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Disposable wearable electronics are valuable for diagnostic and healthcare purposes, reducing maintenance needs and enabling broad accessibility. However, integrating a reliable power supply is crucial for their advancement, but conventional power sources present significant challenges. To address that issue, a novel paper-based moist-electric generator is developed that harnesses ambient moisture for power generation. The device features gradients for functional groups and moisture adsorption and architecture of nanostructures within a disposable paper substrate. The nanoporous, gradient-formed spore-based biofilm and asymmetric electrode deposition enable sustained high-efficiency power output. A Janus hydrophobic-hydrophilic paper layer enhances moisture harvesting, ensuring effective operation even in low-humidity environments. This research reveals that the water adsorption gradient is crucial for performance under high humidity, whereas the functional group gradient is dominant under low humidity. The device delivers consistent performance across diverse conditions and flexibly conforms to various surfaces, making it ideal for wearable applications. Its eco-friendly, cost-effective, and disposable nature makes it a viable solution for widespread use with minimal environmental effects. This innovative approach overcomes the limitations of traditional power sources for wearable electronics, offering a sustainable solution for future disposable wearables. It significantly enhances personalized medicine through improved health monitoring and diagnostics., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

Distorted urea levels indicate several liver, kidney, or metabolic diseases; however, traditional clinical urea detection relies on urease-based methods enslaved to well-known limitations of high-price, unstable properties, complicated sample pretreatment and analysis procedures, and difficult visual real-time monitoring. Herein, nonenzymatic paper-based fluorescent materials (UFP-BP) are strategically integrated with an on-demand fluorescent-sensor (UFP) self-aggregated nanoparticle on commercial filter paper for pre-dilution-free and visual real-time urea monitoring. The UFP is synthesized and self-aggregated into the fluorescent nanoparticles for selective urea recognition. Then, the nanoparticles are interstitially loaded on filter paper to nanoengineer the UFP-BP, achieving selective quantitative urea detection in the normal concentration range (10-1000 mm). UFP and UFP-BP can successfully monitor urea levels in real rat urine, artificial simulants, and milk. The proposed sensing platform, integrated with smartphones, offers accurate, quantitative, nonenzymatic, noninvasive, pre-dilution-free, on-site, rapid, low-cost, easy-to-operate, real-time visual urea detection in food samples and human body fluids. The designed sensing system can provide early warnings of abnormal nitrogen-based health issues., (© 2024 Wiley‐VCH GmbH.)

Electrochemical paper-based microfluidics has attracted much attention due to the promise of transforming point-of-care diagnostics by facilitating quantitative analysis with low-cost and portable analyzers. Such devices harness capillary flow to transport samples and reagents, enabling bioassays to be executed passively. Despite exciting demonstrations of capillary-driven electrochemical tests, conventional methods for fabricating electrodes on paper impede capillary flow, limit fluidic pathways, and constrain accessible device architectures. This account reviews recent developments in paper-based electroanalytical devices and offers perspective by revisiting key milestones in lateral flow tests and paper-based microfluidics engineering. The study highlights the benefits associated with electrochemical sensing and discusses how the detection modality can be leveraged to unlock novel functionalities. Particular focus is given to electrofluidic platforms that embed electrodes into paper for enhanced biosensing applications. Together, these innovations pave the way for diagnostic technologies that offer portability, quantitative analysis, and seamless integration with digital healthcare, all without compromising the simplicity of commercially available rapid diagnostic tests., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

Abstract Here the performance of phase change material (PCM)‐coated paper made from unbleached kraft pulp is introduced. The applied PCM consists of a mixture of ethylene glycol distearate (EGDS), a well‐known PCM wax material, and a fully substituted cellulose stearoyl ester (CSE). Transfer of the PCM material onto/into paper is achieved by spray as well as blade coating of EGDS + CSE mixture. It is shown that the kind of coating method used does not interfere with observed PCM properties. The significantly higher melt viscosity of the EGDS + CSE blends ensures that the EGDS wax is not bleeding out of the paper, which avoids the use of further encapsulation processes. The PCM behavior, as observed by thermal load measurements, and the thermal buffering of the coated paper is a function of the applied mass of the PCM material applied. The thermal retention exhibited a quasi‐isothermal behavior at ≈65 °C with EGDS + CSE coatings. These effects can offset fluctuations in temperature, and the PCM papers can be employed to achieve a more uniform temperature setting. PCM‐modified papers are therefore interesting candidates for paper‐based packaging or for use in paper‐based sensors, where overheating can strongly affect reliability of results.

We developed a simple, paper-based device that enables sensitive detection by mass spectrometry (MS) without solid phase extraction or other sample preparation. Using glass fiber filter papers within a 3D printed holder, the device employs electrokinetic manipulations to stack, separate, and desalt charged molecules on paper prior to spray into the MS. Due to counter-balanced electroosmotic flow and electrophoresis, charged analytes stack on the paper and desalting occurs in minutes. One end of the paper strip was cut into a sharp point and positioned near the inlet of a MS. The stacked analyte bands move toward the paper tip with the EOF where they are ionized by paper spray. The device was applied to analysis of PFAS in tap water with sub part-per-trillion detection limits in less than ten minutes with no sample pretreatment. Analysis of opioids in urine also occurs in minutes. The crucial parameters to enable stacking, separation, and MS ionization of both positively and negatively charged analytes were determined and optimized. Experimental and computational modeling studies confirm the electrokinetic stacking and analyte transport mechanisms. On-paper separations were carried out by stacking analyte bands at different locations depending on their electrophoretic mobility, achieving baseline separation in some cases., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Abstract Paper finishing, in particular, coating paper with desired barrier functions is well‐developed as of today. However, due to large amounts of material and process energy as well as the use of non‐renewable resources for such coatings, common technologies are not sustainable. Given the increasing importance of paper in manifold applications, more sustainable routes with low‐energy processes as well as biogenic material alternatives are highly needed. To address this challenge, a solvent‐free and material‐efficient approach is proposed to bio‐based paper coatings by depositing chia oil‐based plasma polymers using a jet‐induced sliding discharge concept at atmospheric pressure. Depending on the amount of coating and the paper porosity, this treatment retards water absorption. Coating visualization is enabled through confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Like chia oil, safflower oil, and olive oil show the ability to hydrophobize paper and the great potential within plasma polymerized vegetable oils to make the paper coating more sustainable.

