Search

An industry compatible chemo-refining approach was tested for preparation of micro-nanofibrillated cellulose (MNFC) from bleached softwood pulp using sodium meta-periodate and sodium chlorite as oxidizers followed by refining in Valley beater. SEM and FTIR analyses confirmed micro-nano scale fibrillation and chemical functional group modification in laboratory prepared MNFC, respectively. The water retention value, carboxyl content and viscosity of MNFC were found comparable with imported NFC as reference (R-NFC). To evaluate MNFC as strength enhancer for paper properties, 5% MNFC addition to bleached mixed hardwood pulp showed 6% reduction in bulk with 36%, 24% and 97% increment in breaking length, burst index and double fold of the handsheets, respectively without affecting tear index and optical properties than the control. Surface properties were also improved. Pulp drainability (37°SR) after MNFC addition was found suitable for papermaking. These laboratory results confirmed the potential of MNFC as a suitable strength additive for paper quality improvement.

In this study, a microfluidic paper-based analytical device (mu PAD) was integrated with a smartphone app capable of offline (without internet access) image processing and analysis for the rapid colorimetric detection of glucose. A self-inking stamp was used to form hydrophobic channels on a piece of paper-towel due to its superior water absorption efficiency. As demonstrated, the developed sensor was employed for the colorimetric detection of glucose in artificial saliva in the linear scope of 0 - 1 mM with a calculated detection limit of 29.65 mu M. The experimental results show that the quantitative analysis of glucose with the proposed smartphone platform could be completed in less than one minute. The app developed for the smartphone platform is capable of extracting the color-changing area with an embedded image processing tool which could address the problem of color uniformity in the detection zones of mu PAD. The integrated platform has great potential to be used for non-invasive measurements of glucose in body fluids, like tears, sweat and saliva.

Paper grade pulp production across the globe is dominated by the kraft process using different lignocellulosic raw materials. Delignification is achieved around 90% using different chemical treatments. A bottleneck for complete delignification is the presence of residual covalent bonds that prevail between lignin and carbohydrate even after severe chemical pulping and oxygen delignification steps. Different covalent bonds are present in native wood that sustain drastic pulping conditions. In this study, 100% birch wood was used for producing paper grade pulp, and the lignin carbohydrate bonds were analyzed at different stages of the kraft cook. The lignin carbohydrate bonds that were responsible for residual lignin retention in unbleached pulp were compared and analyzed with the original lignin-carbohydrate complex (LCC) bonds in native birch wood. It was shown that lignin remaining after pulping and oxygen delignification was mainly bound to xylan, whereas the lignin bound to glucomannan was for the most part degraded.

The work presented in this paper is focussed on study of structure and properties of coating layers based on natural pigments (ground calcium carbonate and clay) and butadiene acrylonitrile latex as binder in correlation with functional properties of the final coated paper. It is quantified the influence of binder content and pigment type on the structural and liquids penetration properties of coating layer. The obtained results confirm that by increasing of binder content in the coating formulations a reduced efficiency of light-scattering and increased roughness for coated surfaces is obtained. At the high binder amounts (over 15 pph), the coating layer porosity is reduced and as result a lower liquids penetration in the coated papers is obtained.

Paper-based products are similar to paper wasps’ “nests” built by “biofiber separation” and “biofiber reassembly”, where they add “saliva” for structural reinforcement and waterproofing. Rice leave...

Paper is a common material that is promising for constructing microfluidic chips (lab-on-a-paper) for diagnostics and drug delivery for biomedical applications. In the past decade, extensive research on paper-based microfluidics has accumulated a large number of scientific publications in the fields of biomedical diagnosis, food safety, environmental health, drug screening and delivery. This review focuses on the recent progress on paper-based microfluidic technology with an emphasis on the design, optimization and application of the technology platform, in particular for medical diagnostics and drug delivery. Novel advances have concentrated on engineering paper devices for point-of-care (POC) diagnostics, which could be integrated with nucleic acid-based tests and isothermal amplification experiments, enabling rapid sample-to-answer assays for field testing. Among the isothermal amplification experiments, loop-mediated isothermal amplification (LAMP), an extremely sensitive nucleic acid test, specifically identifies ultralow concentrations of DNA/RNA from practical samples for diagnosing diseases. We thus mainly focus on the paper device-based LAMP assay for the rapid infectious disease diagnosis, foodborne pathogen analysis, veterinary diagnosis, plant diagnosis, and environmental public health evaluation. We also outlined progress on paper microfluidic devices for drug delivery. The paper concludes with a discussion on the challenges of this technology and our insights into how to advance science and technology towards the development of fully functional paper devices in diagnostics and drug delivery.

With the increasing popularity of coated paper, it has been more widely used in printing, publishing, product packaging and commercial promotion. However, coated paper is prone to cracks after printing and folding which exposes to a white area which is referred to as fold cracking. This study investigated the coating properties of paper and coating factors influencing the fold cracking and aimed to provide guidance on how to reduce the problems of fold cracking. This paper mainly discusses the effects of pigment proportion, binder dosage, solids content, coating thickness and calendering pressure on fold cracking of coated paper after printing. Experiments show that when the coating consisted entirely of calcium carbonate, the degree of fold cracking is most serious. With the addition of kaolin, the fold cracking reduces. When the ratio of the number of parts of calcium carbonate to kaolin is 25/75, the area of fold cracking reaches its minimum value of 10.28 %. With increasing solids content of the coating, the fold cracking decreases initially and then increases. When the solids content is 55 %, the fold cracking reaches a minimum. Increased latex content reduced coating thickness and an increase in calendering pressure gradually reduce the degree of fold cracking.

We demonstrate a versatile and easily fabricated paper-based CO2 sensor. The sensor consists of a specially designed fluorescent color-shift chromophore infused into standard filter paper. The emission color of the resulting fluorescent paper changes upon exposure to CO2 due to the formation of carbonic acid, which underlies the sensing mechanism. By using a ratiometric method, the undesirable effects of photobleaching can be eliminated, leading to a stable and repeatable sensor performance. These multiuse sensors have a response time on the order of 1 min and feature low detection limits for a paper-based CO2 gas sensor, suggesting possible low-cost applications in smart buildings or other facilities in which CO2 levels are required to be continuously monitored.

