating and dip‐coating techniques. The effect of the coating methods was studied by investigating the mechanical and barrier properties of the coated paper. A significant decrease of the water vapor and oxygen transmission rates at various temperatures and relative humidity conditions was observed. Considering the growing need for renewable and biodegradable alternatives to conventional plastics, the coated paper described herein may have strong potential for applications in the food packaging sector. [ABSTRACT FROM AUTHOR]

Paper and board are used for packaging of moist as well as dry food. According to Regulation (EC) No. 1935/2004, food contact materials (FCM) must not bring about a deterioration in the organoleptic characteristics of foodstuffs. For testing the transfer of off-flavour (taint) from packaging to food via the gas phase (DIN EN 1230-2), relative humidity (rH) has to be adjusted. In contrast, rH is neither taken into account when testing the odour (DIN EN 1230-1), nor in chemical migration of volatile organic substances (VOC) onto the adsorbent Tenax® (DIN EN 14338). In this work, effect of different rHs on the desorption of VOC from paper and board was investigated by GC-MS analysis as well as by human sensory tests. Raising humidity led to an increase in VOC transfer, which was observed by increasing peak areas as well as the detection of more substances in GC-MS. Analytical results were in line with human sensory tests. The odour profile of the paper at 33 and 58% rH was described as cardboard-like, sweet and smoky. Impact substances for these olfactory impressions were (E)-2-nonenal, vanillin and 2-methoxyphenol as identified by GC with an olfactory detection port (GC-ODP). The increase to 75 and 100% rH resulted in the additional perception of cheesy/sweaty and fatty/rancid impressions, which were primarily caused by short-chain fatty acids and di-unsaturated aldehydes. [ABSTRACT FROM AUTHOR]

Paper-based electronics have attracted much attention due to their softness, degradability, and low cost. However, paper-based sensors are difficult to apply to high-humidity environments or even underwater. Here, we report a fully paper-integrated piezoresistive sensing system that exhibits flexibility, waterproofing, air permeability, and biocompatibility. This system consists of hydrophobic paper as the substrate and encapsulation layer, conductive paper with a double 'zig-zag' and dotted surface structure as the sensing layer, and silver paste films as the interconnects. The structural design of the sensing layer helps to increase the contact area in adjacent layers under pressure and further improves the pressure sensitivity. The piezoresistive system can be worn on human skin in the ambient environment, wet environment, and water for real-time monitoring of physiological signals with air permeability and waterproofing due to its hydrophobic fiber structure. Such a device provides a reliable, economical, and eco-friendly solution to wearable technologies. [ABSTRACT FROM AUTHOR]

The frequency‐domain dielectric spectroscopy (FDS) of humid insulating paper has been measured at different temperatures. The data show three independent dielectric processes: electrode polarization, hopping conductivity and interfacial polarization. The dielectric properties of humid insulating paper are composed of hopping conductivity and interfacial polarization, and its equivalent dielectric model can be represented by a Havriliak‐Negami (HN) relaxation branch parallel hopping conductivity. At high temperatures and low frequencies, the measured dielectric spectroscopy bends downward, which is caused by the electrode polarization. In this case, the equivalent dielectric model is composed of the body impedance of insulating paper and the electrode polarization in series. According to the equivalent dielectric model, the components of electrode polarization, hopping conductivity, and interface polarization can be separated, thereby eliminating the parasitic effect of electrode polarization on the dielectric properties of insulating paper. Both of hopping conductivity and interface polarization of insulating paper move toward high‐frequency direction with temperature increasing. For humid insulating paper with a moisture content of 5.9%, the activation energies of hopping conductivity and interface polarization are 1.18 and 0.99 eV, respectively. This difference in activation energies results in the inability of the spectrums of insulating paper to overlap with each other at different temperatures. Based on the insulating paper without oil immersion, the results obtained in this article are not affected by oil or oil‐immersion operations. This provides a reference for exploring the dielectric properties and physical mechanisms of oil‐paper composite insulation materials widely used in high‐voltage equipment. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Paper flowers are frequently, for example as indoor decorations and in wedding bouquets. But these traditional paper flowers can only maintain static conditions, greatly affecting their sensory effects, vividness, and appreciation. The design of novel paper flowers with dynamic shape deformation could effectively broaden the application of paper flowers. Here, inspired by Chinese calligraphy, a novel polyvinyl butyral (PVB)/carbon/cellulose composite (PCC) magic paper with a sandwiched structure is prepared. The hygroscopicity difference between hydrophobic PVB and hydrophilic cellulose layer endows the PCC paper with humidity responsiveness, and the maximum bending angle is up to 91.4° upon exposure to humidity environment. Carbon in the interlayer with strong light–heat conversion capacity could further accelerate water desorption and deformation speed, resulting in highly sensitive light responsiveness. The recovery time of PCC paper from maximum bending to the original flat state is shorter than 1 s. The PCC paper has good flexibility and processability, which can be cut and assembled into flowers with different shapes, and these unique magic flowers could freely bloom and furl upon external stimulus. All these results indicate that PCC paper has great potential in the production of magic props, artworks, and intelligent household decorations fields. [ABSTRACT FROM AUTHOR]

