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Co‐contamination of mycotoxins produced by fungi in foodstuffs and feeds causes a tremendous health risk to humans and animals. The simultaneous detection of multiple mycotoxins using a cost‐effective and point‐of‐care technology is key to ensuring food safety. In this study, a disposable biosensor with two individual sensing channels is prepared on an affordable cellulose paper substrate and used to simultaneously detect fumatoxin B1 (FB1) and aflatoxin B1 (AFB1). The biosensor pattern is outlined by polydimethylsiloxane (PDMS) and the hydrophobic interface of the sensing channels is created using octadecyltrichlorosilane (OTS). Semiconducting single‐wall carbon nanotubes (s‐SWCNTs) are deposited onto the central zones to serve as the sensing elements and SWCNTs are deposited into the bilateral areas as wire. After functionalization of the s‐SWCNTs, anti‐FB1 and anti‐AFB1 are separately immobilized on the different sensing regions to capture the targeted mycotoxins. Under the optimal conditions, this developed s‐SWCNTs‐based biosensor array achieved a limit of detection (LOD) of 8.23 pg mL−1 for FB1 and 7.48 pg mL−1 for AFB1. As a demonstration, spiked corn samples are measured using this biosensor and recovery rates are not inferior to commercial enzyme‐linked immune sorbent assay (ELISA) kits. Overall, the cost‐effective, highly sensitive, and multiplexed biosensor platform fabricated by this approach shows great potential for detecting multiple mycotoxins. [ABSTRACT FROM AUTHOR]

Electrochemical paper-based analytical devices (ePADs) offer an innovative, low-cost, and environmentally friendly approach for real-time diagnostics. In this study, we developed a functional all-inkjet paper-based electrochemical immunosensor using gold (Au) printed ink to detect salivary cortisol. Covalent binding of the cortisol monoclonal antibody onto the printed Au surface was achieved through electrodeposition of 4-carboxymethylaniline (CMA), with ethanolamine passivation to prevent non-specific binding. The ePAD exhibited a linear response within the physiological cortisol range (5–20 ng/mL), with sensitivities of 25, 23, and 19 Ω·ng/mL and R2 values of 0.995, 0.979, and 0.99, respectively. Additionally, interference studies against tumor necrosis factor-α (TNF-α) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) yielded excellent results. This novel ePAD, fabricated using inkjet printing technology on paper, simplifies the process, reduces environmental impact, and lowers fabrication costs. [ABSTRACT FROM AUTHOR]

In this study, a redox reaction is employed to synthesize manganese oxide (Mn3O4) nanoparticles using potassium permanganate as a precursor in the presence of diethyl amine. The structural characterization reveals the formation of the tetragonal phase of Mn3O4 nanoparticles with a space group of I41/amd. A free‐standing Mn3O4‐based paper electrode is fabricated and its electrochemical performances are investigated. The electrode exhibits a maximum specific capacitance value of ~353 F g−1 and an areal capacitance of ~530 mF cm−2 at a current density of 0.2 A g−1. A symmetric supercapacitor‐based device is also designed using Mn3O4 nanoparticles as an active material in a gel electrolyte configuration. The Mn3O4 device achieves specific and areal capacity values of ~208 mAh g−1 and 260 mA cm−2, respectively, at a current density of 0.3 A g−1. The device delivers maximum energy and power density values of ~104 Wh kg−1 and ~220 W kg−1, respectively, with ~92 % specific capacity retention at 0.3 A g−1 after 5000 cycles. The above results suggest that the Mn3O4‐based device has the potential for energy storage applications. [ABSTRACT FROM AUTHOR]

Abstract Co‐contamination of mycotoxins produced by fungi in foodstuffs and feeds causes a tremendous health risk to humans and animals. The simultaneous detection of multiple mycotoxins using a cost‐effective and point‐of‐care technology is key to ensuring food safety. In this study, a disposable biosensor with two individual sensing channels is prepared on an affordable cellulose paper substrate and used to simultaneously detect fumatoxin B1 (FB1) and aflatoxin B1 (AFB1). The biosensor pattern is outlined by polydimethylsiloxane (PDMS) and the hydrophobic interface of the sensing channels is created using octadecyltrichlorosilane (OTS). Semiconducting single‐wall carbon nanotubes (s‐SWCNTs) are deposited onto the central zones to serve as the sensing elements and SWCNTs are deposited into the bilateral areas as wire. After functionalization of the s‐SWCNTs, anti‐FB1 and anti‐AFB1 are separately immobilized on the different sensing regions to capture the targeted mycotoxins. Under the optimal conditions, this developed s‐SWCNTs‐based biosensor array achieved a limit of detection (LOD) of 8.23 pg mL−1 for FB1 and 7.48 pg mL−1 for AFB1. As a demonstration, spiked corn samples are measured using this biosensor and recovery rates are not inferior to commercial enzyme‐linked immune sorbent assay (ELISA) kits. Overall, the cost‐effective, highly sensitive, and multiplexed biosensor platform fabricated by this approach shows great potential for detecting multiple mycotoxins.