A complete mathematical model for electromigration in paper-based analytical devices is derived, based on differential equations describing the motion of fluids by pressure sources and EOF, the transport of charged chemical species, and the electric potential distribution. The porous medium created by the cellulose fibers is considered like a network of tortuous capillaries and represented by macroscopic parameters following an effective medium approach. The equations are obtained starting from their open-channel counterparts, applying scaling laws and, where necessary, including additional terms. With this approach, effective parameters are derived, describing diffusion, mobility, and conductivity for porous media. While the foundations of these phenomena can be found in previous reports, here, all the contributions are analyzed systematically and provided in a comprehensive way. Moreover, a novel electrophoretically driven dispersive transport mechanism in porous materials is proposed. Results of the numerical implementation of the mathematical model are compared with experimental data, showing good agreement and supporting the validity of the proposed model. Finally, the model succeeds in simulating a challenging case of free-flow electrophoresis in paper, involving capillary flow and electrophoretic transport developed in a 2D geometry. Fil: Schaumburg, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Kler, Pablo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentina Fil: Berli, Claudio Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina

Paper-based packaging is widely employed in industries ranging from food to beverages to pharmaceuticals because of its attractive advantages of biodegradability, recyclability, good strength, low cost, and lightweight. However, paper products usually have poor water barrier resistance properties because of paper and fibers porous microstructure. In this study, an ecofriendly water-resistant (hydrophobic) oil from biological origin, namely, palm kernel oil (PKO) was used to coat paper by using a facile and cost-effective dip-casting approach. PKO formulation was prepared by mixing with a solvent and furfuryl alcohol (FA). The water resistance, structural properties, and thermal and mechanical properties of the coated papers obtained under different processing conditions were reported and compared to understand the performance of coated paper. Contact angle (CA), Fourier transform infrared (FTIR), and thermal gravimetry (TGA) were used for analysis and characterization of coated papers. Data from contact angle measurements showed that the PKO formulation could considerably improve the liquid water barrier property of the paper, with a measured water contact angle (CA) of ∼120° and reduce the water vapor transmission rate (WVTR) by 22%. This novel, green, low-cost, and water-resistant paper coating made with biological and biodegradable oil is a potential candidate for replacing petroleum-based coatings used in a broad range of applications and will also be able to make an additional full use of the palm kernel oil.

Pathogen detection is crucial for human, animal, and environmental health; crop protection; and biosafety. Current culture-based methods have long turnaround times and lack sensitivity. Nucleic acid amplification tests offer high specificity and sensitivity. However, their cost and complexity remain a significant hurdle to their applications in resource-limited settings. Thus, point-of-need molecular diagnostic platforms that can be used by minimally trained personnel are needed. The nuclease protection assay (NPA) is a nucleic acid hybridization-based technique that does not rely on amplification, can be paired with other methods to improve specificity, and has the potential to be developed into a point-of-need device. In traditional NPAs, hybridization of an anti-sense probe to the target sequence is followed by single-strand nuclease digestion. The double-stranded target-probe hybrids are protected from nuclease digestion, precipitated, and visualized using autoradiography or other methods. We have developed a paper-based nuclease protection assay (PB-NPA) that can be implemented in field settings as the detection approach requires limited equipment and technical expertise. The PB-NPA uses a lateral flow format to capture the labeled target-probe hybrids onto a nitrocellulose membrane modified with an anti-label antibody. A colorimetric enzyme-substrate pair is used for signal visualization, producing a test line. The nuclease digestion of non-target and mismatched DNA provides high specificity while signal amplification with the reporter enzyme-substrate provides high sensitivity. We have also developed an on-chip sample pretreatment step utilizing chitosan-modified paper to eliminate possible interferents from the reaction and preconcentrate nucleic acids, thereby significantly reducing the need for auxiliary equipment. Graphical abstract.

Achieving an efficient catalyst in the ATRP system with a simple design, preparation from available materials, and high recyclability is a significant challenging issue. To attain the goal, herein, we used chitosan (CS)-modified cellulose filter paper (FP) as a green support for the synthesis of dip catalyst. The preparation of this catalyst involved surface treatment of the FP strips by CS coating through a dipping method, which increased the affinity of the substrate for adsorbing copper ions in the next step. The Cu@CS-FP catalyst was prepared without the requirement of any ligands. The synthesized dip-catalyst, in the form of the strips, was employed for the first time in the ATRP reaction of methyl methacrylate to assay catalytic activity. Catalytic insertion/ removal (ON/OFF) experiments were carried out during the polymerization. A reasonable control over the molecular weight with high conversion (68%) and polydispersity index of 1.32 under mild reaction conditions were obtained. Significantly, because of the facile separation of the catalyst, the amount of copper that remained in the polymer was very low (2.7 ppm). Also, the recyclability of the catalyst was investigated for five runs. The conversion in the final run was 64% without a loss of catalyst efficiency.

Aim of the present work was to deepen the knowledge on the effects of funori on cellulose fibers with particular attention paid to their consolidation. Compared to canvas, paper samples (untreated or artificially aged) show different fiber packaging and liquid-absorbing properties. Herein, we conducted observations of cellulose fibers by scanning electron microscopy (SEM) in order to evaluate the seaweed extraction method employed in this work, as well the consolidation action had on the fibers through multiple additions of the prepared solutions. Surface homogeneity and fiber stiffness observed by us increased over time and the fibers, initially frayed and disordered, were eventually incorporated into the purified funori after several solution additions accompanied also by a progressive occlusion of the pores. The achieved consolidation effect was confirmed by means of mechanical tests. Moreover, the method herein developed was slightly modified in view of the application of the funori solution to a cultural asset of historical and botanical interest, still scarcely studied. Electronic microscopy allowed us to evaluate the consolidation and gluing effect obtained through subsequent funori applications.

Competitive immunoassays comprise the standard means of detecting small molecules. However, conventional methods using microwells are difficult to apply during point-of-care tests (POCT) because they require complicated handling and are time consuming. Although paper-based analytical devices (PAD) have received considerable focus because of their rapid and straightforward operation, only a few devices have been proposed for competitive immunoassays. Herein, we describe a novel universal PAD format with a 3-dimensional configuration for competitive immunoassays that rapidly and sensitively detects small molecules. The proposed device comprised a layered structure with uniform color formation and high capture efficiency between antigen and antibody that results in rapid and reproducible results. The device rapidly (90 s) assayed biotin as a model target, with a limit of detection (LOD) of 5.08 ng mL−1, and detected progesterone with an LOD of 84 pg mL−1 within 5 min. Moreover, sample volumes and reagent consumption rates were minimized. Thus, our device could be applied to competitive immunoassays of various small molecules in POCT.

