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This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sensing applications in healthcare, environmental monitoring, and food safety. Researchers have developed innovative sensing platforms for detecting pathogens, pollutants, and contaminants by leveraging the paper's unique properties, such as biodegradability and affordability. These portable, low-cost sensors facilitate rapid diagnostics and on-site analysis, making them invaluable tools for resource-limited settings. This review discusses the fabrication techniques, principles, and applications of paper microfluidics, showcasing its potential to address pressing challenges and enhance human health and environmental sustainability. [ABSTRACT FROM AUTHOR]

This manuscript offers a concise overview of paper microfluidics, emphasizing its sustainable sensing applications in healthcare, environmental monitoring, and food safety. Researchers have developed innovative sensing platforms for detecting pathogens, pollutants, and contaminants by leveraging the paper’s unique properties, such as biodegradability and affordability. These portable, low-cost sensors facilitate rapid diagnostics and on-site analysis, making them invaluable tools for resource-limited settings. This review discusses the fabrication techniques, principles, and applications of paper microfluidics, showcasing its potential to address pressing challenges and enhance human health and environmental sustainability.

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit.

The possibility of analyzing the general and functional diversity of the ecosystem is considered, as is unambiguous interpretation of the results obtained based on our work experience and previously obtained data. The prospects for studying small mammals without removal from the wild are discussed. We discuss distinguishing in a sample the resident component, which makes it possible to characterize local resource flows, and the nonresident component, dependent on the state of the territory as a whole. A description of the capture–mark–recapture protocol, methods for assessing spatial activity, calculating the density of the resident population per unit area, and the completeness of species richness estimate is provided. The estimates of animal numbers per unit of trapping effort in pooled sample, the population density of residents, and the index of the nonresident flow are compared. The possibility of analyzing the resource flows in "historical," "novel," and "hybrid" ecosystems, as well as using data to analyze the resilience of the ecosystem and detect the threshold point, is considered. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel filter paper patterning method based on parylene C. • A paper-based colorimetric sensor for detection of Al (III) using a smartphone platform. • The detection range of the sensor for Al (III) detection is 0.05 to 10 mg/mL. The detection limit is 0.05 mg/mL. • The assembled paper-based smartphone sensor platform has the potential to detect other biochemical molecules. The paper-based analytical platforms have been applied in biochemical detection and environmental monitoring due to their low cost and easy operation. Despite their advantages, the complexity of fabrication has limited their further application. Here, a simple and innovative approach using parylene C, a material commonly used in semiconductors, is reported to fabricate paper-based chips and construct a point-of-care testing (POCT) platform through smartphones. Parylene C is deposited on the filter paper through a polydimethylsiloxane (PDMS) clamp and forms a hydrophobic barrier. A three-channel paper-based chip was utilized to detect aluminum (Al) ions on a smartphone platform by the chromogenic method. The color change after Al3+ detection is represented with △E which was photographed and calculated by app on smartphone. The detection limit is 0.05 mg/L and the detection range is from 0.05 mg/L to 10 mg/L which indicates the application potential in the field of biochemical detection. This new paper-based sensing method and smartphone-based portable detection platform are simple, low-cost, fast, and highly sensitive, and provides a potential application for on-site, visual detection of ions and even other substances. [ABSTRACT FROM AUTHOR]

Printable biosensors have gained numerous exciting advancements towards downstream applications in fundamental biomedical research, healthcare, food safety, environmental monitoring and governance, and to name a few. Particularly, paper-based printable biosensors have gained rising popularity in providing affordable platforms due to their merits, such as cost-effective, accurate, simple, and efficient detection of diseases for clinical diagnosis. In addition to advantages and opportunities in point-of-care detection, printable biosensors are also facing challenges. Herein, this review aims to provide a systematic summary of the development of printable biosensors, with a special focus on paper-based printable biosensors. Different types of substrates for printable biosensors are highlighted with a focus on paper substrates which have superior properties like low-cost, simple, flexible, lightweight, recyclable, etc. In addition, current printing technologies to fabricate paper-based sensors, including wax printing, photolithography, screen printing, inkjet printing, and laser printing summarize, are discussed, together with strategies for biomolecular fabrication on substrates and transducers. Finally, we also discuss the challenges and possible future perspectives, hoping to provide researchers and clinicians with informative insights into paper-based printable biosensors for smart and effective point-of-care detection. [ABSTRACT FROM AUTHOR]

Pulp and paper industries emit various odorous gases during the pulp production and paper-making phase, which are unpleasant and have harmful effects on the human body. The working staffs are continuously exposed to these gases and develop various health issues. Hence, regular monitoring and analysis of such gases are necessary to avoid any sudden high concentration exposure and to prevent adverse health effects on the staff. An electronic nose (EN) has an array of gas sensors with an alert system for early detection of gases. Various ENs have been developed for varying applications till date. The detailed knowledge of the sensors used, their sensitivity and technology is helpful in development of any EN. The objective of this study is to comprehensively review various developed ENs with respect to their gas sensing and pattern recognition (PR) technologies. The information on gases released from pulp and paper industries is also compiled. The evolution of EN technology, its various applications, challenges in developing EN and its utility in safeguarding the industrial workers' life have been described. Further, gap analysis among previously developed EN, contemporary EN and wireless sensor network (WSN) is elaborated. It will facilitate future researchers for better selection of sensors and PR technologies while developing EN. The commonly used sensing technologies are described with their advantages, disadvantages and working principles. Metal oxide semiconductor (MOS) gas sensor and ANN algorithm show better result and hence recommended in the development of EN, whereas ZigBee protocol has been widely used for WSN. [ABSTRACT FROM AUTHOR]

In this paper, the behavior of the Bi-Material Cantilever (B-MaC) response deflection upon fluidic loading was experimentally studied and modeled for bilayer strips. A B-MaC consists of a strip of paper adhered to a strip of tape. When fluid is introduced, the paper expands while the tape does not, which causes the structure to bend due to strain mismatch, similar to the thermal loading of bi-metal thermostats. The main novelty of the paper-based bilayer cantilevers is the mechanical properties of two different types of material layers, a top layer of sensing paper and a bottom layer of actuating tape, to create a structure that can respond to moisture changes. When the sensing layer absorbs moisture, it causes the bilayer cantilever to bend or curl due to the differential swelling between the two layers. The portion of the paper strip that gets wet forms an arc, and as the fluid advances and fully wets the B-MaC, the entire B-MaC assumes the shape of the initial arc. This study showed that paper with higher hygroscopic expansion forms an arc with a smaller radius of curvature, whereas thicker tape with a higher Young's modulus forms an arc with a larger radius of curvature. The results showed that the theoretical modeling could accurately predict the behavior of the bilayer strips. The significance of paper-based bilayer cantilevers lies in their potential applications in various fields, such as biomedicine, and environmental monitoring. In summary, the novelty and significance of paper-based bilayer cantilevers lie in their unique combination of sensing and actuating capabilities using a low-cost and environmentally friendly material. [ABSTRACT FROM AUTHOR]

The use of paper as a multifunctional material in electrochemical sensing has been intensively explored over the last decade. The combination among different kinds of paper as well as their coupling with different electrochemical cell configurations have been demonstrated, disclosing innovative sensing performances and features that are still to be fully investigated. This ongoing research has found applications in a variety of fields, including the biomedical, agri-food, security, and environmental ones, thanks to the high versatility and adaptability of the paper material. In this review, we report a critical and comparative analysis of electrochemical devices based on paper published within 2010–2021 and applied for the detection of pollutants of environmental interest in fresh water, seawater, and other real environmental matrices. Several paper types, from common office paper to Whatman filter paper with different filtering grades, were proved to be useful in this field. In detail, the multifarious roles played by the paper are discussed, highlighting how the paper can be a suitable material for electrochemical sensing while being capable of simplifying the measurement of complex real matrices or realizing programmable origami-like structures. Among the most important pollutants, a special focus is dedicated to the emerging pollutants. Furthermore, the unique advantages achieved by the paper have been analyzed and highlighted, reporting the future perspectives regarding the use of this surprising material.