Electrochemical paper-based analytical devices (ePADs) offer an innovative, low-cost, and environmentally friendly approach for real-time diagnostics. In this study, we developed a functional all-inkjet paper-based electrochemical immunosensor using gold (Au) printed ink to detect salivary cortisol. Covalent binding of the cortisol monoclonal antibody onto the printed Au surface was achieved through electrodeposition of 4-carboxymethylaniline (CMA), with ethanolamine passivation to prevent non-specific binding. The ePAD exhibited a linear response within the physiological cortisol range (5–20 ng/mL), with sensitivities of 25, 23, and 19 Ω·ng/mL and R2 values of 0.995, 0.979, and 0.99, respectively. Additionally, interference studies against tumor necrosis factor-α (TNF-α) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) yielded excellent results. This novel ePAD, fabricated using inkjet printing technology on paper, simplifies the process, reduces environmental impact, and lowers fabrication costs.

Paper-based devices have aroused researchers' enormous interest due to the increasing need for disposable flexible optoelectronic devices. Here, we used a straightforward painting method to integrate semiconducting materials on an A4 paper substrate to create high-performance photodetectors. A solvent-free 2D SnSe film painted on paper allowed electrons to separate from holes more effectively, thereby reducing the level of recombination between holes and electrons. The paper-based SnSe photodetectors that we prepared demonstrated a robust, sensitive response over a wide range of spectral ranges from ultraviolet (254 nm) to near-infrared (1550 nm). The devices were characterized by fast response times (rise time of 0.066 s and fall time of 0.066 s). A high-performance photodetector was achieved by combining a photoconductive and pyroelectric effect. Additionally, we constructed the carbon nanotube (CNTs) films as electrodes in order to form an ohmic contact between the carbon nanotubes and the semiconductor, and the photogenerated electrons were able to efficiently move through the carbon nanotubes. Our research could contribute to the development of flexible photodetection devices that are low-cost, eco-friendly, and disposable. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to predict a suitable paper substrate which has high capillary pressure with the tendency of subsequent fluid wrenching in onward direction for the fabrication of microfluidics device application. Design/methodology/approach: The experiment has been done on the WhatmanTM grade 1, WhatmanTM chromatography and nitrocellulose paper samples which are made by GE Healthcare Life Sciences. The structural characterization of paper samples for surface properties has been done by scanning electron microscope and ImageJ software. Identification of functional groups on the surface of samples has been done by Fourier transform infrared analysis. A finite elemental analysis has also been performed by using the "Multiphase Flow in Porous Media" module of the COMSOL Multiphysics tool which combines Darcy's law and Phase Transport in Porous Media interface. Findings: Experimentally, it has been concluded that the paper substrate for flexible microfluidic device application must have large number of internal (intra- and interfiber) pores with fewer void spaces (external pores) that have high capillary pressure to propel the fluid in onward direction with narrow paper fiber channel. Originality/value: Surface structure has a dynamic impact in paper substrate utilization in multiple applications such as paper manufacturing, printing process and microfluidics applications. [ABSTRACT FROM AUTHOR]

Due to the rising problem of deforestation, slow renewability, and higher cost of wood sources, it is of great importance for the paper and packaging industry to find suitable, environmentally friendly alternative sources of cellulose fibers. Much of the research has focused on studying the use of non-wood sources from various annual or perennial plants from which cellulose fibers can be obtained with equal quality to those from wood sources, since they are a fast-growing, renewable, and cheap source of fibers. This research focuses on the laboratory production and stability valorization of a paper substrate for packaging containing virgin fibers from triticale straw mixed with recycled wood pulp in various amounts up to 30%, printed with black ink through a simulation of the offset printing technique under controlled conditions. For stability analysis, printed paper substrates were subjected to three treatments essential for packaging: aging, rubbing, and chemical treatment. The stability of the prints was evaluated after treatments though spectrophotometric measurements (ΔE*ab, ΔR, ΔL*, Δa*, Δb*) and Fourier transform infrared analysis. The aging, rubbing, and chemical stability of the prints with the addition of triticale virgin fibers was improved for all product packaging except for products containing soybean oil. [ABSTRACT FROM AUTHOR]

Purpose: Sensing technology has been extensively researched and used due to its applications in industrial production and daily life. Due to inherent limitations of conventional silicon-based technology, researchers are now-a-days paying more attention to flexible electronics to design low-cost, high-sensitivity devices. This observational and analytical study aims to emphasis on carbon monoxide gas sensor. This review also focuses the challenges faced by flexible devices, offers the most recent research on paper-based gas sensors and pays special focus on various sensing materials and fabrication techniques. Design/methodology/approach: To get the better insight into opportunities for future improvement, a number of research papers based on sensors were studied and realized the need to design carbon monoxide gas sensor. A number of parameters were then gone through to decide the flexibility parameter to be considered for design purposes. This review also focuses on the challenges faced by flexible devices and how they can be overcome. Findings: It has been shown that carbon monoxide gas, being most contaminated gas, needs to be fabricated to sense low concentration at room temperature, considering flexibility as an important parameter. Regarding this parameter, some tests must be done to test whether the structure sustains or degrades after bending. The parameters required to perform bending are also described. Originality/value: Due to inherent limitations of conventional silicon-based technology, now-a-days attention is paid towards flexible electronics to design low-cost, high-sensitivity devices. A number of research articles are provided in the literature concerning gas sensing for different applications using several sensing principles. This study aims to provide a comprehensive overview of recent developments in carbon monoxide gas sensors along with the design possibilities for flexible paper-based gas sensors. All the aspects have been taken into consideration for the fabrication, starting with paper characterization techniques, various sensing materials, manufacturing methodologies, challenges in the fabrication of flexible devices and effects of bending and humidity on the sensing performance. [ABSTRACT FROM AUTHOR]