Compared with a single chemical indicator, the use of multivariate chemical indicators in aging status assessment of transformer cellulose paper insulation can improve the reliability of the evaluation. In this study, a non-destructive method based on multivariate chemical indicators was proposed to evaluate the remaining life of cellulosic paper insulation. The selected chemical indicators closely related to the aging of the insulating paper were analyzed. Additionally, by applying the subjective and objective weighting method, the evaluation information of each indicator was fully extracted to obtain reasonable comprehensive evaluation weights. Besides, the comprehensive evaluation index of multivariate chemical indicators was obtained by using the technique for order preference by similarity to ideal solution method, which is consistent with the deterioration law of paper insulation. Then, the correlation lifespan model between the comprehensive evaluation index of multivariate chemical indicators and the degree of polymerization of insulating paper under different aging stages was established. The effectiveness of the proposed model was verified by experiments. This promising model can increase the accuracy of the condition assessment for the transformer cellulosic paper insulation.

Flexible paper-based sensors may be applied in numerous fields, but this requires addressing their limitations related to poor thermal and water resistance, which results in low service life. Herein, we report a paper-based composite sensor composed of carboxylic carbon nanotubes (CCNTs) and poly-m-phenyleneisophthalamide (PMIA), fabricated by a facile papermaking process. The CCNT/PMIA composite sensor exhibits an ability to detect pressures generated by various human movements, attributed to the sensor's conductive network and the characteristic "mud-brick" microstructure. The sensor exhibits the capability to monitor human motions, such as bending of finger joints and elbow joints, speaking, blinking, and smiling, as well as temperature variations in the range of 30-90 °C. Such a capability to sensitively detect pressure can be realized at different applied frequencies, gradient sagittas, and multiple twists with a short response time (104 ms) even after being soaked in water, acid, and alkali solutions. Moreover, the sensor demonstrates excellent mechanical properties and hence can be folded up to 6000 times without failure, can bear 5 kg of load without breaking, and can be cycled 2000 times without energy loss, providing a great possibility for a long sensing life. Additionally, the composite sensor shows exceptional Joule heating performance, which can reach 242 °C in less than 15 s even when powered by a low input voltage (25 V). From the perspective of industrialization, low-cost and large-scale roll-to-roll production of the paper-based sensor can be achieved, with a formed length of thousands of meters, showing great potential for future industrial applications as a wearable smart sensor for detecting pressure and temperature, with the capability of electric heating.

The plasmonic properties of gold nanoparticles (AuNPs) are a promising tool to develop sensing alternatives to traditional, enzyme-catalyzed reactions. The need for sensing alternatives, especially in underdeveloped areas of the world, has given rise to the application of nonenzymatic sensing approaches paired with cellulosic substrates to biochemical analysis. Herein, we present three individual, low-step, wet-chemistry, colorimetric assays for three target biomarkers, namely, glucose, uric acid, and free cholesterol, relevant in diabetes control and their translation into paper-based assays and microfluidic platforms for multiplexed analysis. For glucose determination, an in situ AuNPs synthesis approach was applied into the developed μPAD, giving semiquantitative measures in the physiologically relevant range. For uric acid and cholesterol determination, modified AuNPs were used to functionalize paper with a gold-on-paper approach with the optical properties changing based on different aggregation degrees and hydrophobic properties of particles dependent on analyte concentration. These paper-based assays show sensitivity ranges and limits of detection compatible for target analyte level determination and detection limits comparable to those of similar enzymatic, colorimetric systems, relying only on plasmonic transduction without the need for enzymatic activity or other chromogenic substrates. The resulting paper-based assays were integrated into a single 3D, multiplex paper-based device using paper microfluidics, showing the capability for performing different colorimetric assays with distinct requirements in terms of sample flow and sample uptake in test zones using a combination of both horizontal and vertical flows inside the same device. The presented device allows for multiparametric, colorimetric measures of different metabolite levels from a single complex sample matrix drop using digital color analysis, showing the potential for development of low-cost, low-complexity tools for diagnostics toward the point-of-care.

Gelatine sizing was used extensively for western papermaking before the nineteenth century and this technique is still applied nowadays for restoration purposes. Despite its wide use, the relationships between gelatine types, the strength of the size and its distribution inside the paper sheet are still unclear. Different concentrations of three gelatines of various origins and types (A/B) were used to size model papers. The gelatine uptake, the strength of the size and the presence of gelatine at the papers surface were investigated by using a water drop test method and ATR-FTIR spectroscopy. At a given concentration, similar uptakes were found for all gelatines but great variations were observed in terms of size strength and of gelatine ability to cover the surface of paper sheets. In addition, Scanning transmission X-ray microscopy was performed on paper fibres cross sections to map the distribution of the organic compounds (both cellulosic and proteinaceous) on a nanometer scale. This showed that gelatine coats but does not penetrate the fibres. It can be inferred that the different size strengths observed between the tested gelatines are mainly due to different ways of filling holes between fibres inside the paper mat, some gelatines being more prone to go inside the sheet than others which remain mostly distributed near the surface.

Loop-mediated isothermal amplification (LAMP) has been widely used to detect many infectious diseases. However, minor inconveniences during the steps of adding reaction ingredients and lack of simple color results hinder point-of-care detection. We therefore invented a fluorometric paper-based LAMP by incorporating LAMP reagents, including a biotinylated primer, onto a cellulose membrane paper, with a simple DNA fluorescent dye incubation that demonstrated rapid and accurate results parallel to quantitative polymerase chain reaction (qPCR) methods. This technology allows for instant paper strip detection of methicillin-resistant Staphylococcus aureus (MRSA) in the laboratory and clinical samples. MRSA represents a major public health problem as it can cause infections in different parts of the human body and yet is resistant to commonly used antibiotics. In this study, we optimized LAMP reaction ingredients and incubation conditions following a central composite design (CCD) that yielded the shortest reaction time with high sensitivity. These CCD components and conditions were used to construct the paper-based LAMP reaction by immobilizing the biotinylated primer and the rest of the LAMP reagents to produce the ready-to-use MRSA diagnostic device. Our paper-based LAMP device could detect as low as 10 ag (equivalent to 1 copy) of the MRSA gene mecA within 36-43 min, was evaluated using both laboratory (individual cultures of MRSA and non-MRSA bacteria) and clinical blood samples to be 100% specific and sensitive compared to qPCR results, and had 35 day stability under 25 °C storage. Furthermore, the color readout allows for quantitation of MRSA copies. Hence, this device is applicable for point-of-care MRSA detection.

