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• Co-Ag/PANI-PPY/IL material prepared by chemical oxidative polymerization method. • Proposed sensor translated to a handmade paper sensor for real sample application. • Analysis time on handmade paper sensor was only 5 minutes. • Handmade paper sensor employed for direct detection of vitamin D 3 in real samples. • Excellent recovery in real samples making it suitable for point of care device. This paper describes the synthesis of novel material and its application to fabricate a sensing tool for the diagnosis of vitamin D deficiency. A simple and economical route for the synthesis of novel composite material based on silver-cobalt (Co-Ag) doped polyaniline-polypyrrole (PANI-PPY) copolymer and ionic liquid (IL) has been described and used as sensing material for vitamin D 3 detection. The synthesized composite was characterized using structural, morphological and electrochemical techniques. Co-Ag/PANI-PPY/IL was first used to modify the glassy carbon electrode (GCE) and applied for vitamin D 3 detection. Later a conductive ink of the proposed material was prepared and a handmade paper sensor was fabricated. Co-Ag/PANI-PPY/IL@GCE and paper electrode showed excellent electrochemical behavior towards vitamin D 3 oxidation within the concentration range of 0.0125–22.5 µM and 0.025–0.125 µM with the acceptable detection limit of 0.0073 µM and 0.015 µM respectively. Co-Ag/PANI-PPY/IL@GCE and paper electrode were successfully applied for the detection of vitamin D 3 in serum and urine samples. [ABSTRACT FROM AUTHOR]

• Dual-readout paper-based sensor via enzyme-mediated alginate hydrogelation. • Converting solution viscosity and pH to diameter and color readout. • Smartphone-based device to record and analyze both signals for quantitative detection. • Excellent reproducibility and selectivity for on-site detection of penicillinase. A dual-readout paper-based sensor with smartphone detection is developed for quantitative determination of penicillinase. The sensor is accomplished with the aid of penicillinase-mediated alginate hydrogelation, which changes both the viscosity and pH of the reaction solution. The solution is dropped on a mixed cellulose ester filter paper for sensing, which is coated with a color indicator, bromothymol blue-cetyltrimethylammonium bromide-alginate complex. Dual signals of the targets are easily achieved from the sensing spot on the paper since the modulations of viscosity and pH of the reaction solution would result in changes of diffusion diameter and color of the spot, respectively. A smartphone-based readout device is developed to record and analyze both the diffusion diameter and color signal for quantitative detection of penicillinase. The wide linear range (8.00 × 10−3 - 2.67 mU/μL for distance-readout and 8.00 × 10-2 to 2.67 mU/μL for color-readout) with low limit-of-detection (2.67 × 10-3 mU/μL for distance-readout and 2.67 × 10-2 mU/μL for color-readout) have been achieved using the dual-readout paper-based sensors. The proposed method is successfully applied for the detection of penicillinase in milk samples with excellent sensitivity and reproducibility, showing its potential value for analysis of complex real samples. [ABSTRACT FROM AUTHOR]

In this paper, a highly sensitive paper-based humidity sensor is designed and fabricated to overcome the typically low sensitivity and small quality factor of paper-based chipless radio-frequency identification (RFID) humidity sensors. A toroidal inductor-interdigitated electrodes (IDE) capacitor is used as the resonator structure of the new sensor, and the structural parameters of the sensor are optimized using the software of high frequency structure simulator (HFSS) to improve the quality factor. Three paper-based sensor samples were fabricated via screen printing using regular printing paper, Kodak photo paper, and double-sided copper-coated paper as the substrate. In addition, the resonance characteristics, sensitivity, recovery characteristics, stability and other sensor performances were tested. The results show that the sensitivity of the copper-coated-paper-based sensor is significantly better than the two other paper-based sensors. The simulation and test results of the moisture-sensitive characteristics are consistent for graphene oxide (GO) films, which were prepared using the spray method on the surface of the copper-coated-paper-based sensor with mass concentrations of 1 mg/mL, 2 mg/mL, and 5 mg/mL. This indicates that GO films can significantly improve sensor sensitivity when combined with paper-based moisture sensing. Furthermore, the sensitivity increases with increasing GO concentration, the 5 mg/mL GO sensor show a sensitivity of 6.25 MHz/%RH and a range of 60 % RH 90 % RH. The 1 mg/mL GO humidity sensor shows good recovery characteristics (92.4 % recovery). Based on the presence of hydrophilic functional groups in the GO material, a moisture sensing mechanism that GO could improve the sensitivity of the sensor is analyzed. [Display omitted] • The paper-based RFID sensor has both a high quality factor and a standard operating frequency. • The microstructure of paper surface will affect the sensor's performances. • The synergistic sensing of graphene oxide and paper substrate can significantly improve the sensitivity of the sensor. • The sensor has low cost and can be applied to food packaging, medicine storage and other fields. [ABSTRACT FROM AUTHOR]

Toxic and nontoxic volatile organic compound (VOC) gases are emitted into the atmosphere from certain solids and liquids as a consequence of wastage and some common daily activities. Inhalation of toxic VOCs has an adverse effect on human health, so it is necessary to monitor their concentration in the atmosphere. In this work, we report on the fabrication of inorganic nanotube (INT)-tungsten disulfide, paper-based graphene–PEDOT:PSS sheet and WS2 nanotube-modified conductive paper-based chemiresistors for VOC gas sensing. The WS2 nanotubes were fabricated by a two-step reaction, that is oxide reduction and sulfurization, carried out at 900 °C. The synthesized nanotubes were characterized by FE-SEM, EDS, XRD, Raman spectroscopy, and TEM. The synthesized nanotubes were 206–267 nm in diameter. The FE-SEM results show the length of the nanotubes to be 4.5–8 µm. The graphene–PEDOT:PSS hybrid conductive paper sheet was fabricated by a continuous coating process. Then, WS2 nanotubes were drop-cast onto conductive paper for fabrication of the chemiresistors. The feasibility and sensitivity of the WS2 nanotube-modified paper-based chemiresistor were tested in four VOC gases at different concentrations at room temperature (RT). Experimental results show the proposed sensor to be more sensitive to butanol gas when the concentration ranges from 50 to 1000 ppm. The limit of detection (LOD) of this chemiresistor for butanol gas was 44.92 ppm. The WS2 nanotube-modified paper-based chemiresistor exhibits good potential as a VOC sensor with the advantages of flexibility, easy fabrication, and low fabrication cost. [ABSTRACT FROM AUTHOR]