To overcome the problems of easy aggregation, poor reproducibility and homogeneity of metal nanosols, a SERS substrate with good sensitivity, homogeneity and reproducibility was designed and prepared for the detection of disease markers in urine. Silver nanocubes (Ag NCs) were firstly prepared and then dispersed in cationic cellulose (C-CNF) to form a homogeneous gel, which was dropped on a filter paper to develop a substrate with good SERS activity. This substrate combines the superior SERS properties of Ag NCs with the stability of C-CNF and has a minimum detection concentration of 10−9 M for R6G. The homogeneity of this substrate was good and the RSD value was much <20 %. The SERS substrate was employed for the quantification of creatinine and uric acid, with linear ranges were 5 × 10−3–5 × 10−7 M and 10−2–10−6 M. The recoveries of creatinine and uric acid were calculated to be 98.3 % ∼ 103.12 % and 96.72 % ∼ 104.48 %, respectively, in the spike recovery experiments, with the relative standard deviations of <10 %. The experimental results show that the method can provide a scientific and reliable experimental basis for screening, condition monitoring and treatment of kidney and other diseases. • Preparation of a highly sensitive, stable and homogeneous Ag NCs/C-CNF paper-based SERS substrate. • Positively charged C-CNF hydrogel and Ag NCs repel each other to form NCs arrays. • The Ag NCs/C-CNF paper-based SERS substrate enables sensitive detection of creatinine and uric acid. [ABSTRACT FROM AUTHOR]

Anticounterfeiting of goods is an urgent need both for luxury and cheap everyday life products. Their identification is usually based on overt technologies as printed codes, easy to produce but to be cloned as well. In this work, a standard QR‐code printed on office paper but hidden by a plasmonic multilayer system is exploited. The covert label is then protected by a peculiar reading mechanism, which is only possible in specific illumination conditions. The overall photonic structure consisting of the metal –insulator –metal –insulator, the printed random QR code and the paper substrate results in a strong physical unclonable function (PUF) that provides a multi‐level identification and authentication of goods ensuring uniqueness of nominally quasi‐identical tags and resistance to tampering/cloning attacks. The proposed paper‐based camouflage physical unclonable function (PC‐PUF) can be easily fabricated by low cost and large area techniques paving the way for an easy integration in an industrial supply‐chain as tags devoted to protect consumer merchandises. [ABSTRACT FROM AUTHOR]

Recently, as the use of wearable devices and the demand for eco-friendly energy have increased, many studies have been conducted on triboelectric nanogenerators (TENGs), which can economically harvest energy. Paper is considered a promising substrate and frame material that can be used to manufacture self-powered TENGs, owing to its flexibility, low cost, and accessibility. Herein, we present a sandwich-structured foldable paper-based TENG (FP-TENG) that comprises flexible materials and uses paper as a substrate. The FP-TENG can generate up to 572 mW/m2 of power via contact–separation of the triboelectric electrified body at the top and bottom. With more folds of the FP-TENG, the triboelectric cross-sectional area increases, and, thus, the electrical output increases. In addition, the proposed TENG exhibits excellent durability without signal degradation under 5000 cycles of repeated pushing motions. To demonstrate its practicality, the FP-TENG was manufactured in the form of a wristwatch Velcro and connected to an electronic watch panel to supply power. Various deformations are possible with origami, and they can drive wristwatches through external forces. Therefore, the FP-TENG is expected to be utilized as a sustainable and promising eco-friendly energy source for small electronic devices. [ABSTRACT FROM AUTHOR]

Advancements in technology have made it easier to construct flexible broadband photodetectors for wearable devices, improving light harvesting and detecting capabilities. This work described a new study that used bimetallic sulfide nanosheets (FeSnS) to produce flexible and broadband photodetectors on paper substrates using hand-print method. A simple, economical, one-step hydrothermal technique was employed to synthesise FeSnS materials, which were characterised using XRD, UV–Vis Spectroscopy, FESEM, EDS, XPS, and UPS. Photodetection tests found that 2-FeSnS (Fe at 2 wt%) outperformed similar work on paper-based devices, with a responsivity of 32.4 mA/W under a 470 nm incident wavelength, high specific detectivity, and a response time of 1.16 s. Durability and flexibility testing validated the robustness of the device. The use of a simple hydrothermal synthesis and hand-print fabrication method to create high-performance, eco-friendly, and flexible photodetectors is novel, expanding their potential applications in wearable electronics, environmental monitoring, and low-cost disposable sensing platforms. • Using bimetallic sulfide (FeSnS) nanosheets in photodetectors taps into their unique properties, enhancing performance. • FeSnS materials are synthesized using a single-step hydrothermal technique. • Hand-printed devices on flexible, eco-friendly paper substrates combine sustainability with cost-effective production. • High specific detectivity, fast response times (1.16), and high responsivity (32.4 mA/W) were attained at 470 nm wavelength. [ABSTRACT FROM AUTHOR]