Natural cellulose paper is flame retarded using ammonium polyphosphate/montmorillonite (APP/MMT) nanocompound through coating method. Their morphologies are assessed by scanning electron microscopy, chemical components by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, chemical structure by Fourier transform infrared, thermal stability by thermo-gravimetric analysis and fire retardancy by 45° horizontal burning test. The results show that the thermal stability and flame retardancy of coated paper samples are enhanced obviously, and all samples are self-extinguishing during the tests due to the char formation reaction between APP/MMT and cellulose. Then the treated paper, AM-18.3, as surface flame retardant treatment for low specific surface area (SSA) polypropylene (PP) specimens (PP@AM-18.3) also is investigated using cone calorimeter. Compared with two controlled samples, PP@AM-18.3 shows significantly increased time to ignition, the lowest fire growth index and highest fire performance index. This may give a new flame retarded approach for low SSA polymer materials with little amount flame retardants.

Wastewater containing heavy metal ions is considered as the serious environmental problem in human society. Adsorption as the widely used method plays an important role in wastewater treatment, which is based on the physical interaction between metal ions and sorbents. Drumsticks are reported to have efficient adsorbing property. It has been found that Moringa causes alteration in testosterone levels, preventing testicular damage and hence is capable of protecting against the toxic effect of hazardous material. Based on this phenomenon of adsorption by Moringa species, we are trying to remove heavy metals from aqueous sample. The bio sorption of heavy metals by non-living biomass of plant origin is an innovative and alternative technology for the removal of the pollutants from aqueous solution and offers several advantages such as low-cost bio sorbents, high efficiency, minimization of chemical and/or biological sludge, and regeneration of the bio sorbent. Moringa oleifera (drumsticks) has a number of advantages including low cost, biodegradable sludge production and lower sludge volume, and also it does not affect the pH of the water. Apart from turbidity removal, Moringa oleifera seeds also possess antimicrobial properties. Amount of adsorption is considerably larger when activated charcoal is used. Thus, this work reports preparation of activated charcoal from drumsticks seeds and fibres. These are generally part of kitchen waste; thus, its preparation and utilisation for heavy metal toxicity not only controls water pollution but also help in reduction of kitchen waste. It will serve as an effective, cheap and robust and green tool for toxicity control. The paper reports the removal of heavy metal (Pb, Ni, Cd, As in this study) by application of prepared activated charcoal tablets via MATLAB assisted paper based sensors. These tablets will surely serve as point-of- care devices for removal of heavy metal toxicity.

Herein, combined with a pervasive smartphone installed with a color recognition app, dual-responsive CDs@Eu/GMP ICPs were designed as a red-to-blue paper-based colorimetric sensor for the point-of-use analysis of cerebral acetylcholinesterase (AChE) upon Cd2+ exposure. Blue-emitting CDs with multi-functional groups as guests were encapsulated into the network of Eu/GMP ICPs to obtain CDs@Eu/GMP ICPs with the sensitized red fluorescence of Eu3+. With the presence of thiocholine (TCh), derived from acetylthiocholine (ATCh) hydrolyzed by AChE, the coordination environment of the CDs@Eu/GMP ICPs was interrupted, leading to the collapse of the CDs@Eu/GMP ICP network and the corresponding release of guest CDs into the surrounding environment. Consequently, the sensitized red fluorescence of Eu3+ decreased and the blue fluorescence of the CDs increased. This obvious red-to-blue fluorescent color changes of CDs@Eu/GMP ICPs on test paper could then be integrated with the smartphone for point-of-use analysis of cerebral AChE upon Cd2+ exposure, which not only offers a new analytical platform for a better understanding of the environmental risk of Alzheimer's Dementia (AD), but also holds great potential in the early diagnosis of AD even at the asymptomatic stage with the decrease in CSF AChE as an early biomarker.

Edible oils form an integral component in the human diet as well as in the industrial preparations. Any adulteration in oil is concerning from nutritional as well as economical perspective. Although analytical techniques exist for detection of adulterants in oil, most of them require sophisticated instruments, and trained professionals. Microfluidic based lab-on-a-chip technologies have rapidly progressed over the recent years and offer promising alternatives in this regard. In this work, we report development of a paper-based microfluidic lab-on-a-chip for detection of palm oil contamination in sunflower oil. We use the paper-based microfluidic colorimetric detection approach that indicates the presence of adulteration in a visual manner. The data is analyzed using digitally acquired images along with ultraviolet–visible spectrophotometry. The paper-based microfluidic device is fabricated and tested for 10–50% (v/v) palm oil adulteration in sunflower oil. Further, we employ the device for free fatty acid content tests in oil samples. Visual signal acquired from the device is optimized by varying phenolphthalein proportions. The stability of visual colorimetric signal is examined over time and is found to remain steady over the trial period of six days considered in this work. The integration of the detection device with smartphone imaging can prove to be useful for onsite data collection. We believe the approach presented here can be extended to food quality monitoring portable platforms.

Introduction We developed low-cost, portable paper-based diagnostic devices for detection of human immunoglobulin M (IgM) and immunoglobulin G (IgG) in serum without any sample preparation. These devices can be used to help identify presence of diseases, used to provide rapid results ( Materials and Methods We successfully accomplished colorimetric detection of human IgG and human IgM using a sandwich-style assay within the microfluidic paper device via vertical flow immunoassay configuration. The reaction zone in the wax printed paper layer is a small circular pattern. Gold nanoparticles conjugated with anti-human IgG and IgM antibodies have been used for colorimetric detection of IgG or IgM by naked eye. Colorimetric signal can be precisely quantified through implementation of image analysis software which can be developed as an app for a smartphone. The size of the device is 2 cm × 2 cm × 1 mm. Results Colorimetric detection of human IgG was accomplished at 100 fg/mL concentration using a gold nanoparticle–conjugated anti-human IgG antibody. The developed platform has a dynamic range of IgM and IgG concentrations between 0.1 pg/mL and 100 μg/mL. These devices provided a color readout in Conclusions Because of the inherent simplicity of the device operation and their ease of use, there is no variation between samples and users of the device. This low-cost approach enables multiplexing with >1 measurement performed in parallel at the same time. We anticipate that because of the sensitivity, specificity, ease of use, and overall reliability, this approach will become a standard for diagnosis of diseases and health conditions.

This work investigates the influence of blending waste paper and cement at fixed proportion with varying proportions of chicken feather fiber (CFF) and wood saw dust (WSD) as reinforcements. Samples produced were tested for flexural properties and water absorption potentials. The outcome showed that with increasing CFF content and reducing WSD content, water absorption reduced while flexural strength, modulus of ruptures (MOR) and modulus of elasticity (MOE) increases. MOR and MOE were at peaked when the ratio of CFF to WSD was 3:2 while flexural strength reached it crescendo at 4:1 of CFF to WSD. It was noticed that higher CCF content from 3 to 5 wt% gave better results in most of the investigated properties compared to WSD. Therefore, it was concluded that low quantity of WSD is needed to form a synergy with CFF in order to achieve optimum results. Well dispersed CFF-WSD phase in waste paper-cement based composites was observed to be responsible for the enhancement in the investigated properties.