Phototransistors are used in plenty of diverse applications such as optical communication systems, light sensors, imaging devices, and biomedical instruments for detecting and amplifying light signals. Herein, an approach for the large‐scale production of low‐cost and flexible phototransistors by integrating the inks of PEDOT:PSS, and graphite with paper, which serves as an ionic conductor material to gate the PEDOT:PSS channel, is proposed. The fabrication of the devices is carried out by sequentially depositing the PEDOT:PSS channel and graphite electrodes onto paper using a benchtop XY plotter. To characterize device‐to‐device variability, 200 devices are fabricated and their electrical and optical properties are statistically analyzed. By performing a detailed characterization on the optical properties under varying wavelength, power, and bias conditions, it is found that devices exhibit good photoresponse across a wide spectrum range. Moreover, devices maintain their photoactive characteristics even when subjected to high mechanical tensile strain, indicating the suitability of these paper‐supported devices for flexible electronic applications. Time and photocurrent magnitude can be tuned via gate voltages applied through the graphite‐based back‐gate configuration.

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

Salmonella, the most prevalent food-borne pathogen, poses significant medical and economic threats. Swift and accurate on-site identification and serotyping of Salmonella is crucial to curb its spread and contamination. Here, a synthetic biology cascade reaction is presented on a paper substrate using CRISPR-Cas12a and recombinase polymerase amplification (RPA), enabling the programming of a standard toehold RNA switch for a genome of choice. This approach employs just one toehold RNA switch design to differentiate between two different Salmonella serotypes, i.e., S. Typhimurium and S. Enteritidis, without the need for reengineering the toehold RNA switch. The sensor exhibits high sensitivity, capable of visually detecting as few as 100 copies of the whole genome from a model Salmonella pathogen on a paper substrate. Furthermore, this robust assay is successfully applied to detect whole genomes in contaminated milk and lettuce samples, demonstrating its potential in real sample analysis. Due to its versatility and practical features, genomes from different organisms can be detected by merely changing a single RNA element in this universal cell-free cascade reaction., (© 2024 Wiley‐VCH GmbH.)

Microfluidic paper-based analytical devices (µPADs) are indispensable tools for disease diagnostics. The integration of electronic components into µPADs enables new device functionalities and facilitates the development of complex quantitative assays. Unfortunately, current electrode fabrication methods often hinder capillary flow, considerably restricting µPAD design architectures. Here, laser-induced graphenization is presented as an approach to fabricate porous electrodes embedded into cellulose paper. The resulting electrodes not only have high conductivity and electrochemical activity, but also retain wetting properties for capillary transport. Paper-based electrofluidics, including a lateral flow device for injection analysis of alkaline phosphatase in serum and a vertical flow device for quantitative detection of HPV16 with a CRISPR-based assay are demonstrated. It is expected that this platform will streamline the development of diagnostic devices that combine the operational simplicity of colorimetric lateral flow tests with the added benefits and possibilities offered by electronic signaling., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

In this work, multiscale techniques to model the pressure driven and electroosmotic flows in porous materials with paper-like microstructures are studied and applied. The multiscale technique is based on the definition of a representative volume element (RVE) of the material, where the microstructure is built from connected channels, where the fluid moves inside the void of the porous material. For fluid flow, the velocity is solved under incompressible flow conditions in the Stokes regime at the microscale level, while the homogeneous Darcy problem is solved at the macroscale level. Similarly, for electroosmotic flow, the velocity and pressure are also solved at the microscale under incompressible flow conditions in the Stokes regime. However, in this case a Helmholtz-Smoluchowsky term is considered at the surface of the solid microstructure. Such term is calculated by solving the electric field via the charge conservation equation. Consequently, the electroosmotic velocity is included in the fluid dynamic problem as a boundary condition, significantly reducing the computational demand. Afterward, once the homogenized velocity field of the microscale problem is obtained, an effective pressure-based permeability and an effective electroosmotic permeability are estimated at the macroscale. To validate the results, a comparison is made with experimental data and other numerical studies reported in the literature for common papers used in microfluidics, such as Whatman # $\#$ 1 and Munktel 00A, but also through comparisons with direct numerical simulations. Finally, we propose a microcell structure for representing such papers for matching fluid flow and electrical properties. With such topology, electroosmotic and mixed fluid flow are solved in order to demonstrate the capabilities of the multiscale technique for representing different phenomena involved in paper-based microfluidics. With these microcells will be also possible to predict other physicochemical phenomena which are important for paper-based microfluidics such as capillary imbibition or scalar dispersion, among others., (© 2025 Wiley‐VCH GmbH.)

Copper-based pigments, such as verdigris, have caused severe damage to many important historical documents, and their preservation remains a significant concern for paper conservators and researchers. This study re-evaluates the efficacy of two promising antioxidants, tetrabutylammonium bromide (TBABr) and benzotriazole (BTA), as stabilization agents for paper documents containing verdigris pigment. The evaluation was conducted under mild accelerated degradation conditions using historically accurate mock-up paper samples. To assess the stability of the mock-up papers, various parameters were measured during accelerated degradation, including colour, molecular weight (Mw), and pH value. Size exclusion chromatography measurements of Mw confirmed that TBABr provided superior stabilization compared to BTA. Additionally, the total colour change was slightly more pronounced in the samples treated with BTA compared to those treated with TBABr. However, during degradation, some paper samples containing thicker application of pigment exhibited significant black and brown spots, regardless of treatment (untreated, treated with BTA, or TBABr). X-ray photoelectron spectroscopy confirmed the presence of both Cu(I) and Cu(II) oxidation states in all samples, with a higher Cu(II) content on the surface of TBABr treated samples compared to those treated with BTA. This may indicate differences in the mechanisms of degradation. Raman spectroscopy identified the spots on both untreated and TBABr-treated samples as copper(II) oxide., (© 2025 The Author(s). ChemPlusChem published by Wiley-VCH GmbH.)

Per- and polyfluoroalkyl substances (PFAS) are a widely used class of synthetic chemicals that pose a significant global environmental and health threat due to their persistent and bioaccumulation toxicity caused by strong C-F bonds in their structures. PFAS usually exist in trace concentrations in environmental water bodies, which poses great challenges for environmental analysis. In this study, environmentally friendly cellulose was modified with polyaniline through in situ oxidative polymerization, and used as the filter paper for solid-phase extracting 23 PFAS in water. Characterization techniques such as scanning electron microscope, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer, and thermogravimetric analysis indicated the successful synthesis of structurally stable polyaniline-modified cellulose filter paper (PANI/CFP). Then, a high-performance liquid chromatograph-triple quadrupole mass spectrometry determination method was established for 23 PFAS from water using PANI/CFP extraction. The optimal adsorption occurred at a solution pH of 3.0-5.0, and the best elution efficiency can be achieved using methanol with 2% added ammonia water. The adsorption mechanism of 23 PFAS by PANI/CFP can be considered as the result of synergistic effects between physical and chemical adsorption. The recovery rates for 23 PFAS in groundwater, surface water, and wastewater ranged from 65.8% to 105%, with limits of detection and quantification from 0.44 to 36.5 ng/L. After being reused five times, PANI/CFP can still maintain a good extraction recovery rate for PFAS. This study successfully prepared PANI/CFP and established an experimental method flow for its application in the extraction and detection of 23 PFAS in water. The PANI/CFP has the characteristics of stable structure and properties, and easy operation., (© 2025 Wiley‐VCH GmbH.)