Low-cost, flexible broadband photodetectors fabricated from two-dimensional transition metal chalcogenides have garnered attention because of their excellent absorption coefficient and photoconductivity. Likewise, vertical heterojunctions fabricated from two two-dimensional (2D) transition metal chalcogenides (TMCs) also have drawn major curiosity lately owing to their superior optical performance. This work reports a p-p type II vertical Van der Waal's heterojunction structure by depositing thin film of NiS over SnS on a flexible paper substrate. Morphological and structural characterization confirms presence of a rhombohedral β-NiS crystal structure along with traces of Ni(OH) 2 on orthorhombic SnS nanoparticles. The device fabrication method made use of the inexpensive, clean room free SILAR (Successive Ionic Layer Adsorption and Reaction) technique. A purposeful modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment. The fabricated device records optical responsivity of 0.92 mA/W under UV illumination, 5.32 mA/W under Visible illumination, and 0.8 mA/W under NIR illumination. A maximum EQE of 1.3 % is observed along with superior response times of 0.114 s (UV),0.103 s (Visible) and 1.34 s (NIR). The acquired photo response is due to superior absorption property of NiS in UV region and SnS in the visible and NIR region. The difference in fermi level between two materials causes efficient separation of the charge carriers that results in junctional electric field upon light illumination. The device underwent flexibility testing and shown exceptional resistance to bending force making it suitable for numerous applications like wearable healthcare monitoring, security purposes and flexible image sensors. [Display omitted] • This work introduces a broadband photodetector using type II vertical Van der Waal's heterojunction fabricated from 2D-photoresponsive Transition metal chalcogenides. • The device is fabricated on cellulose paper using Successive Ionic Layer Adsorption and Reaction(SILAR)technique having remarkable responsivities in UV, visible, NIR region along with superior response times of 0.114 s,0.103 s and 1.34 s and high photostability up to 1050 bending cycles. • A modification of narrow bandgap property of NiS is done by depositing it in an alkaline environment which makes it suitable for broadband photodetection applications. [ABSTRACT FROM AUTHOR]

A Self-powered energy and display system (SPEDS) has been developed by integrating functionalities of energy harvesting, storage, and multicolor display, heralding innovative solutions for integrated electronic devices. An all-in-one multi-information SPEDS is proposed through incorporating a multicolor electrochromic supercapacitor device (ESCD) with a dual-sided triboelectric nanogenerator (TENG), all screen-printed on a paper substrate. The synergistic enhancement in the conductive, capacitive, and electrochromic performance is realized by exploiting the complementary properties of PEDOT:PSS/PANI:PSS to form a simplified structure of ESCD, in which the electrode and electrochromic layers are integrated into one shared layer, resulting in a wide color gamut and an enhanced capacitive performance of 3.4 mF/cm². Electrochromic electrodes having identical composition exhibit independent color changes at the anode and cathode, thereby featuring a combined color display indicating multi energy-related information. Moreover, the conductive layer fabricated through patterned printing on the paper substrate, serves as both the electrode layer for TENG and the interconnect circuitry with the prepared ESCD. Furthermore, a double-sided TENG was realized by exploiting the triboelectric properties of the paper substrate and then a self-powered energy display wristband was constructed, exemplifying a novelty application utilizing the multi-information indicator properties for energy display derived from the dual-sided friction power generation. [Display omitted] • Complementary features synergistically enhance energy storage and color modulation. • Dual-electrode construction with identical composition achieves combined color display. • A dual-sided paper-based TENG is developed. • All-in-one SPEDS printed and integrated on a single paper substrate. [ABSTRACT FROM AUTHOR]

The need for disposable, simpler, and accurate paper‐based analytical devices represents an open research field that is focused on simpler fabrication methods. To achieve this, four feasible methodologies are proposed for the direct printing of an electrochemical sensor on a biodegradable paper substrate using commercial gold and silver inks, which are compatible with inkjet printing technology. Four substrate treatment strategies are evaluated: printing the active elements directly on the hydrophilic bare paper, a hydrophobic gas‐phase coating over all the substrate, a hydrophobic silane ink that is selectively printed on the paper, and a hydrophobic coating that is selectively printed and blocks the surface porosity. Thanks to the ability of the inks to conform the cellulose fibers, the resulting working electrodes tune their electrochemical active area, showing higher active electrochemical areas when the roughness is increased. The most planar consideration is achieved blocking the paper porosity with SU‐8 and the direct printing on bare paper maximizes the electrochemical response with the smallest geometric area, with current values 2.7‐times higher than the theoretical one. Although all methods allow a functional electrochemical sensor, the highest reproducible results are accomplished with the blocked paper, consequently allowing a higher controlled and robust manufacturing approach. [ABSTRACT FROM AUTHOR]

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

Metal halide semiconductors have huge potential on X‐ray detection, due to their high atomic number, adjustable photoluminescence wavelength, superior stability, and simple fabrication process. Here, cesium lead halide nanocrystals (CsPbX3 NCs) are fabricated on paper substrate as scintillator screen for the first time. By means of all‐solution processed spray‐coating method with optimization of polymethyl methacrylate, large‐area (>600 cm2) and low‐cost (0.0975 dollar cm−2) flexible scintillator screens are obtained with high resolution (≈5 lp mm−1), low detection limit (2.97 μGy s−1), high light yield (≈30000 photons/MeV), and fast response speed (<15 ms). The screen can achieve high‐resolution X‐ray non‐distortion imaging for non‐planar objects and realize battery check and safety monitoring at a broad range of photon energy (10–160 keV). In addition, real‐time dose rates can be easily estimated through counting the luminous arcs of the designed visible indicator. More important, the screen shows remarkable tolerance to high‐dose X‐ray radiation (tolerance over 60 Gyair continuous radiation with only 3% performance degradation), water soaking (2000 h), and conventional storage (over 300 days without apparent deterioration under ambient conditions). Hence, this work may provide huge potential in the field of medical diagnosis, non‐planar detection, and safety monitoring in the future. [ABSTRACT FROM AUTHOR]