Paper-based diagnostics are leading the field of low-cost, point of care analytical techniques. However, large scale testing facilities such as hospitals are still primarily using the gel column agglutination technique. This is because paper-based systems are single use tests that are generally more time consuming and less automatable than traditional methods. Here, we present a novel, rapid and scalable, paper-based blood typing method that can produce test results in under ten seconds. We believe this is the fastest blood typing test that is appropriate for large scale automation. The test consists of placing a drop of antibody solution on paper, followed by a drop of blood on the same locus, and measuring the evolution of blood stain area as a function of time. Positive reactions for both forward and reverse tests have significantly slower growth rates and smaller final stain sizes when compared to negatives. We analyse the effect paper type, red blood cell concentration, antibody specificity (A, B and D) and antibody dilution have on the sensitivity and reproducibility of the technique. A high sensitivity is found in papers with a low density and thickness. The optimum red blood cell concentration is determined from a balance between wicking rate, strength of reaction and optical contrast. A and B antibodies give more sensitive results than D; however, the D antigen can still be successfully identified. This technique has the potential to significantly cut down the time and cost of blood typing tests and enable design of a new high throughput and fully automatable system.

The present work describes a sensitive, simple, cost-effective and fast analytical procedure to detect the parabens in industrial waste effluent water samples using novel activated carbon nanofiber (CNF) modified filter paper based solid phase extraction technique coupled with liquid chromatography with photodiode array detector (UPLC-PDA). The carbon nanofiber coated filter paper was used as an adsorbent and also characterized by field emission scanning electron microscope (FESEM) showed superior porous structure. Various factors effecting the adsorption and desorption process were studied. The optimum parameters which improve the efficiency are paper length 1 cm × 2 cm, adsorption time 15 min, eluent methanol, eluent volume 5 mL, sample pH 7, desorption time 2 min, 2% salt addition and 300 rpm stirring rate respectively. The parabens exhibited superior linearity ranging from 0.1-50 ng mL-1. The regression coefficient (R2) value ranging from 0.9981-0.9989. This method exhibited good sensitivity with the quantification limit (LOQ) between 0.5-0.75 ng mL-1 and detection limit (LOD) over the range of 0.1-0.25 ng mL-1. The precision was expressed from the RSDs values from 0.74-0.97 %. The spiked analytes revealed excellent recoveries in the range of 95.30-116.72 % with RSD less than 5.72 % for all the water samples also applied for real samples.

Lab-on-paper, or microfluidic paper-based analytical devices (μPADs), use paper as a substrate material, and are patterned with a system of microchannels, reaction zones and sensing elements to perform analysis and detection. The sample transfer in such devices is performed by capillary action. As a result, external driving forces are not required, and hence the size and cost of the device are significantly reduced. Lab-on-paper devices have thus attracted significant attention for point-of-care medical diagnostic purposes in recent years, particularly in less-developed regions of the world lacking medical resources and infrastructures. This review discusses the major advances in lab-on-paper technology for blood analysis and diagnosis in the past five years. The review focuses particularly on the many clinical applications of lab-on-paper devices, including diabetes diagnosis, acute myocardial infarction (AMI) detection, kidney function diagnosis, liver function diagnosis, cholesterol and triglyceride (TG) analysis, sickle-cell disease (SCD) and phenylketonuria (PKU) analysis, virus analysis, C-reactive protein (CRP) analysis, blood ion analysis, cancer factor analysis, and drug analysis. The review commences by introducing the basic transmission principles, fabrication methods, structural characteristics, detection techniques, and sample pretreatment process of modern lab-on-paper devices. A comprehensive review of the most recent applications of lab-on-paper devices to the diagnosis of common human diseases using blood samples is then presented. The review concludes with a brief summary of the main challenges and opportunities facing the lab-on-paper technology field in the coming years.

Highly foldable and flexible energy materials are a requisite for actual applications in self-powered wearable electronics and complex environments. Unfortunately, thermoelectric (TE) materials showing excellent foldability and flexibility under external mechanical stresses have rarely been reported so far. Herein, foldable and flexible TE materials based on Chinese traditional Xuan paper (a bio-based material) and commercialized conducting polymer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are reported. With a facile dip-coating and subsequent drying process, PEDOT:PSS is wrapped on the surfaces of cellulose fibers of Xuan paper via hydrogen-bond interactions. The resulting composite films exhibit outstanding mechanical and decent TE properties. In particular, the PEDOT:PSS/Xuan paper composite films exhibit excellent foldability and flexibility, and can be easily processed into various shapes with no distinct damage to their electrical conductivity and TE performances. This work paves the way for imparting TE performance to insulating paper-based materials, and the unique foldability may widen the TE applications in complex and extreme environments.

Paper-based sensors open a new avenue to produce easy-to-handle, inexpensive and simple-use analytical devices for widespread application fields in biological systems involving diagnosis, drug discovery and biosensing. In this manuscript, we constructed a fluorescence sensor based on functionalized paper coupled with silver nanoparticles (AgNPs) etching for hydrogen peroxide (H2O2) determination in biological systems. A significant fluorescence signal was achieved by immobilizing CDs onto the surface of cellulose filter paper by covalent bonds. The CDs functionalized paper coupled with AgNPs composites platform (PCD/AgNPs) consisted of CDs functionalized paper (PCD) and a AgNPs layer which acted as a fluorescence quencher of CDs via a physical adsorption mechanism. With the introduction of H2O2, the AgNPs were etched accompanied by the fluorescence recovery. As the target, a good linear relationship of a fluorescence turn-on response toward H2O2 between 10 and 120 μM was obtained with a limit of detection of 1.38 μM in our sensor. The designed sensor demonstrated good specificity and would have broad application prospects in the detection of milk samples and determination of H2O2 released from cancer cells.