Abstract Home‐based Nucleic Acid Amplification Tests (NAATs) for viral infections would be an important step to improve public health, but sample preparation remains an important obstacle, particularly for the protection of target RNA from RNases in samples. Here, a new method for RNase deactivation in saliva samples is presented. This method uses Proteinase K (PK) immobilized on nitrocellulose membrane to store and deliver the enzyme, capable of digesting nucleases present in the sample. The immobilized PK is also separated from the amplification reagents, so that it does not disrupt DNA amplification, thus omitting the need for heat‐deactivation or dilution steps. Treatment by PK nitrocellulose at 50 °C dramatically decreases the RNase activity of RNase A, in diluted saliva samples, and even shows promising results at 42 °C. The potential of this method to protect RNA from digestion is further demonstrated, by pretreating diluted saliva samples spiked with Influenza Virus A (IVA) genomic RNA, which allows its amplification and colorimetric detection by lateral flow strips. In the absence of PK pretreatment, the RNA is digested by RNase, which leads to false negative results. These findings show that immobilized PK enables the integration of sample preparation of viral samples toward home‐based NAATs.

Abstract This study identifies important factors for designing an effective biomimetic paper‐based fog harvesting substrate by examining the harvesting properties of different surfaces, including glass, polyethylene, and superhydrophobic paper. In laboratory‐scale fogging tests, the wetting behavior of the substrates is characterized, and the importance of the tilt angle of the respective surface relative to the fog flow is elaborated. Because successful fog harvesting requires both efficient accumulation of water droplets on the surface (by condensation and collision) and sufficient but not excessive roll‐off of the liquid, the amount of water finally collected is clearly related to the pinning effect, which should prevent the smallest droplets from being carried away by the wind but must not lead to full and permanent wetting of the surface. Coalescence is identified as a major phenomenon to improve droplet roll‐off. In this context, superhydrophobic paper indicates to be a more effective water collector than glass or polyethylene, especially when oriented vertically, since it allows the droplets to roll off very efficiently. Finally, the addition of glass particles to the superhydrophobic coating is proposed as a means of enhancing pinning and improving the fog harvesting efficiency.

Abstract 3D tissue‐engineered models are poised to facilitate understanding of skeletal muscle pathophysiology and identify novel therapeutic agents to improve muscle health. Adopting these culture models within the broader biology community is a challenge as many models involve complex methodologies and significant investments of time and resources to optimize manufacturing protocols. To alleviate this barrier, a protocol with commercially available reagents is developed to cryopreserve myoblasts in a 96‐well compatible format that allows tissues to be transferred to users without expertise in 2D or 3D skeletal muscle cell culture. This report validates that myoblasts encapsulated in a hydrogel and cryopreserved in paper‐based scaffolds maintain cell viability, differentiation, and function via acetylcholine‐induced transient calcium responses. Furthermore, successful shipping of myoblasts cryopreserved in paper‐based scaffolds to intra‐provincial and international collaborators is demonstrated who successfully thaw, culture, and use the 3D muscle tissues. Finally, the application of this method is confirmed for studying muscle endogenous repair by seeding freshly isolated skeletal muscle stem cells to cryopreserved then differentiated and injured tissues, demonstrating expected responses to a known stimulator of muscle stem cell self‐renewal, p38α/β MAPKi. Altogether, the 3D myoblast cryopreservation protocol offers broadened access of a complex skeletal muscle tissue model to the research community.

Abstract The synergy resulting from the high conductivity of graphene and catalytic properties of metal nanoparticle has been a resource to improve the activity and functionality of electrochemical sensors. This work focuses on the simultaneous synthesis of copper nanoparticles (CuNPs) and laser‐induced graphene (LIG) derived from paper, through a one‐step laser processing approach. A chromatography paper substrate with drop‐casted copper sulfate is used for the fabrication of this hybrid material, characterized in terms of its morphological, chemical, and conductive properties. Appealing conductive properties are achieved, with sheet resistance of 170 Ω sq−1 being reached, while chemical characterization confirms the simultaneous synthesis of the conductive carbon electrode material and metallic copper nanostructures. Using optimized laser synthesis and patterning conditions, LIG/CuNPs‐based working electrodes are fabricated within a three‐electrode planar cell, and their electrochemical performance is assessed against pristine LIG electrodes, demonstrating good electron transfer kinetics appropriate for electrochemical sensing. The sensor's ability to detect glucose through a non‐enzymatic route is optimized, to assure good sensing performance in standard samples and in artificial sweat complex matrix.

Abstract Paper, an inexpensive material with natural biocompatibility, non‐toxicity, and biodegradability, allows for affordable and cost‐effective substrates for unconventional advanced electronics, often called papertronics. On the other hand, polymeric elastomers have shown to be an excellent success for substrates of soft bioelectronics, providing stretchability in skin wearable technology for continuous sensing applications. Although both materials hold their unique advantageous characteristics, merging both material properties into a single electronic substrate reimagines paper‐based bioelectronics for wearable and patchable applications in biosensing, energy generation and storage, soft actuators, and more. Here, a breathable, light‐weighted, biocompatible engineered stretchable paper is reported via coaxial nonwoven microfibers for unconventional bioelectronic substrates. The stretchable papers allow intimate bioconformability without adhesive through coaxial electrospinning of a cellulose acetate polymer (sheath) and a silicone elastomer (core). The fabricated cellulose‐silicone fibers exhibit a greater percent strain than commercially available paper while retaining hydrophilicity, biocompatibility, combustibility, disposable, and other natural characteristics of paper. Moreover, the nonwoven stretchable cellulose‐silicone fibrous mat can adapt conventional printing and fabrication process for paper‐based electronics, an essential aspect of advanced bioelectronic manufacturing.

Abstract Paper‐based devices have attracted considerable attention in point‐of‐care testing (POCT) due to their simple operation and portability. The performance of paper‐based POC assays is further enhanced by coupling with functional nucleic acids (FNAs), which are able to selectively recognize and bind to targets, amplify and transduce signals. Several high‐performance paper‐based POC assays have been developed, resulting from the different spatial structures of the paper‐based device and detection strategies using different FNAs. In this review, we first introduce FNAs and paper‐based devices, including their concepts, classifications and advances. The following section focuses on the application of these FNAs in POC assays using paper‐based devices, taking into account their spatial one‐, two‐ and three‐dimensional structures. Finally, the challenges and perspectives of the application of FNAs in paper‐based POCT are discussed.