With the spread of COVID-19, more and more attention has been paid to the self-monitoring of healthy breathing. In this paper, we propose a humidity sensor which is simple to manufacture, low cost, good flexibility and visualization. The humidity sensor based on cellulose filter paper (FP) exhibited a good moisture-dependent voltage response over a wide relative humidity (RH) range due to the capillary structure of porous cellulose films and highly hydrophilic material of cobalt chloride (CoCl 2), which facilitated water molecule adsorption and diffusion. The cellulose film colour shifted from blue to red when RH changed from 11% to 98%, and this colour shift was reversible. A moisture-driven sensor, based on the diffusive flow of water in cellulose networks, can provide an output voltage of 200 mV in a highly moist environment. Due to the high flexibility of cellulose fibres, the sensor maintained a constant output voltage even after 3000 folds. Moreover, the device was successfully applied for human respiratory monitoring and movement frequency tracking. The uniqueness of this new wearable humidity sensor technology can establish a new application field for the development of intelligent textiles and personal health products in the future Internet-of-things. [ABSTRACT FROM AUTHOR]

[Display omitted] • Contactless conductivity sensor from printed-circuit board for μPADs. • μPADs with in-situ gas separation feature employed for selective detection. • Mechanism of SO 2 -absorption and equivalent circuit of the detection are proposed. • Simple and rapid μPADs-method for quantifying sulfite in wines and juices. The work presents the latest exploitation of capacitively coupled contactless conductivity detector (C4D) produced from printed-circuit board as durable detector for in-situ headspace microfluidic paper-based analytical devices (μPADs). This is the first reagent-free operating paper-based method for direct determination of sulfite, with storage of acid reagent during μPAD fabrication. In the procedure, the detection zone is first moistened with deionized water, and the μPAD turned over and placed on the C4D sensing area with the moist-zone faced down. Sample is loaded at the top layer of μPAD where it flows into the adjacent covered reaction zone, containing the absorbed acid, forming SO 2(g). The gas diffuses through the in-situ headspace in the middle layer and is absorbed into the moist detection zone at the base layer giving a prompt change in the C4D signal due to the change in conductivity from the generated conductive ionic species, viz. H+ (aq) and HSO 3 − (aq). The working range of the C4D-μPAD is 8–100 mg L-1 sulfite, with the limit of detection of 6.61 mg L-1. Compared with other paper-based methods that detect SO 2(g) , this is the only in-situ method and most rapid method (3.3 min per sample) for fruit juices, white and red wines. [ABSTRACT FROM AUTHOR]

Quantum dots (QD) have seen a rapid uptake in display applications, especially as photoluminescent color conversion layers. In parallel, QD absorbers promise efficient photodetector components, with absorption peak tunability and monolithic integration. In this paper, we describe QD stack integration into infrared imagers, enabling accessible sensors for various display interfaces. [ABSTRACT FROM AUTHOR]

This paper presents a novel optical type in‐cell fingerprint sensor (iFP) technology, which can detect a user's fingerprint on display. By using low temperature polysilicon (LTPS) TFT process, new sensor material, and active pixel sensor circuit (APS), this sensor can detect a fingerprint image with good performance. The FPS/Touch/Display Driver IC (FTDI) is also implemented in this work, and successfully demonstrated. [ABSTRACT FROM AUTHOR]

Optical fibers, serving as sensors and data conduit, are particularly relevant for long-term health monitoring of civil structures. Nevertheless, many challenges associated with the on-site application of such sensors have to be solved, these are mainly related to the application methodology. The objective of this current research is to assess the feasibility and reliability of strain measurements by utilising FBG (Fiber Bragg Grating) optical sensors embedded in two types of FRP (Fiber Reinforced Plastic) packaging. The first device consists of an FRP reinforcing sheet with embedded FBG sensor, conceived for external application on the structural element surface. The FRP packaging of the second device consists of a FRP rebar, conceived for internal or Near Surface Mounted (NSM) applications. These two FRP packages provide the optical fiber with the necessary protection against accidental damage during handling and installation. The mechanical characteristics of the packaging material allow the use of the device for structural reinforcing purpose as well. The paper discusses the various steps in the development of the technology set-up, the physical and the mechanical testing and the in situ validation for the two devices. [ABSTRACT FROM AUTHOR]

In their paper on the last glaciation of Shetland, Golledge et al. (2008) concluded on the basis of a remote sensing study that during that period Shetland had been overrun by ice from Scandinavia. Since the method of study they used does not reveal the sense of the direction in which the ice flowed and since they ignored earlier ground-based work involving striations which do reveal the sense of direction of ice flow their conclusions have no scientific basis. [ABSTRACT FROM AUTHOR]

This paper proposes and evaluates two robust sheet tension estimation algorithms based on unwind and rewind variables, respectively. The proper sheet tension estimation is guaranteed by a continuous monitoring of the differences between the actual estimated values and the values predicted from the last calibration of the estimation parameters. The evaluation was performed with the aid of a developed winder emulator that allowed the offline testing in a real-time field environment, including the initial setting of the estimation constants, and evaluation of both four- and six-shipping-roll cycles. The sheet tension estimation results confirm the precise and stable operation of the proposed robust estimation algorithms, in tests conducted with signals from a winder model, and with tests involving actual field signals from an operational winder. [ABSTRACT FROM AUTHOR]