Detecting vascular endothelial growth factor C (VEGF-C), a kind of tumor biomarker, is of significant clinical importance in evaluating the prognosis of patients with cancer. However, laboratory analyses are usually not suitable for point-of-care testing because they are expensive and time consuming. In response to these challenges, we fabricated an origami paper-based microfluidic electrochemical device. To improve the specificity of VEGF-C detection, nanocomposites, synthesized by new methylene blue (NMB), amino-functional single-walled carbon nanotubes (NH2-SWCNTs), and gold nanoparticles (AuNPs), were used to modify the surface of working electrodes. Results of electrochemical detection showed that the immunosensor had excellent linearity, ranging from 0.01 to 100 ng mL−1 (R2 = 0.988), and the limit of detection was 10 pg mL−1. To confirm the high specificity of the device under real-world conditions, we evaluated the device using clinical serum samples from our hospital. The results demonstrated that the device had an excellent performance and could provide a platform for real-time detection of cancers., Sun, Wang et al. report an origami paper-based immunosensor for the electrochemical detection of the VEGF-C biomarker in blood serum. The immunosensor is made by modifying the surface of working electrodes with new methylene blue, amino-functional single-walled carbon nanotubes, and gold nanoparticles and demonstrates excellent performance with a limit of detection in the range of picograms per milliliter.

Leukocyte esterase (LE) is a useful marker that can be used in establishing a diagnosis of urinary tract infections (UTIs). The development of a UTI diagnostic method with quantitative determinations of biomarkers across all age groups is becoming more important. In this report, microfluidic resistance sensors based on silver ink (Ag ink) and silver ink mixed with ZnO nanoparticles (Ag-ZnO ink) were synthesized and coated on cellulose paper, namely LE-Ag-μPADs and LE-Ag-ZnO-μPADs, respectively, for the sensitive detection of LE. The microfluidic design increases the precision of data and further allows for quantitative determination and early detection of LE in human urine. The quantification of LE relies on the change in the resistance readout coating with Ag ink as well as Ag-ZnO ink in the detection zone. A mixture of 3-(N-tosyl-l-alaninyloxy)-5-phenylpyrrole (PE) and 1-diazo-2-naphthol-4-sulfonic acid (DAS) was deposited in the sample zone to selectively recognize LE, and the resulting nonconductive products, i.e., azo compounds, further reacted with the Ag ink and Ag-ZnO ink to increase resistance. The quantitative detectable LE concentrations between 2 to 32 (×5.2 U mL-1), i.e. ≈12 to 108 μg L-1, cover the commercial dipstick range of trace, +1 and +2. The minimum detectable concentration of LE in urine was 1 (×5.2 U mL-1). The lower concentrations of LE detectable by LE-Ag-μPADs (1-8 × 5.2 U mL-1) are below the value achieved with the ELISA LE kit. Urine samples from inpatients with indwelling urinary catheters were used, and the LE levels measured by the present device were highly correlated with those determined by a commercial urine analyser.

The paper corrugation tube is an innovative kind of energy absorbing structure and shock absorber which can play an important role on the cushioning energy absorption for airdrop equipments and transportation packaging. The deformation characteristics and failure modes of the regular triangle, quadrangle, pentagon and hexagon paper corrugation tubes were comparatively studied by a series of axial static compression experiments, the cushioning energy absorption was evaluated by the seven characteristic parameters (e.g. initial peak force, mean crush force, total energy absorption, specific energy absorption, crush force efficiency, unit area energy absorption and stroke efficiency), and the influences of tube direction, cross-sectional shape, tube length and compression rate on failure modes and cushioning energy absorption were analyzed and compared. These researches showed that the tubes along X direction only have the accordion deformation mode, yet the tubes along Y direction have four deformation modes including steady state progressive buckling, Euler buckling, angular tear and transverse shear. For the paper corrugation tubes along Y direction, the cross-sectional shape has obvious influence on the cushioning energy absorption of structures, and the specific energy absorption and unit area energy absorption of regular triangle and pentagon tubes are better than those of the tubes with regular quadrilateral and hexagonal cross-section at compression rates of 12 and 48mm/min. The tube length of 150 mm or compression rate of 72 mm/min would cause the increase of contribution proportion of non-ideal deformation mode and the decrease of cushioning properties. The paper corrugation tubes along X direction have more stable and controllable deformation mode, yet the paper corrugation tubes along Y direction have better cushioning energy absorption.

The waste of paper or the paper dump is a serious problem and its occurrence is widespread in various institutions. Wastepaper can be recycled to produce some important and usable products that are ecological and biodegradable. For example, it is used to extract new paper from the old by chemical decomposition. Other products such as paper plates, paper cups, paper spoons, tiles, toys, crafts, etc. can be formed from the slurry. This project also initiates a mould that makes cups and plates from the wastepaper management circuit. With learning institutions being the main consumers, most paper are usually eliminated after its use. The waste remains undeveloped and unused, although is a valuable resource. Studying the design of a manual, economical and efficient paper recycling machine, it can be surmised that the design uses the integration of the knowledge gained about the recycling technology that exists manually from the paper recycling machines used to form a cheap but effective paper recycling system. The advantages of the machine are not only of recycled paper, but also the advantages of the interaction of the manual drive system, which will also reduce the high cost. As the design is not 100% effective, the transmission, belt and chain transmission correspond to the estimated 90% efficiency using the 90% for the design. The power consumption for the design is 450 W and since an average user can produce 100 W constant, it takes 5 people to drive the machine.

We report a simple and cost-effective paper-based and colorimetric dual-mode detection of As(iii) and Pb(ii) based on glucose-functionalized gold nanoparticles under optimized conditions. The paper-based detection of As(iii) and Pb(ii) is based on the change in the signal intensity of AuNPs/Glu fabricated on a paper substrate after the deposition of the analyte using a smartphone, followed by processing with the ImageJ software. The colorimetric method is based on the change in the color and the red shift of the localized surface plasmon resonance (LSPR) absorption band of AuNPs/Glu in the region of 200-800 nm. The red shift (Δ

In recent years there has been increasing interest in the use of recycled paper waste in the production of concrete to reduce environmental pollution. This study aims to investigate the use of raw paper waste to produce lightweight cement mortar and to study the effect of the aluminium sulphate treatment of raw paper waste on the compressive strength, absorption ratio and hardened density of mortar. This study used raw paper waste as a replacement for fine aggregate, with percentages of 5%, 10%, 15%, 20% and 30%. The same percentages were examined for the aluminium-sulphate-treated paper waste. The study aims to achieve a similar workability and fixed flow rate for all mixes; therefore, the water–cement ratios were changed for mixes containing paper waste to balance the water absorbed by the paper waste. The study found that the treatment of paper waste with aluminium sulphate helps to reduce the amount of water absorbed by the paper waste and also reduces the amount of water required to maintain its workability, with a higher paper-waste content requiring a larger water content to achieve a similar workability. It was found that the higher the paper-waste content, the lower the wet and dry densities. The compressive strength at both an early and mature age decreased with the increased content of paper waste. Finally, the treatment of paper waste with aluminium sulphate increases the early age compressive strength for similar replacement percentages of up to 19%.

