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The remarkable properties of layered semiconductor nanosheets (LSNs), such as scalable production, bandgap tunability and mechanical flexibility, have promoted them as promising building blocks for nanoelectronics and bioelectronics. However, it is still a challenge to efficiently control the charge transport in LSNs. Here, we demonstrate a novel LSN field-effect transistor (FET) using ionic paper (i-paper) as a solid-like gate dielectric, achieving a highly efficient ionic control of hole and electron transport in MoS2 and WSe2 LSNs, respectively. The i-paper contains a three-dimensional (3D) nanopore structure that allows ionic liquids (ILs) to infiltrate the LSN surface, providing a very large ion/carrier interfacial region as well as an efficient ion transport channel. We achieve an ultra-high current on–off ratio of over 105 for both p-type and n-type i-paper gated LSN FETs. By directly attaching one common i-paper to both n-type and p-type LSN layers, a flexible LSN-based inverter circuit with a gain of ∼3 is realized. Moreover, high-performance i-paper gated LSN FETs are capable of detecting a temperature change as low as 0.02 K. Our results can hold great implications for wide applications of i-paper gated LSN FETs in the future. [ABSTRACT FROM AUTHOR]

In recent years, the development of multi-functional supercapacitors with high flexibility and strong environmental adaptability has gradually become a focus of attention. In this work, a multi-functional paper-based supercapacitor with excellent temperature adaptability, plasticity, tensile strength, strong adhesion, and self-healing properties is obtained by introducing PVA and ZnCl2 into carbonized paper-based materials (APC-PVA@ZnCl2). The as-obtained APC-PVA@ZnCl2 supercapacitor has excellent adaptability to the environment, even in a low-temperature environment below zero, still maintaining a high volumetric specific capacitance of 3438.45 mF cm−3 and high volumetric specific energy density of 44 mW h cm−3. Moreover, the APC-PVA@ZnCl2 supercapacitor can be stretched beyond 2400–2500% strain, indicating good tensile properties. In addition, the APC-PVA@ZnCl2 composite can also be used as a sensing material to detect current signals with different characteristics generated by the movement of different parts of the human body, showing excellent sensing performance. Besides, the APC-PVA@ZnCl2 composite also displays outstanding thermoelectric properties. It is hoped that this work can provide a reference for the development of green multi-functional supercapacitors. [ABSTRACT FROM AUTHOR]

As a part of our ongoing research, we have synthesized a new fluorescence probe, p-C4A, based on a calix[4]arene substituted with 4-aminoquinoline moieties with amide linkages. p-C4A can selectively recognize Li+ and PO43− ions and has been characterized via an emission study, an absorption study, ESI-MS spectroscopy, a 1H NMR study and cyclic voltammetry. The fluorescence sensor p-C4A can operate over a concentration range of 5–170 nM for Li+ sensing and 5–80 nM for PO43− sensing. The R2 values obtained for the sensing of Li+ and PO43− ions are 0.9962 and 0.9911, respectively. p-C4A demonstrates a minimum detection limit of 6.15 nM for Li+ and 9.0 nM for PO43−. The quantum yields of p-C4A as its Li+ and PO43− ion complexes were found to be 0.014 and 0.27, respectively. Herein, we report an easy-to-use, low-cost, disposable, paper-based, fluorescent, wax-printed device for the rapid chemical screening of Li+ and PO43−. This device can be used as a quick, portable, multiple-test panel that is simple, lightweight, and disposable. Moreover, in order to assess its analytical applicability, the prepared sensor was successfully used for the determination of Li+ and PO43− from wastewater samples, validating the proposed ion recovery method with 96–99% recovery rates. [ABSTRACT FROM AUTHOR]

In this work, zinc-doped carbon dots (Zn-CDs) were anchored on a three-dimensional wheel type paper-based microfluidic chip, and were decorated with 6-mercaptonicotinic acid (MNA) and L -cysteine (L -Cys) for highly sensitive and rapid fluorescence detection of Cu2+. Zn-CDs were first anchored on paper through the amide bonds between the carboxyl groups of the Zn-CDs and the amino groups of the paper. Afterwards, Zn-CDs were decorated with MNA and L -Cys, effectively preventing the Zn-CDs from aggregation. The nitrogen atom on the pyridine ring and the carboxylic acid groups in MNA and L -Cys coordinated with Cu2+ to form a nonfluorescent ground-state complex, causing the fluorescence quenching of the Zn-CDs. The three-dimensional rotary design could simplify the operation process and achieve simultaneous analysis of multiple samples with different concentrations. Under optimal conditions, the fluorescent sensor exhibits linear response for the determination of Cu2+ in the range from 0.1 to 60 μg L−1 with the detection limit (LOD) of 0.018 μg L−1. The proposed strategy provides a novel way for the highly sensitive detection of Cu2+ in a complex water environment. [ABSTRACT FROM AUTHOR]