Interdisciplinary research in biotechnology and related scientific areas has increased tremendously over the past decade. This rapid pace, in conjunction with advances in microfabricated systems, computer hardware, bioengineering and the availability of low-powered miniature components, has now made it feasible to design bio-inspired materials, sensors and systems with tremendous potential for defence and security applications. To realize the full potential of biotechnology and bio-inspiration, there is a need to define specific requirements to meet the challenges of the changing world and its threats. One approach to assisting the defence and security communities in defining their requirements is through the use of a conceptual model. The distributed or intelligent autonomous sensing (DIAS) system is one such model. The DIAS model is not necessarily aimed at a single component, for instance a sensor, but can include a system, or even a system of systems in the same way that a single organism, a multi-cellular organism or group of organisms is configured. This paper provides an overview of the challenges to and opportunities for bio-inspired sensors and systems together with examples of how they are being implemented. Examples focus on both learning new things from biological organisms that have application to the defence and security forces and adapting known discoveries in biology and biochemistry for practical use by these communities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Changes in recognition of sensor TQB for Ag+ can be observed with the naked eye in ambient or ultraviolet light. • The detection limit of sensor TQB is 0.65 μM to Ag+. • Sensor TQB can be applied for recognition of Ag+ in test strips. In this study, a novel, highly sensitive fluorescent sensor (E)-2-((2-(benzo[d] thiazol-2-yl) quinolin-8-yl) oxy)-N'-(4-(5, 5-difluoro-1, 3, 7, 9-tetramethyl-5H-4λ4, 5λ4-dipyrrolo [1, 2- c :2', 1'- f ] [1, 3, 2] diazaborinin-10-yl) benzylidene) acetohydrazide (TQB) was developed for dual mode of Ag+ detection (colorimetric/fluorescence), and its structural and spectral properties were characterized by 1H NMR, ESI-MS, X-ray, ultraviolet and fluorescence photometry. It is found that TQB could specifically and efficiently identify Ag+ among many other metal ions in CH 3 OH/H 2 O (7:3 v/v, pH = 7.23) buffer. The maximum absorption wavelength of TQB is red-shifted while its fluorescence is quenched with a quenching rate of 88.7%. The energy difference between TQB and TQB -Ag+ complex was calculated by DFT, and the applicability of TQB was verified by paper strip test. In addition, TQB has been successfully applied to the determination of Ag+ in real water samples with good reversibility and recoveries. [ABSTRACT FROM AUTHOR]

This paper firstly introduces a flexible hybrid integration (FHI) architecture based on organic thin‐film transistors (OTFTs) for ubiquitous sensor systems, followed by description of the low power OTFT technologies. Then, progresses on sensor integration based on the OTFTs for FHI are discussed, proving the versatility of the technology. [ABSTRACT FROM AUTHOR]

Tunable piezoresistive sensors based on a drawing on paper with different grades of pencils are proposed. While an external mechanical strain is applied to U-shape resistors prepared by pencil drawings on paper, an increase in the gauge factor with an increase in the graphite resistance is found. The result is attributed to the tunneling effect between neighboring graphite during the drawing process, further suggesting that different-grade pencil drawings can tune the piezoresistive properties. Through many cycles of repeatedly applied and released force, the output voltage for an HB pencil was found to be more sensitive than that for a 9B pencil. [ABSTRACT FROM AUTHOR]

Paper has been extensively accepted as an ideal platform for fabricating low‐cost, flexible, and environmentally friendly electronics. However, current paper‐based pressure sensors have not fully demonstrated the unique merits of paper, such as cost efficiency, disposability, cuttability, and foldability, mainly because of the limitation of the applied metal electrodes and device configuration. Here, an all‐organic, all‐paper, cuttable, and foldable pressure sensor is demonstrated for the first time, with the high‐conductivity polypyrrole (PPy) printing paper as electrode and the low‐conductivity PPy tissue paper as active layer. Hollow and 3D all‐paper sensors are realized through fabricating the kirigami or origami structure since the device can be freely cut and folded, presenting a universal strategy promising for flexible device design. The cuttability and foldability of device create a unique 3D perception capability. The devices show high sensitivity (4.8 kPa−1 at < 5.5 kPa, 1.7 kPa−1 at 5.5–40 kPa) and wide detection range (up to 40 kPa), providing a capability for full‐range detection of human physiological and motion signals. These results open a feasible route to realize hollow and 3D sensors and fully demonstrate the potential of paper sensors for diverse applications to new‐generation green electronics and portable electronics. [ABSTRACT FROM AUTHOR]

Herein, we present the first paper‐based device for facing one of the worldwide concerns of the Modern age: the corrosion‐induced deterioration of reinforced concrete. Indeed, the monitoring of corrosion extent in reinforced concrete constructions has been acknowledged as a priority for public safety. In this work, the porosity properties of a paper‐based screen‐printed Ag/AgCl electrode were exploited for realising a smart analytical tool to be directly applied on the solid surface of concrete for the evaluation of corrosion. The analysis was carried out by measuring the electrochemical potential between the metallic reinforcement and the sensor, needing only 70 μL of electrolyte solution. The sensor was firstly tested in the laboratory using reinforced concrete samples and then applied on the real outdoor artwork Music Collection Session by Arman (Milan, Italy). A summary of the main available non‐destructive techniques for corrosion monitoring is reported to provide a critic overview. [ABSTRACT FROM AUTHOR]

We present a deep learning-based framework to design and quantify point-of-care sensors. As a use-case, we demonstrated a low-cost and rapid paper-based vertical flow assay (VFA) for high sensitivity C-Reactive Protein (hsCRP) testing, commonly used for assessing risk of cardio-vascular disease (CVD). A machine learning-based framework was developed to (1) determine an optimal configuration of immunoreaction spots and conditions, spatially-multiplexed on a sensing membrane, and (2) to accurately infer target analyte concentration. Using a custom-designed handheld VFA reader, a clinical study with 85 human samples showed a competitive coefficient-of-variation of 11.2% and linearity of R2 = 0.95 among blindly-tested VFAs in the hsCRP range (i.e., 0–10 mg/L). We also demonstrated a mitigation of the hook-effect due to the multiplexed immunoreactions on the sensing membrane. This paper-based computational VFA could expand access to CVD testing, and the presented framework can be broadly used to design cost-effective and mobile point-of-care sensors. [ABSTRACT FROM AUTHOR]

We evaluate and compare the performance of a 15.6‐inch mini‐LED backlit LCD (mLCD) with a commercial OLED panel. Results show that the mLCD exhibits advantages over the OLED panel in peak brightness, gamma curve, color volume, power consumption, and ambient contrast ratio. The LMK imaging photometer with a high‐resolution CMOS sensor is employed to characterize the halo effect and reconstruct the real luminance profiles based on the non‐ideal profile of the OLED display. We have also proposed a novel strategy to measure the backlight's point spread function. [ABSTRACT FROM AUTHOR]