Sensor arrays, which draw inspiration from the mammalian olfactory system, are fundamental concepts in high-throughput analysis based on pattern recognition. Although numerous optical sensor arrays for various targets in aqueous media have demonstrated their diverse applications in a wide range of research fields, practical device platforms for on-site analysis have not been satisfactorily established. The significant limitations of these sensor arrays lie in their solution-based platforms, which require stationary spectrophotometers to record the optical responses in chemical sensing. To address this, this review focuses on paper substrates as device components for solid-state sensor arrays. Paper-based sensor arrays (PSADs) embedded with multiple detection sites having cross-reactivity allow rapid and simultaneous chemical sensing using portable recording apparatuses and powerful data-processing techniques. The applicability of office printing technologies has promoted the realization of PSADs in real-world scenarios, including environmental monitoring, healthcare diagnostics, food safety, and other relevant fields. In this review, we discuss the methodologies of device fabrication and imaging analysis technologies for pattern recognition-driven chemical sensing in aqueous media. [Display omitted] • Cross-reactive sensors are applied to paper-based arrays for simultaneous detection. • Portable digital recorders can be used for detecting various responses. • Imaging analysis techniques can accelerate accurate data processing. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based point-of-care assays are a highly valuable technology with many promising applications in public health and environmental monitoring. High-sensitivity detection of certain trace substances is one of the critical important considerations for practical usage of microfluidic point-of-care techniques. Over the past decade, luminescence nanoprobes have been increasingly emerged as powerful toolboxes to achieve exceptional sensitivity and low detection limits for many chemical sensors. In this Review, we provide an overview of the fundamental principles underlying paper-based microfluidic point-of-care detection. We highlight various luminescence nanoprobes, including nano-diamonds, upconversion luminescent nanoparticles, inorganic quantum dots, and carbon dots, along with their corresponding sensing mechanisms. In subsequent sections, we emphasize the requisite utilization of specialized readout equipment for the effective implementation of fluorescence detection. Moreover, we summarize key microfluidic design strategies capable of achieving enhanced precision in the detection processes. We also discuss future research directions and the main challenges to be addressed for fluorescence nanoprobes-inspired paper-based microfluidic point-of-care technology. • Microfluidic point-of-care paper-based Luminescence assays. • Luminescence nanoprobes and corresponding mechanism. • Portable devices for signal readout and diagnosis. [ABSTRACT FROM AUTHOR]

Screen-printing technology has revolutionized many fields, including that of electrochemical biosensing. Due to their current relevance, this review, unlike other papers, discusses the relevant aspects of electrochemical biosensors manufactured using this technology in connection to both paper substrates and wearable formats. The main trends, advances, and opportunities provided by these types of devices, with particular attention to the environmental and biomedical fields, are addressed along with illustrative fundamentals and applications of selected representative approaches from the recent literature. The main challenges and future directions to tackle in this research area are also pointed out.

Microfluidic paper-based analytical devices (µPADs) have become promising tools offering various analytical applications for chemical and biological assays at the point-of-care (POC). Compared to traditional microfluidic devices, µPADs offer notable advantages; they are cost-effective, easily fabricated, disposable, and portable. Because of our better understanding and advanced engineering of µPADs, multistep assays, high detection sensitivity, and rapid result readout have become possible, and recently developed µPADs have gained extensive interest in parallel analyses to detect biomarkers of interest. In this review, we focus on recent developments in order to achieve µPADs with high-throughput capability. We discuss existing fabrication techniques and designs, and we introduce and discuss current detection methods and their applications to multiplexed detection assays in relation to clinical diagnosis, drug analysis and screening, environmental monitoring, and food and beverage quality control. A summary with future perspectives for µPADs is also presented.

Environmental toxic pollutants and pathogens that enter the ecosystem are major global issues. Detection of these toxic chemicals/pollutants and the diagnosis of a disease is a first step in efficiently controlling their contamination and spread, respectively. Various analytical techniques are available to detect and determine toxic chemicals/pathogens, including liquid chromatography, HPLC, mass spectroscopy, and enzyme-linked immunosorbent assays. However, these sensing strategies have some drawbacks such as tedious sample pretreatment and preparation, the requirement for skilled technicians, and dependence on large laboratory-based instruments. Alternatively, biosensors, especially paper-based sensors, could be used extensively and are a cost-effective alternative to conventional laboratory testing. They can improve accessibility to testing to identify chemicals and pollutants, especially in developing countries. Due to its low cost, abundance, easy disposal (by incineration, for example) and biocompatible nature, paper is considered a versatile material for the development of environmentally friendly electrochemical/optical (bio) sensor devices. This review presents an overview of sensing platforms constructed from paper, pointing out the main merits and demerits of paper-based sensing systems, their fabrication techniques, and the different optical/electrochemical detection techniques that they exploit. [ABSTRACT FROM AUTHOR]

Paper-based biosensors offer low-cost platforms for fast and easy detection of a biomarker in clinical diagnostics and other fields such as food and environmental monitoring. Since paper is a versatile substrate that enables passive solution flow and is biocompatible, it is suitable to use as a biosensing platform. This perspective article discusses current trends of paper-based biosensors in terms of fabrication and detection techniques in clinical diagnostics. Recently, low performance and manufacturing limitations on large scale are factors limiting microfluidics biosensors commercialization. Key aspects and methods to enhance performance and increase commercialization are proposed in this perspective. [ABSTRACT FROM AUTHOR]