A novel miniaturized and sustainable platform exploiting two merged paper-based substrates has been applied for the programmable pre-concentration of analytes of interest and electrochemical detection of mercury traces in drinking water using printable sensor strips. This strategy represents a novel versatile possibility in merging humble materials maximizing their impacts on analytical and remediation challenges. [ABSTRACT FROM AUTHOR]

Exosomes are vesicles released by healthy and cancer cells into the extracellular matrix and bodily fluid. Cancer cell-derived exosomes have attracted much attention in early-stage detection and prognostication of treatment response. Thus, detecting exosomes is of great interest to biology and medicine. However, many conventional detection methods require high-cost equipment and centralized laboratory facilities, making diagnostics inaccessible in limited-resource settings. This study reports a proof-of-concept low-cost electrochemical paper-based analytical device to quantify both the total bulk and cancer cell-derived exosomes in cell culture media. The device employs a sandwich immune assay design, where exosomes are initially captured using the electrode-bound generic antibodies (i.e. CD9) and subsequently detected via ovarian cancer-specific CA125 antibodies. Our proposed device quantifies the total bulk exosome concentration with a detection limit of 9.3 × 107 exosomes per mL and ovarian cancer cell-derived exosomes with a detection limit of 7.1 × 108 exosomes per mL, with a relative standard deviation of <10% (n = 3). We suggest that this low-cost and simple electrochemical paper-based device could be an alternative tool for detecting disease-specific exosomes in biological samples with the potential to be further developed for point-of-care diagnosis. [ABSTRACT FROM AUTHOR]

Photonic paper with dynamically tunable color has been widely investigated due to its excellent ability to change its optical patterns under external variation. Herein, a UV-responsive metal–insulator–metal (MIM) Fabry-Perot cavity is proposed to prepare dynamic photonic paper through introducing disulfide bonds containing polyurethane as an insulating layer. The as-prepared MIM cavity based photonic paper shows dynamically tunable color variation in almost the whole visible gamut under different UV-irradiation durations. In addition, by simply adjusting the UV-irradiation duration at each point with the aid of a photomask, multicolor patterns could be "written" onto the as-prepared MIM photonic paper. What's more, thanks to the dynamic feature of the disulfide bond, the color patterns on the photonic paper could also be "erased" by thermal treatment, making the photonic paper "rewritable". Together with all these features, the proposed UV-responsive MIM photonic paper would exhibit great potential for application in information anticounterfeiting, dynamic color display devices and environment-friendly inkless color printing. [ABSTRACT FROM AUTHOR]

Paper-fluidic devices are a popular platform for point-of-care diagnostics due to their low cost, ease of use, and equipment-free detection of target molecules. They are limited, however, by their lack of sensitivity and inability to incorporate more complex processes, such as nucleic acid amplification or enzymatic signal enhancement. To address these limitations, various valves have previously been implemented in paper-fluidic devices to control fluid obstruction and release. However, incorporation of valves into new devices is a highly iterative, time-intensive process due to limited experimental data describing the microscale flow that drives the biophysical reactions in the assay. In this paper, we tested and modeled different geometries of thermally actuated valves to investigate how they can be more easily implemented in an LFIA with precise control of actuation time, flow rate, and flow pattern. We demonstrate that bulk flow measurements alone cannot estimate the highly variable microscale properties and effects on LFIA signal development. To further quantify the microfluidic properties of paper-fluidic devices, micro-particle image velocimetry was used to quantify fluorescent nanoparticle flow through the membranes and demonstrated divergent properties from bulk flow that may explain additional variability in LFIA signal generation. Altogether, we demonstrate that a more robust characterization of paper-fluidic devices can permit fine-tuning of parameters for precise automation of multi-step assays and inform analytical models for more efficient design. [ABSTRACT FROM AUTHOR]