Coated paper sheets were prepared by immobilizing a thin coating layer of cross-linked polydimethylsiloxane (PDMS) and inorganic particles onto Whatman filter paper Grade 1 (WFP) substrates. Several coatings that differed in terms of their PDMS molecular masses were sprayed onto WFP substrates to investigate the effect of this variation on the (i) wettability and (ii) mechanical properties of the samples. Different samples having clay or silica particles in the coating formulation were investigated separately. Nonwettable coated paper sheets with promising mechanical properties were achieved and further investigated in terms of (iii) thermal resistance. [ABSTRACT FROM AUTHOR]

Here we report broad range, tunable and foldable paper-based passive components and filter circuits. Reported electronics fabricated through solvent-free garage fabrication techniques using inexpensive and off-the-shelf materials like graphite pencils, aluminum foil, copper tape, paper, and such Previously reported paper-based passive electronic circuits are single-valued and lack real-time tunability. Broad range passive components and tunable RC filter circuits fabricated through inexpensive, eco-friendly, and cleanroom-free fabrication techniques like hand drawing of graphite pencils on paper and garage fabrication techniques like cutting-pasting of readily available materials demonstrated expected functionalities with tunable cut-off frequencies. Cut-off frequencies of low and high pass filters are tunned from 15 to 190 kHz by penciling graphite flakes of different graphite content pencils. The paper-based passive electronic circuits showed robust performance against applied stress during bending and folding. To the best of our knowledge, no studies have been reported on tunable paper-based passive electronic circuits. These paper-based electronic components and circuits open pathways for green and foldable power electronics, flexible and foldable printed circuit boards and consumer electronics, touchpads, disposable security systems, soft robotics, and many more. [ABSTRACT FROM AUTHOR]

Sustainable and low-cost cellulose-based metallisation is the prerequisite for wearable and disposable electronics fabrication. In this paper, to realize the simplified, low-cost and high efficient metallisation, a new method had been proposed without both the noble metal activators and the corrosive chemicals. The modified electroless plating processes had been employed in activation and deposition procedure. The nickel ions were first physiadsorbed on the cellulose paper (CP) fibers and then reduced into clusters by reducing agent which can act as the seeds to initiate the electroless plating process. The gold galvanic displacement was conducted further to modify the nickel surface. Via these processes, the cellulose paper was metallised with Ni-P and Au/Ni-P successfully. The morphological and microstructural properties of the resulted Ni-P/CP and Au/Ni-P/CP hybrids were evaluated. The Ni-P/CP composites had a low surface resistance below 0.5 Ω sq-1 while the Au/Ni-P/CP composites are below 0.1 Ω sq-1. The relationship between the mechanical and electrical properties with the plating parameters is discussed. The results indicated that Au/Ni-P/CP had good electrical conductivity and mechanical flexibility. Finally, the application demonstration for supercapacitor with the modified metallisation method was exhibited. This work offers a facile and non-toxic path to develop high-performance metallisation for functional cellulose-based materials.

For the problems of the current flexible metal interconnect conductor based on the inkjet printing - based printed electronics technology, such as easy clogging of nozzles, poor accuracy of conductor lines, and the process requires heating, a reliable and low - cost flexible metal interconnect conductor is proposed, which is the method of preparing metal interconnect conductor by combining the roll - to - roll printing process and the chemical deposition technique. The flexible substrate material used herein is Teslin paper, which has more excellent mechanical strength and water resistance than ordinary paper. A roll - to - roll flexography machine is used to print the metal interconnect conductor pattern on the flexible substrate material. The ink film on the substrate is dried by ultraviolet curing technology, and the metal copper conductor is obtained on the substrate surface by chemical deposition technology. The advantage of this craft is that the prepared metal copper conductor has high accuracy and the process do not require high temperature equipment. In addition, since a roll - to - roll 1lexography printing machine is utilized, it has the prospect of large - scale flow production in the industry. The SEM, XRD, EDS and adhesion test of the metal layer of the metal interconnect conductor prove that the surface of the metal layer of the interconnect conductor has advantages including dense surface, high crystallinity, good adhesion, low resistivity ( 2.62 x10-8 Ω· cm), and excellent mechanical prope1iies (1000 bending test) . [ABSTRACT FROM AUTHOR]

A superhydrophobic paper with excellent robustness was fabricated by roll coating with modified nano-TiO2. First, nano-TiO2 particles were hydrophobically modified by γ-aminopropyltriethoxysilane and 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (POTS). Then the paper coating composed of modified nano-TiO2 particles as pigments and epoxy resin (EP) as adhesives was coated on a paper surface to create the desired surface morphology and surface energy. Compared with the uncoated filter paper, the prepared paper showed an improved rough surface morphology owing to the uniform layer of TiO2 microclusters deposited on the fiber network. The superhydrophobic paper exhibited water contact angles (WCA) about 153° ± 1.5°, and water sliding angles (WSA) about 3.5° ± 0.5°, low surface adhesion and excellent bounce ability. The superhydrophobic paper can withstand a variety of wear and tear, such as tape stripping and knife scraping. The as-prepared superhydrophobic paper showed mechanical durability even after 20 wear cycles with sandpaper,thus sustaining excellent superhydrophobicity on the filter paper surface. Moreover, it remains fully functional even in environments with high concentrations of acid and alkali for 96 h. The superhydrophobicity was not affected after storage for 6 months in a natural environment. It was confirmed that the superhydrophobic paper surface exhibited excellent chemical stability, long-term stability and self-cleaning properties. The entire production process was operated under normal environment, without complex equipment; and, as such, has the possibility for large-scale production and application in industry. [ABSTRACT FROM AUTHOR]