In the first part of the review article "General considerations" we give information about conventional flexible platforms and consider the advantages and disadvantages of paper when used in humidity sensors, both as a substrate and as a humidity-sensitive material. This consideration shows that paper, especially nanopaper, is a very promising material for the development of low-cost flexible humidity sensors suitable for a wide range of applications. Various humidity-sensitive materials suitable for use in paper-based sensors are analyzed and the humidity-sensitive characteristics of paper and other humidity-sensitive materials are compared. Various configurations of humidity sensors that can be developed on the basis of paper are considered, and a description of the mechanisms of their operation is given. Next, we discuss the manufacturing features of paper-based humidity sensors. The main attention is paid to the consideration of such problems as patterning and electrode formation. It is shown that printing technologies are the most suitable for mass production of paper-based flexible humidity sensors. At the same time, these technologies are effective both in the formation of a humidity-sensitive layer and in the manufacture of electrodes. [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy) has high electrical conductivity, good environmental stability, and reversible electrochemical redox characteristics, which makes PPy responsive to changes in environmental humidity values. In this work, a humidity sensor with a good response to humidity was prepared using in situ polymerization of PPy in filter paper doping with acetic acid. A possible sensing mechanism of conductive polymers is proposed and the conjecture is verified by experiments. The results demonstrated that the PPy/filter paper-based humidity sensor provides an electron migration channel with the capability of detecting the relative humidity. External humidity stimulation can regulate the electrochemical reaction of PPy. The reduction reaction occurs near the water side to generate the nucleophilic product OH–. The PPy system loses electrons to form carrier directional channels, resulting in changes in the output voltage measured between the two electrodes. The PPy/filter paper-based humidity sensor exhibits the moisture dependent voltage response over a wide range from a relative humidity of 11–98%, and a response/recovery time of 43/51 s as it was placed between relative humidity of 33% and 98%. In addition, unlike the traditional sensing mechanism, the voltage sensing mechanism raised here shows self-powered ability with no need for an additional power unit. This provides a new idea for self-powered sensor devices, and this sensor shows good performance in non-contact sensing applications such as breath detection. [ABSTRACT FROM AUTHOR]

Biomimetic actuators are typically constructed as functional bi- or multilayers, where actuating and resistance layers together dictate bending responses upon triggering by environmental stimuli. Inspired by motile plant structures, like the stems of the false rose of Jericho (Selaginella lepidophylla), we introduce polymer-modified paper sheets that can act as soft robotic single-layer actuators capable of hygro-responsive bending reactions. A tailored gradient modification of the paper sheet along its thickness entails increased dry and wet tensile strength and allows at the same time for hygro-responsiveness. For the fabrication of such single-layer paper devices, the adsorption behavior of a cross-linkable polymer to cellulose fiber networks was first evaluated. By using different concentrations and drying procedures fine-tuned polymer gradients throughout the thickness can be achieved. Due to the covalent cross-linking of polymer with fibers, these paper samples possess significantly increased dry and wet tensile strength properties. We furthermore investigated these gradient papers with respect to a mechanical deflection during humidity cycling. The highest humidity sensitivity is achieved using eucalyptus paper with a grammage of 150 g m−2 modified with the polymer dissolved in IPA (~13 wt%) possessing a polymer gradient. Our study presents a straightforward approach for the design of novel hygroscopic, paper-based single-layer actuators, which have a high potential for diverse soft robotic and sensor applications. [ABSTRACT FROM AUTHOR]

The novel paper-based Bi-Material Cantilever (B-MaC) valve allows the autonomous loading and control of multiple fluid reagents which contributes to the accurate operation of paper-based microfluidic devices utilized for biological and chemical sensing applications. In this paper, an extensive parametric study is presented to evaluate the effects of key geometric parameters of the valve, such as paper direction, cantilever width, paper type, tape type, and sample volume, in addition to the effects of relative humidity and temperature on the functionality of the B-MaC and to provide a better understanding of the rate of fluid flow and resulting deflection of the cantilever. Machine direction, cantilever width, paper type, and tape type were found to be important parameters that affect the B-MAC's activation time. It was also observed that the rate of fluid imbibition in the B-MaC is considerably affected by change in humidity for high (55 °C) and low (25 °C) temperatures, while humidity levels have no significant effect during imbibition in the B-MaC at an ambient temperature of 45 °C. It was also found that a minimum distance of 4 mm is required between the B-MaC and the stationary component to prevent accidental activation of the B-MaC prior to sample insertion when relative humidity is higher than 90% and temperature is lower than 35 °C. The rate of fluid imbibition that determines the wetted length of the B-MaC and the final deflection of the cantilever are critical in designing and fabricating point-of-care microfluidic paper-based devices. The B-MaC valve can be utilized in a fluidic circuit to sequentially load several reagents, in addition to the sample to the detection area. [ABSTRACT FROM AUTHOR]

The perforated paper honeycomb structure with double-hole in cell walls is one kind of innovative sandwich structure also to improve drying process of traditional honeycomb paperboard. Based on the analytical calculation, experiment inspection and finite element analysis, this paper is focus on the paper honeycomb core layer with double-hole in cell walls, and especially studies the bending and folding deformation and the compressive strength under out-of-plane quasi-static compression for different humidity. The structure first appears elastic buckling and folds near the circular holes in the cell wall, and goes on buckling, folding and crushing until to the densification with the continuously increase of compression set. Its quasi-static compressive stress and strain curve mainly shows four kinds of compression deformation processes, such as linear elastic stage, elastic yielding stage, plastic collapse stage, and densification stage. The critical stress and plateau stress of the structure slowly decrease with the increase of humidity and aperture, and the multiple linear regression analysis result illustrates that the relative humidity has much more influence on the critical stress and plateau stress. For different humidity and aperture, the analytical calculation result is close to the experiment result. However, the finite element simulation result greatly deviates from the above two results, especially for relative humidity 50% and 60% cases. [ABSTRACT FROM AUTHOR]