Respiratory syncytial virus (RSV) infection is the most common clinical infectious disease threatening the safety of human life. Herein, we provided a sensitive and specific method for detection and differentiation of RSV subgroups A (RSVA) and B (RSVB) with colorimetric toehold switch sensors in a paper-based cell-free system. In this method, we applied the toehold switch, an RNA-based riboswitch, to regulate the translation level of β-galactosidase (lacZ) gene. In the presence of target trigger RNA, the toehold switch sensor was activated and the expressed LacZ hydrolyzed chromogenic substrates to produce a colorimetric result that can be observed directly with the naked eye in a cell-free system. In addition, nucleic acid sequence-based amplification (NASBA) was used to improve the sensitivity by amplifying target trigger RNAs. Under optimal conditions, our method produced a visible result for the detection of RSVA and RSVB with the detection limit of 52 aM and 91 aM, respectively. The cross-reaction of this method was validated with other closely related respiratory viruses, including human coronavirus HKU1 (HCoV-HKU1), and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Furthermore, we used the paper-based carrier material that allows stable storage of our detection elements and rapid detection outside laboratory. In conclusion, this method can sensitively and specifically differentiate RSVA and RSVB and generate a visible colorimetric result without specialized operators and sophisticated equipment. Based on these advantages above, this method serves as a simple and portable detector in resource-poor areas and point-of-care testing (POCT) scenarios. [Display omitted] • Proposing colorimetric toehold switch sensors to differentiate RSV subgroups A and B. • Using nucleic acid sequence-based amplification (NASBA) to enhance the sensitivity. • Validating the specificity with other closely related respiratory viruses. • Achieving the simple and portable detection based on a paper-based cell-free system. [ABSTRACT FROM AUTHOR]

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• Thiomalic acid modified CDTE was utilized for visual detection of Ag+. • High sensitivity and selectivity for Ag+were achieved. • The detection limit of fluorescence spectrometry method for Ag+ was 13.16 nmol/L. • Paper-based sensors for Ag+ was carried out in a rapid, simple and effective way. • PLSR accurately quantified concentrations of Ag+ in matrices based on paper images. A fluorescence paper-based sensor method by simply using thiomalic acid modified CdTe (TMA-capped CdTe) was proposed for visual detection of silver ions (Ag+). Red-emission TMA-capped CdTe with a large amount of carboxyl groups on the surface could be combined with Ag+ by electrostatic interaction, thus leading to the fluorescence quenching. It was found that the adding of amino acids contributed to fluorescence recovery by the leaving of Ag+ on the surface of TMA-capped CdTe. Moreover, the more amino group, benzene and thiol group equipped in the structure of amino acid, the stronger fluorescence restoring of CdTe could be achieved. This fluorescence spectrometry method for Ag+ showed low detection of limit with the value of 13.16 nmol/L, with no response to other heavy metals, which demonstrating its high sensitivity and high selectivity for Ag+. More importantly, this paper-based sensor method combined with chemometrics could accurately identify and quantify different concentrations of Ag+ in different complex matrices. This fast, economical, accurate and effective approach exhibited a new idea for the on-site detection of Ag+, and was expected to be extended to the on-site detection of Ag+ in biological and environmental fields. [ABSTRACT FROM AUTHOR]

• GO-PA paper is prepared by an evaporation-induced self-assembly method. • Fire sensor based GO-PA exhibits ultrasensitive and durable warning response. • Enhancement in fire resistance of GO is attributed to in situ phosphorus doping. Although traditional fire detectors are widely used in many occasions, they still show some limitations, such as slow fire response and poor resistance to severe conditions. Thus, it is urgent to design and exploit early fire-warning device with ultrafast response and flame-retardant ability to provide timely and fast alarm. Herein, graphene oxide paper functionalized with phosphoric acid (GO-PA) is fabricated by a facile and environmentally friendly water evaporation-induced self-assembly approach. Based on the flame-induced electrical resistance transformation characteristic of GO-PA, a fire-warning detector is designed to reliably monitor early fire. Fire alarm can be triggered within 0.5 s when GO-PA samples are attacked by fire. The GO-PA composite paper is more sensitive than GO-based fire sensors reported in the literature. Phosphorus atoms are in situ doped into graphene structure during flame exposure. Combustion reaction of GO is significantly retarded by the incorporated PA, thus fire duration time of GO is greatly improved. This work paves a new way to improve fire detection performance of GO-based sensors. This work provides a guide for the development of advanced fire detection and early-warning sensors to provide reliable and continuous alarm signals. [ABSTRACT FROM AUTHOR]

• The preparation of fully inkjet printed PEDOT:PSS/ZnO/Nafion sensor on commercial printing paper.. • A paper based electrochemical sensor for hydrazine sensing with a good selectivity and reproducibility. • Sensitivity comparison of PEDOT:PSS/Nafion and PEDOT:PSS/ZnO/Nafion sensors. • Characterization of PEDOT:PSS and ZnO through SEM, XPS and AFM. • Excellent detection in real samples with a recovery of 98.7–104.2 %. Hydrazine is widely used in industries as a precursor for blowing agents, pharmaceuticals, and pesticides. It is a highly toxic compound; therefore, it is of paramount interest to develop new analytical methods for the detection and control of hydrazine exposure. In this work, we describe the fabrication of an all inkjet-printed paper sensor composed of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrode functionalized with zinc oxide (ZnO) and encapsulated in a Nafion matrix for the amperometric determination of low concentrations of hydrazine. The electrochemical properties of the fully inkjet-printed PEDOT:PSS/Nafion and PEDOT:PSS/ZnO/Nafion sensors are compared in the presence and absence of different concentrations of hydrazine. The stability and sensitivity of these electrodes are significantly enhanced after modification with ZnO particles. The layer-by-layer deposition of the materials on the electrode surface is characterized by SEM, XRD, and AFM. The printed sensor exhibits a linear response in the 10–500 μM hydrazine concentration range and a ∼5 μM detection limit (at S/N = 3). The electrochemical sensitivity is 0.14 μA μM−1 cm−2, and the best working voltage is 0.5 V. The developed sensor was applied successfully for the determination of hydrazine content in tap, sea, and mineral water samples validating the accuracy of this sensor. [ABSTRACT FROM AUTHOR]