An essential requirement for colorimetric paper-sensor is to allow the target analytes (heavy metal ions) to access the chromophore while maintaining strong chromophore immobilization on the porous substrate surface. This work evaluates the selection of sensitive chromophores (dithizone, 1-(2-pyridylazo) 2-naphthol and 4-(2-pyridylazo)-resorcinol) and their immobilization strategies on paper sensors. Dithizone (DTz) are capable of producing a significant color transition at unadjusted pH, observed by UV–Vis absorption spectroscopy and visible recognition. After immobilizing DTz on a paper substrate (cellulose acetate/chitosan substrate), the DTz-paper sensor showed a distinctive color change from blue-green to peach-pink upon reaction with Pb2+ ions, and the color intensity was proportional to the metal concentration. Quantitative analysis using RGB (R:Red; G:Green; B:Blue) plots showed that increasing DTz concentration on the CA/CS paper sensor increases the difference in total color intensity (∆IT) and the difference in red code intensity (∆IR). This is due to the formation of more DTz-Pb2+ complexes on the CA/CS paper substrate. The CA/CS paper strips immobilized with 100 ppm DTz showed practical potential for rapid detection of heavy metal ions. The DTz-CA/CS paper sensor showed significant color change when detecting spiked heavy metals ions (0.1 ppm Pb2+, 2.0 ppm Zn2+, and 0.2 ppm Cu2+) in river water samples that prepared at the maximum permissible limit for industrial effluent in Malaysia. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) have developed rapidly in recent years, because of their advantages, such as small sample volume, rapid detection rates, low cost, and portability. Due to these characteristics, they can be used for in vitro diagnostics in the laboratory, or in the field, for a variety of applications, including food evaluation, disease screening, environmental monitoring, and drug testing. This review will present various detection methods employed by μPADs and their respective applications for the detection of target analytes. These include colorimetry, electrochemistry, chemiluminescence (CL), electrochemiluminescence (ECL), and fluorescence-based methodologies. At the same time, the choice of labeling material and the design of microfluidic channels are also important for detection results. The construction of novel nanocomponents and different smart structures of paper-based devices have improved the performance of μPADs and we will also highlight some of these in this manuscript. Additionally, some key challenges and future prospects for the use of μPADs are briefly discussed. [ABSTRACT FROM AUTHOR]

Since the monumental work conducted by Whitesides et al. in 2007, research and development of paper-based microfluidics has been widely carried out, with its applications ranging from chemical and biological detection and analysis, to environmental monitoring and food-safety inspection. Paper-based microfluidics possesses several competitive advantages over other substrate materials, such as being simple, inexpensive, power-free for fluid transport, lightweight, biodegradable, biocompatible, good for colorimetric tests, flammable for easy disposal of used paper-based diagnostic devices by incineration, and being chemically modifiable. Myriad methods have been demonstrated to fabricate paper-based microfluidics, such as solid wax printing, cutting, photolithography, microembossing, etc. In this study, fabrication of paper-based microfluidics was demonstrated by spray on the printed paper. Different from the normally used filter papers, printing paper, which is much more accessible and cheaper, was utilized as the substrate material. The toner was intended to serve as the mask and the patterned hydrophobic barrier was formed after spray and heating. The processing parameters such as toner coverage on the printing paper, properties of the hydrophobic spray, surface properties of the paper, and curing temperature and time were systematically investigated. It was found that, after repetitive printing four times, the toner was able to prevent the hydrophobic spray (the mixture of PDMS and ethyl acetate) from wicking through the printing paper. The overall processing time for fabrication of paper-based microfluidic chips was less than 10 min and the technique is potentially scalable. Glucose detection was conducted using the microfluidic paper-based analytical devices (µPADs) as fabricated and a linear relationship was obtained between 1 and 10 mM. [ABSTRACT FROM AUTHOR]

The sustainable goal of technological advancement is to go from lab to site through the development of a sensitive, specific and portable sensor for pollution monitoring. Herein, we report a completely portable colorimetric prototype device for the selective monitoring of lead (Pb) pollution, mainly in air, which relies on a new aspect of analysing the colorimetric assays on paper strips by the direct measurement of the retroreflective information, other than the available tedious image analysis methods. Our indigenously developed citrate-functionalized silver nanoparticles (AgNPs) embedded in cellulose paper strips showed significant localized surface plasmonic resonance (LSPR) peaks in the blue region and with the increase in the Pb concentration, the LSPR band in the blue region decreased and a new peak appeared in the green region of the electromagnetic spectrum due to the formation of larger aggregates. The prototype device monitored these spectral changes and accordingly gave the Pb content present in the sample. In this work, we made the sample under study by the acid digestion of one of the widely present air-suspended particulates, i.e., PbO2. The prototype device is a suitable fielddeployable technique for environmental Pb sensing and will open up new perspectives for future advancement in low-cost paper-based sensing. [ABSTRACT FROM AUTHOR]

In the last decades, the increase in global industrialization and the consequent technological progress have damaged the quality of the environment. As a consequence, the high levels of hazardous compounds such as metals and gases released in the atmosphere and water, have raised several concerns about the health of living organisms. Today, many analytical techniques are available with the aim to detect pollutant chemical species. However, a lot of them are not affordable due to the expensive instrumentations, time-consuming processes and high reagents volumes. Last but not least, their use is exclusive to trained operators. Contrarily, colorimetric sensing devices, including paper-based devices, are easy to use, providing results in a short time, without particular specializations to interpret the results. In addition, the colorimetric response is suitable for fast detection, especially in resource-limited environments or underdeveloped countries. Among different chemical species, transition and heavy metals such as iron Fe(II) and copper Cu(II) as well as volatile compounds, such as ammonia (NH3) and acetaldehyde (C2H4O) are widespread mainly in industrialized geographical areas. In this work, we developed a colorimetric paper-based analytical device (PAD) to detect different contaminants, including Fe2+ and Cu2+ ions in water, and NH3 and C2H4O in air at low concentrations. This study is a “proof of concept” of a new paper sensor in which the intensity of the colorimetric response is proportional to the concentration of a detected pollutant species. The sensor model could be further implemented in other technologies, such as drones, individual protection devices or wearable apparatus to monitor the exposure to toxic species in both indoor and outdoor environments.

Objectives Paper dust has previously been linked to adverse health effects. However, a comprehensive dataset of paper dust exposures does not appear to have been published previously. Our study was intended to address this need by describing a large dataset of measurements made in Swedish soft tissue paper mills. Methods We compiled personal and area total dust exposure measurements collected from a range of operations by our research staff at four soft tissue paper mills in Sweden. We also compiled measurements made by the occupational health staff at each mill and the Swedish Work Environment Authority. We analyzed these measurements to describe patterns and trends in exposures and used mixed-effects regression models to identify measurement characteristics that predicted exposure levels. Results We compiled 1578 measurements from 1971 to 2009, of which 1026 (65%) were personal samples. Statistically significant differences were found between measurements made by research, mill, and Swedish Work Environment Authority staff, as well as between personal and area measurements. The measurement data suggest that, beginning in the 1980s, exposures declined at three of the four mills, but that overexposures were still common at the end of the period. Papermaking and converting operations had the highest observed dust exposures. One mill had significantly lower exposures than the others. Type of measurement (personal versus area) and source of measurement (research staff, company, or regulatory agency) were not significant predictors of measured total dust exposure after controlling for mill, operation, and time. Conclusions Our analysis of measured paper dust exposures may be useful for historical and contemporary exposure assessment in our own and other epidemiological studies. We have identified specific characteristics (i.e. papermaking operations and mill) and time trends that are important data features to consider, and documented continuing overexposure situations. Our results highlight the ongoing need for application of exposure controls to reduce paper dust exposures in the soft tissue paper industry. [ABSTRACT FROM AUTHOR]

Fluid flow behaviour in paper is of increasing interest due to the advantages and expanding use of microfluidic paper-based analytical devices (known as µPADs). Applications are expanding from those which often have low sample fluid volumes, such as diagnostic testing, to those with an abundance of sample fluid, such as water quality testing. The rapid development of enhanced features in μPADs, along with a need for increased sensitivity and specificity in the embedded chemistry requires understanding the passively-driven fluid motion in paper to enable precise control and consistency of the devices. It is particularly important to understand the influence of parameters associated with larger fluid volumes and to quantify their impact. Here, we experimentally investigate the impacts of several properties during imbibition in paper, including geometry (larger width and length) and the surrounding conditions (humidity and temperature) using abundant fluid reservoirs. Fluid flow velocity in paper was found to vary with temperature and width, but not with length of the paper strip and humidity for the conditions we tested. We observed substantial post-wetting flow for paper strips in contact with a large fluid reservoir.