Bioelectronic implants delivering electrical stimulation offer an attractive alternative to traditional pharmaceuticals in electrotherapy. However, achieving simple, rapid, and cost-effective personalization of these implants for customized treatment in unique clinical and physical scenarios presents a substantial challenge. This challenge is further compounded by the need to ensure safety and minimal invasiveness, requiring essential attributes such as flexibility, biocompatibility, lightness, biodegradability, and wireless stimulation capability. Here, a flexible, biodegradable bioelectronic paper with homogeneously distributed wireless stimulation functionality for simple personalization of bioelectronic implants is introduced. The bioelectronic paper synergistically combines i) lead-free magnetoelectric nanoparticles (MENs) that facilitate electrical stimulation in response to external magnetic field and ii) flexible and biodegradable nanofibers (NFs) that enable localization of MENs for high-selectivity stimulation, oxygen/nutrient permeation, cell orientation modulation, and biodegradation rate control. The effectiveness of wireless electrical stimulation in vitro through enhanced neuronal differentiation of neuron-like PC12 cells and the controllability of their microstructural orientation are shown. Also, scalability, design flexibility, and rapid customizability of the bioelectronic paper are shown by creating various 3D macrostructures using simple paper crafting techniques such as cutting and folding. This platform holds promise for simple and rapid personalization of temporary bioelectronic implants for minimally invasive wireless stimulation therapies., (© 2024 Wiley‐VCH GmbH.)

Abstract Urinary tract infections (UTIs) are the most common nosocomial infection in North America leading to over $12 billion in annual health care costs. UTIs can significantly reduce the quality of life and, in severe cases, result in sepsis and mortality. According to Public Health Ontario, over 80% of long‐term care home (LTCH) residents with asymptomatic bacteriuria are treated with antibiotics, however, less than 50% of the antibiotic treatments for UTIs show clinical benefit. Current confirmatory processes for UTIs are primarily dependent on the completion of urine cultures which can result in a delay of more than 24 h. Therefore, there is a need to develop new efficient diagnostic methods to provide timely test results and prevent multidrug resistance. Emerging nanomaterials with special physical and chemical properties have demonstrated great potential in rapid detection of UTI‐associated bacteria. This review paper provides a thorough analysis of current diagnostic tools for UTIs. Emerging nanostructured biosensors are reviewed to elucidate the most recent progress in the detection of uropathogens. It is believed that advanced biosensors integrated with nanotechnology will contribute to the timely diagnosis of UTIs and improve the accuracy of the results, which will lead to better treatment of this prevalent clinical condition.

Nowadays, gastroesophageal reflux disease (GERD) has emerged as one of the major hazards to the health of the upper gastrointestinal tract, and there is an urgent need for a low-cost, user-friendly, and non-invasive detection method. Herein, a paper-based sensor (CP sensor) for the non-invasive screening of GERD is proposed. The sensor is structured as a specially shaped cellulose paper strip embedded with fluorescent colloids, which are self-assembled from a cleavable synthetic fluorescent polymer (P4). Benefiting from the introduction of amide bonds and the unique assembled structure of the nanocolloids, the pepsin in the sample solution will hydrolyze the water-soluble branches in the micellar shell during detection, resulting in a corresponding output of the fluorescent signal. This responsiveness, which can be observed by the naked eye, is so sensitive with a minimum detectable concentration for pepsin as low as 0.3 ng·mL -1 . Clinical trials have further demonstrates that the designed paper sensor is capable of providing improved accuracy in the early diagnosis of GERD., (© 2025 Wiley‐VCH GmbH.)

In Singapore's hot and humid climate, watercolor papers are particularly prone to a paper oxidation issue known as foxing, which refers to the discoloration forming yellowish-brown stains on paper, changing the visual outcome of the watercolor artworks. This research investigates two most popular types of watercolor paper, made from 100 % cotton and cotton-wood-pulp mixture. Foxing was generally categorized into two types: biotic and abiotic foxing caused by fungi activities and the presence of metallic contaminants catalytic fungi growth. However, recent hypotheses further relate it to heterogeneous cellulose structures. Watercolor paper is typically produced in a well-controlled environment, which should theoretically reduce the occurrence of foxing, catalyzed by metallic contaminants. The research involved a comprehensive analysis of aged samples, from old watercolors, dating back to the 1990s and fresh watercolor paper samples. focusing on understanding the origin and causes of watercolor paper foxing based on cellulose content & structures. By comparing 100 % cotton and cotton wood-pulp blended watercolor paper, the susceptivity of foxing was hinted to be related to cellulose packing density. These findings will support further research in developing strategies for the conservation and storage of watercolor artworks., (© 2024 Wiley-VCH GmbH.)

Abstract Cellulose paper has emerged as an ideal sensing element for wearable pressure sensors owing to its inherent flexibility, high porosity, and light weight. However, traditional paper‐based pressure sensors use metal‐based materials as electrodes, which significantly limits the unique advantages of paper, particularly in terms of degradability. In this study, a degradable pressure sensor is designed by combining the highly conductive poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) Xuan paper electrode with a low‐conductivity PEDOT:PSS tissue paper sensitive layer. Notably, Xuan paper, also called rice paper, has been a prominent substrate owing to its softness and good durability. By introducing a perforated structure in the sensitive layer, a novel sensing mechanism, conductivity conversion under pressure, is realized to improve the sensitivity. The obtained sensor exhibits a high sensitivity (13.9 kPa−1 at < 8.3 kPa, 151 kPa−1 at 8.3–20.8 kPa), ensuring that it can precisely monitor the full‐range human activities. Additionally, as the sensor does not rely on metal materials, it can degrade in water or fire without causing any negative environmental impacts. These findings establish a new approach to producing highly sensitive degradable sensors, which hold significant potential for application in green electronics, paper‐based sensing matrices, new prosthetics, and other fields.

The escalating needs in information protection underscore the urgency of developing advanced encryption strategies. Herein we report a novel chemical approach that enables information encryption by on-paper electrochemiluminescence (ECL). Dendritic porous silica nanospheres modified with polyetherimide and bovine serum albumin were prepared as the chemical ink to write the secret message on a paper. Attaching the paper to an electrode, immersing it in a solution containing tris(2,2'-bipyridyl)ruthenium (Ru(bpy) 3 2+ ) and then applying a suitable voltage, a remote "catalytic route" electrochemical reaction produces ECL that functions as the key to decrypt and visualize the message by imaging. In addition, proteins can be also used as the biological ink to write the secret message, which is then decrypted by a combined use of immunochemistry and ECL imaging as two keys. We believe the ECL-based strategy holds great promise in high-safety and multilevel information encryption, as it is protected not only by encoding, like conventional invisible inks, but also by the unique ECL decoding approach., (© 2024 Wiley-VCH GmbH.)