This work presents a capacitively coupled contactless conductivity detector (C4D) etched out from a printed circuit board (PCB) as potential sensor for paper-based analytical systems. Two lines of any desirable pattern forming 35-μm thick planar copper electrodes were produced on a PCB plate (40 mm × 60 mm) by photolithography. The final PCB plate was covered with polypropylene film to serve as the insulating layer for the C4D detector. The film also protected the copper electrodes from corrosion. Electrodes made in this planar geometry make the PCB-C4D suitable as sensor for flat devices such as paper-based analytical devices. For this work, plain paper strips were employed as sample reservoir and as fluidic channel without hydrophobic pattern. A dried paper strip was first placed over the sensor, followed by dispensing a fixed volume of the liquid sample onto the paper. Entrapment of the liquid sample in the paper strip leads to reproducible size and position of the detection zone of the sample liquid for the capacitive coupling effect. High precision was obtained with %RSD ≤1% (n = 18) for standard solutions of KCl. Soil suspensions could be analyzed without prior filtration by placing a drop onto the paper strip extending away from the detector zone. The paper strip filtered out soil particles at the surface of the paper. Therefore, only soil filtrate moved towards the detection zone by lateral flow. The C4D detection using paper strip showed high tolerance to soil suspension with turbidity up to 6657 NTU, offering direct analysis of soil salinity. Cleaning with moist tissue paper between samples is adequate even for dirty samples such as soil suspension. We also monitored conductivity of acid-base reaction in the microfluidic paper channels, which was later applied to the quantification of bicarbonate in water and in antacid tablet ("Soda Mint Tablet"). Contactless conductivity detector from printed circuit board as a universal detector for paper-based analytical systems. Image 1 • Contactless conductivity detector for entrapped liquid on plain paper. • Easily cleaned with household tissue to remove liquid residues and dirt. • Direct measurement of soil salinity with high tolerance to soil suspension. • Potential detector for paper-based analytical systems. [ABSTRACT FROM AUTHOR]

Human access to safe water has become a major problem in many parts of the world as increasing human activities continue to spill contaminants into our water systems. To guarantee the protection of the public as well as the environment, a rapid and sensitive way to detect contaminants is required. In this work, a paper-based microbial fuel cell was developed to act as a portable, single-use, on-site water quality sensor. The sensor was fabricated by combining two layers of paper for a simple, low-cost, and disposable design. To facilitate the use of the sensor for on-site applications, the bacterial cells were pre-inoculated onto the device by air-drying. To eliminate any variations, the voltage generated by the microorganism before and after the air-drying process was measured and calculated as an inhibition ratio. Upon the addition of different formaldehyde concentrations (0%, 0.001%, 0.005%, and 0.02%), the inhibition ratios obtained were 5.9 ± 0.7%, 6.9 ± 0.7%, 8.2 ± 0.6%, and 10.6 ± 0.2%, respectively. The inhibition ratio showed a good linearity with the formaldehyde concentrations at R2 = 0.931. Our new sensor holds great promise in monitoring water quality as a portable, low-cost, and on-site sensor. [ABSTRACT FROM AUTHOR]

A CO 2 laser can be used to pyrolyze the surface of common paperboard to produce a conductive carbon material for subsequent use as an electrode for general electrochemical measurements. In this work, a laser-pyrolyzed electrochemical paper-based analytical device (LP-ePAD) of this type was combined with a gas-diffusion microextraction (GDME) unit for the square-wave voltammetric analysis of sulphites in commercial beverages. The fabricated LP-ePAD had a resistivity at room temperature of 11 ± 4 Ω per square electrical sheet (measured with a four-point probe system). The developed methodology showed a limit of detection of 1 mg L−1 for sulphite analysis, with good repeatability and reproducibility (coefficient of variation below 7%), as well having as the desirable qualities of portability and low price. Unlabelled Image • Electroanalysis using low-cost pyrolyzed electrochemical paper-based analytical sensor. • Paper electrodes are fabricated using a CO 2 laser in a single reagentless step. • The paper electrodes had a sheet resistivity of ca. 11 Ω/sq. [ABSTRACT FROM AUTHOR]

• Porous papers allow the glue or resin to penetrate the paper and bridge it • Some papers could be printed with a resolution similar to PET. • Paper additives can catalyse or inhibit the cross-linking of glues or resins. • Printed sensors on pH-neutral porous papers allow an unaltered in-situ analysis. Engineered wood, a high-tech material of the 21st century demonstrates the revival of timber for the construction of green urban eco-buildings. However, the testing of wood-based materials is still based on destructive methods known for centuries. In-situ monitoring of curing, cross-linking, and aging is essential for the optimisation of glues, resins and coatings. For press moulding, impedance spectroscopy is the only practical way for in-line detection of the crosslinking. Flat sensors that can be integrated into glue joints are known, but the substrate material of these sensors weakens the glue joint as they do not interact with the commonly used wood glues. Sensors printed on porous paper and wood can solve this problem. We show that although almost every tested paper is printable but not all of them are suitable for the detection of cross-linking analysis, since paper additives can catalyse or inhibit the cross-linking of glues or resins. Printed impedance sensors on pH-neutral porous papers allow an unaltered in-situ analysis of the cross-linking in complex glue joints. The porous papers allow the glue or resin to penetrate the paper and bridge it. Integrated sensors can provide valuable information about the state (aging, moisture) of bonding throughout the life cycle of the engineered wood. With the help of paper-based sensors, wood can be equipped integratively, network-compatible and communicative. Damage in the glue joints can be detected on time. With this innovative sensor technology, wood is not only an ingenious material, but also an intelligent one. [ABSTRACT FROM AUTHOR]

The present comment concerns some doubtful results included in the above paper. • The paper concerns the MHD squeezed flow of water functionalized metallic nanoparticles over a sensor surface. • The function for channel height is irrational and wrong. • The equation representing the transformed temperature is wrong. [ABSTRACT FROM AUTHOR]

The article discusses role of FrameQR-PADs to overcome the limitation of manual test labeling associated with traditionally designed microPADs and support the use of proposed assays in telehealth settings. It mentions use for the quantitative determination of clinically important analytes and demonstrated their use by optimizing them for ALP analysis.

The annual amount of food waste or loss is about one-third of the total edible food globally produced for human consumption. Continuous and real-time monitoring by spoilage detectors can significantly reduce food waste. A novel paper-based pH-sensitive meat spoilage detector was developed. A mixture of soybean hulls (SBHs) (hydrothermally-treated in an acidic environment), bentonite, and bromocresol purple (BCP) was coated on paper to produce the detector. The resultant meat spoilage detector was evaluated as a real-time freshness and spoilage indicator of catfish fillets (Ictalurus punctatus). Freshness and spoilage of fish meat with varying weights and headspace were determined by tailoring the detector's pH. Elemental, structural, and functional analysis verified the formation of a packed SBH-bentonite matrix with enhanced gas adsorption capacity and effective BCP-immobilization. Binder nanofibrillation increased the overall visual color vibrancy and decreased the binder demand in the coating formulation. Headspace volume in the studied range (40 and 160 cm3) did not affect the activation time of the detectors. However, increasing fish weight decreased the detectors' optimum activation time and pH. The findings of this study show that the developed detectors can be tailored for a wide range of sample and packaging sizes by simply adjusting the pH of the detector. Image 1 • A cost-effective and scalable real-time freshness monitoring method was developed. • A novel coating binder was produced by full utilization of soybean hulls (SBHs). • Application of bentonite enhanced gas impermeability and color change durability. • The developed detectors can be tailored for fish weight and headspace volume. [ABSTRACT FROM AUTHOR]

