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Herein is presented a novel and efficient portable paper-based sensing platform using paper-incorporated histidine stabilized gold nanoclusters (His-AuNCs), for the sensitive and selective detection of Fe ions from low-volume real water samples based on photoluminescence (PL) quenching. Highly photoluminescent colloidal His-AuNCs are obtained via a novel microwave-assisted method. The His-AuNCs-based sensor reveals a limit of detection (LOD) as low as 0.2 μM and a good selectivity towards Fe ions, in solution. Further, the fabricated portable sensing device based on paper impregnated with His-AuNCs proves to be suitable for the easy detection of hazardous Fe levels from real water samples, under UV light exposure, through evaluating the level of PL quenching on paper. Photographic images are thereafter captured with a smartphone camera and the average blue intensity ratio (I/I0) of the His-AuNCs-paper spots is plotted against [Fe2+] revealing a LOD of 3.2 μM. Moreover, selectivity and competitivity assays performed on paper-based sensor prove that the proposed platform presents high selectivity and accuracy for the detection of Fe ions from water samples. To validate the platform, sensing assays are performed on real water samples from local sources, spiked with 35 μM Fe ions (i.e., Fe2+). The obtained recoveries prove the high sensitivity and accuracy of the proposed His-AuNCs-paper-based sensor pointing towards its applicability as an easy-to-use, fast, quantitative and qualitative sensor suitable for on-site detection of toxic levels of Fe ions in low-volume real water samples. [ABSTRACT FROM AUTHOR]

The adverse effect of ultraviolet (UV) radiation on human beings has sparked intense interest in the development of new sensors to effectively monitor UV and solar exposure. This paper describes a novel low-cost and flexible graphene oxide (GO)-based paper sensor capable of detecting the total amount of UV or sun energy delivered per unit area. GO is incorporated into the structure of standard printing paper, cellulose, via a low-cost fabrication technique. The effect of UV and solar radiation exposure on the GO paper-based sensor is investigated using a simple color change analysis. As a result, users can easily determine the amount of ultraviolet or solar energy received by the sensor using a simple color analysis application. A neural network (ANN) model is also explored to learn the relation between UV color intensity and exposure time, then digitally display the results. The accuracy for the developed ANN reached 96.83%. The disposable, cost-effective, simple, biodegradable, safe, and flexible characteristics of the paper-based UV sensor make it an attractive candidate for a variety of sensing applications. This work provides new vision toward developing highly efficient and fully disposable GO-based photosensors. [ABSTRACT FROM AUTHOR]