This paper presents the design, fabrication, and characterization results of a paper-based, low-cost, easy-to-use, comfortable and wearable tactile sensor array for human health monitoring applications. Paper substrate and spray-deposited metallic electrodes and traces are employed to achieve a low fabrication cost. Capacitive sensing scheme employing a deformable triangular PDMS sensing membrane is chosen due to its high sensitivity and zero DC power dissipation. Trade-offs among different sensor array designs are investigated to achieve an optimal design, which consists of a $1\times 5$ sensor array occupying an area of 10 mm $\times10$ mm. Each sensor in the array achieves a nominal capacitance value and sensitivity of approximately 1 pF and 30 fF/mmHg, respectively. Fabricated sensor array can be comfortably attached to an individual’s temporal region and ankle area to monitor real-time blood pressure (BP) pulse waveform with high fidelity, from which heart rate and heart rate variability information can be accurately obtained. In addition, the prototype sensor array demonstrates its capability of detecting atrial fibrillation (AFib) from BP pulse waveform measured from an AFib patient. [2020-0179] [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 porous characteristic of tlie paper substrate causes penetration and difusion of tlie li(_uid material on the surface. Therefore，it is extremely difficult to form an RFIDtag metal antenna by electroless deposition on the surface of the paper substrate. Aiming at this problem，the stannous chloride colloid solution \as applied to avoid the catalytic ink penetration in the paper - based substrate. Moreover， paper substrate was immersed in chitosan solu- tion， which could bring functional group and improve the conductivity and adhesion of RFID metal antenna. The SEM，XRD，EDS and adhesion test of the metal layer antenna of the RFID tag proved that the surface of the metal layer of tlie tag antenna had advantages including dense surface， high crystallinity， good adhesion， low resistivity (2.58X10-8 # + cm)，good mechanical properties (1000 bending test). [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) spectroscopy is an effective approach for trace-level detection of molecular substance. Plasmonic metallic nanostructures with high distribution densities and small gap widths are always expected for constructing SERS substrates. We report here a paper-based SERS substrate, where the three-dimensional (3D) network of paper fibers was used as the platform for supporting the gold nanoparticle clusters. Such a 3D arrangement of plasmonic porous clusters supplies high-density hotspots with large total volume and large surface area for the interaction with molecules. Comparison between different papers found that the filter papers commonly available in labs are the best choice. An enhancement factor higher than 104 has been achieved in the detection of R6G molecules. The preparation of such SERS substrates is very simple and convenient, implying low-cost, disposable, and environment-friendly SERS techniques. Furthermore, the paper-based flexible SERS substrates can be easily tailored into different shapes and sizes for fitting different applications. [ABSTRACT FROM AUTHOR]

• MoS 2 /Bi 2 S 3 heterojunction photodetectors were prepared on nylon paper substrates. • The performance is different when the photodetectors are prepared in different order. • The devices exhibit good photoresponse in the range of 365 nm-980 nm. • The response time of the MoS 2 /Bi 2 S 3 photodetector is only 53 ms under UV light. • The devices have excellent bendability and stability. Flexible photodetectors are receiving increasing attention due to their promising applications in wearable optoelectronic devices, bendable imaging sensors, and implantable optoelectronic devices. In this work, a novel strategy for constructing flexible photodetectors based on a hybrid heterojunction of Bi 2 S 3 and MoS 2 was proposed. The devices are fabricated on a biodegradable paper substrate using a simple hydrothermal process and vacuum filtration techniques and exhibit a broadband photoresponse from ultraviolet to near-infrared (NIR). Especially, the specific detectivity (D*) of the MoS 2 /Bi 2 S 3 photodetectors is 3.25 × 1010 Jones under 365 nm, and the rise/decay time is 0.053 s/0.119 s in the NIR region. In addition, the performance of Bi 2 S 3 /MoS 2 photodetectors realizes a maximum responsivity (R) of 27.45 mA/W and a fast response time (∼0.470 s). These devices exhibit a stable photoresponse under repeated bending. Inexpensive materials and easy fabrication techniques provide a viable strategy for the design and performance optimization of flexible bimetallic sulfide photodetectors. [Display omitted] [ABSTRACT FROM AUTHOR]

A compact, flexible crossed-dipole circular polarized antenna using commercially available paper substrate is presented which caters North American frequency band. The crossed-dipoles have meandered lines for reduction of size as well as increased inductivity in the antenna. Dipoles have asymmetric T-shaped rectangular endings to provide the required compactness. Two semicircles are induced between the orthogonal dipoles and meandering matching structure to accomplish circular polarization excitation. Good impedance matching with the chip is achieved through a modified meander line matching structure. The proposed design dimensions are 32 × 32 × 0.4 mm3. Systematic analysis revealed the results comprising circular polarization 3dB-AR bandwidth of 11MHz (909–920 MHz) and power transmission coefficient bandwidth of 36MHz (900–936 MHz). Time delay between interrogating signal and backscattered signal is measured and relative distance is calculated. Linear Least Square (LLS) method is applied to approximate the position of tag in interrogation area. The proposed tag is placed at known locations and its position is measured to analyze accuracy of the method by simulating the positioning algorithm code in MATLAB. Six valid tag positions 0.5–2 m read range and 0°–150° angular resolution has been investigated.