• A novel and sensitive fire early alarm was designed based on GO-BA composite paper. • The sensitivity and stability of this novel alarm was excellent. • Flame alarm mechanism of GO-BA paper was described. Boric acid-modified graphene oxide (GO-BA) paper is prepared by a green and facile water evaporation-induced self-assembly method, and its application as an early fire-alarm sensor is investigated. The nacre structure is constructed by assembling graphene oxide (GO) and boric acid (BA) as brick and mortar, respectively. Compared with pure GO paper, improved thermal-oxidative stability is obtained for GO-BA. GO nanosheets are bonded with BA molecules by forming hydrogen bonds between hydroxyl in BA and the rich oxygen-containing functional groups on GO. Notably, the insulating GO-BA paper can be rapidly thermally reduced to conductive reduced graphene oxide under flame exposure, thus providing an ideal fire-alarm response with a quick flame-detection time of ∼0.8 s. In addition, boron oxide formed under flame attack covers the surface of GO, inhibiting further oxidation of GO paper, and effectively extending the duration time of GO-BA under combustion. These results indicate that the GO-BA paper prepared has a broad prospect in the field of fire early-alarm. [ABSTRACT FROM AUTHOR]

• The conductive TOCFs network is achieved by an electrostatic self-assembly process. • The paper sensor shows high sensitivity, excellent linearity, and long-time stability. • The paper sensor exhibits superior bending and folding durability. • The sensor shows good responses to human breath, fingertip humidity, and air humidity. Humidity sensors have been widely used for humidity monitoring in industrial fields. However, the application of conventional sensors is limited due to the structural rigidity, high cost, and time-consuming integration process. Owing to the good hydrophilicity, biodegradability, and low cost of cellulose, the sensors built on cellulose bulk materials are considered a feasible method to overcome these drawbacks while providing reasonable performance. Herein, we design a flexible paper-based humidity sensor based on conductive 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose fibers/carbon nanotubes (TOCFs/CNTs) conformal fibers network. The CNTs are dispersed by cationic cetyl trimethyl ammonium bromide (CTAB), which introduces positive charges on the CNTs surface. The conductive fibers are achieved by an electrostatic self-assembly process that positively charged CNTs are adsorbed to the surface of negatively charged TOCFs. The vast number of hydrophilic hydroxyl groups on the surface of TOCFs provide more water molecules adsorption sites and facilitate the electron transfer from water molecules to CNTs, endowing the sensor with an excellent humidity responsive property. Besides, the swelling of the TOCFs greatly damages the conductive CNTs network and further promotes the humidity sensitive performance of the sensor. Benefiting from the unique structure, the obtained sensor exhibits a maximum response value of 87.0% (ΔI/I 0 , and the response limit is 100%), outstanding linearity (R2 = 0.995) between 11 and 95% relative humidity (RH), superior bending (with a curvature of 2.1 cm−1) and folding (up to 50 times) durability, and good long-time stability (more than 3 months). Finally, as a proof of concept, the sensor demonstrates an excellent responsive property to human breath, fingertip humidity, and the change of air humidity, indicating a great potential towards practical applications. [ABSTRACT FROM AUTHOR]

Bismuth sulphide nanoflowers based flexible paper laser detector. • Printing paper based high performance flexible laser detector was fabricated successfully. • The photoelectric properties were studied upon 450 nm, 532 nm, 650 nm and 780 nm laser beam irradiation. • The flexible laser detector can measure the 3.3 mW/cm2 weak laser signal of 450 nm. Development of the flexible electronics, especially electronic skin, put forward new requirements for flexible substrates and sensing materials. Herein, using printing paper substrate and Bi 2 S 3 microflowers, the high performance flexible laser detector is successfully fabricated. The laser detector has a flexible and fast response to 450, 532, 650 and 780 nm laser beams of different intensity. The flexible laser detector is able to measure as weak laser signal as 3.3 mW/cm2 at 450 nm. The mechanism of the photo response of laser detector based on Bi 2 S 3 microflowers is discussed. Our work here opens up opportunities for the fabrication of flexible optoelectronic devices with quite high and stable spectral property. [ABSTRACT FROM AUTHOR]

Electrical fire is the most frequently occurred fire accident, and fire sensors with self-cutting and ultrasensitive fire-alarm response capability are urgent to be designed and developed. Herein, conductive reduced graphene oxide paper (RGOP) with hierarchical structure is prepared by a facile evaporation-assisted self-assembly of graphene oxide (GO) dispersion and then reduction by hydrazine hydrate vapor. The oxidative decomposition of RGOP containing sodium chloride (RGOP-NaCl) is promoted by the addition of NaCl. When being exposed to flame, RGOP-NaCl strips are readily ruptured. Based on this distinctive self-cutting performance of RGOP-NaCl under fire attacking, a novel fire detection and alarm device is designed by establishing controlling and operation circuits. Under fire encountering, an ultrafast warning response (approximately 5.3 s) of RGOP-NaCl is triggered. Fire-alarm time of RGOP-NaCl is adjustable by varying the content of NaCl. Furthermore, this RGOP-NaCl has the function of fuse and can cut off the conductive circuit timely under fire attacking. This finding will provide a novel thought for the design of advanced fire-alarm sensor and will also expand the application of graphene paper. Image 1 • Conductive RGOP-NaCl is prepared by evaporation-induced self-assembly method. • This RGOP-NaCl exhibits ultrasensitive fire-warning response. • RGOP-NaCl has the function of fuse and self-cutting performance under fire attack. [ABSTRACT FROM AUTHOR]