Paper and board are used for packaging of moist as well as dry food. According to Regulation (EC) No. 1935/2004, food contact materials (FCM) must not bring about a deterioration in the organoleptic characteristics of foodstuffs. For testing the transfer of off-flavour (taint) from packaging to food via the gas phase (DIN EN 1230-2), relative humidity (rH) has to be adjusted. In contrast, rH is neither taken into account when testing the odour (DIN EN 1230-1), nor in chemical migration of volatile organic substances (VOC) onto the adsorbent Tenax® (DIN EN 14338). In this work, effect of different rHs on the desorption of VOC from paper and board was investigated by GC-MS analysis as well as by human sensory tests. Raising humidity led to an increase in VOC transfer, which was observed by increasing peak areas as well as the detection of more substances in GC-MS. Analytical results were in line with human sensory tests. The odour profile of the paper at 33 and 58% rH was described as cardboard-like, sweet and smoky. Impact substances for these olfactory impressions were (E)-2-nonenal, vanillin and 2-methoxyphenol as identified by GC with an olfactory detection port (GC-ODP). The increase to 75 and 100% rH resulted in the additional perception of cheesy/sweaty and fatty/rancid impressions, which were primarily caused by short-chain fatty acids and di-unsaturated aldehydes. [ABSTRACT FROM AUTHOR]

This paper focuses on proton exchange membrane fuel cell (PEMFC) operation at current densities in the order of 6 A/cm2. Such high current densities are conceivable when the traditional carbon fiber papers are replaced with perforated metal plates as the gas diffusion layer to enhance waste heat removal, and at the same time the relative humidity inside the fuel cell is kept below 100% by applying appropriate operating conditions as was found in previous one-dimensional modeling work. In the current paper, we applied a three-dimensional, multi-phase computational fluid dynamics model based on Ansys-CFX to obtain additional insight into the underlying physics. The calculated pressure drops are in very good agreement with previous one-dimensional modeling work, and the current densities in all case studies are in the order of 5–6 A/cm2, but different from the previous one-dimensional study, the results suggest that the relative humidity is very close to 100% throughout the entire channel length when the inlet relative humidity is 100%, ensuring best hydration cell conditions and hence best performance. Importantly, the model results suggest that fuel cell performance at a high current density in conjunction with relatively low stoichiometric flow ratios around 1.5–2 is possible. [ABSTRACT FROM AUTHOR]

Fiber-gypsum board is a composite material, in which fiber is used as the reinforcement in the matrix of gypsum. The purpose of this research was to investigate the effect of adding different amounts of waste paper fibers on the strength, and the fracture behavior of fiber-gypsum board. For this purpose, zero, 5, 10, 15, 20, 25 and 35 percent gypsum was substituted by waste paper fibers in the mixture. The results of bending strength, internal bonding and moisture absorption after one month exposure to 100% relative humidity measurement showed that increasing the percentage of fibers up to 20% increased the mechanical properties. In general, using twenty percent fibers in the mixture increased the bending strength by 50% and the internal bonding was increase two and half times compared to the control samples. The load-displacement curve shows that the dosage of 5 to 15 percent of fibers does not change the fracture behavior of the fibergypsum board and exhibited brittle fracture as in control samples. While at higher dosage, the flexibility increases and the failure becomes ductile. Therefore, the best conditions in terms of strength, resistance, and flexibility was reached at 20% substitution of gypsum with waste paper fibers. [ABSTRACT FROM AUTHOR]

Paper degradation menaces the useful lifetime of books, manuscripts, and works on paper during storage, circulation, and display in libraries, archives, and museums. Severe damages such as embrittlement, decay, and mold often occur to the paper that might threaten to lose cultural heritage. However, the shelf life of papers stored in suitable conditions can be extended by hundreds of years. The most important external factors affecting the deterioration of paper-based materials include, in particular, changes in temperature and air humidity. In this study, the effects of accelerated aging under different conditions, including substantially different relative humidity, were considered relative to the strength properties of the paper sheets. These include the mechanical strength, such as breaking length, tear resistance, and bursting strength of the paper samples before and after dry heat aging and hydrothermal aging. Samples with various content of lignin produced in neutral pH were examined to exclude the adverse influence of acidity on paper properties. The results indicate that impact of moisture on tensile properties and pH-value of paper is much greater than the effect of increased temperature. The results of this work are intended to consolidate and expand the theoretical foundation and provide technical support for the conservators and library staff on the storage of paper cultural relics. [ABSTRACT FROM AUTHOR]