Antimicrobial stewardship practices are critical in preventing the further erosion of treatment options for bacterial infections. Yet, at the same time, determination of an infection's antimicrobial susceptibility requires multiple rounds of culture and expensive lab automation systems. In this work, we report the use of paper-based surface enhanced Raman spectroscopy (SERS) sensors and portable instrumentation to phenotypically discriminate multi-drug resistance with fewer culture steps than conventional clinical microbiology. Specifically, we demonstrate the identification of resistance to varying generations of β -lactam antibiotics by detecting the activity of particular β -lactamase enzymes in a multiplexed assay. The method utilizes molecular reporters that consist of β -lactams with SERS barcodes. Hydrolysis of the β -lactam by β -lactamase enzymes in the sample expels the barcode; the released sulfur-containing barcode is then detected via SERS. Using this approach, we demonstrate the differentiation of E. coli strains with (1) extended spectrum β -lactamase (ESBL), (2) narrow-spectrum β -lactamase, and (3) no resistance, using only a single measurement on a single sample. In addition, we experimentally validate an approach to expand the library of reporters through the simple chemical synthesis of new barcoded β -lactams. Importantly, the reported method determines the susceptibility based on phenotypic β -lactamase activity, which is aligned with current microbiology lab standards. This new method will enable the precise selection of effective β -lactam antibiotics (as opposed to defaulting to drugs of last resort) faster than current methods while using simple steps and low-cost portable instrumentation. Image 1 • We demonstrate phenotypic detection of β-lactamase activity using paper SERS sensors and portable instrumentation. • We show discrimination of β -lactamases with different degrees of resistance in a single sample on a single sensor. • We demonstrate a simple synthesis method to expand the library of SERS-based β -lactamase reporters. • We accomplish β-lactamase discrimination in significantly less time than conventional microbiology. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to develop flexible sensors for detection of different concentrations of bacteria, such as Pseudomonas aeruginosa and Staphylococcus aureus, in saline. Design/methodology/approach: The sensors were fabricated using ink-jet printing technology and they consist of a pair of silver interdigitated electrodes printed on mechanically flexible substrates – foil and paper. In house measurement setup for testing and characterization of sensors has been developed. Structural, electrical and mechanical properties of flexible sensors have been determined and compared. Findings: The characteristics of sensor – the resonant frequency as a function of different concentrations of each bacteria – are presented. The obtained results demonstrate different resonant frequencies for each dilution of Pseudomonas aeruginosa and Staphylococcus aureus in physiological saline. Research limitations/implications: Both sensors showed accurate measurements of bacterial count, which can be achieved with detection of resonant frequency, and this is reflective of the number of bacterial cells within a sample. Practical implications: The findings suggest that the newly developed method based on measuring resonant frequency corresponds well with bacterial cell count, thus establishing a new proof-of-concept that such method can have significant applications in bacterial cell counting that are economic and easily maintained. Social implications: Fast, cost-effective, accurate and non-invasive method for detection of different bacteria from saline was developed. Originality/value: For the first time, comparison between performances of flexible sensors on foil and paper for bacteria detection is demonstrated. Almost linear dependence between shift of resonant frequency of developed sensors and concentration of bacteria has been obtained. [ABSTRACT FROM AUTHOR]

The measurement of water inside a transformer is essential to maintain its reliable operation, as the water content can increase as the transformer ages. This measurement is frequently performed by a utility as a part of its periodic maintenance activities. In this paper, the application of optical fiber sensors as an online method to measure water content of paper inside an operating transformer is presented. There are several advantages of using these sensors, including their size, lightweight, flexibility, multiplexing, no-electromagnetic interference, etc. A unique benefit of fiber optic technology is that sensors can be embedded into the winding structure and operate in areas of high electric field strength. For this work, fiber optic water and temperature sensors are investigated by comparing their measurements to a commercial water activity probe immersed in oil. The study found that the determination of water content by fiber optic sensors compared closely with other techniques, which lead to the conclusion that they can be an effective technology for water measurement in an operational transformer. [ABSTRACT FROM AUTHOR]

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

In the past few years, point-of-care testing (POCT) technology has crossed the boundaries of laboratory determination and entered the stage of practical applications. Herein, the latest advances and principal issues in the design and fabrication of paper-based bipolar electrode electrochemiluminescence (BPE-ECL) sensors, which are widely used in the POCT field, are highlighted. After introducing the attractive physical and chemical properties of cellulose paper, various approaches aimed at enhancing the functions of the paper, and their underlying principles are described. The materials typically employed for fabricating paper-based BPE are also discussed in detail. Subsequently, the universal method of enhancing BPE-ECL signal and improving detection accuracy is put forward, and the ECL detector widely used is introduced. Furthermore, the application of paper-based BPE-ECL sensors in biomedical, food, environmental and other fields are displayed. Finally, future opportunities and the remaining challenges are analyzed. It is expected that more design concepts and working principles for paper-based BPE-ECL sensors will be developed in the near future, paving the way for the development and application of paper-based BPE-ECL sensors in the POCT field and providing certain guarantee for the development of human health. • Preparation and application prospect of paper-based BPE-ECL sensor are discussed. • Approaches to boost functionalization of paper and existing limitations are described. • Fabricating BPE from classical electrode materials are introduced exhaustively. • Strategies of enhancing ECL signal to improve device sensitivity are displayed. [ABSTRACT FROM AUTHOR]