A direct mass spectrometry method utilizing reactive paper spray ionization was developed for sensitive cannabinoid quantitation in biofluid matrices. The ca. 2-minute sample measurements used on-paper derivatization to significantly increase paper spray mass spectrometry (PS-MS) positive ion mode sensitivity while minimizing sample preparation steps. Calibrations demonstrate high linearity, with R2 > 0.99 for (−)-trans-Δ9-tetrahydrocannabinol (THC) in oral fluid and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) in urine. The limit of detection and lower limit of quantitation were 0.78 and 10 ng mL−1 for THC in oral fluid and 1.3 and 10 ng mL−1 for THC-COOH in urine, respectively. THC-COOH levels measured by reactive PS-MS in seven spiked human urine samples showed bias of −9.4 to 5.9%, and percent difference values of −16.8 to 9.8% in comparison with a reference LC-MS method. Based upon the method simplicity, validation experiments, sensitivity, and rapidity, we conclude that reactive PS-MS has potential applications for rapid cannabinoid drug testing in urine and oral fluid. [ABSTRACT FROM AUTHOR]

Paper-based flexible sensors have attracted much attention due to their abundant resource, low cost and good degradability in the natural environment leaving no electronic waste (e-waste). However, the mechanical properties of paper still need to be strengthened and the output stability may be impacted by water or high humidity because of the hydrophilicity of cellulose fibers. In order to solve these problems, for the first time, a paper-based flexible sensor with available running data under water without encapsulation was fabricated using softwood cellulose fibers and graphite nanoplates through a papermaking technique in this work. The cellulose nanofibers (CNFs) were added to reinforce the paper and the alkyl ketene dimer (AKD) emulsion was coated on the paper to endow it with super-hydrophobicity. The sensor can be used for both strain and pressure detection. As a strain sensor, the gauge factor (GF) was 18.99 and the response time was 0.3 s. It can be used to monitor human motions such as the bending of fingers, the wrist, and elbow. Interestingly, it was proven to be able to monitor finger bending at high humidity and under water due to its super-hydrophobicity. As a pressure sensor, it exhibited sensitivity S1 = 0.019 kPa−1 in the range of 0 to 316.5 kPa, and S2 = 0.01 kPa−1 in the range of 316.5 to 1421 kPa, with the response time of 0.3 s. The detecting range is much wider than that of reported sustainable flexible pressure sensors. Furthermore, this sensor can be easily disposed of by burning, thus avoiding the production of e-waste. This multifunctional flexible paper-based sensor may find potential in sport and health monitoring, soft robotics and human–machine interfaces. [ABSTRACT FROM AUTHOR]

Here, we introduce the synthesis and deposition of organic/inorganic composite ink on cellulose paper using a rapid ultrasonic spray deposition approach that can be incorporated as a counter electrode (CE) in flexible dye-sensitized solar cells (FDSSCs). The composite ink comprised a copper indium sulfide (CuInS2) nanostructure ink and dispersion of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) in water. Fabricated counter electrodes are biodegradable, environment-friendly, flexible, and economical and meet the requirements for sustainable green energy. To evaluate the catalytic activities and power conversion efficiencies of DSSCs, the produced CuInS2/PEDOT:PSS composite ink-based CEs were compared with PEDOT:PSS counter electrodes. Cyclic voltammetry studies found that CuInS2/PEDOT:PSS had a greater cathodic charge transfer current density (Jc) (−1.23 mA cm−2). Moreover, it was found that the potential separation values are small, which indicate a stronger catalytic activity than PEDOT:PSS counter electrodes. The observed exchange current density (J0) was 3.98 mA cm−2, while the limiting current density (Jlim) increased to 45.7 mA cm−2, indicating a fast redox diffusion rate of the CuInS2/PEDOT:PSS CE. The photovoltaic performances of CuInS2/PEDOT:PSS and PEDOT: PSS-based DSSC's were measured and determined to be 5.66% and 4.41%, respectively, while the performance of CuInS2/PEDOT:PSS FDSSC composed of cellulose paper was 1.06%. [ABSTRACT FROM AUTHOR]