Cyanide ( CN - ) is a deleterious chemical and can cause serious health effects upon exposure even at low concentrations. Different sensors have been developed to monitor cyanide in water, which, however, suffers from complex mechanisms and high-cost. Curcuma longa or turmeric is a commercially available natural dye (usually in powder form) used as medicine. The phenolic substance curcumin is responsible for its yellow color and is capable of sensing environmentally significant analytes such as CN - . In this study, a colorimetric sensor for cyanide in aqueous solution was fabricated by the immobilization of crude curcumin on ordinary filter paper. The curcumin was extracted from locally available turmeric powder using a simple extraction method. Its successful integration in the filter paper was validated by FT-IR spectroscopy. UV–Vis analysis showed that the curcumin-based paper sensor was sensitive to CN - (down to 5.0 ppm), producing a visual change from yellow to dark red. The fabricated sensor also demonstrated high selectivity towards CN - in the presence of N a + , K + , and F - . Its response time was found to be inversely proportional to the concentration of the CN - in the solution. Assessment of reusability revealed that the sensor was reusable for up 8 cycles before significant changes in colorimetric response were observed. Importantly, the fabricated sensor exhibited applicability for actual cyanide monitoring in real water samples.

Infectious diseases cause millions of deaths annually in the developing world. Recently, microfluidic paper-based analytical devices (μPADs) have been developed to diagnose such diseases, as these tests are low cost, biocompatible, and simple to fabricate. However, current μPADs are difficult to use in resource-limited areas due to their reliance on external instrumentation to measure and analyze the test results. In this work, we propose an electricity and external instrumentation-free μPAD sensor based on the colorimetric enzyme-linked immunosorbent assay (ELISA) for the diagnosis of infectious disease (3D-tPADs). Designed based on the principle of origami, the proposed μPAD enables the sequential steps of the colorimetric ELISA test to be completed in just ∼10 min. In addition, in order to obtain an accurate ELISA result without using any instrument, we have integrated an electricity-free "timer" within the μPAD that can be controlled by the buffer viscosity and fluid path volume to indicate the appropriate times for washing and color development steps, which can avoid false positive or false negative results caused by an extended or shortened amount of washing and development times. Due to the low background noise and high positive signal intensity of the μPAD, positive and negative detection results can be distinguished by just the naked eye. Furthermore, the ELISA result can be semi-quantified by comparing the results shown on the μPAD with a color chart diagram with a detection limit of HIV type 1(HIV-1) p24 antigen as low as 0.03 ng mL-1. These results demonstrate the proposed sensor can perform infectious disease diagnosis without external instrumentation or electricity, extending the application of the μPAD test for on-site detection and use in resource-limited settings.

Paper-based microfluidic devices are popular for their ability to automate multistep assays for chemical or biological sensing at a low cost, but the design of paper microfluidic networks has largely relied on experimental trial and error. A few mathematical models of flow through paper microfluidic devices have been developed and have succeeded in explaining experimental flow behavior. However, the reverse engineering problem of designing complex paper networks guided by appropriate mathematical models is largely unsolved. In this article, we demonstrate that a two-dimensional paper network (2DPN) designed to sequentially deliver three fluids to a test zone on the device can be computationally designed and experimentally implemented without experimental trial and error. This was accomplished by three new developments in modeling flow through paper networks: (i) coupling of the Richards equation of flow through porous media to the species transport equation, (ii) modeling flow through assemblies of multiple paper materials (test membrane and wicking pad), and (iii) incorporating limited-volume fluid sources. We demonstrate the application of this model in the optimal design of a paper-based signal-enhanced immunoassay for a malaria protein, PfHRP2. This work lays the foundation for the development of a computational design toolbox to aid in the design of paper microfluidic networks. ©

Lightweight yet strong paper with high toughness is desirable especially for impact protection. Herein we demonstrated electrically conductive and mechanically robust paper (AP/PB-GP) made of reduced graphene oxide via interfacial crosslinking with 1-aminopyrene (AP) and 1-pyrenebutyrat (PB) small molecules. The AP/PB-GP with thickness of over ten micrometer delivers a record-high toughness (∼69.67 ± 15.3 MJ m−3 in average), simultaneously with superior strength (close to 1 GPa), allowing an impressive specific penetration energy absorption (∼0.17 MJ kg−1) at high impact velocities when used for ballistic impact protection. Detailed interfacial and structural analysis reveals that the reinforcement is synergistically determined by π-π interaction and H-bonding linkage between adjacent graphene lamellae. Especially, the defective pores within the graphene platelets benefit the favorable adsorption of the pyrene-containing molecules, which imperatively maximizes the interfacial binding, facilitating deflecting crack and plastic deformation under loading. Density functional theory simulation suggests that the coupling between the polar functional groups, e.g., −COOH, at the edges of graphene platelets and −NH2 and −COOH of AP/PB are critical to the formation of hydrogen bonding network.

Neotame is an artificial sweetener with increasing consumption in recent years, excessive intake of it may bring potential health risk. In this work, a rapid method was developed to detect neotame in instant grain beverages, which was based on surface-enhanced Raman scattering (SERS) technique and filter paper-based silver nanoparticles (AgNPs@FP) substrates. The designed substrate exhibits good SERS activity with an enhancement factor of 105 because of the synergistic effect of the concentrated silver nanoparticles and filter paper. Meanwhile, the stability and repeatability of this fabricated substrate have been investigated with the relative standard deviation of 6.1%. In addition, it shows an excellent linear relationship (R 2 = 0.997) between the SERS signal and the logarithm concentration of neotame with a wide concentration range (0.05–5 g/kg) in the quantitative analysis. The limit of detection of neotame can be as low as 0.01 g/kg in instant grain beverages, which is below the maximum allowable addition level for neotame in instant grain beverages set in China (GB2760-2014, 0.16 g/kg). The proposed method has great potential for the identification and quantification of neotame in food safety applications with high sensitivity.

Food safety is always one of the most important issues for human being. With the variety of food, it is required to develop rapid, low-cost and convenient detection techniques for food safety. As a representative, paper-based detection techniques have developed rapidly from simple test papers to various microfluidic paper-based devices. The paper-based analytical devices combining paper platform with a variety of advanced analytical methods have shown great application prospects for rapid testing of food safety. In this review, the surface functionalization and modification of paper are introduced. Then, the construction and development of various detection techniques are discussed, including colorimetric analysis, fluorescent analysis, electrochemical analysis, surface enhanced Raman spectroscopic analysis, and multimethods on paper-based platforms for the application in rapid detection for food safety. Finally, the prospects and future challenges of rapid detection techniques in food safety are also discussed.