A field paper-based heavy metal strip was designed and implemented for simultaneous detection of the heavy metals Zn, Cr, Cu, Pb and Mn in wastewater samples. The colorimetric paper strip was fabricated by drop-casting of chromogenic reagents onto detection zones. When the fabricated paper strip was exposed to Zn, Cr, Cu, Pb and Mn, multiple colors appeared that were then recorded with a smartphone followed by processing in the Color Picker application. After optimizing the analytical parameters, such as the chromogenic concentration, pH and reaction time, the paper strip achieved detection limits of 0.63, 0.07, 0.17, 0.03 and 0.11 mg/L for Zn, Cr, Cu, Pb and Mn, respectively. Five heavy metals analyses were able to be performed within 1 min on one paper strip. This paper strip is accurate with recoveries from 87 to 107%. The results of the proposed paper strip correlated well with those determined by inductively coupled plasma-optical emission spectrometry of wastewater samples. The use of a single paper strip integrated with a smartphone for the detection of five heavy metals in wastewater represents an all-in-one device with on-site detection, leading to cost-effective and rapid assays that show a great application potential for on-site environmental monitoring. [ABSTRACT FROM AUTHOR]

Point-of-care testing (POCT) technology is urgently required owing to the prevalence of the Internet of Things and portable electronics. In light of the attractive properties of low background and high sensitivity caused by the complete separation of excitation source and detection signal, the paper-based photoelectrochemical (PEC) sensors, featured with fast in analysis, disposable and environmental-friendly have become one of the most promising strategies in POCT. Therefore, in this review, the latest advances and principal issues in the design and fabrication of portable paper-based PEC sensors for POCT are systematically discussed. Primarily, the flexible electronic devices that can be constructed by paper and the reasons why they can be used in PEC sensors are expounded. Afterwards, the photosensitive materials involved in paper-based PEC sensor and the signal amplification strategies are emphatically introduced. Subsequently, the application of paper-based PEC sensors in medical diagnosis, environmental monitoring and food safety are further discussed. Finally, the main opportunities and challenges of paper-based PEC sensing platforms for POCT are briefly summarized. It provides a distinct perspective for researchers to construct paper-based PEC sensors with portable and cost-effective, hoping to enlighten the fast development of POCT soon after, as well as benefit human society. • The merits of functionalized paper for PEC sensor are introduced. • Photosensitive material and signal amplification strategy of paper-based PEC sensor are discussed. • The application of paper-based PEC sensor in the field of POCT is highlighted. • The limitations and challenges of paper-based PEC sensor are summarized. [ABSTRACT FROM AUTHOR]

Low-cost paper-based analytical devices are the latest generation of portable lab-on-chip designs that offers an innovative platform for the on/off-site analysis (biosensing) of target analytes, especially in rural and remote areas. Recently, microfluidic paper-based analytical devices (μPADs) have attained significant recognition owing to their exciting fundamental features such as: ease of fabrication, rapid operation, and precise interpretations. The incorporation of enzymes with paper-based analytical devices significantly improves analytical performance while exhibiting excellent chemical and storage stability. In addition to that, these devices are highly compact, portable, easy-to-use, and do not require any additional sophisticated equipment for the detection and quantification of target analytes. This review provides a holistic insight into design, fabrication, and enzyme immobilization strategies for the development of enzyme-μPADs, which enables them to be widely implemented for in-field analysis. It also highlights the recent application of enzyme-μPADs in the area of: biomedical, food safety, and environmental monitoring while exploring the mechanisms of detection involved. Further, in order to improve the accuracy of analysis, researchers have designed a smartphone-based scanning tool for multi-variant point-of-care devices, which is summarized in the latter part of the review. Finally, the future perspectives and outlook of major challenges associated with enzyme-μPADs are discussed with their possible solutions. The development of enzyme integrated μPADs will open a new avenue as an exceptional analytical tool to explore various applications. Enzyme embedded paper-based analytical devices are a revolution in the field of biosensing. The design, fabrication, and enzyme immobilization on μPADs have been comprehensively discussed. The application of enzyme-μPADs food safety, environmental monitoring, and clinical diagnostic have been reviewed. Smartphones can be used as an on-site, user-friendly, and compact next-gen scanning tool for biosensing. [ABSTRACT FROM AUTHOR]

Accurate and up‐to‐date biodiversity forecasts enable robust planning for environmental management and conservation of landscapes under a wide range of uses. Future predictions of the species composition of ecological communities complement more frequently reported species richness estimates to better characterize the different dimensions of biodiversity. The models that make community composition forecasts are calibrated with data on species' geographic patterns for the present, which may not be good proxies for future patterns. The future establishment of novel communities represents data on species interactions unaccounted for by these models. However, detecting them in a systematic way presents challenges due to the lack of monitoring data for landscapes with high environmental turnover, where such communities are likely to establish. Here, we propose lightweight monitoring over both ecological and anthropogenic disturbance gradients using passive sensors (i.e., those that operate continuously without much human input) to detect novel communities with the aim of updating models that make community composition forecasts. Monitoring over these two gradients should maximize detection of novel communities and improve understanding of relationships between community composition and environmental change. Further, barriers regarding cost and effort are reduced by using relatively few sensors requiring minimal upkeep. Ongoing updates to community composition forecasts based on novel community data and better understanding of the associated uncertainty should improve future decision‐making for both resource management and conservation efforts. [ABSTRACT FROM AUTHOR]

Heavy metals are the main pollutants present in aquatic environments and their presence in human organisms can lead to many different diseases. While many methods exist for analysis, colorimetric and electrochemistry are particularly attractive for on-site analysis and their integration on a single platform can improve multiplexed metals analysis. This report describes for the first time a "plug-and-play" (PnP) assembly for coupling a microfluidic paper-based device (μPAD) and a screen-printed electrochemical paper-based device (ePAD) using a vertical and reversible foldable mechanism for multiplexed detection of Fe, Ni, Cu, Zn, Cd and Pb in river water samples. The integration strategy was based on a reversible assembly, allowing the insertion of a pretreatment zone to minimize potential chemical interfering agents and providing a better control of the aspirated sample volume as well as to a lower sample evaporation rate. In comparison with lateral flow and electrochemical assays performed using independent devices, the integrated prototype proved that the reversible coupling mechanism does not interfere on the analytical performance (95% confidence interval). The limit of detection (LOD) values calculated for metals determined varied from 0.1 to 0.3 mg L−1 (colorimetric) and from 0.9 to 10.5 μg L−1 (electrochemical). When compared to other integrated devices based on horizontal designs, the use of a foldable coupling mechanism offered linear response in a lower concentration range and better LOD values for Fe, Ni and Cu. The proposed method successfully measured heavy metals in river water samples with concentrations ranging from 16 to 786 μg L−1, with recovery studies ranging from 76 to 121%. The new method also showed good correlation with conventional atomic absorption spectroscopic methods (95% significance level). Thus, the integration of μPADs and ePADs by a vertical folding mechanism was efficient for multiplexed heavy metal analysis and could be exploited for environmental monitoring. [ABSTRACT FROM AUTHOR]