Stimuli-responsive fluorescent materials are ideal materials for paper anti-counterfeiting applications. However, the single responsiveness and the lacking of dynamics present the risk of being deciphered. Herein, we designed a series of cyanostilbene derivatives (ACNs) with fluorescence responses to acid or base. ACN1 with pyridine and hydroxyl groups exhibit dually responsive fluorescence "ON" in the solid state due to the ionization-enhanced intramolecular charge transfer (ICT) effect. Other ACNs with either pyridine or hydroxyl unit show only single responsiveness. Fluorescence papers (FPs) prepared by a simple dipping into the solutions of ACNs maintain the responsive fluorescence performance. FP1H with high ACN1 content exhibits time-dependent dynamic fluorescent colour changes by hydrogen chloride (HCl) vapour fumigation. The applications of paper anti-counterfeiting and information encryption are developed by combining ACN1 with other single-responsive ACNs. Moreover, a four-dimensional (4D) code with time-dependent information changes is designed. Our work provides new materials for the field of paper fluorescent anti-counterfeiting encryption. [ABSTRACT FROM AUTHOR]

Quantitative nucleic acid amplification tests (qNAATs) are critical in treating infectious diseases, such as in HIV viral load monitoring or SARS-CoV-2 testing, in which viral load indicates viral suppression or infectivity. Quantitative PCR is the gold standard tool for qNAATs; however, there is a need to develop point-of-care (POC) qNAATs to manage infectious diseases in outpatient clinics, low- and middle-income countries, and the home. Isothermal amplification methods are an emerging tool for POC NAATs as an alternative to traditional PCR-based workflows. Previous works have focused on relating isothermal amplification bulk fluorescence signals to input copies of target nucleic acids for sample quantification with limited success. In this work, we show that recombinase polymerase amplification (RPA) reactions on paper membranes exhibit discrete fluorescent amplification nucleation sites. We demonstrate that the number of nucleation sites can be used to quantify HIV-1 DNA and viral RNA in less than 20 minutes. An image-analysis algorithm quantifies nucleation sites and determines the input nucleic acid copies in the range of 67–3000 copies per reaction. We demonstrate a mobile phone-based system for image capture and onboard processing, illustrating that this method may be used at the point-of-care for qNAATs with minimal instrumentation. [ABSTRACT FROM AUTHOR]

A portable paper-based electrochemical sensor has been developed to determine 5-hydroxymethylfurfural (5-HMF). A screen-printed carbon electrode (SPCE) was facilely fabricated for the first time on poster paper which showed a very satisfactory electrochemical response. The analytical performance of the electrode was enhanced by electrochemical deposition of silver microdendrites (AgMDs). The cathodic peak of 5-HMF occurred at approximately −1.48 V, lower than that obtained from the bare poster-SPCE. Moreover, the modified electrode showed a higher current response than the bare electrode, revealing that the AgMDs not only exhibited highlighted electrocatalytic features but also improved the electrical conductivity and increased the electrode surface area. Afterward, some influencing conditions were optimized, including scan rate and the number of scan cycles for AgMD deposition, pH, temperature, and square wave voltammetric parameters. Under the optimal conditions, the analytical characteristics of the proposed sensor were evaluated. The cathodic peak current increased linearly according to 5-HMF concentration over the range of 3–100 ppm, and the detection limit was 1.0 ppm. This low-cost, disposable electrochemical sensor provided environmentally friendly, simple and rapid detection, acceptable precision, good stability, and high selectivity. Additionally, this method can be applied to quantify 5-HMF in honey samples with satisfying accuracy. [ABSTRACT FROM AUTHOR]

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

The integration of smartphones with visual-based paper strips has gained great attention because of the rapid, low-cost, and relible analysis. Herein, we report on the synthesis of a red luminescent europiumbased metal organic framework (Eu-MOF) for the detection of folic acid in pharmaceutical formulations. The Eu-MOF showed strong and stable red emission fluorescence (excited at 270 nm), and the emission was significantly quenched upon exposure to folic acid due to the inner filter effect. A fluorometric assay in solution and visual detection based on fluorescence on a paper strip were used independently to quantify folic acid. The paper strips were prepared using chromatography paper and with the aid of a smartphone, folic acid was visually detected. In solution, the calculated LOD was 0.3 mM with a dynamic linearity range from 1.0 to 12.50 mM. Meanwhile, in the visual detection based on a smartphone integrated with a paper test strip, the linearity was from 1.0 to 9.0 mM with 0.12 mM as the LOD. Color analysis, from the photographs taken with a smartphone, was performed via analyzing the RGB coordinates using the Image-J program. The luminescent probe was applicable to detect folic acid in various drug tablets with recovery data ranging from 95 to 103%. The application of smartphones and fluorescent paper strips provides reliable detection of folic acid for on-site analysis, particularly in remote rural areas. [ABSTRACT FROM AUTHOR]