This study presents the design, simulation, implementation, and experimental characterization of a paperbased perforated disposable weight sensor system with a double piezoresistive layer. The demonstrated system is designed to achieve highly sensitive weight sensing operations with low-cost materials. For that purpose, the main fabrication material of the proposed disposable sensor is selected as a 289-µm-thick Strathmore 400 series Bristol paper. Approximately 48-µm-thick piezoresistive graphite paste is coated onto both sides of the paper-based cantilever beam with the aim of acquiring more sensitive weight-sensing capability. Additionally, the proposed paper-based structure has rows of closely spaced perforations at prespecified locations to facilitate the bending of the cantilever beam and to further increase the sensitivity of the system. A peripheral electronic read-out circuitry is developed and integrated into the system. It is experimentally demonstrated that the proposed weight-sensing system can measure miniature weights ranging to 2 g with a resolution of 20 mg. The implemented sensor has a sensitivity of 17.13 mV/mN or 168.01 mV/g. [ABSTRACT FROM AUTHOR]

A new planar sorptive phase based on the simple immobilization of polymeric ionic liquids on paper is proposed. The sorptive phase can develop hydrophobic or mixed-mode (combining hydrophobic and ion exchange) interactions with the target analytes. The polymer is prepared by the Radziszewski reaction, which takes place in aqueous media, and it has been thoroughly characterized by different techniques including infrared spectroscopy, matrix-assisted laser desorption/ionization coupled to high-resolution mass spectrometry and proton nuclear magnetic resonance. Three different strategies aimed to immobilize the polymeric ionic liquid on paper have been evaluated. Among them, simple thermal curing at 120 °C was selected. The as-prepared paper has been evaluated for the extraction of several non-steroidal anti-inflammatory drugs from urine, the analytes being finally determined by liquid chromatography with tandem mass spectrometry. The method detection limits were 3.8, 7.2, 6.8, 9.4, 15.7, and 5.1 μg/L for indomethacin, diclofenac, tolmetin, ketoprofen, naproxen, and ibuprofen, respectively. Calibration models were linear (R2 > 0.9949) up to 1000 μg/L. The intra-day precision, expressed as relative standard deviation and calculated at three different concentrations levels (limit of quantification, 250 μg/L, and 1000 μg/L), varied between 1.1 and 13%. The accuracy, calculated as relative recovery, was in the range from 72 to 95%, thus being considered appropriate. The easiness of polymeric ionic liquid paper synthesis and the multi-sample extraction protocol designed allows the processing of a high number of samples at the same time. Image 1 • The simple synthesis of paper modified with polymeric ionic liquids is presented. • Polymeric ionic liquids are synthesized by the Radziszewski reaction. • The polymer is anchored to conventional paper to synthesize the planar sorptive phase. • The planar sorptive phase is applied for the determination of selected drugs in urine. [ABSTRACT FROM AUTHOR]

In this study, we developed a hydrogen sensor based on a palladium microfiber network on a paper substrate. A 60-nm pure palladium film was deposited on photocopy paper using a vacuum evaporation technique. The photocopy paper was employed as the sensor substrate because of its low cost and the simple and rapid fabrication process. The texture of the microfiber network on the paper greatly increased the surface area to volume ratio for the palladium thin film, which is crucial for rapid response sensors. The experimental results showed that the hydrogen sensor exhibited a rapid response and linear gas response characteristics at room temperature and pressure. The gas response of the paper–substrate sensor was much higher compared with the glass substrate. • Simple and low cost hydrogen sensor fabrication process for mass production. • Large surface to volume ratio for palladium achieved using normal photocopy paper. • Gas response of paper–substrate sensor higher than glass substrate counterpart. [ABSTRACT FROM AUTHOR]

• Single-step bacterial sample preparation combining thermal lysis and DNA amplification on paper in 30 min. • No intermediate intervention or wash steps are needed. • Bacteria are completely disinfected on paper at 60 °C in 5 min for E. coli and 15 min for M. smegmatis. • We achieved a limit of detection of 100 CFU/mL using our integrated assay. Developing sensors for food safety, soil analysis, water quality monitoring and healthcare often requires distinguishing between different species of bacteria. The most rapid, sensitive and specific method to identify bacteria is to analyse their DNA sequence, which comprises of disinfection and lysis of bacterial cells, amplification of the isolated DNA and detection of the amplified sequence. Seamless integration of these steps on a paper substrate is a big challenge. This problem is even more complex for mycobacteria as its thick cell wall structure impedes lysis and the high GC-content of the genome requires careful optimization of enzymatic denaturation. Here we successfully combine thermal lysis and loop-mediated isothermal amplification (LAMP) into a single reaction step on paper. We demonstrate our integrated assay by amplifying DNA from 100 CFU/mL of Escherichia coli (MG1655) and Mycobacterium smegmatis (mc2155) cells in 30 min on a paper substrate. We also confirm that E. coli and M. smegmatis can be completely disinfected on paper by heating at 60 °C for 5 min and 15 min respectively, making this assay safe and suitable for incorporation into diverse paperfluidic sensors for field use. [ABSTRACT FROM AUTHOR]