The second cycle of the pulp and paper environmental effects monitoring (EEM) program reported its results on April 1, 2000, and preliminary analysis of the fish survey results have been conducted. The EEM program is a cyclical evaluation of the receiving water impacts associated with the discharge of effluent, consisting of evaluations of fish populations, benthic invertebrate communities, effluent toxicity and other components. This paper represents a summary of the preliminary evaluations of 114 EEM surveys for the fish survey results, as reported by the consulting companies to the mills. Less than 10% of the cases failed to find a statistical difference in the key measurements of gonad size, liver size and condition factor. When effects were seen in a sex of one species, 67% of the time, a similar effect was seen in the opposite sex and when a difference was seen in one sex of one species, 54% of the time, the same difference was seen in the same direction in a second species sampled at that site. This reflects that differences were often consistent between sexes and consistent between species. Results, problems encountered, and lessons learned will be compared for cycle 1 and 2 data, and general response patterns and national trends in reported data will be presented. A summary of research needs is presented, as are recommendations for cycle 3 pulp and paper. New developments in the program reflect some of the adaptations developed for metal mining EEM, including a) setting alpha and beta equal, and its consequences for study design and interpretation, b) discussion of the role of effect size in power analysis and study design, and c) non-lethal sampling protocols for EEM. [ABSTRACT FROM AUTHOR]

Environmental effects monitoring (EEM) is a requirement for pulp and paper mills in Canada discharging effluent directly into receiving environments under the Pulp and Paper Effluent Regulations of the Fisheries Act. The objective of the EEM program is to assess effects on fish, fish habitat and the use of fisheries resources by humans, potentially affected by the deposit of mill effluent in aquatic receiving environments. The information provided by the monitoring program will contribute to assessing the adequacy of the regulations. Difficulties encountered in the first round of monitoring led to an extensive science review of key components and resulted in improvement to process, scientific defensibility of the monitoring data and site-specific flexibility of the EEM program. The second cycle of EEM was, overall, markedly more successful than Cycle 1. However, problems were still evident for fish surveys conducted in marine and estuarine environments. The adoption of improved alternative monitoring approaches (e.g., caged bivalves, mesocosms) should alleviate many of these problems. An overview of the EEM program, results to date, alternative monitoring approaches, and research priorities to fill data gaps are presented. Environmental effects monitoring (EEM) is a requirement for pulp and paper mills in Canada discharging effluent directly into receiving environments under the Pulp and Paper Effluent Regulations of the Fisheries Act. The objective of the EEM program is to assess effects on fish, fish habitat and the use of fisheries resources by humans, potentially affected by the deposit of mill effluent in aquatic receiving environments. The information provided by the monitoring program will contribute to assessing the adequacy of the regulations. Difficulties encountered in the first round of monitoring led to an extensive science review of key components and resulted in improvement to process, scientific defensibility of the monitoring data and... [ABSTRACT FROM AUTHOR]

Objectives Bisphenol A (BPA) is the most used colour developer in thermal paper for cashiers receipts, labels, and tickets. BPA can migrate onto the skin and be absorbed when handling these papers. BPA is a known endocrine disruptor and is therefore being replaced in thermal paper by some alternatives such as Bisphenol S (BPS), D-8, and Pergafast 201® (PF201). To our knowledge, no studies have characterized skin permeation of these BPA alternatives. Methods We measured/characterized skin absorption for BPA, BPS, D-8, and PF201 through ex vivo human skin using flow-through diffusion cells according to OECD guideline 428. Skin samples were 7–12 per test substance from three different skin donors. Skin metabolism was studied for BPA. Dermal absorption was expressed as the amount of the BPA alternatives in the receptor fluid over applied dose in percent (%). Results The absorbed dose after 24 h of exposure was 25% for BPA, 17% for D-8, 0.4% for BPS, and D-8 >> BPS > PF201. These results are in agreement with their log K ow and molecular weights. We provided here the necessary data to estimate the extent of skin absorption of BPA analogues, which is a necessary step in risk assessment, and ultimately evaluate public health risks posed by D-8, BPS, and PF201. [ABSTRACT FROM AUTHOR]

Nowadays, great efforts are made in developing new technology for rapid detection of specific DNA sequences, for environmental monitoring, forensic analysis and rapid biomedical diagnosis applications. Microfluidic paper-based analytical devices are suitable platforms for the development of point of care devices, due to their simple fabrication protocols, ease of use and low cost. Herein, a methodology for in situ detection of single strand DNA by using a colorimetric assay based on the formation of a DNAzyme within a paper substrate was developed. A DNAzyme that could only be formed in the presence of a specific sequence of the Y human amelogenin gene was designed. The performance of the DNAzyme was followed colorimetrically first in solution and then in paper substrates. The reaction was found to be specific to the Y fragment selected as analyte. The DNAzyme reaction on paper enabled the unequivocal colorimetric identification of the Y single strand DNA fragment both qualitatively, with the naked eye (143 ng), and quantitatively by image analysis (45.7 ng). As a proof of concept, a microfluidic paper-based device, pre-loaded with all DNAzyme reagents, was characterized and implemented for the simultaneous detection of X and Y single strand DNA fragments. Image 1 • Optimized methodology for in situ DNA detection in a paper device format. • Detection based on a DNAzyme using Y human amelogenin fragment. • Presents a non-enzymatic, colorimetric and rapid way to detect DNA sequences. • Detection: quantitatively by calculating the grey intensity values. • Detection: qualitatively by the presence of a green color "coffee ring". [ABSTRACT FROM AUTHOR]

The recognition and detection of metal ions present in biological and environmental samples have attracted great attention in recent years. Various analytical techniques are used to detect metal ions. Among these, the fluorescence technique is among the emerging methods because of its simplicity, selectivity, and applicability to bioimaging. Thus, this review particularly explores paper-based fluorescence chemosensors involved in metal ion detection. Significantly, the first section addresses relevant research on metal ion detection involving various techniques. In the second section, several sensing strategies such as photoinduced electron transfer, fluorescence resonance energy transfer, intramolecular charge transfer, chelation enhanced fluorescence, excited-state intramolecular proton transfer, and aggregation-induced emission for the detection of target metal ions (aluminum, copper, iron, lead, mercury, and zinc) are investigated. The third section particularly discusses the role of fluorescence sensor materials (e.g., fluorescein, rhodamine, naphthalimide, BODIPY, carbon dots, quantum dots) involved in the detection processes and their advantages and limitations. Overall, this article reviews 90 research articles on paper-based fluorescence chemosensors for metal ion detection published until 2021. [ABSTRACT FROM AUTHOR]