Soft robots based on actuators that can work in both on-ground and on-water situations are environmentally adaptable and can accomplish tasks in complex environments. However, most current amphibious actuators need external stimuli to move on water and require complex preparation processes. Herein, amphibious Ink-paper/polyethylene programmable actuators and robots are proposed, which are fabricated by rapidly brushing Chinese ink on paper. The actuator can bend on the ground and move autonomously on the water. On one hand, the actuator shows a maximum bending curvature of 2.66 cm -1 under near-infrared light, and the actuation performance can be programmed by ink concentration. Moreover, actuators with pen-brushed information can be shape-programmed for dynamic information display. On the other hand, the actuator can autonomously move on the water by using Chinese ink as Marangoni fuel. The maximum moving velocity is 4.73 cm s -1 . When the ink is saturated in the water, the actuator can further be driven by an infrared laser. Finally, three soft robots with diverse programmable amphibious motions are designed. Both the crawling/bending motion on the ground and autonomous linear/rotary movement on the water can be programmed by altering actuator structures. This research will provide new inspirations for next-generation amphibious actuators and soft robots., (© 2025 Wiley‐VCH GmbH.)

Although paperless technologies are becoming ubiquitous, paper and paper-based materials remain one of the most widely used resources, predicted to exceed an annual total of 460 million metric tons by 2030. Given the environmental challenges, deleterious impact on natural resources, and waste associated with conventional wood-based paper manufacturing, developing more sustainable strategies to source, produce, and recycle paper from natural materials is essential. Here, the development and production of reusable and recyclable paper are reported. This approach offers a pathway for easily producing natural pollen grains via ecofriendly, economical, scalable, and low-energy fabrication routes. It is demonstrated that the pollen-based paper exhibits high-quality printability, readability, and erasability, enabling its reuse. Based on the pH-responsive morphological responses of engineered pollen materials, a method for hygro stable printing and on-demand unprinting is presented. The reusability of the pollen paper renders it more advantageous than conventional single-print wood-based paper. This study thus provides possible pathways to utilize non-allergenic pollen, which is renewable and naturally abundant, as a sustainable source of reusable paper. While this work primarily deals with paper, the methods described here can be extended to produce other products such as cartons and containers for the storage and transport of liquid and solid materials., (© 2022 Wiley-VCH GmbH.)

Electroextraction (EE) encompasses a range of sample preparation methods whose effectiveness, selectivity, and efficiency are significantly influenced by the physical-chemical characteristics of analytes, samples, and instrumental conditions. This article explores, for the first time, various strategies aimed at enhancing the extraction efficiency of a recent approach of EE utilizing a paper point (PP) combined with a hollow fiber (HF) (abbreviated as PP-HF-EE) to extract various cationic and anionic model compounds from water samples. The study also explores, experimentally, the impact of agitation, organic filter composition, PP diameter, and PP brand on extraction performance, and proves that all these factors are quite important, especially when digital image analysis is utilized for determination. Furthermore, this work demonstrates the ease and feasibility of simultaneously extracting cations and anions using PP-HF-EE and proposes a straightforward method to enhance analyte concentration on the vertex of the PP through a base-to-vertex focusing. Lastly, it is demonstrated, using capillary electrophoresis coupled to a UV-Vis detector, that for PP-HF-EE, the extraction efficiency and pre-concentration factor are less dependent on other parameters when multiple PPs per sample are utilized, with signal enhancement values of up to 111 and 339 for nortriptyline and haloperidol, respectively. All the findings and strategies presented herein constitute significant contributions that can facilitate future research in method development, particularly in the utilization of PP-HF-EE and similar EE approaches., (© 2024 Wiley‐VCH GmbH.)

Accurate quantification of disease-signature microRNAs (miRNAs) in biomedical samples is in high demand for clinical diagnosis but still challenging because of the low abundance of miRNAs and complicating interferences in the milieus. Here, we report a multi-amplification strategy based on paper-spray mass spectrometry (PS MS) for the analysis of miRNAs in blood. A toehold-mediated DNA-strand-displacement reaction (TSD) is employed to amplify the signal chain and to ensure the specificity. The signal chain is then cleaved by UV light to release signal molecules for detection. Moreover, the paper spray method can efficiently filter out interfering substances in the blood and further enhance the sensitivity of detection. This concept is successfully demonstrated in the prototypical detection of the cancer biomarker miRNA-141 in blood and serum. The proposed TSD-PS MS approach provides an efficient method for the sensitive detection of oligonucleotides at low concentration in complicated milieus., (© 2021 Wiley-VCH GmbH.)

Abstract Health monitoring using wearable artificial intelligence (AI) sensors with sensing and cognitive capabilities has garnered significant attention. The development of self‐contained AI sensors that can operate with low power consumption, akin to the human brain, is necessary. Physical reservoir computing (PRC), which mimics the human brain using physical phenomena, offers a low‐power consumption architecture. Nevertheless, creating a flexible and easily disposable sensors using PRC capable of processing optical signals with sub‐second response times suitable for biological signals presents a challenge. In this study, a disposable and flexible paper‐based optoelectronic synaptic devices are designed, which are composed of nanocellulose and ZnO nanoparticles, for PRC. This device exhibits synaptic photocurrent in response to optical input. To assess its performance, a classification and time‐series forecasting tasks are conducted. The memory capacity of short‐term memory task, indicating the device's ability to store past information, is 1.8. The device can recognize handwritten digits with an accuracy of 88%. These results highlight the potential of the device for PRC. In addition, subjecting the device to 1000 rounds of bending do not affect its accuracy. Furthermore, the device burn in a few seconds, much like regular office paper, demonstrating its disposability.