Abstract Ag triangular nanoplates have been widely used as the SERS substrate due to their anisotropic morphology and sharp corners. In this work, SERS activity of Ag triangular nanoplates on glass and paper substrates was investigated with different concentration and size. A tiny triangular nuclei based synthesis method was employed to produce Ag triangular nanoplates with different size. And the extinction coefficients of Ag triangular nanoplates with different size were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM). With definite concentration, Ag triangular nanoplates with small size showed stronger SERS intensity on glass substrate at high concentrations, while large Ag triangular nanoplates exhibited better SERS effect on paper substrate at low concentrations. The possible reasons for distinct SERS activity of Ag triangular nanoplates on glass and paper were discussed with scanning electron microscope (SEM) characterization. These results exhibited important implications for fabricating Raman substrates using Ag triangular nanoplates and could be applied to the SERS sensing with flexile substrate. Highlights • The extinction coefficients of Ag triangular nanoplates (Ag TPs) with different size were quantified. • Ag TPs showed distinct SERS activity on glass and paper substrates. • Ag TPs with small size showed better enhancement than that of big ones on glass substrates. • Ag TPs with big size exhibited stronger SERS intensity than that of small ones on paper substrates. [ABSTRACT FROM AUTHOR]

A diverse range of materials (e.g., metallic nanoparticles, semiconductor oxides, composites, polymers, and MOFs) have been reported for sensing applications in water samples based on several transduction techniques (e.g., absorbance, fluorescence, Raman, colorimetry, voltammetry, and plasmon resonance). Recently, carbon quantum dots (CQDs) have gained significant interest as fluorescent and small carbonaceous nanostructures for designing sensing devices (either as-produced or through modification) for heavy metals due to their excellent properties (e.g., photostability, facile surface modification, optical tunability, and environmental friendliness). This review provides a comprehensive overview on the role of CQDs as sensors for heavy metals in water. This work will help open up opportunities for the use of CQDs under the diverse field conditions. [ABSTRACT FROM AUTHOR]

Advanced gold (Au) and silver (Ag) nanostructures were produced by laser techniques on printer paper substrate. Surface-enhanced Raman spectroscopy (SERS) analyses of the fungicide mancozeb (Dithane DG) and insecticide thiamethoxam (Aktara 25 BG) in quantities smaller than usually applied in agricultural medicine were performed for the first time assisted by the structures fabricated. The investigations and results show an easy alternative and cheap way to detect small amounts or residue of harmful environmental pollutants, which has a direct bearing on food quality and thus on human health. [ABSTRACT FROM AUTHOR]

A highly efficient, flexible and cost-effective ammonia (NH 3) gas sensor is developed on a biodegradable paper substrate. The polyaniline (PANI) film as an active sensing material was deposited by a simple in-situ polymerization method and optimized for NH 3 detection. The PANI film was investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) for structural and morphological properties. The sensor was tested for its efficiency to detect the NH 3 gas over the concentration range of 12–1000 ppm at room temperature. The sensor showed excellent repeatability, stability and selectivity towards NH 3 detection. At concentrations of 12 ppm (lower level), 200 ppm (intermediate level), and 1000 ppm (higher level), the sensor exhibited effective response values of 3.60, 6.85, and 9.33, respectively. The sensor exhibited a quick response time of 30–9 s when subjected to 12–1000 ppm of NH 3. The sensor can detect ammonia gas in real-time, which makes it useful for identifying rapid changes in NH 3 concentration. The sensor response was reduced by 5.5% towards 200 ppm NH 3 despite a significant variation in relative humidity from 20% to 80%. Based on these results, our flexible PANI sensor is a viable option for efficient and cost-effective on-site NH 3 detection. [Display omitted] • We fabricated a room temperature operational, highly sensitive and selective polyaniline based ammonia gas sensor. • The sensor is fabricated over the bio-degradable paper substrate which makes it flexible and cost-effective. • The sensor exhibited a linear response with increasing NH 3 concentration along with excellent repeatability and stability. • The effect of relative humidity on the sensor response has been thoroughly investigated. [ABSTRACT FROM AUTHOR]

With the growing significance of printed sensors on the electronics market, new demands on quality and reproducibility have arisen. While most printing processes on standard substrates (e.g., Polyethylene terephthalate (PET)) are well-defined, the printing on substrates with rather porous, fibrous and rough surfaces (e.g., uncoated paper) contains new challenges. Especially in the case of inkjet-printing and other deposition techniques that require low-viscous nanoparticle inks the solvents and deposition materials might be absorbed, inhibiting the formation of homogeneous conductive layers. As part of this work, the sheet resistance of sintered inkjet-printed conductive silver (Ag-) nanoparticle cross structures on two different, commercially available, uncoated paper substrates using Van-der-Pauw’s method is evaluated. The results are compared to the conductivity of well-studied, white heat stabilised and treated PET foil. While the sheet resistance on PET substrate is highly reproducible and the variations are solely process-dependent, the sheet resistance on uncoated paper depends more on the substrate properties themselves. The results indicate that the achievable conductivity as well as the reproducibility decrease with increasing substrate porosity and fibrousness.

Significant improvements in terms of bandwidth of reflectarray antennas have been achieved by introduction of innovative paper substrate dielectric materials. Three differently custom composed organic dielectric substrates have been characterized for dielectric properties using a broadband technique based on open ended coax cable method. The substrates show low dielectric permittivities of 1.81, 1.63 and 1.84 along with a loss tangent of 0.053, 0.047 and 0.057. Validation of using the proposed substrates for reflectarray antenna was done by modelling and fabricating reflectarray unit elements on the three substrates. Scattering parameter analysis of unit reflectarray elements show encouraging results with a broadband frequency response of 340 MHz at a phase gradient of 0.14°/MHz. Thus the proposed substrate could serve exceptionally to address the narrow bandwidth problem in reflectarray antennas. [ABSTRACT FROM AUTHOR]