• Twin-sensors on paper have been produced. • Development of a screening method for the detection of analytes in water. • Partial least squares – discriminant analysis and support vector machine are employed as classification methods. • Quality performance metrics were collected and applied to evaluate of the performance of the classifications. Chemometrics has proven to be a powerful tool for processing multivariate analytical data aimed at locating and extracting useful information relating to a particular analyte or material system in a complex sample from non-specific analytical signals that have been previously acquired and recorded by one or more analytical instruments or devices. In this paper, the basis for the application of both classification and quantitation multivariate methods is described, using a colorimetric twin sensor produced on a microfluidic paper-based analytical device (μPAD) as instructive example. The selected twin sensor provides a dual analytical signal for four anions (acetate, cyanide, fluoride and phosphate) in aqueous solution (concentration interval 0–0.1 M) from two reagent dyes (alizarin and 4-nitrophenol), which are immobilised in parallel on the same device containing four microfluidic channels designed in the form of an X. In this way, a data vector is obtained from each test whose elements are the colour coordinates obtained from the four responses, which is then used to build the chemometric models to be applied. Two multivariate classification methods (partial least squares discriminant analysis and support vector machine classification) are explored and the latter makes it possible to detect the presence or absence of each anion in an aqueous solution mixture. Single (each dye dataset separately) and fused (merging the two dye datasets) models were built and a support vector machine was shown to be the best classification method, obtaining sensitivity and precision values of 100% in almost all cases. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are considered as the potential biomarkers for many cancers. To determine miRNAs in cancer cells is significant for realizing these diseases. In this work, a microfluidic paper-based laser-induced fluorescence sensor based on duplex-specific nuclease (DSN) amplification was developed and applied to selectively and sensitively determine miRNAs in cancer cells. An interface for laser-induced fluorescence detection was firstly applied to perform the sample detection on the paper-based chip. Under the optimal conditions, DSN (3 μL 0.10 U) and Taqman probes (2 μL 2.5 × 10−7 M) were preserved on the circles (Diameter 4 mm) of the folded paper chip. When miRNA solution was added, the mixed solution could trigger fluorescence signal amplification by cyclically digesting hybrids of miRNAs and Taqman probes by DSN. The whole determination, including sample heating process, could be accomplished within 40 min. The detection limits for miRNA-21 and miRNA-31 were 0.20 and 0.50 fM respectively, corresponding to only 1.0 and 1.5 zmol consumption of miRNAs. The testing of mismatched miRNAs showed that the method had good specificity. Finally, the method was applied to determine miRNA-21 and miRNA-31 in lysates of cancer cells of A549 and HeLa, and hepatocyte LO2. MiRNA-21 and miRNA-31 could be successfully found from the two cancer cells. The concentrations for miRNA-21 and miRNA-31 were 1.74 × 10−13 M and 6.29 × 10−14 M in HeLa cell lysate (3.75 × 104 cells/mL), 3.07 × 10−15 M and 3.28 × 10−15 M in A549 cell lysate (8.33 × 106 cells/mL) respectively. The recoveries ranged from 87.30% to 111.83%, indicating the results were reliable. The developed method was effective, selective and sensitive in the determination of miRNAs in cancer cells. Image 1 • Realization of sensitive laser-induced fluorescence detection with an interface. • Performing duplex-specific nuclease amplification on the paper-based chip. • The applicable method determined low abundance miRNAs from cancer cells. [ABSTRACT FROM AUTHOR]

This work presents the evaluation of a multiparametric sensing device on paper fabricated by inkjet printing, for applications such as smart packaging-labeling and disposable biosensors where biocompatibility and low cost are key factors. The device is able to measure simultaneously relative humidity, temperature and compressive and tensile bending. Commercial silver nanoparticle ink and PEDOT:PSS were printed onto inkjet photo glossy paper using a drop-on-demand inkjet printer forming an interdigitated electrode array and a meander shaped micro-ribbon. Humidity measurements revealed that sensor response, which is effectively expressed by the relationship between paper substrate resistance and relative humidity was similar for both materials utilized as electrodes. Temperature coefficients of resistance (TCR) were extracted for Ag-nanoparticle and PEDOT:PSS - based temperature sensors respectively in the range of 25–45 °C. The bending tests indicated that both materials exhibited similar trend in tensile bending, with resistance increasing in a linear manner up to a maximum tensile length of 900 μm. Ag-nanoparticle ink outperformed PEDOT:PSS ink in terms of repeatability, sensitivity and hysteresis. In compressive bending measurements Ag-nanoparticle and PEDOT:PSS gauge factors exhibited similar gauge factor of opposite sign. Unlabelled Image • Paper can be used as an active material for sensing relative humidity with different inkjet-printed materials as electrodes • Metal-based and conductive polymer materials can be inkjet-printed and utilized as resistive temperature sensors • Compressive and tensile bending sensors can be incorporated onto inkjet glossy paper with mechanical deformation limit of 9% • Ag-nanoparticle bending sensors show greater mechanical durability than PEDOT:PSS sensors under long-term bending tests [ABSTRACT FROM AUTHOR]

Paper Sensor detection methods are attractive in wide analytical applications. Presented herein is a paper sensor and fluorescence methods that was firstly developed to detect curcumin (Cur) based on fluorescence resonance energy transfer (FRET) between nitrogen-doped carbon quantum dots (NCQDs) and Cur. The facile fluorescent method was demonstrated to detect Cur in the range of 0–2600 μM with a detection limit of 0.13 μM. And facile paper sensor of Cur was fabricated and displayed at concentration of 0 μM, 100 μM, 200 μM, 300 μM, 400 μM, 500 μM and 600 μM, respectively. In additions, it was realized for determination of Cur in real samples including orange juice and curry solution. Compared with the reported methods, the present method is simple, rapid and sensitive for detecting Cur. Image 1 • A novel FRET system was constructed base on NCQDs as donor, and Cur as acceptor. • Highly selective paper sensor was used to detect Cur for the first time. • The spiked test for Cur in orange juice has higher recovery efficiency. • Visual inspection of Cur in curry powder has good practical application. [ABSTRACT FROM AUTHOR]

A novel and efficient fluorescent sensor with a pyrazine triphenylamine unit was developed. The sensor exhibits large Stokes shift (216 nm) due to the excited-state intramolecular proton transfer (ESIPT) process. After complexing with Cu2+, the ESIPT process was blocked and the fluorescence of the sensor was quenched. Job's plot and ESI-MS results indicated that the stoichiometric ratio between the sensor and Cu2+ was 1:1. The detection limit was determined to be 2.47 × 10−8 mol L−1. The sensor could be used to detect Cu2+ in practical samples with high accuracy. Furthermore, the sensor also could be made into test paper strips for the qualitative and quantitative detection of Cu2+. A high selective fluorescent sensor with a pyrazine unit has been synthesized. The sensor not only could be applied to determine Cu2+ in practical water samples, but also could be made into test paper strips for qualitative and quantitative determination of Cu2+. Image 1 • This paper reports a fluorescent chemosensor with a hexafluorocyclophentene unit and a pyrazine unit for the first time. • The sensor could be applied to detect Cu2+ in practical samples with high accuracy. • The sensor also could be made into test paper strips for qualitative and quantitative determination of Cu2+. [ABSTRACT FROM AUTHOR]