The enormous demand for self-powered sensors in industry 4.0 has drawn a lot of research interest in these vital devices that do not need external power sources. This study presents the development of a self-powered paper-based humidity sensor that uses copper and aluminium as electrodes and a composite of MgCl 2 and carbon nanotubes (CNTs) as sensing material. The results demonstrate a significant improvement in humidity sensing performance as a result of the addition of CNTs and MgCl 2. In particular, the self-powered paper-based humidity sensor with MgCl 2 /CNTs composites has impressive repeatability, broad detection ranging from 11 % to 97 % relative humidity, and quick response and recovery times of 10 and 46 s, respectively. Furthermore, the self-powered paper-based humidity sensor can generate a maximum voltage of 1.07 V and a maximum power of approximately 1.984 µW. Furthermore, connecting the paper-based humidity sensors in series increases their voltage output, making them useful for charging capacitors and lighting up to six LEDs. This endeavour offers a straightforward, cost-effective, and highly responsive self-powered paper-based humidity sensor that is ideal for high-performance applications in humidity sensing within power generation fields. [Display omitted] • This study proposed a paper-based humidity sensor with MgCl 2 /CNTs composites. • The developed sensor has quick response and recovery times of 10 and 46 s. • The sensor exhibited impressive repeatability and a broad detection ranging of 11–97 % RH. • The sensor can generate a maximum voltage of 1.07 V and a maximum power of 1.984 µW. [ABSTRACT FROM AUTHOR]

Irregularities in breathing patterns can be detected using breath monitor sensors, and this help clinicians to predict health disorders ranging from sleep disorders to heart failures. Variations in humidity during the inhalation and exhalation of breath have been utilized as a marker to detect breath patterns, and graphene-based devices are the favored sensing media for relative humidity (RH). In general, most graphene-based RH sensors have been used to explore resistance change as a measurement parameter to calibrate against the RH value, and they are prone to noise interference. Here, we fabricated RH sensors using graphene ink as a sensing medium and printed them in the shape of interdigital electrodes on glossy paper using an office inkjet printer. Further, we investigated the capacitance change in the sensor for the RH changes in the range of 10–70%. It exhibited excellent sensitivity with 0.03 pF/% RH, good stability, and high intraday and interday repeatability, with relative standard deviations of 1.2% and 2.2%, respectively. Finally, the sensor was embedded into a face mask and interfaced with a microcontroller, and capacitance change was measured under three different breathing situations: normal breathing, deep breathing, and coughing. The result show that the dominant frequency for normal breath is 0.22 Hz, for deep breath, it is 0.11 Hz, and there was no significant dominant cough frequency due to persistent coughing and inconsistent patterns. Moreover, the sensor exhibited a short response and recovery time (<5 s) during inhalation and exhalation. Thus, the proposed paper-based RH sensor is promising wearable and disposable healthcare technology for clinical and home care health applications. [ABSTRACT FROM AUTHOR]

The water-soluble bromophenoxy-substituted naphthalimide derivative 1 and its copolymer P1 with acrylamide were synthesized and the photophysical properties of their host–guest complexes with cucurbit[8]uril (CB[8]) were studied. Notably, the host–guest complex CB[8]·1 showed long-lived RTP on filter paper and demonstrated a humidity response, making it suitable for use as an encryption ink. Furthermore, the solid powder of the host–guest complex between P1 and CB[8] exhibited a 4 s afterglow emission. [ABSTRACT FROM AUTHOR]

The scope of the Nordtest method is to evaluate the moisture buffer value (MBV) of materials exposed to indoor air. The test is intended to simulate daily variations with relative humidity (RH) between 75 % during 8 hours and 33 % during 16 hours. The specimens follow a recipe that consists of waste paper, glue and water. Specimens made of paper plaster were covered with different colours. The results of the experiment showed that the type of paint used and the number of layers applied affected the MBV. Natural colours have a better moisture permeability than chemical paints, but the number of natural colour layers affects the MBV. The higher the number of layers, the lower the MBV. [ABSTRACT FROM AUTHOR]

This review article covers all types of paper-based humidity sensor, such as capacitive, resistive, impedance, fiber-optic, mass-sensitive, microwave, and RFID (radio-frequency identification) humidity sensors. The parameters of these sensors and the materials involved in their research and development, such as carbon nanotubes, graphene, semiconductors, and polymers, are comprehensively detailed, with a special focus on the advantages/disadvantages from an application perspective. Numerous technological/design approaches to the optimization of the performances of the sensors are considered, along with some non-conventional approaches. The review ends with a detailed analysis of the current problems encountered in the development of paper-based humidity sensors, supported by some solutions. [ABSTRACT FROM AUTHOR]

The Nordtest method evaluates the moisture buffer value (MBV) of materials that are being exposed to indoor air. The test simulates daily variations (high RH of 75% for 8 hours, low RH of 33% for 16 hours) in MBV, which in this context refers to the moisture uptake/release in the material when it is exposed to relative humidity (RH) in a square wave. We are looking for ways to increase clay plaster's ability to buffer moisture. Which material has simultaneously a higher ability to buffer moisture and can be added to the clay plaster mixture? The recipe for the specimen included the following: waste paper (newspaper paper), glue (methylcellulose), clay and water. Our research showed that adding paper plaster mixture to the clay plaster mixture increases the moisture buffering ability of the plaster. The bigger the amount of added paper plaster, the better the plaster's ability to buffer moisture. [ABSTRACT FROM AUTHOR]