Recently, the interest in active packaging utilization has increased with population growth, food demand and new consumer trend like food delivery services. This new system, however, requires the use of additives to extend the food product quality and safety as well as in maintaining the shelf-life. This study was to prepare the antimicrobial paper from I. cylindrica coated anionic nanocellulose crosslinked cationic to create a system with the ability to actively control microbe growth in the packaging materials. The process involved pulping of I. cylindrica using semi-chemical and soda chemical method. The antimicrobial paper was prepared by printing the pulp suspension in 60 g/m2 grammage in mold followed by the spray of anionic nanocellulose and subsequent soaking of the paper in cationic solution. The results showed the I. cylindrica paper coated anionic nanocellulose crosslinked with H+ and Al3+ cations were successfully produced. The paper produced was also observed to have antimicrobial activity against Gram-negative of E. coli and S. typhi as well as Gram-positive of S. aureus and B. subtilis bacteria. Furthermore, the best coating method was found on antimicrobial paper coated anionic nanocellulose crosslinked Al3+ as evidenced by smoother and compact surface structure.

There is growing demand for simple to operate, sensitive, on-site quantitative assays to investigate concentrations of drug molecules in pharmaceutical preparations for quality assurance. Here, we report on the development of two colorimetric analysis methods for the study the antibiotic doxycycline hyclate (DOX) and the nasal decongestant oxymetazoline hydrochloride (OXY), in solution as well as in their respective formulations. We compare a UV/vis spectrophotometry method with a color change recorded on a microfluidic paper-based analytical device (μPAD). Detection is based on the pharmaceutical compounds coupling with diazotized 4-aminoacetophenone (DAAP) under alkaline conditions to produce colored azo-dye products. These azo-compounds were monitored by absorbance at 425 nm for DOX and 521 nm for OXY, with linear calibration graphs in the concentration range of 0.5–35 mg L−1 (DOX) and 1.0–40 mg L−1 (OXY) and limits of detection of 0.24 mg L−1 (DOX) and 0.32 mg L−1 (OXY). For the μPAD method, color intensity was measured from photographs and a linear increase was observed at concentrations from above approximately 15 mg L−1 for both compounds and up to 35 mg L−1 for DOX and 40 mg L−1 for OXY. The developed methods were also applied to the formulated pharmaceuticals and no interference was found from the excipient. Thus, the paper-based device provides an inexpensive, simple alternative approach for use outside centralized laboratories with semi-quantitative capability.

Paper-based colorimetric sensor array has attracted extensive attention due to its low-cost, easy-operation, powerful discrimination, good selectivity, rapid response and versatility. It combines the advantages of paper-based analytical devices and colorimetric sensor array, and extends its application fields in analytical chemistry. This review described the recent progress in paper-based colorimetric sensor array and summarized its applications in biomedicine, environmental and food safety. Moreover, the sensing materials, characteristics and performances of different paper-based colorimetric sensor arrays were investigated. The prospects of future research for the paper-based colorimetric sensor array were discussed.

In this work, we prepared novel cellulosic paper by incorporating tannin into the kraft pulp for potential application in active food packaging. The kraft pulp fibers were firstly periodate oxidized to obtain the dialdehyde cellulosic fibers, and then reacted with varied dosages of tannin to incorporate them into the fibers by covalent bondings between aldehyde groups on cellulose and active hydrogen on tannin. Handsheets were prepared using the tannin incorporated fibers through papermaking process and the properties were characterized. The percentage of tannin in the paper increased with the increase of the tannin dosage. FT-IR spectra confirmed the successful incorporation of tannin into the cellulosic fibers. It was found that paper after incorporation of tannin turned to be surface hydrophobic with contact angles higher than 90°, which may probably due to the covalent bonds between tannin and cellulose. The handsheets show high antioxidative and UV-shielding properties, which both increased with the increase of the tannin percentage in the paper. Water vapor transmission rate (WVTR) decreased after the incorporation of tannin, and this could facilitate its application in food packaging. The breaking length of tannin incorporated paper decreased insignificantly, less than 10% with the tannin percentage as high as 45%.

The growing need for reliable analytical tools to perform measurements at the point-of-need has prompted the development of novel sensors that are low cost, portable, sensitive, easy to use, and capable of multiplexed analysis. Miniaturization of the sensors into microfluidic platforms has become a promising approach to achieve these self-contained sensors. However, traditional microfluidics often require relatively expensive and complicated pumping mechanisms that increase the cost and limit the portability of the sensors. From a material perspective, paper is an attractive substrate for constructing point-of-need sensors because of its affordability, vast availability, and self-pumping ability, particularly when combined with electrochemical detection. In this mini-review, we discuss various strategies to achieve multiplexing or simultaneous detection of multiple analytes in electrochemical paper-based devices and provide a brief guide on selecting the detection strategy based on the electrochemical property of the analytes.

A novel nacre-like flame-retardant paper based on graphene oxide (GO), and phytic acid (PTA) is fabricated via evaporation-induced self-assembly. This facile method is time saving and low energy consuming. A facile approach is proposed to improve thermal oxidative stability of GO paper by in situ phosphorus doping during flame exposure. Then fire-alarm system is designed based on the high-temperature thermal reduction characteristic of GO. The GO paper functionalized with PTA (GO-PTA) can provide ultrasensitive, reliable and longtime fire early-warning signal. Fire alarm can be triggered at approximately 0.50 s when GO-PTA samples are attacked by fire. Phosphorus atoms are in situ doped into graphene layers during fire exposure, endowing GO-PTA paper with outstanding thermal oxidative stability, and thus alarm duration time of GO is greatly improved. The work develops advanced fire detection and early-warning sensors that provide reliable and continuous signals, which provide more available time for fire evacuation.

This study demonstrates a method for patterning paper-based microfluidic devices. An octadecyltrichlorosilane (OTS) solution is used to coat a chromatography paper to make it hydrophobic. A low-temperature (~ 32.9 °C) atmospheric-pressure dielectric-barrier-discharge jet with a shadow mask is then used to pattern hydrophilic stripes on the OTS-coated hydrophobic paper. In this manner, 1-mm-wide hydrophilic stripes are patterned successfully. Liquids are demonstrated to be transported and mixed in the hydrophilic stripes. Water contact angle measurement, X-ray photoelectron spectroscopy, surface profiler, optical emission spectroscopy, and scanning electron microscopy are used to characterize effect of pattering.

Biodegradable coated paper materials represent one of the most promising alternatives to petroleum-based materials, including plastics and plastic-paper composite materials. Herein, fully biodegrad...