Triboelectric nanogenerators (TENGs) represent a promising technology for energy harvesting and self-powered sensing with a wide range of applications. Despite their potential, challenges such as the need for cost-effective, large-area electrodes and engineering sustainable triboelectric materials remain, especially given the impending restrictions on single-use engineering plastics in Europe. To address these challenges, engineering nano-graphite-coated paper is presented as a sustainable and high-performance alternative for triboelectric layers. Moreover, this material, which can be produced on an industrial scale, offers a viable replacement for metal electrodes. The combination of nano-graphite and paper, with its large contact area and inherent surface roughness, enables ultra-high power densities exceeding 14 kW m -2 , driven by electrostatic discharge at the surface. Beyond energy harvesting, smart sensors are developed for floors and walls that detect movements for security purposes and smart sheets that monitor body movements and physiological activities during sleep. The findings highlight the potential of this engineering paper to serve as an eco-friendly alternative to engineering plastics in TENGs and electrodes, opening new avenues for future applications., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Lignin has been extensively researched as a cathode active material in secondary batteries. In the present work, the energy storage potential of lignin naturally present in papers made of softwood chemi-thermomechanical pulp (CTMP) is explored. More specifically, effects from softwood CTMP fines on the electrochemical characteristics have been studied. Compared to pulp fibers, fines are higher in lignin content and have higher specific surface area. It was expected that this would be positive for the electrode performance; however, the result points to the opposite. The fines do not significantly contribute to a higher lignin specific capacity, and they deteriorate the cycling stability. Higher fines content was found to result in a higher oxidative activity as well as more abundant competing reactions. These competing reactions are believed to be linked to the cycle stability. Therefore, we hypothesize that the electrochemical stability of lignin can be better understood by studying differences between fines and fiber lignin. As the theoretical specific capacity of this material is about 20 times larger than obtained here, identification of the reasons for this capacity discrepancy is needed to realize the full potential of lignin-based paper batteries., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

As sustainable and eco-friendly replacements to conventional paper, rewritable paper is a very attractive alternative for communication, information circulation, and storage. Development is made for rewritable paper using chromogenic materials that change its color in presence of external stimuli. However, the new techniques have faced several major challenges including feasible operational method, eco-friendly approach. Herein, a simple, convenient, and eco-friendly strategy is described for the preparation of rewritable paper substrate, and multi colored ink for efficient use in writing, painting or printing purpose. In addition, writing with "invisible ink" on the rewritable paper can be realized for potential anti-counterfeiting application. The written, painted, or printed information on the paper substrate can be easily erased using an aqueous solution. Thus, the original paper can be retrieved and the paper substrate can be reused multiple times. Besides, the written or printed information can be retained for a prolonged time at ambient conditions. Overall, this approach shows the rewritable paper as a prototype of multicolor writing/painting application, offering a sustainable solution for reducing paper waste and promoting environmental stewardship., (© 2024 Wiley‐VCH GmbH.)

Abstract Miniaturized paper‐based electrochemical sensors were fabricated using kraft paper and CO2 laser, dispensing the need for chemical reagents and controlled atmospheric conditions. This study initially evaluated the paper type and laser processing parameters, enhancing the electrodes′ robustness, electrochemical response, and electrical resistance. The sensors were also treated by applying −1 V for 60 s in 1.0 mol L−1 KCl, which is a simple and rapid procedure. The electrochemical treatment increased the electroactive area and roughness, confirmed by scanning electron microscopy. These aspects helped modulate the sensors′ electrochemical response for nitrite determination, improving selectivity and sensitivity for this compound. The sensors also showed repeatability and batch‐to‐batch reproducibility, with 2.2 and 10 % RSD, respectively. Therefore, this work brings a protocol to fabricating competitive electrochemical sensors through a sustainable strategy, opening possibilities for designing new analytical systems.

Abstract An increase in the environmental and health concerns over fluorochemical‐based, wax‐based, and extrusion‐based paper coatings has led to a growing interest in bio‐based, biodegradable, and repulpable alternatives to obtain water‐ and oil‐repellent coatings. Reported herein is a fluorine‐free, plastic‐free, and cost‐effective water and grease resistant paper coating approach that utilizes blends of corn‐starch (S) and a novel chitosan‐graft‐polydimethylsiloxane (CP) copolymer. The hydrophobic and oleophobic performance of the S/CP‐coated paper was evaluated by varying the ratio of S and CP in the overall blend. The S/CP‐coated papers were observed to have low cobb60 values (water absorptivity) of 13 ± 0.9 g m−2 and an excellent kit rating (oil resistance) of 12/12. The S/CP‐coated paper substrate surface profile was analyzed via scanning electron microscopy (SEM). The repulpability of the coated paper is also demonstrated by washing the coating materials from the paper and recovering the pulp.

Transparent paper manufactured from wood fibers is emerging as a promising, cost-effective, and carbon-neutral alternatives to plastics. However, fully exploring their mechanical properties is one of the most pressing challenges. In this work, a strong yet tough transparent paper with superior folding endurance is prepared by rationally altering the native fiber structure. Microwave-assisted choline chloride/lactic acid deep eutectic solvent (DES) pulping is first utilized to isolate wood fibers from spruce wood. During this process, the S1 layer within the fibers is partially disrupted, forming protruding microfibrils that play a crucial role in enhancing cellulose accessibility. Subsequently, carboxymethylation treatment is applied to yield uniformly swollen carboxymethylated wood fibers (CM fibers), which improves the interaction between CM fibers during papermaking. The as-prepared transparent paper not only shows a 90% light transmittance (550 nm) but also exhibits impressive mechanical properties, including a folding endurance of over 26 000, a tensile strength of 248.4 MPa, and a toughness of 15.6 MJ m -3 . This work provides a promising route for manufacturing transparent paper with superior mechanical properties from wood fibers and can extend their use in areas normally dominated by high-performance nonrenewable plastics., (© 2024 Wiley‐VCH GmbH.)

Abstract This study reports the selective hydroxylation of macroscopic carbon surfaces that renders initially hydrophobic carbon fiber paper hydrophilic for more than one year (62 weeks) so far. This long time of sustained hydrophilicity is unprecedented and transforms the utility of macroscopic carbon materials. Quantification of surface oxygenates of a systematic series of 13 chemical treatments reveals that surface hydroxyls are predictors of long‐lasting hydrophilicity. The rapid, mild, acid‐free, transition‐metal‐free treatment does not leave surface residues, inhibits overoxidation of graphitic carbon beyond hydroxyls, and introduces the highest edge density on carbon surfaces, without altering the mesostructure of carbon fiber network architectures and without lowering the flexural strength of carbon fiber paper. Graphitic edges are required for enhanced stability of surface oxygenates that retain a threshold amount of adsorbed water, which is necessary for keeping carbon fiber paper hydrophilic. Application of hydrophilic carbon fiber paper as high‐surface‐area working electrode supports for alkaline water oxidation catalyzed by [NiFe]‐layered double hydroxide nanosheets demonstrates a factor of 60 higher mass activity compared to catalysis on flat basal‐plane highly ordered pyrolytic graphite electrodes.