We present a flexible humidity sensor comprising a reduced graphene oxide/polyaniline (RGO/PANI) composite film on a polypropylene filter paper substrate. Graphene oxide was reduced with sodium borohydride (NaBH4), then PANI was prepared by the oxidative polymerization of aniline to produce the RGO/PANI composite. The suspension of the asprepared RGO/PANI composite was simply filtered on the paper substrate for sensor fabrication. The structure and morphology of the obtained composite were investigated by SEM, Fourier transform IR spectroscopy, and Raman spectroscopy. The experimental results revealed that the RGO/PANI composite film on the paper substrate can be used for humidity sensing with low hysteresis, good repeatability, and a large response in a broad humidity range. Moreover, our sensor has the potential to be applied in wearable devices because of the flexible substrate. [ABSTRACT FROM AUTHOR]

Flexible respiratory monitoring devices have become available for outside-hospital application scenarios attributable to their improved system wearability. However, the complex fabrication process of such flexible devices results in high prices, limiting their applications in real-life scenarios. This study proposes a flexible, low-cost, and easy-processing paper-based humidity sensor for sleep respiratory monitoring. A paper humidity sensing model was established and sensors under different design parameters were processed and tested, achieving high sensitivity of 5.45 kΩ/%RH and good repeatability with a matching rate of over 85.7%. Furthermore, the sensor patch with a dual-channel 3D structure was designed to distinguish between oral and nasal breathing from origin signals proved in the simulated breathing signal monitoring test. The sensor patch was applied in the sleep respiratory monitoring of a healthy volunteer and an obstruct sleep apnea patient, demonstrating its ability to distinguish between different respiratory patterns as well as various breathing modes. [ABSTRACT FROM AUTHOR]

Condition assessment of works of art created with oil media on paper could be a complex matter when presenting problems of damage due to the absorption of oil binders by the paper support, since they depend on several factors and occur in variable conditions. The present work refers to the results of an investigation on the effect of linseed oils on the color, opacity, morphology, tensile strength, and chemical properties of lignocellulosic papers, in comparison to that of pure cellulosic papers. Lignocellulosic papers are involved in research on new, yet significant, parameters that might influence the behavior of the oil-impregnated areas of the supports upon aging. The research was applied to mock-ups, made of two types of lignocellulosic paper impregnated with three types of linseed oil and subjected to accelaratated ageing in specific conditions of relative humidity and temperature in closed environment. The research involved colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS. The results indicated that thermal-humid ageing caused the gradual darkening of the oil-impregnated mock-ups, alterations in opacity, and decrease of pH values, depending mainly on the formulation of linseed oil, as well as a reduction in tensile strength. FTIR analysis results indicated that the chemical changes that occur upon ageing supported the recorded optical and mechanical alterations, while VOC emissions are both associated with the paper type and the kinetics of degradation of the different types of linseed oil. [ABSTRACT FROM AUTHOR]

The furfural concentration in oil is a well-accepted chemical marker indicating the aging condition of power transformers. However, recent researches suggest that the furfural concentration in oil is affected by moisture, because moisture influences the furfural partitioning ratio in oil-paper insulation system. In this study, the correlation of moisture and furfural partitioning ratio was investigated. The accelerated thermal aging test and moisture absorption test were conducted to prepare oil-paper samples with different furfural and moisture concentrations. For samples with different moisture concentrations, the furfural partitioning ratios between oil and paper were compared. Results showed that samples with high humidity exhibited a high furfural mass fraction in oil. This finding implied that high humidity promoted the furfural diffusion from paper to oil. Further, the interference of moisture on aging assessment of insulation paper was analyzed. Results showed that the increase of moisture concentration in oil-paper system would significantly affect the accuracy of insulation paper aging assessment. A corrected equation for aging assessment of insulation paper with different moisture concentrations was established. Verification result showed that the equation could effectively correct the interference of moisture and enhance the accuracy of the aging assessment of insulation paper. [ABSTRACT FROM AUTHOR]

In paper containing multilayer composite structures and laminates, polarization is usually investigated under dry environmental conditions. The aim of this research is to determine polarization dependence of paper and paper-dielectric structures on environmental relative humidity (RH). The role of each component was identified. The obtained and recorded data are used for identification and clarification of the physical mechanism of polarization. The polarization was studied by applying a dosed charging and forced discharge method and was evaluated by a depolarization potential and its formation kinetics. The polarization level of investigated structures increases with RH and is determined mainly by the paper (cellulose) and moisture content in it. In composite structures of the paper between dielectric films and dielectric on paper the polarization dependence on RH correlates with moisture absorption isotherm. It was found that the surface electrical conductivity of paper distorts the results of the paper and structure paper on dielectric. Analysis of the formation kinetics of the depolarization potential together with the potential decay of the charged paper has determined the role of orientation polarization and space charges. The formation of space charges is faster than orientation polarization and dominates in polarization process at higher RH. The process modeling by superposition of two exponents confirms this polarization mechanism. [ABSTRACT FROM AUTHOR]

• Preparation of dual functional humidity humidity-sensitive paper using sustainable nanoclay and beeswax. • Increment of actuation degree up to 110° (30 %RH) from 40° (90 %RH). • Able to detect humidity from changes in electrical resistances (150-700kΩ). A highly humidity-responsive paper can detect moisture or OH-attached molecules at the sub-micron or nano level range. Applying hydrophilic nanoclay as an active material for water sensing would reduce the fabrication cost while remaining environmentally friendly. In this communication, we report the preparation of a nanoclay-inspired dual-responsive smart film that can signal humidity levels from mechanical and electrical responses. The paper will bend as the nanoclay layer swells whereas the resulting bending strain will trigger the electrical resistance changes in the hydrophobic electrically conductive graphite-beeswax layer. [ABSTRACT FROM AUTHOR]