Ion-selective electrodes (ISEs) are an efficient and versatile tool for ion detection. However, portability and applicability for field applications are often limited by the need of a conditioning step, and high cost of the needed bulky reference electrode. Herein, the traditional conditioning protocol of ISEs has been eliminated and a paper-based solid-contact ISE (PBSC-ISE) has been integrated with a paper-based solid-contact reference electrode (PBSC-RE) in a single strip format for on-site analysis. The PBSC-RE is based on the copolymer methyl methacrylate-co-decyl methacrylate (MMA-DMA) (support matrix), combined with ionic liquids (ILs) to create and maintain a stable potential that is un-affected by a change in ionic activity. This single-strip ready-to-use sensor yields a Nernstian response towards Na +, K + , and I − ions with submicromolar limits of detection, and is able to be used for multiplex analysis. [ABSTRACT FROM AUTHOR]

The utility of strikingly simple and cheap optoelectronic detectors operating according to a Paired-Emitter-Detector-Diode (PEDD) principle for microfluidic paper-based analytical devices (μPAD) has been experimentally confirmed. The prototypes of these compact detectors have been made of only two customary light emitting diodes without any additional optical parts like lens, filters, fibers etc. Moreover, for their operation economic and portable equipment is required (low-power circuit and ordinary voltmeter). Photometric and fluorometric PEDDs for paper devices are developed. In both cases the possibility of their applicability in transmittance and reflectance modes of measurements are presented. In these investigations as model analytes some coloured and fluorescence substances have been handled, but the utility of several developed systems for real chemical analysis has also been demonstrated. The results of photometric determination of hemoglobin in human blood, as well as fluorometric determination of quinine in tonics and calcium ions in mineral waters using various PEDD-μPAD systems have been shown. [ABSTRACT FROM AUTHOR]

Paper-based materials have attracted a great deal of attention in sensor applications because they are readily available, biodegradable, inexpensive, and mechanically flexible. Although paper-based sensors have been developed, but important obstacles remian, which include the retention of chemical and mechanical stabilities when paper is wetted. Herein, we develop a simple and scalable process for fabrication of newspaper-based platforms by coating of parylene C and patterning of metal layers. As-prepared parylene C-coated newspaper (PC-paper) provides low-cost, disposable, and mechanically and chemically stable electrochemical platforms for the development of potentiometric ion sensors for the detection of electrolyte cations, such as, H + and K + . The pH and K + sensors produced show near ideal Nernstian sensitivity, good repeatability, good ion selectivity, and low potential drift. These disposable, flexible ion sensors based on PC-paper platforms could provide new opportunities for the development of point-of-care testing sensors, for diagnostics, healthcare, and environment testing. [ABSTRACT FROM AUTHOR]

Inkjet printing is an advanced printing technology that has been used to develop conducting layers, interconnects and other features on a variety of substrates. It is an additive manufacturing process that offers cost-effective, lightweight designs and simplifies the fabrication process with little effort. There is hardly sufficient research on tactile sensors and inkjet printing. Advancements in materials science and inkjet printing greatly facilitate the realization of sophisticated tactile sensors. Starting from the concept of capacitive sensing, a brief comparison of printing techniques, the essential requirements of inkjet-printing and the attractive features of state-of-the art inkjet-printed tactile sensors developed on diverse substrates (paper, polymer, glass and textile) are presented in this comprehensive review. Recent trends in inkjet-printed wearable/flexible and foldable tactile sensors are evaluated, paving the way for future research. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Facile, Flexible, and Fast sensing of spike protein with SERS paper sensor. • Low-cost / Ecofriendly green assisted production of spherical silver nanoparticles. • Paper sensor detectability is 2.4 pg/ul of spike protein of SARS-CoV-2 virus. • Spike protein sensing in saliva is achieved with SERS paper sensor. • Lab on paper ensures environment sustainability by its safe disposal. Rapid investigation on the detection of spike protein with paper sensor is projected with Surface Enhanced Raman Spectroscopy (SERS). SERS sensor with lab on paper is preceded with facile, cost-effective strategy. Silver nanoparticles with average size of 20–30 nm were produced by green chemistry approaches, followed by loading the nanoparticles on hydrophobic paper surfaces. The very low %RSD (∼1.5) with mapping scan ensembles high reproducibility. Spike protein detection analysis derived the prominent finger print regions of amide bands as well abundant amnio acids (Phenylalanine-1003 cm−1, Tryptophan- 680 cm−1, Tyrosine-1473 cm−1) respectively. The detectability of sensor is gauged to be 2.4 pg / µL. Real time analysis on human saliva spiked with spike protein exhibited diagnosis within 2 min. Developed paper sensor provide us the scope of SERS technique to bring state of art in early detection of covid infections and safe disposal after its use. [ABSTRACT FROM AUTHOR]