Sublethal toxicity tests successfully measured the improved quality of pulp mill effluents from the first cycle of environmental effects monitoring (1992-1996) to the second cycle (1997-2000). Test endpoints showed notable shifts to higher concentrations (less toxic). During the second cycle of monitoring, significantly more tests showed no effect in full-strength effluent. Five case studies were considered as part of this exercise. Most of the improvement came with installation of secondary treatment. Twelve Ontario mills with secondary treatment showed reduced toxicity, compared to results with primary treatment. All 29 sets of sublethal data showed higher IC25s during the second cycle, and 23 of these differences were statistically significant. Any other changes between the two cycles of study caused only marginal overall improvement in toxicity, judging by 12 freshwater mills in British Columbia which had secondary treatment during both cycles. Sublethal tests successfully predicted the zone of potential effect in receiving water, agreeing with effects observed in biological surveys. Overlapping zones from multiple discharges could also be demonstrated. In a situation near Niagara Falls, sublethal tests estimated the proportions of toxic loading that four mills contributed to one water body. The prediction was realistic; the actual toxicity found for a mixed effluent was 57% of that predicted from separate toxicities. The conservative prediction agrees with the usual less-than-additive sublethal action of combined toxicants. [ABSTRACT FROM AUTHOR]

Pathogens cause various infectious diseases and high morbidity and mortality which is a global public health threat. The highly sensitive and specific detection is of significant importance for the effective treatment and intervention to minimise the impact. However, conventional detection methods including culture and molecular method gravely depend on expensive equipment and well-trained skilled personnel, limiting in the laboratory. It remains challenging to adapt in resource-limiting areas, e.g., low and middle-income countries (LMICs). To this end, low-cost, rapid, and sensitive detection tools with the capability of field testing e.g., a portable device for identification and quantification of pathogens, has attracted increasing attentions. Recently, paper-based microfluidic analytical devices (μPADs) have shown a promising tool for rapid and on-site diagnosis, providing a cost-effective and sensitive analytical approach for pathogens detection. The fast turn-round data collection may also contribute to better understanding of the risks and insights on mitigation method. In this paper, critical developments of μPADs for in-field detection of pathogens both for clinical diagnostics and environmental surveillance are reviewed. The future development, and challenges of μPADs for rapid and onsite detection of pathogens are discussed, including using the cross-disciplinary development with, emerging techniques such as deep learning and Internet of Things (IoT). [Display omitted] • The state-of-the-art on μPAD is critically reviewed. • μPAD enables onsite detections of biochemical markers from molecules to organisms. • Insights is provided highlighting on multidisciplinary aspects. [ABSTRACT FROM AUTHOR]

Dissolved sulfide tends to species transformation and loss upon leaving the matrix, thus the development of a practical on-site determination of sulfide is crucial for environmental monitoring and human health. In this work, a novel paper-based ratiometric fluorescence sensor was developed for the field analysis of sulfide, which system was constructed by the inner filter effect (IFE) of CdS quantum dots (QDs) toward carbon dots (C-dots). Instead of an aqueous phase system, the conversion of sulfide to its hydride would induce the in-situ formation of CdS QDs on the paper, which acted as an energy acceptor to quench the emission of C-dots, leading to a variation of ratiometric fluorescence from blue to yellow with the increasing concentration of sulfide. Moreover, we proposed a smartphone-based fluorescence capture device integrated with a programmed Python program, accomplishing both color recognition and accurate detection of sulfide. Under the optimal condition, this ratiometric fluorescence sensor allowed for the on-site analysis of sulfide with a limit of detection of 0.05 μM. The accuracy of the sensor was validated via the successful field analysis of environmental water samples with satisfactory recoveries. Compared to other fluorescence methods used for sulfide analysis, this developed system retains the advantages of label-free, low-cost, ease of operation, and miniaturization, showing great potential for the measurement of sulfide on-site, as well as environmental monitoring. [Display omitted] • A paper-based fluorescence sensor was developed for the field analysis of sulfide. • Sulfide induced the IFE between C-dots and CdS QDs and caused fluorescence change. • The portable device for sulfide analysis is low-cost and easy to operate. • The developed system shows great potential for the measurement of sulfide on-site. [ABSTRACT FROM AUTHOR]

The simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater samples was performed. In this report, we designed and fabricated functionalized paper test strips featuring detection zones that use 3-aminopropyltriethoxysilane (APTES) for the immobilization of chromogenic substrates to detect free chlorine, hydrogen sulfide and formaldehyde. After multiple chromogenic reactions, red, blue and purple colors were obtained on the detection zones and analyzed using a smartphone. Under optimum conditions, the paper test strips showed 1.7, 1.8 and 1.7 orders of magnitude for free chlorine, hydrogen sulfide and formaldehyde, respectively. This sensitivity is caused by the formation of homogeneous complexes on detection zones resulting from the chromogenic reagents immobilized on the detection zone via APTES. Through this strategy, free chlorine, hydrogen sulfide and formaldehyde analysis was achieved within 5 min with detection limits of 0.08, 0.14 and 0.13 mg L−1, respectively. The developed paper test strip was able to selective detection of free chlorine, hydrogen sulfide and formaldehyde even in the presence of common interfering agents therefore, the test strip was highly selective. In a further demonstration, the developed functionalized paper test strip was successfully used for simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater in the field and exhibited with high precision and accuracy in detecting free chlorine, hydrogen sulfide and formaldehyde in wastewater samples. Compared to other methods, this assay was advantageous in terms of its low detection limit, time savings, good stability and highly portable format, which facilitates rapid on-site environmental monitoring with a smartphone. Image 1 • A functionalized paper strip test enables two-fold improvement of detection limit. • Simultaneous detection of free chlorine, hydrogen sulfide and formaldehyde was achieved within 5 min with low detection limits. • A platform integrating functionalized paper strip test with a smartphone was successfully applied for ready-to-use for detection of free chlorine, hydrogen sulfide and formaldehyde in wastewater samples. [ABSTRACT FROM AUTHOR]

Here, an inkjet printed paper electrode (PPE) decorated with graphene (Gr)-silver (Ag) nanocomposite was exploited as an electrochemical sensing probe for analysis of 4-nitrophenol (4-NP) in environmental water samples. In this work, 4% Gr-Ag nanocomposite ink (NI) was prepared in ethanol, ethylene glycol, and glycerol in the ratio of 50:45:5, which possess surface tension and viscosity of 36 mN m−1 and 11 mPa s, respectively. The office inkjet printer was employed to print formulated Gr-Ag NI on digital photo paper, followed by sintered at 200 °C for 30 min to make effective conducting tracks for the sensing of 4-NP. Gr-Ag NI-based PPE was used as a working electrode in cyclic voltammetry. The working principle of detection is based on the electrocatalytic reduction process of 4-NP on the electrode surface. A good linearity range of 3.125–100 μM was observed, achieving a detection limit of 2.7 μM to measure 4-NP. Thus, the developed PPE holds considerable potential and offers an economical, biodegradable, and user-friendly sensor for future applications in the monitoring of 4-NP in environmental water samples. [Display omitted] • Printed paper electrode (PPE) with graphene (Gr)-silver (Ag) was used as electrochemical sensing for 4-nitrophenol (4-NP). • Inkjet printer was employed to print formulated Gr-Ag NI on photo paper and sintered at 200 °C for 30 min to make electrode. • Gr-Ag/PPE was used as a working electrode in cyclic voltammetry for 4-NP determination. • Gr-Ag/PPE provides a low cost, decomposable, and user-friendly sensor for monitoring of 4-NP in environmental water sample. [ABSTRACT FROM AUTHOR]