This paper proposes the use of simulation modelling to explore the effect of conservation strategies on the preservation of paper collections. Agent-based simulation was chosen as the simulation approach in order to capture the individual characteristics of the collections, their size, and the values of pH and degree of polymerisation (DP) for individual items. This approach enabled the simulation of the chemical degradation of different types of collections during their lifetime and under different preservation scenarios. We conducted a series of computational experiments on three types of collections, acidic, modern, and mixed, to explore the effect of slightly lowering the temperature and relative humidity in the repositories, the deacidification of part of the collection at different rates, and the delay in making the decision to start a deacidification treatment. The results indicated that a small change, lowering the storage conditions from 18°C to 16°C and from 50% to 40% RH, can protect up to 30% of the collection from reaching the critical DP of 300 within a time horizon of 500 years. On the other hand, to obtain similar results through deacidification, 45% of the mixed collection and 70% of the acidic collection should be deacidified within a period of 100 years. The experiments also indicated that better results are obtained when the priorities for deacidification are acidic records with a pH value below 5. This study shows that modelling the heterogeneity of the collections can support preservation management, particularly if the concern is not the preservation of a part of the collection but the collection as a whole. [ABSTRACT FROM AUTHOR]

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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.

This research successfully synthesized a cross-linking modified MXene composite material, which could be used in preparation of the paper-based humidity sensor to endow it with structural stability, antioxidant property, and efficient real-time humidity monitoring performance. [Display omitted] • The PMX6-A7 was prepared by the PEI/AgNO 3 cross-linking modifying MXene. • The flexible humidity sensor presented excellent moisture sensitivity and stability. • The assembled monitor possessed effective real-time humidity monitoring performance. • The ECP technology endowed this research potential for large-scale application. With an abundance of hydrophilic active sites present on the surfaces, MXene exhibits significant potential for application in the field of humidity monitoring. Nevertheless, achieving the high response intensity, excellent response sensitivity, structural stability, and oxidation resistance in the MXene-based humidity sensors remains a formidable challenge. Herein, we propose a humidity sensor made from the paper-based flexible sensor with copper electrode and polyethyleneimine/silver nitrate cross-linking modified MXene composite materials. The humidity sensor prepared in this work presents a satisfactory capacitance response rate (819.9 % in 97 % RH) and favorable sensitivity (6.9/11.9 s for response/recovery time). Meanwhile, the humidity sensor possesses outstanding structural stability (less than 3 % attenuation of the capacitance response after 100 bending cycles) and superior oxidation resistance. Moreover, the real-time humidity monitor assembled based on the humidity sensor has realized the effective monitoring of human skin humidity and dynamic respiration. Consequently, this study provides a viable approach for achieving reliable real-time humidity monitoring, demonstrating significant potential in the realms of intelligent actuators, sensing devices, and health care. [ABSTRACT FROM AUTHOR]

Flexible humidity sensors have been widely used in wearable electronics, owing to their flexibility and compatibility with electronic device substrates. This study fabricated a flexible paper-based humidity sensor with a grid-like sensing film using the near-field electrohydrodynamic direct writing (NFEDW) method. A grid-like sensing layer with a dense network of carbon nanotubes/cellulose nanofiber (CNTs/CNF) was prepared, and induced by a voltage field applied during printing. The effects of the substrates and pattern width on the performance of the sensor were systematically investigated. The prepared sensor exhibited high sensitivity of 101 % at 95 % relative humidity (RH). An interlocking structure formed between the CNTs/CNF composite and the paper substrate, endowing the sensor with outstanding bending (minimum diameter of 5 mm) and folding (up to 100 times) durability. Furthermore, the prepared sensor exhibited rapid response performance (17 % within 10 s). This addresses the issue of long response time, which is typically associated with CNTs-based sensors, making these sensors more suitable to practical applications. The above-mentioned advantages enable the sensor to be used for respiration monitoring and even for vocal recognition. Finally, a real-time respiration monitoring platform was developed to demonstrate the sensor's potential in wearable devices. • The high precision printing method is used for preparing the sensing film. • Various pattern widths are achieved by altering printing height. • Printing paper as the substrate to improve the performance of the sensor. • Substantially improved response time for the CNT-based sensors. • Wireless monitoring platform is developed for real-time respiration monitoring. [ABSTRACT FROM AUTHOR]

In this investigation , effects of different humidity and heat on quality of Corrugated board , was studied , and optimum treatment indicated Variables in this Paper was : Corrugator speed (50,100,150m/min) ,wraping angle of the paper around preheaters (90,180,300 degree) and moisture of paper (6.5%,7%,8.5%). Papers that treated for this purpose was included : 125gsm kraft liner ,127 gsm medium paper and 140gsm test liner paper. A flut type of 3ply Corugated board was selected for this study.Moisture of paper was measured in 3 places : Paper on roll stand before single facer , paper after singlefacer preheater and paper before incoming doublefacer in hot plate unit. Also temprature was measured in corrugator rolls ,hot Plates in double facer and final Board after Exiting of the Machine. Results show that , warp of final board decreased in speed 50 and 100m/min ,moisture 7% and 1800 wraping angle of the paper around preheater. That means lower speeds and higher wraping angles cause to more heat on corrugated board and decreasing in warp content resulted.It should be noted that lower humidity more than 7% and increase wraping angle more than 180 degree cause to over drying and intensive moisture decrease in final board that cause to reverse warp in final board.