Current methods of monitoring breathing require cumbersome, inconvenient, and often expensive devices; this requirement sets practical limitations on the frequency and duration of measurements. This article describes a paper-based moisture sensor that uses the hygroscopic character of paper (i.e. the ability of paper to adsorb water reversibly from the surrounding environment) to measure patterns and rate of respiration by converting the changes in humidity caused by cycles of inhalation and exhalation to electrical signals. The changing level of humidity that occurs in a cycle causes a corresponding change in the ionic conductivity of the sensor, which can be measured electrically. By combining the paper sensor with conventional electronics, data concerning respiration can be transmitted to a nearby smartphone or tablet computer for post-processing, and subsequently to a cloud server. This means of sensing provides a new, practical method of recording and analyzing patterns of breathing. [ABSTRACT FROM AUTHOR]

SUMMARY This paper is concerned with the distributed [ABSTRACT FROM AUTHOR]

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

We demonstrate novel graphite-on-paper piezoresistive devices. The graphite was used as sensing component. The fabrication process can be finished in a short time with simple tools (e.g., a scissor and a pencil). A small array of six paper-based piezoresistive devices is made. The whole device is flexible. The test results showed that the change of resistance was proportional to the applied force. A paper-based weighing balance was also made as an example of applications. This novel array of paper-based piezoresistive devices will open wide applications in force and acceleration sensing areas. [ABSTRACT FROM AUTHOR]

Abstract: A novel method for the fabrication of paper-based microfluidic diagnostic devices is reported; it consists of selectively hydrophobizing paper using cellulose reactive hydrophobization agents. The hydrophilic–hydrophobic contrast of patterns so created has excellent ability to control capillary penetration of aqueous liquids in paper channels. Incorporating this idea with digital ink jet printing techniques, a new fabrication method of paper-based microfluidic devices is established. Ink jet printing can deliver biomolecules and indicator reagents with precision into the microfluidic patterns to form bio-chemical sensing zones within the device. This method thus allows the complete sensor, i.e. channel patterns and the detecting chemistries, to be fabricated only by two printing steps. This fabrication method can be scaled up and adapted to use high speed, high volume and low cost commercial printing technology. Sensors can be fabricated for specific tests, or they can be made as general devices to perform on-demand quantitative analytical tasks by incorporating the required detection chemistries for the required tasks. [Copyright &y& Elsevier]

In this paper, the feasibility of inkjet printing of circuit and microwave structures on paper-based substrates is investigated for the first time in the implementation of a complete low-cost wireless platform for sensors. First, the system-level design of the module including the amplifier characterization were carried out to ensure optimum performance of the sensor modules in the UHF bands used in RF identification communication. These results were then used to design two different antenna structures, which are printed on paper along with their respective circuit layouts using inket-printing technology. Different techniques were investigated for the assembly of circuit components on the silver printed layouts. Finally, wireless link measurements on the assembled prototypes verified the good performance on the wireless and sensing sides. [ABSTRACT FROM AUTHOR]

Silicon carbide has attracted considerable attention in recent years as a potential material for sensor devices. This paper reviews the current status of SiC technology for a wide range of sensor applications. It is shown that SiC MEMs devices are well-established with operational devices demonstrated at high temperatures (up to 500 °C) for the sensing of motion, acceleration and gas flow. SiC sensors devices using electrical properties as the sensing mechanism have also been demonstrated principally for gas composition and radiation detection and have wide potential use in scientific, medical and combustion monitoring applications. [ABSTRACT FROM AUTHOR]