Stable isotope analysis of a novel combination of carbon and nitrogen pools traced inputs and processing of primary- treated (PE) and secondary-treated effluent (SE) from a paper and pulp mill (PPM) in a temperate Australian estuary. Distinct carbon stable isotope ratios of dissolved organic carbon (DOC) near the PPM outfall indicated large PE and reduced SE inputs of DOC. DOC was remineralized to dissolved inorganic carbon regardless of season, but rates were lower in winter. PE discharge in winter elevated DOC concentrations along much of the estuary. Distinct stable isotope ratios confirmed particulate organic matter (POM) input from PE and SE to the water column and into the sediment This was relatively localized, indicating rapid POM settlement regardless of season SE discharge increased nutrient inputs and enhanced algal productivity, particularly in summer when chlorophyll-a concentrations were elevated throughout the estuary. SE discharge reduced pCO2 from levels associated with PE discharge. However, the estuary remained heterotrophic as subsequent respiration or decomposition of algal material offset reductions in PPM organic matter input. The influence of the PPM was apparent throughout the estuary, demonstrating the ability of anthropogenic inputs, and changes to these, to affect ecosystem functioning. [ABSTRACT FROM AUTHOR]

Land cover dynamics is a challenging and vigorous process that associates natural and human systems that have undeviating effects on atmosphere, water and soil which lead to many environmental problems worldwide. Urbanization is one of a major land cover change that is highly correlated with many environmental problems that need emphasis. This paper aimed to review and present level and effect of land use land cover changes, urbanization, factors affecting land cover change and application of geographic information system & remote sensing in monitoring land cover changes. Over the past 300 years, about 1.2 million kilometer square of forests and 5.6 million kilometer square of pasture and rangeland were replaced by other uses worldwide, while cultivated land increased by 12 million km2. Inm1950, monlym30 percent of themworldmpopulationmlivedminmurban settings, themfraction raised tom55%mbym2018. This led to about roughly 60% of the ecosystem services are being destroyed or used in unsustainable ways worldwide. Population expansion, change of technology, high land value, corruption, lack of awareness, migration of people and political pressure are among major driving force of land cover changes. Geo-informatics technology specially GIS and Remote Sensing is found to be an excellent tool for study of land cover change that enables observation across large area of earth's surface with low cost, better efficient and high accuracy. Therefore monitoring, analyzing and evaluation of land cover dynamics with the help of geo-informatics is decisive for improved management & characterizing land cover alteration processes, and determining its environmental consequences. [ABSTRACT FROM AUTHOR]

Paper-based sensors are a new alternative technology for fabricating simple, low-cost, portable and disposable analytical devices for many application areas including clinical diagnosis, food quality control and environmental monitoring. The unique properties of paper which allow passive liquid transport and compatibility with chemicals/biochemicals are the main advantages of using paper as a sensing platform. Depending on the main goal to be achieved in paper-based sensors, the fabrication methods and the analysis techniques can be tuned to fulfill the needs of the end-user. Current paper-based sensors are focused on microfluidic delivery of solution to the detection site whereas more advanced designs involve complex 3-D geometries based on the same microfluidic principles. Although paper-based sensors are very promising, they still suffer from certain limitations such as accuracy and sensitivity. However, it is anticipated that in the future, with advances in fabrication and analytical techniques, that there will be more new and innovative developments in paper-based sensors. These sensors could better meet the current objectives of a viable low-cost and portable device in addition to offering high sensitivity and selectivity, and multiple analyte discrimination. This paper is a review of recent advances in paper-based sensors and covers the following topics: existing fabrication techniques, analytical methods and application areas. Finally, the present challenges and future outlooks are discussed. [ABSTRACT FROM AUTHOR]

Microfluidic devices have emerged as advantageous tools for detecting environmental contaminants due to their portability, ease of use, cost-effectiveness, and rapid response capabilities. These devices have wide-ranging applications in environmental monitoring of air, water, and soil matrices, and have also been applied to agricultural monitoring. Although several previous reviews have explored microfluidic devices' utility, this paper presents an up-to-date account of the latest advancements in this field for environmental monitoring, looking back at the past five years. In this review, we discuss devices for prominent contaminants such as heavy metals, pesticides, nutrients, microorganisms, per- and polyfluoroalkyl substances (PFAS), etc. We cover numerous detection methods (electrochemical, colorimetric, fluorescent, etc.) and critically assess the current state of microfluidic devices for environmental monitoring, highlighting both their successes and limitations. Moreover, we propose potential strategies to mitigate these limitations and offer valuable insights into future research and development directions. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) represent a modest and feasible alternative for conventional analytical methods. However, the inadequate sensitivity of these devices limits the possible applications of μPADs. In this scenario, inducing ion concentration polarization (ICP) on μPADs has shown promise to overcome this limitation by preconcentrating the analytes of interest. Here, we report a μPAD implementing ICP using an off-shelf Nafion® membrane as the perm selective membrane. Two types of devices with a geometrical configuration of a straight channel converging at the middle connecting to circular reservoirs at the end of channels were fabricated. The devices are comprised of a single input channel and an absorption channel. The Nafion membrane is attached to the absorption channel of the device, which is encased by heating with paraffin films at both sides to lower the electro-osmotic flow generated by an applied DC electric field that is needed for ICP. The field induced ICP enables obtaining a maximum concentration factor of more than 2000 folds for fluorescein sodium salt solution on the μPAD. Also, since evaporation of the sample solution was reported to be of great influence on the concentration factor, we analyze the effect of sample solution evaporation on sample preconcentration. Furthermore, our reported fabrication method for μPAD can lower the fabrication cost down to 0.3 USD. This device shows the potential to be developed for serving as a diagnostic and environmental monitoring platform. [ABSTRACT FROM AUTHOR]

Paper-based electrochemical sensors (PESs) have been evidenced as analytical strategies for employing simple, low-cost, portable and disposable sensing platforms that can be used in many application areas. Recently, PESs have gained extensive attention because of their advantages of advanced sensitivity and selectivity during detection provided by electrochemistry, compared with microfluidic paper-based analytical devices (μPADs) that still lack these advantages. Also, it can be expected that PESs can better meet current user demands, making them a stand-out analytical tool because of their capability for multiple analyte detection and their compatibility in a variety of application areas, like clinical diagnosis, environmental monitoring and food quality control. Herein, in this mini review, we present an overview of recent developments in PESs over the last decade, focusing on existing fabrication techniques and application areas, specifically in relation to clinical diagnostics, food quality control and environmental monitoring, where simple and portable analytical devices are greatly needed. A summary and future outlooks for PESs are also discussed. [ABSTRACT FROM AUTHOR]