Oil media on paper, such as oil paintings, sketches, prints, and books, occasionally present problems associated with the effect of oil medium on the paper support, raising a composite matter of condition assessment as it depends on several factors. The present work examines the effect of linseed oil on paper and, in particular, the changes caused by three types of linseed oil on the optical, morphological, mechanical, and chemical properties of pure cellulosic paper, employing mock-ups submitted to artificial ageing in controlled conditions of relative humidity and temperature in airtight vessels. The study involved colorimetry, opacity, tensile strength, pH measurements, SEM, FTIR, and VOC analysis with GC-MS. Processing of the results has so far indicated that thermal-humid ageing caused the gradual darkening of the oil-impregnated mock-ups, as well as alterations in opacity, intense fall of pH values, and severe reductions in tensile strength, while linseed oil processing during manufacture has a significant impact. FTIR spectra have indicated that chemical changes upon ageing are in accordance with those of optical and mechanical changes, while VOC emissions are mostly associated with the drying and degradation of the different types of linseed oil. [ABSTRACT FROM AUTHOR]

The role of humidity sensors in different industries and field applications, such as agriculture, food monitoring, biomedical equipment, heating, and ventilation, is well known. However, most commercially available humidity sensors are based on polymers or electronic materials that are not degradable and thus contribute to electronic waste. Here, we report a low-cost, flexible, easy-to-fabricate, and eco-friendly parallel-plate capacitive humidity sensor for field applications. The sensor is fabricated from copper tape and tissue paper, where copper tape is used to create the plates of the capacitor, and tissue paper is used as a dielectric sensing layer. Along with the low cost, the high sensitivity, better response and recovery times, stability, and repeatability make this sensor unique. The sensor was tested for relative humidity (RH), ranging from 40% to 99%, and the capacitance varied linearly with RH from 240 pF to 720 pF, as measured by an Arduino. The response time of the sensor is ~1.5 s, and the recovery time is ~2.2 s. The experiment was performed 4–5 times on the same sensor, and repeatable results were achieved with an accuracy of ±0.1%. Furthermore, the sensor exhibits a stable response when tested at different temperatures. Due to the above advantages, the presented sensor can find ready applications in different areas. [ABSTRACT FROM AUTHOR]

Laser‐induced graphene (LIG) produced by irradiation of paper (paper‐LIG)holds substantial promise for flexible devices. This article presents paper‐LIG humidity and temperature sensors fabricated by single‐step irradiation of common filter paper with a pulsed UV laser (355 nm). The influence of the process parameters on the conversion of cellulose fibers into LIG is discussed based on the resulting morphology, structure, conductivity, and chemical composition, revealing a distinct barrier to transformation and a propagation behavior not seen under CO2 laser irradiation. The obtained material is constituted by a porous, electrically conductive network of fibers. The paper‐LIG relative humidity (RH) and temperature sensors with sensitivities of up to 1.3 × 10−3%RH−1 and ‐ 2.8 × 10−3 °C−1, respectively, are examined in terms of their linearity, reproducibility, and response time. A detailed discussion on the response mechanism is presented in the context of literature, pointing towards the absorption of water molecules in the interlayer spacing of graphene as the main reason for the increase in resistance with RH. Additionally, a contribution from variable range hopping along the ab plane of graphene at high RH is suggested. These results demonstrate the potential of paper‐LIG for low‐cost, sustainable, and environmentally friendly sensing. [ABSTRACT FROM AUTHOR]

[Display omitted] • MOF-199@melamine enabled fast and sensitive colorimetric detection of water. • MOF-199@melamine-based test paper was developed for real-time sensing portably. • The material and its test paper both could be regenerated and recycled. • Mechanisms of material interacted with water and DMF were explored. • Sensing strategy achieved water detection in multiple organic solvents and ambient relative humidity. Herein, we fabricate a melamine modified metal organic framework-199 composite (MOF-199@melamine), of which the structure is affected by the dynamics of the guest H 2 O molecule with significant color change. It realizes the visualized quantitative detection of water in a variety of organic solvents within 30 s. Moreover, DMF restored the original structure by replacing H 2 O molecules, realizing the regeneration of the materials. On this basis, PTFE-MOF-199@melamine test paper is developed to portably detect water content in organic solvents (maximum 0 %-98 % (v/v) water content) and ambient relative humidity (11–85 %). The test paper can be recycled four times with a regeneration rate higher than 90 %. The results are expected to solve the problems of existed electrochemical or fluorescence strategy such as the complicated operation process and signal output/reading system. [ABSTRACT FROM AUTHOR]

Absorption of liquid or vapor water in paper designed for conversion processes is a critical phenomenon. In particular, the dimensional stability of the paper as the water content changes is crucial for the success of all the conversion processes, including copying and printing. Appropriate chemical treatments of the fibers can limit the phenomena of water absorption, allowing a better workability of the paper substrates. In the present study, moisture absorption tests were conducted under isothermal conditions on untreated papers and treated by coatings with silane, organo-siloxane and silicone agents, as well as with polyelectrolytes using layer-by-layer techniques. The treated and untreated papers were tested by changing the relative humidity between 0 and 80% relative humidity. The Guggenheim–Anderson–de Boer model was used to study moisture absorption isotherms, showing the increase in the dimensional stability of the papers after the chemical treatments of the fibers. [ABSTRACT FROM AUTHOR]