The ability to manipulate semiconductor surfaces and interfaces has gained significant attention in the past few years, in particular to design novel routes for the development of sensors and new materials, like intelligent tissues, for bio-physics applications. In this paper, we review some recent results on the atomic manipulation of cubic silicon carbide (SiC) surfaces, as obtained by ab initio simulations, and compare them with the available experimental data. The main focus will be the study of the interaction and adsorption mechanism of simple molecules on SiC surfaces. SiC, and in particular the cubic polytype, is a wide-gap semiconductor, that for its inertness and transparency has been and still is considered a leading candidate material for biocompatible devices. [ABSTRACT FROM AUTHOR]

Abstract: The (CR–LR) difference technique, based on the CR-39 and LR 115 detectors, for the determination of implanted 210Po in glass after deposition of short-lived radon progeny, was analyzed in details in this paper. The sensitivities of both detectors were calculated using the Monte Carlo method with V functions particularly derived in our previous works for the detectors used in the present experiments. The dependency of the sensitivity ratio on the removed layer of both detectors was determined and verified experimentally. The simulated sensitivity ratios correlate well with the experimental ones. A major finding of the present work is that the sensitivity ratio between the CR-39 and LR 115 detectors depends only weakly on the ratio between the 238U and 232Th concentrations in the glass samples. This is crucial for the application of the (CR–LR) difference technique for retrospective radon exposure assessments, since measurements of the 238U and 232Th concentrations in the relatively small real-life glass samples will make the retrospective radon exposure assessments impractical. [Copyright &y& Elsevier]

The article discusses the study on how far optical paper quality characterization can reach on its own merits. The study involves the use of a combination of digital image acquisition, followed by the angle measurement technique (AMT). Fourteen selected paper quality parameters were evaluated using new image analytical techniques for characterization and monitoring of paper quality. The results show that the new remote sensing image technique shows promising application potential for online product monitoring of the specified physical qualities.

Fabriano paper was aged by irradiation with ultraviolet light (λ=310) in a veterometer for 300 hours. At fixed time intervals, samples of the paper under test were analysed by titanium dioxide photosensor to determine electrochemically the ‘environmental persistence’ index, by a suitable conductimeter method, to determine the specific conductivity variation and by thermogravimetry to determine the moisture content, the onset temperature of the cellulose degradation process and the value of the activation energy of the same process. The behaviour of these different types of indicators displayed approximately monotonous trends as a function of time. [ABSTRACT FROM AUTHOR]

Paper‐based superomniphobic surfaces are of great interest because paper is flexible, inexpensive, lightweight, breathable, and recyclable. Prior reports on paper‐based superomniphobic surfaces have failed to demonstrate high mobility with low surface tension liquids. In order to overcome this issue, in this work, superomniphobic papers are developed through growth of nanofilaments on inherent microfibers of papers without noticeably altering their microscale features (i.e., diameter and distance of the microfibers). These superomniphobic papers display very low roll‐off angle, indicative of ultra‐high droplet mobility, even with low surface tension liquids. Here, a facile method is also developed to control the motion and adhesion of the droplets on the superomniphobic paper. Utilizing such liquid mobility in a controlled manner on these superomniphobic papers, a simple on‐paper pH sensor is fabricated. It is anticipated that this on‐paper, simple, and rapid detection methodology can also be extended to the colorimetric sensing of protein and chemical assays. Further, these superomniphobic papers have potential applications in water–oil separation and enhanced weight‐bearing capacity. [ABSTRACT FROM AUTHOR]

The article announces several awards which include best poster award to Intelligent Event Management with Bluetooth Sensors Networks, best demo award to Personalized In-Vehicle Information Systems: Buildingand Application Infastructure for Smart Cars in Smart Spaces and best paper to An Approach for Secure Role Assignment.