Abstract Paper-based immunosensors are regarded as attractive analytical tools for performing point-of-care and in-field assays in medical diagnostics, environmental monitoring and food safety control. In this review, we provide a general overview of the types and applied detection techniques of paper-based immunosensors published in recent years and analyse the current trends in these two aspects. The first section introduces the background of paper-based immunosensors and critically discusses the necessity and distinct features of existing paper-based immunosensors. The second section summarizes the types of current paper-based immunosensors, including paper-based lateral-flow assays (LFAs), microfluidic paper-based analytical devices (μPADs) and some other device types. In the third section, we describe various detection techniques currently applied in paper-based immunosensors, covering optical, electrochemical and some multiple detection techniques. Finally, current trends and future perspectives are also discussed. We hope this review will be a helpful reference for readers of various fields. Highlights • The application value of paper-based immunosensors is emphasized. • Current paper-based immunosensors are outlined according to two aspects. • Representative examples of paper-based immunosensors are elaborated. • The current trends and prospect of paper-based immunosensors are discussed. [ABSTRACT FROM AUTHOR]

Pressure sensor, as one of the most common components in the sensing systems, has attracted plenty of attention in recent years with urgent needs. Herein, a highly sensitive flexible pressure sensor based on conducting polymer (CP)-coated paper is developed via an ultra-simple approach of synthesis and fabrication. This paper-based sensor displays an ultra-low detection limit as low as 0.3 Pa level, and outstanding sensitivity (∼2 kPa −1 , P  ≤ 75 Pa), which can rank the top among that of the reported pressure sensors. The advantages based on paper framework such as low cost, portability, and easy disposability further enhance its feasibility. Meanwhile, combining its rapid and precise response at room temperature and the recognized stability of PPy in the ambient environment, the sensor would ensure direct and continuous environment monitoring with low energy consumption. [ABSTRACT FROM AUTHOR]

In recent years, paper-based point-of-care testing (POCT) has been widely used in medical diagnostics, food safety and environmental monitoring. However, a high-cost, time-consuming and equipment-dependent sample pretreatment technique is generally required for raw sample processing, which are impractical for low-resource and disease-endemic areas. Therefore, there is an escalating demand for a cost-effective, simple and portable pretreatment technique, to be coupled with the commonly used paper-based assay (e.g. lateral flow assay) in POCT. In this review, we focus on the importance of using paper as a platform for sample pretreatment. We firstly discuss the beneficial use of paper for sample pretreatment, including sample collection and storage, separation, extraction, and concentration. We highlight the working principle and fabrication of each sample pretreatment device, the existing challenges and the future perspectives for developing paper-based sample pretreatment technique. [ABSTRACT FROM PUBLISHER]

The development of cost-effective sensing system for Hg2+ quantitation is highly demanded for environmental monitoring. In this work, we reported an on-site, rapid and portable smartphone-based Hg2+ sensing system integrating coumarin-modified paper as a probe and smartphone readout device as a processing platform. For fluorescent sensing of Hg2+, the modified paper was fabricated by chemically grafting a coumarin-based probe N-((7-hydroxy-coumarin-3-yl)carbamothioyl)acetamide (HCCA) onto paper, and its physicochemical properties and sensing performance were characterized by elemental analysis, FTIR, XPS, SEM, and fluorescence spectral analysis. The modified paper displayed high selectivity and sensitivity for Hg2+, accompanied with a distinct fluorescence color change. For portable detection of the fluorescent sensors, a smartphone readout device was designed, consisting of a removable 3D-printed hardware device and an application. Remarkably, the smartphone readout device in cooperation with the modified paper is highly selective and sensitive to Hg2+ with the limit of detection (LOD) of 0.46 ppb, which avoids the requirement of sophisticated equipment and complex operation. The cost-effective sensing system based on smartphone shows a great potential for monitoring of Hg2+ in environmental water. [Display omitted] • A coumarin-modified paper was fabricated by chemical grafting. • The modified paper showed good fluorescent sensing performance for Hg2+. • A smartphone readout device was designed containing hardware and software. • The smartphone-based sensing system could quantify Hg2+ reliably and portably. [ABSTRACT FROM AUTHOR]

A standard desktop printer with multiple ink cartridges can accurately deposit a broad variety of biomaterials on microfluidic paper-based analytical devices (μPADs) which have been extensively applied to environmental monitoring and screening of food and beverage contamination. Finding ways to realize sample quantitative control by tuning the CMYK value, however, remains challenging. Herein, we studied the influence of the CMYK value on the ink volume jetted by ink cartridges. The regularity research on a single-color and two-colors was performed in two print mode-grayscale printing and color printing. The results demonstrated that the number of ink dots increased with the increase of the gray value and opacity value, which means that the amount of the bio-ink increases with the increase of the CMYK value. The 3,3′,5,5′-tetramethylbenzidine–horseradish peroxidase–hydrogen peroxide, glucose oxidase–horseradish peroxidase and bull serum albumin–citrate buffer–tetrabromophenol blue systems were chosen as examples to prove the print regularity. Samples and assay reagents can be quantitatively deposited on a substrate by adjusting the CMYK value with as many as four ink cartridges. The present approach has been successfully applied to assay the targets in real serum samples, showing the potential application of the most common office piezoelectric printer in μPADs. [ABSTRACT FROM AUTHOR]

Highlights • Definition of passive envelope indexes and caracterization of libraries in La Plata. • Environmental monitoring: achievement of preventive conservation indexes. • Correlation between passive envelope indexes and preventive conservation indexes. • Determination of the most influential passive envelope indexes for the achievement of preventive conservation indexes. Abstract The common approach for libraries to preserve their paper-based collections from irreversible deterioration is by controlling quantitative parameters, such as temperature and relative humidity. Variations of these parameters for preventive conservation can be expressed by the "performance index" (PI) and the "amplitude index" (AI). Building envelope is the first filter of the external climate, buffering the external weather fluctuations and maintaining the building's indoor climate stable. Its shape, window areas and envelope materials are the most influential parameters. As they capture the relationship of a few geometric and physical variables with the building's performance, the envelope characteristics can be expressed as certain passive envelope indexes. This paper studies the relationship of certain passive envelope indexes and the preventive conservation indexes for books for several libraries and archives located in La Plata, Argentina. The results show the impact of every passive envelope index upon the preventive conservation indexes. The compactness, heaviness, adjacency to spaces and adjacency to ground have a positive linear correlation meanwhile transparency and global transmittance are parameters with a negative correlation. In general, the most influential parameter is the relative area adjacent to other spaces, followed by global transmittance, transparency, heaviness, relative area adjacent to ground and compactness. [ABSTRACT FROM AUTHOR]

Developing an inexpensive, sensitive, and point-of-use biosensor for pesticide detection is becoming an important area in sensing. Such sensors can be used in food packaging, agricultural fields, and environmental monitoring of pesticides. The present investigation has developed a zinc oxide (ZnO)-based biosensor on porous, flexible substrates such as carbon paper and carbon cloth to detect organophosphates such as paraoxon (OP). Here, the influence of morphology and underlying substrate on biosensor performance was studied. The biosensors were fabricated by immobilizing the acetylcholinesterase (AChE) enzyme on ZnO, which is directly grown on the flexible substrates. The ZnO biosensors fabricated on the carbon cloth demonstrated good performance with the detection limit of OP in the range of 0.5 nM–5 µM, higher sensitivity, and greater stability. [ABSTRACT FROM AUTHOR]