Abstract Flexible conducting materials are required for the design and fabrication of a host of applications involving flexible electronic items. A flexible substrate like paper or polymer is generally employed for deposition of metal by a variety of processes. Among many physical properties, the roughness of the substrate is considered an important parameter, although, its exact role on effective conductivity of the coating is not known. Nor any study has been carried out to understand how the three‐dimensional porous structure of the substrate surface affects the microscopic packing of grains that constitute the metal coating. With the objective of elucidating the effect of substrate roughness on the conductivity of paper electrodes, we have used six different commonly available papers for vacuum coating with copper. For a smooth substrate, the grains that constitute the coating appear spherical, however, turns ellipsoidal as the substrate roughness and heterogeneity is increased; ellipsoidal grains result in higher packing efficiency leading to higher conductivity. We have also presented a model to relate the packing efficiency to the asphericity, polydispersity, and skewness of size distribution of grains.

Although photochromic molecules have attracted widespread interest in various fields, solid-state photochromism remains a formidable challenge, owing to the substantial conformational constraints that hinder traditional molecular photoisomerization processes. Benefiting from the significant color change upon radical generation, chemical systems enabling a photoinduced radical (PIR) behavior through photoinduced electron transfer (PET) could be ideal candidates for solid-state photochromism within minimized need of conformational freedom. However, the transient nature of radicals causes a dilemma in this Scheme. Herein, we present a general crystal engineering strategy for rapidly generated (7-s irradiation to saturation) and ultra-stable (lasting 12 weeks) PIRs in the solid state, based on the anti-parallel alignment of para-hydroxyphenyl groups of persulfurated arenes to form a strong non-covalent network for efficient PET and radical stabilization. Using this strategy, a PIR platform was constructed, with a superior photochromic behavior remaining in different solid forms (even in the fully-ground sample) due to their transcendent crystallization ability. On this basis, our compounds can be further processed into reusable papers for light-writing, accompanied by water fumigation for modulating the reversible process. This work provides new insights into addressing solid-state photochromism and can inspire a wide range of optical material design from the switchable radical perspective., (© 2024 Wiley-VCH GmbH.)

Lithium (Li) metal is regarded as the most promising anode for next-generation batteries with high energy density. However, the uncontrolled dendrite growth and infinite volume expansion during cycling seriously hinder the application of Li metal batteries (LMBs). Herein, an inorganic/organic protective layer (labeled as BPH), composed of in situ formed inorganic constituents and PVDF-HFP, is designed on the 3D carbon paper (CP) surface by hot-dipping method. The BPH layer can effectively improve the mechanical strength and ionic conductivity of the SEI layer, which is beneficial to expedite the Li-ion transfer of the entire framework and achieve stable Li plating/stripping behavior. As a result, the modified 3D CP (BPH-CP) exhibits an ultrahigh average Coulombic efficiency (CE) of ≈99.7% over 400 cycles. Further, the Li||LiFePO 4 (LFP) cell exhibits an extremely long-term cycle life of over 3000 cycles at 5 C. Importantly, the full cell with high mass loading LiFePO 4 (20 mg cm -2 ) or LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM, 16 mg cm -2 ) cathode exhibits stable cycling for 100 or 150 cycles at 0.5 C with high-capacity retention of 86.5% or 82.0% even at extremely low N/P ratio of 0.88 or 0.94. believe that this work enlightens a simple and effective strategy for the application of high-energy-density and high-rate-C LMBs., (© 2024 Wiley‐VCH GmbH.)

Abstract Nano‐silver conductive inks have attracted the attention of researchers due to their high electrical conductivity, good chemical stability, and wide applicability. As the mainstream conductive ink, it is mostly used in inkjet printing, but its application is limited due to the high sintering temperature. In this paper, silver nanoparticles were synthesized by reducing silver nitrate with sodium borohydride. Using silver nanoparticles as basic conductive fillers and graphene or copper nanoparticles as auxiliary conductive fillers, silver conductive inks, silver/graphene conductive inks and silver/copper conductive inks suitable for micro‐direct writing printing were prepared. Electrode patterns were printed on photo paper by micro‐pen writing printing. The prepared paper electrode can detect nitrate using electrochemical analysis. The results show that the paper electrodes prepared with the three conductive inks can be used for the analysis of potassium ferricyanide and potassium nitrate. The minimum square resistance of paper electrodes prepared with silver conductive ink is 0.11 Ω/sq. It can be cycled 60 times in electrochemical applications with small standard deviation and high reproducibility and stability. Analysis and detection can also be performed in nitrate concentrations ranging from 60 μM to 1000 μM. This low silver‐containing, green, and low resistivity flexible electrode offers a solution for the simplicity and economy of electronic devices.

Abstract Enhanced and rapid surveillance for diseases is critical to public health and meeting United Nations' Sustainable Development Goal for Good Health and Well‐being by allowing for targeted and accelerated prevention and control response strategies. Human malaria, caused by Plasmodium spp. and transmitted by mosquitoes is no exception. Advances in sustainable materials provide an opportunity to improve fast, sustainable, and equitable testing assays. Here, naturally abundant polymers and biomaterials, such as cellulose nanocrystals (CNCs) and chitosan, were used to increase antibody density deposition on the assay detection line when compared to traditional free antibody deposition, and thus the sensitivity, of easily assembled rapid tests designed to detect Plasmodium vivax infective (sporozoite) parasites in mosquitoes, a critical indicator of malaria transmission. The immobilization of antibodies onto chitosan‐coated CNCs allowed for antigen detection with a lower number of antibodies used in each test; likewise, the immobilization allowed to directly place the CNC‐Ab without the traditionally needed blockers layer on the paper like bovine serum albumin (BSA). This bio‐based prototype of a paper‐based dipstick assay shows a promising pathway for the development of rapid disease surveillance tools using sustainable and globally available materials.

Abstract Wearable sensors are establishing themselves as options for real‐time continuous health monitoring in health care and wellness. In particular, the use of flexible interfaces that conform to the skin have attracted considerable interest for the extraction of meaningful pathophysiological information through continuous and painless sampling and analysis of biofluids. In contrast, conventional techniques for biomarkers analysis are difficult to adapt to real‐time portable monitoring due to their invasive sampling protocols, biosample preparation and reagent stabilization. Here a shelf‐stable, non‐invasive, paper‐based colorimetric wearable lactate sensor is reported. This sensor exploits the ability of silk to control the concentration, print, and functionally preserve labile transducing biomolecules in the format of a shelf‐stable digital patch for optical readout. This novel approach overcomes major challenges associated with the commercialization of colorimetric wearable sensors (e.g., enzyme thermal instability, narrow sensing range, low sensitivity, and qualitative response) by showing a combination of unprecedented stability (i.e., up to 2 years in refrigerated conditions), wide sensing range, and high sensitivity. Additionally, real‐time quantitative signal readouts are achieved using machine learning‐driven image analysis enabling physiological status evaluation with a simple smartphone camera.