Surveillance of SARS-CoV-2 infection is critical for controlling the current pandemic. Antigen rapid tests (ARTs) provide a means for surveillance. Available lateral flow assay format ARTs rely heavily on nitrocellulose paper, raising challenges in supply shortage. Vertical flow assay (VFA) with cellulose paper as test material attracts much attention as a complementary test approach. However, current reported VFAs are facing challenges in reading the test signal from the bottom face of the test cassette, complicating the test workflow and hindering translation into rapid test application. Here, we address this gap with an enhanced VFA against SARS-CoV-2 N protein that adapts a cellulose pull-down test format allowing (1) one-step sample application at the top of the test cassette and (2) readout of the test signal from the top. We also demonstrate the feasibility of translating the enhanced VFA into a point-of-care application that can help in SARS-CoV-2 surveillance. [ABSTRACT FROM AUTHOR]

Chronic obstructive pulmonary disease (COPD) has become the third leading cause of global death. Insufficiency in early diagnosis and treatment of COPD, especially COPD exacerbations, leads to a tremendous economic burden and medical costs. A cost-effective and timely prevention requires decentralized point-of-care diagnostics at patients' residences at affordable prices. Advances in point-of-care (POC) diagnostics may offer new solutions to reduce medical expenditures by measuring salivary and blood biomarkers. Among them, paper-based analytical devices have been the most promising candidates due to their advantages of being affordable, biocompatible, disposable, scalable, and easy to modify. In this review, we present salivary and blood biomarkers related to COPD endotypes and exacerbations, summarize current technologies to collect human whole saliva and whole blood samples, evaluate state-of-the-art paper-based analytical devices that detect COPD biomarkers in saliva and blood, and discuss existing challenges with outlooks on future paper-based POC systems for COPD diagnosis and management. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogenation of aromatic rings in benzoic acid derivatives has arisen as a notionally engaging substitute for thermal catalysis under mild conditions. However, the utilization of organic solvents and low faradaic efficiency are incompatible with the principles of green chemistry and energy conservation. Herein, bimetallic PtRu supported on carbon paper developed by co-electrodeposition with optimized atomic ratios maintains an inspiring high conversion of 92.9%, high selectivity of 100% and a high faradaic efficiency of 62.2% for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid in an acidic aqueous electrolyte without external H2, which is the best result to date. The optimized electrocatalyst also exhibits outstanding stability and universality for the electrocatalytic hydrogenation of benzoic acid derivatives. In situ Raman results and theoretical calculations prove that the synergistic effect generated by Ru modifying the electronic structure of Pt simultaneously enhances the capture of benzoic acid molecules and interfacial active hydrogen species and lowers the reaction energy barrier. After adsorbing benzoic acid, more accumulation of electrons around the Ru atom reduces the electron density of phenyl, thereby activating the reaction. Meanwhile, the uniform alloy nanoclusters anchored to the carbon paper surface ensure highly efficient electronic transmission and high dispersion of active components, reducing excessive agglomeration. A proton-exchange membrane reactor is also used to certify the potential of the electrocatalytic hydrogenation of benzoic acid derivatives for large-scale application. [ABSTRACT FROM AUTHOR]

Wood bark is a structurally complex by-product of the pulp and paper industry, which focuses primarily on the valorization of structurally more regular wood xylem components. The aim of this study was the elucidation of the less valorised willow wood counterparts (whole bark, inner bark, sclerenchyma bundles, and parenchymatous tissues) by NMR spectroscopic techniques. This allowed a better understanding of the structural features of macromolecular components of bark (i.e. pectin, hemicellulose, and lignin), thus providing a base for a more rational design of the customized biochemical processes prior to chemical processing of bark. This crucial knowledge contributed to the creation of a protocol/decision tool to select tailored enzymes (discarding the slightest substrate binding) for the biological pre-treatment of bark to a state suitable for chemical pulping. Such a protocol/decision-making tool would significantly improve the efficiency of enzyme selection by 60–70% due to the specific catalytic activity of the enzymes involved. [ABSTRACT FROM AUTHOR]