Porous graphene (PG) devices fabricated in situ from polyimide (PI) adhered onto paper substrates provide a cost‐effective and recycling‐friendly alternative to re‐engineer paper for liquid‐based power sources and sensors. However, paper is generally damaged due to heating during the fabrication of PG devices. Here integrated graphene‐paper electronics with exceptional thermal control through the proposed thermally localized laser graphitization (LLG) process is demonstrated, employing optimized ultrafast laser writing. LLG enables in situ fabrication of localized porous graphene (LPG) devices (>1775 K) on 65 µm thick PI tape adhered to paper without heating above 348 K. Laser parameters for LLG are predicted using an analytical temperature model and validated experimentally. The LLG is demonstrated by fabricating liquid electrolyte LPG micro‐supercapacitors and humidity sensors on liquid susceptible paper. It is envisaged that the scientific concepts proposed and demonstrated here will expedite the development of low‐cost, scalable, and chemically robust LPG devices on thermally sensitive substrates. [ABSTRACT FROM AUTHOR]

The use of papers as substrates in the process of manufacturing flexible electronic components is urgently required to obtain cost-effective products as well as to expand the potential applications of such components. This study aimed to examine the suitability of three different types of paper for sensor applications using an inkjet printing process. Three types of paper (denoted as Types 1, 2, and 3) designed for specific applications in printed electronics were selected and entirely characterized in terms of microscopic and macroscopic properties, such as internal fibers structure, cross-sectional layer structure, surface roughness, and hardness. Dot arrays were printed on these three types of paper to determine how the papers absorb silver ink and which one is the best substrate for manufacturing printed electronic components. After a comprehensive analysis, the paper that exhibited the best feature was further studied as a substrate for printing interdigitated electrodes to develop a humidity sensor. The Type 2 paper-based sensor demonstrated the variation in capacitance in the range from 9.4 to 10.6 pF while changing the relative humidity (RH) from 40 to 90%. Thus, Type 2 has the great potential for application in flexible sensors, suggesting the possibility of industrial scalability and mass production of inexpensive, biodegradable, and conformable electronic components. [ABSTRACT FROM AUTHOR]

An inkjet-printed relative humidity sensor based on capacitive changes which responds to different humidity levels in the environment is presented in this work. The inkjet-printed silver interdigitated electrodes configuration on the paper substrate allowed for the fabrication of a functional proof-of-concept of the relative humidity sensor, by using the paper itself as a sensing material. The sensor sensitivity in terms of relative humidity changes was calculated to be around 2 pF/RH %. The response time against different temperature steps from 3 to 85°C was fairly constant (about 4-5 min), and it was considered fast for the aimed application, a smart label. [ABSTRACT FROM AUTHOR]

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The sensing mechanisms of common humidity sensors related to conductive active materials, which can be simply attributed to the variations in resistivity due to the separation of conductive materials and variations in polymer permittivity, are generally plagued by drawbacks such as cumbersome fabrication processes, high cost and low performance. Herein, we prepared Zn/Cellulose filter paper (CFP)/Nanoscale carbon ink (NCI)/Cu structure humidity power generators (ZHGs) based on the power generation principle of typical zinc-air batteries, using active metals with strong conductivity as electrodes, and the redox reactions that took place in the zinc-air battery can convert the chemical energy in the electrode into a stable electrical energy. The ZHG fabricated in this work can reach an extremely high open circuit voltage (V oc) of 0.803 V at 97 % RH and possesses an excellent power density of 312.24 μW/cm2, which has a good linear relationship (R 2 = 0.9669) over a wide humidity range (20–97 % RH). In addition, 10 ZHGs in series can charge commercial capacitors up to 3.83 V. Finally, the proof of concept demonstrated that the humidity power generation sensor can be well applied in human respiratory monitoring, finger non-contact switch, and power supply for light emitting diode (LED). [Display omitted] [ABSTRACT FROM AUTHOR]

Precious organic cultural relics are easily affected by temperature, humidity, and harmful gases in the environment, resulting in embrittlement, fading, mildew, moth damage and other aging forms. An energy-saving and environmentally friendly material is needed to stabilize humidity and adsorb harmful gases in the environment. In this paper, with an intelligent adjustment function, functional paper containing sepiolite and tourmaline natural minerals was successfully prepared. The component of 80 % of wingceltis and 20 % of straw in dry pulp as main raw material was conducive to the desorption of water molecules. As favorable structure inside functional paper, the adsorption point and the adsorption contact area increased by the rough surface of fiber bundles, the addition of sepiolite and the ordered molecular chains of copolymers destroyed. So, the relative humidity could be adjusted to 55 % ± 3 within 2 hours and was stable with functional paper. At the same time, 1.11 ppm sulfur dioxide and 2.98 ppm ammonia could be effectively adsorbed in 10 and 12 h, respectively, by 1 g of paper in a 5 L container. The pH of the paper was adjusted to neutral with tourmaline, even if the pH was changed by acidic or alkaline gas absorption. Therefore, for long-term organic cultural relic preservation, preparing a constant-humidity and clean environment is of great significance. This is possible through this paper. [ABSTRACT FROM AUTHOR]