Abstract The fabrication of flexible catalytic films with isolated single/dual‐atomic sites and their integration in wearable electronics is challenging. Herein, an efficient method to prepare atomically dispersed binary Ni/Co‐decorated flexible carbon nanofiber (NiCo‐CNF) film using formamide‐derived cyano‐specific NiCo‐NC as nanofillers was developed. The optimized Ni1Co1‐CNF catalytic film, having large‐area, high density of adjacent Ni‐N4 and Co‐N4 active sites, and good mechanical properties under repeated bending and release conditions, possessed high catalytic activity towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The ORR/OER potential difference (ΔE10) for Ni1Co1‐CNF at 10.0 mA cm−2 was highly comparable with the Pt/C+RuO2 mixture. In addition, flexible Ni1Co1‐CNF‐assembled Zn‐air battery displayed very good mechanical robustness and cycling stability. Our work may inspire the fabrication of other atomic metal‐decorated films for membrane electrocatalysis.

Laser-induced graphene (LIG) technology has provided a new manufacturing strategy for the rapid and scalable assembling of triboelectric nanogenerators (TENG). However, current LIG-based TENG commonly rely on polymer films, e.g., polyimide (PI) as both friction material and carbon precursor of electrodes, which limit the structural diversity and performance escalation due to its incapability of folding and creasing. Using specialized PI paper composed of randomly distributed PI fibers to substantially enhance its foldability, this work creates a new type of TENG, which are structurally foldable and stackable, and performance tailorable. First, by systematically investigating the laser power-regulated performance of single-unit TENG, the open-circuit voltage can be effectively improved. By further exploiting the folding process, multiple TENG units can be assembled together to form multi-layered structures to continuously expand the open-circuit voltage from 5.3 to 34.4 V cm -2 , as the increase of friction units from 1 to 16. Last, by fully utilizing the unique structure and performance, representative energy-harvesting and smart-sensing applications are demonstrated, including a smart shoe to recognize running motions and power LEDs, a smart leaf to power a thermometer by wind, a matrix sensor to recognize writing trajectories, as well as a smart glove to recognize different objects., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Silver nanoparticles (AgNPs) are in situ synthesized for the first time on microfibrillated silk (MFS) exfoliated from domesticated Philosamia cynthia ricini (eri) and Bombyx mori (mulberry) silkworm silk fibers. The process is rapid (hours time), does not rely on harmful chemicals, and produces robust and flexible AgNPs coated MFS (MFS-AgNPs) protein papers with excellent handling properties. None of these can be achieved by approaches used in the past to fabricate AgNPs silk systems. MFS bonds the AgNPs strongly, providing good support and stabilization for the NPs, leading to strong wash fastness. The mechanical properties of the MFS-AgNPs papers largely do not change compared to the MFS papers without nanoparticles, except for some higher concentration of AgNPs in the case of mulberry silk. The improved tensile properties of eri silk papers with or without AgNPs compared to mulberry silk papers can be attributed to the higher degree of fibrillation achieved in eri silk and its inherent higher ductility. MFS-AgNPs from eri silk also exhibit strong antibacterial activity. This study provides the basis for the development of smart protein papers based on silk fiber and functional nanomaterials., (© 2020 Wiley-VCH GmbH.)

Electrochemical aptamer-based (E-AB) sensors offer a powerful and general means for analyte detection in complex samples for various applications. Paper-based E-AB sensors could enable portable, low-cost, and rapid detection of a broad range of targets, but it has proven challenging to fabricate suitable three-electrode systems on paper. Here, we demonstrate a simple, economic, and environmentally friendly strategy for fabricating aptamer-modified paper electrochemical devices (PEDs) via ambient vacuum filtration. The material, shape, size, and thickness of the three-electrode PED system can be fully customized. We developed aptamer-modified PEDs that enable sensitive and specific detection of small molecules in minimally processed biosamples. The sensitivity and stability of the PEDs are comparable to E-AB sensors based on commercial gold electrodes. We believe our strategy can lead to the development of high performance PEDs for the on-site detection of a variety of analytes., (© 2020 Wiley-VCH GmbH.)

Bladder cancer is the fourth most common cancer in men, and it is becoming a prevalent malignancy. Most of the regular clinical examinations are prompt evaluations with cystoscopy, renal function testing, which require high-precision instrument, well-trained operators, and high cost. In this study, a microfluidic paper-based analytical device (μPAD) was fabricated to detect nuclear matrix protein 22 (NMP22) and bladder cancer antigen (BTA) from the urine samples. Urine samples were collected from 11 bladder cancer patients and 10 well-beings as experiment and control groups, respectively, to verify the working efficiency of μPAD. A remarkable checkout efficiency of up to 90.91% was found from the results. Meanwhile, this method is feasible for home-based self-detection from urine samples within 10 min for the total process, which provides a new way for quick, economical, and convenient tumor diagnosis, prognosis evaluation, and drug response., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diffusion of colored dye on water saturated paper substrates has been traditionally exploited with great skill by renowned water color artists. The same physics finds more recent practical applications in paper-based diagnostic devices deploying chemicals that react with a bodily fluid yielding colorimetric signals for disease detection. During spontaneous imbibition through the tortuous pathways of a porous electrolyte saturated paper matrix, a dye molecule undergoes diffusion in a complex network of pores. The advancing front forms a strongly correlated interface that propagates diffusively but with an enhanced effective diffusivity. We measure this effective diffusivity and show that it is several orders of magnitude greater than the free solution diffusivity and has a significant dependence on the solution pH and salt concentration in the background electrolyte. We attribute this to electrically mediated interfacial interactions between the ionic species in the liquid dye and spontaneous surface charges developed at porous interfaces, and introduce a simple theory to explain this phenomenon., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A complete mathematical model for electromigration in paper-based analytical devices is derived, based on differential equations describing the motion of fluids by pressure sources and EOF, the transport of charged chemical species, and the electric potential distribution. The porous medium created by the cellulose fibers is considered like a network of tortuous capillaries and represented by macroscopic parameters following an effective medium approach. The equations are obtained starting from their open-channel counterparts, applying scaling laws and, where necessary, including additional terms. With this approach, effective parameters are derived, describing diffusion, mobility, and conductivity for porous media. While the foundations of these phenomena can be found in previous reports, here, all the contributions are analyzed systematically and provided in a comprehensive way. Moreover, a novel electrophoretically driven dispersive transport mechanism in porous materials is proposed. Results of the numerical implementation of the mathematical model are compared with experimental data, showing good agreement and supporting the validity of the proposed model. Finally, the model succeeds in simulating a challenging case of free-flow electrophoresis in paper, involving capillary flow and electrophoretic transport developed in a 2D geometry., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)