Paper microfluidics is a rapidly growing subfield of microfluidics in which paper-like porous materials are used to create analytical devices that are well-suited for use in field applications. 3D printing technology has the potential to positively affect paper microfluidic device development by enabling tools and methods for the creation of devices with well-defined and tunable fluidic networks of porous matrices for high performance signal generation. This critical review focuses on the progress that has been made in using 3D printing technologies to advance the development of paper microfluidic devices. We describe printing work in three general categories: (i) solid support structures for paper microfluidic device components; (ii) channel barrier definition in existing porous materials; and (iii) porous channels for capillary flow, and discuss their value in advancing paper microfluidic device development. Finally, we discuss major areas of focus for highest impact on the next generation of paper microfluidics devices. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic, caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), has become a public health emergency and widely spread around the world. Rapid, accurate and early diagnosis of COVID-19 infection plays a crucial role in breaking this pandemic. However, the detection accuracy is limited for current single-gene diagnosis of SARS-CoV-2. Herein, we develop an autonomous lab-on-paper platform for multiplex gene diagnosis of SARS-CoV-2 by combining reverse transcription recombinase polymerase amplification (RT-RPA) and CRISPR–Cas12a detection. The autonomous lab-on-paper is capable of simultaneously detecting nucleoprotein (N) gene and spike (S) gene of SARS-CoV-2 virus as well as human housekeeping RNAse P gene (an internal control) in a single clinical sample. With the developed platform, 102 copies viral RNA per test can be detected within one hour. Also, the lab-on-paper platform has been used to detect 21 swab clinical samples and obtains a comparable performance to the conventional RT-PCR method. Thus, the developed lab-on-paper platform holds great potential for rapid, sensitive, reliable, multiple molecular diagnostics of COVID-19 and other infectious diseases in resource-limited settings. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) are foundational devices for point-of-care testing, yet suffer from limitations in regards to their sensitivity and capability in handling complex assays. Here, we demonstrate an airflow-based, evaporative method that is capable of manipulating fluid flows within paper membranes to offer new functionalities for multistep delivery of reagents and improve the sensitivity of μPADs by 100–1000 times. This method applies an air-jet to a pre-wetted membrane, generating an evaporative gradient such that any solutes become enriched underneath the air-jet spot. By controlling the lateral position of this spot, the solutes in the paper strip are enriched and follow the air jet trajectory, driving the reactions and enhancing visualization for colorimetric readout in multistep assays. The technique has been successfully applied to drive the sequential delivery in multistep immunoassays as well as improve sensitivity for colorimetric detection assays for nucleic acids and proteins via loop-mediated isothermal amplification (LAMP) and ELISA. For colorimetric LAMP detection of the COVID-19 genome, enrichment of the solution on paper could enhance the contrast of the dye in order to more clearly distinguish between the positive and negative results to achieve a sensitivity of 3 copies of SARS-Cov-2 RNAs. For ELISA, enrichment of the oxidized TMB substrate yielded a sensitivity increase of two-to-three orders of magnitude when compared to non-enriched samples – having a limit of detection of around 200 fM for IgG. Therefore, this enrichment method represents a simple process that can be easily integrated into existing detection assays for controlling fluid flows and improving detection of biomarkers on paper. [ABSTRACT FROM AUTHOR]

Wearable displays with aesthetic design, durability, and washability are highly desired for communication and information gathering wherever and at any time. However, daily wear and washing might damage the characteristics of wearable displays with flexible plastic or extra elastomer substrate, and long-time repeated actuation could also lead to electric fatigue in the display. Here, we proposed a machine-washable, tailorable, and comfortable wearable textile-based electrophoretic electronic paper display (EPD) by encapsulating the electrophoretic ink microcapsules and hot pressing EPD into the daily textile. The gadget exhibited a contrast ratio of 13 and good stability after repeated harsh deformation (e.g., soaking, needling, tailoring, or machine washing). The optimal contrast ratio that benefited from the selected high- κ elastomer waterborne polyurethane (WPU) was achieved in human safety voltage. To demonstrate its potential application, the EPD prototypes of a patterned static display T-shirt and a lightweight dynamic display wristband watch were fabricated by screen printing and laser engraving. The as-fabricated textile-based EPDs with features, including simple fabrication with aesthetic design, excellent waterproofness, low energy consumption, and stretchability, provide important guidance for human and machine interaction for realizing truly wearable displays (i.e., wearing displays). [ABSTRACT FROM AUTHOR]