A dual functional molecularly imprinted polymer (MIP) coated paper (MIP-CP) sensor was firstly proposed for rapid fluorescent (FL) and visual analysis of norfloxacin (NOR) in aqueous solutions. The sensor was fabricated via a sol-gel technique, and characterized by FTIR and SEM. The extraction capacity, selectivity, detection limit, and linear range of the MIP-CP sensor were studied by an FL spectrophotometer. The modified paper sensor showed good selectivity and high extraction capacity for NOR and its structural analogues. For FL analysis of NOR, the linear range and detection limit were found to be 10–100 ng/ml and 2.59 ng/ml, respectively. The visual determination of NOR (under UV light) based on the MIP-CP sensor was also explored, and the determination limit was found to be 0.1 μg/ml. Finally, the proposed methods were successfully applied to the direct determination of NOR in pharmaceutical preparations and cross-validated by UPLC. The MIP-CP sensor might be a potential platform for antibiotic determination due to its multifunction and good analytical performance. A dual functional molecularly imprinted polymer coated paper (MIP-CP) sensor was proposed for fluorescent and visual analysis of norfloxacin. Image 1 • A dual functional paper sensor was firstly fabricated via a sol-gel technique. • A simple fluorescence method was proposed for NOR detection. • A visual fluorescence method was established for NOR detection. [ABSTRACT FROM AUTHOR]

Chemical and biomolecular analysis form an integral part of food contamination testing and healthcare diagnostics. The majority of the currently established detection methods are expensive, sophisticated and time consuming. Microfluidic-based lab-on-a-chip systems offer a promising alternative in this regard by enabling the development of simpler and relatively cost-effective platforms for analytical applications. In this work, we report the fabrication of a portable sensor platform using selective wax impregnation of cellulosic paper. The application of the fabricated paper-based lab-on-a-chip device is demonstrated for the qualitative and quantitative detection of starch contamination in milk using colorimetry. Integration of a detection procedure with smartphone imaging allows for on-the-spot data collection, thus overcoming the challenges of sample storage, handling and transportation to lab facilities. This approach offers a versatile method for diagnostic and sensing applications in resource-limited areas, especially in developing and underdeveloped countries. [ABSTRACT FROM AUTHOR]

• Three new highly luminescent, stable and soluble manganese (II) halide hybrids were prepared. • A paper sensor based on the luminescent manganese(II) halide hybrids was fabricated for ferbam sensing. • The LOD of the proposed sensor for ferbam was lower than the maximum permissible concentration in EU pesticides database. Organic–inorganic metal halide hybrids, which consist of metal halide anions and organic cations, have been widely applied in the sensor design. Instead of general lead (high toxicity) and copper (I) (weak stability) halide hybrids, the low toxic and highly luminescent manganese (II) halide hybrids may be more promising for optical sensors. In this work, a paper sensor based on the organic-inorganic manganese (II) halide hybrids is fabricated as the first attempt. Three new highly luminescent and soluble manganese (II) halide hybrids MnBr 4 (TPA) 2 , MnBr 4 (TEA) 2 and MnCl 4 (btmdme) 2 are prepared, and their quantum yields are 89.23%, 78.86% and 71.28%, respectively. The hybrids are dispersed uniformly and immoblized on the wax-based paper. The as-fabricated sensor is used for the fluorometric determination of pesticide ferbam, and the limit of detection is calculated to be 0.06 ppm, which is even lower than the maximum permissible concentration in EU pesticides database. Moreover, the practical application of ferbam assay for apple and pear samples is described with satisfactory recoveries (91.88–101.32%). The mechanism of ferbam detection is investigated in detail, and tentatively explained by the interaction between the manganese in MnBr 4 (TPA) 2 and the sulfur in ferbam together with the inner filter effect (IFE). [ABSTRACT FROM AUTHOR]

A fiber optic interferometric sensor with an intrinsic transducer along a length of the fiber is presented for ultrasound measurements of the acoustic emission from partial discharges inside oil-filled power apparatus. The sensor is designed for high sensitivity measurements in a harsh electromagnetic field environment, with wide temperature changes and immersion in oil. It allows enough sensitivity for the application, for which the acoustic pressure is in the range of units of Pa at a frequency of 150 kHz. In addition, the accessibility to the sensing region is guaranteed by immune fiber-optic cables and the optical phase sensor output. The sensor design is a compact and rugged coil of fiber. In addition to a complete calibration, the in-situ results show that two types of partial discharges are measured through their acoustic emissions with the sensor immersed in oil. [ABSTRACT FROM AUTHOR]

• A novel MXene@Pd CNC film H2 sensor was facilely designed via an all-colloidal solution-based vacuum-filtration process. • The sensor featured with flexibility, lightweight and a compact, glossy surface and it can be tailored in desired size when necessary. • The film sensor displayed fast H2 response at room temperature at either flat or bent states. Rational and smart design of hydrogen (H 2) sensors especially those featured with flexibility and light weight is highly desirable, to meet the requirements for future development of portable H 2 sensors. In this work, we demonstrate a novel paper film H 2 sensor employing Ti 3 C 2 T x MXene nanosheets with Pd colloidal nanoclusters (Pd CNC) as the activator. The MXene@ Pd CNC paper film was facilely prepared via an all-colloidal solution-based vacuum-filtration process, which is flexible, light-weight and endowed with a compact, glossy surface. The as-obtained MXene@ Pd CNC film sensor displayed moderate H 2 response at room temperature at either flat or bent states. Specially, the MXene@Pd CNC film sensor delivered a response time of (32 ± 7) s and a sensitivity of S = (23.0 ± 4.0)%@4% H 2. In addition, the MXene@Pd CNC sensor enabled "in-situ-mode" H 2 detection directly along a piece of paper film with desired size. The strong H 2 adsorption into lattice of ultrafine Pd CNC altered the work function thus induced the electron doping of MXene, which explained the gas sensing mechanism. Therefore, the facilely designed MXene@Pd CNC sensor is believed to contribute to development of future portable and wearable sensing electronics. [ABSTRACT FROM AUTHOR]

The author comments on the studies on neural networks and sensors. The author wonders on the possibility of the study to be applied in addressing medical applications such as breast cancer. He knows several applications of neural networks in breast cancer in such an instance when a developed website was created that offer predictions of survival probability among cancer patients. The author hopes for an artificial neural network (ANN) expert to investigate on ductal carcinoma in-situ (DCIS).