Search

This research unveils a transformative methodology for fabricating flexible printed circuit boards (PCBs), focusing on the unique attributes of filter paper substrates. A meticulous parametric exploration scrutinizes critical aspects such as buckling resistance, charging current, plating time, and electrode configurations for copper electroplating. Key findings highlight the exceptional stability of copper electroplating on filter paper, exhibiting robust resistance against environmental variations and bending angles spanning +180° to −180°. Utilizing higher pencil grade material and maintaining a minimum 4 cm distance with a voltage range of 3 to 1.44 V ensures uniform, controlled plating without burning, optimizing the electrode area below 1 cm2 for enhanced practicality. The research underscores the longevity and durability of copper‐plated filter paper, with negligible resistance changes even after 1000 folds. Over a year, the shelf‐life assessment emphasizes the excellent stability of electroplated filter paper. Practical applications, including fully functional circuits and a bio‐degradable piano, underscore the versatility and real‐world feasibility of the proposed electroplating technique. [ABSTRACT FROM AUTHOR]

Printed electronic paper identifies its interest in flexible organic electronics and sustainable and clean energy applications because of its straightforward production method, cost‐effectiveness, and positive environmental impact. However, current limitations include restricted material thickness and the use of supporting substrate for printing. Here, 2D and 3D electronic patterned paper are fabricated from direct ink writing (DIW) nanocellulose and PEDOT:PSS‐based materials using syringe deposition and 3D printing. The conductor patterns are integrated in the bulk of the paper, while non‐conductive sections are used as support to form free‐standing paper. The strong interface between the patterns of electronic patterned paper gives mechanical stability for practical handling. The conductive paper‐based electrode has 202 S cm−1 and is capable of handling electric current up to 0.7 A, which can be used for high‐power devices. Printed supercapacitor papers show high specific energy of 4.05 Wh kg−1, specific power of 4615 W kg−1 at 0.06 A g−1, and capacitance retention above 95% after 2000 cycles. The new design structure of electronic patterned papers presents a solution for additive manufacturing of paper‐based composites for supercapacitors, wearable electronics, or sensors for smart packaging. [ABSTRACT FROM AUTHOR]

Korean traditional paper known as Hanji is coupled with Ag nanowires (NWs) to be used as multi‐functional paper windows in wooden flame doors of a traditional Korean house (Hanok). The Ag NW is uniformly embedded in a handmade Hanji, consisting of multiple laminated sheets formed through ssangbal filtering up and spray method. The combination demonstrates a low sheet resistance of 28 Ohm square−1 because of a percolating network structure of Ag NWs, which is apt for interconnectors and electrodes. Owing to the flexibility of the Hanji and Ag NWs, outstanding mechanical flexibility, apt for curved or flexible electronic paper windows, is observed. To further examine the potential of the multi‐functional electronic paper window, anti‐bacterial and electromagnetic interference shield properties of the Hanji are also investigated. It is noted that the functional Hanji sterilizes 99.9% of staphylococcus aureus and Klebsiella pneumonia and shows 15 dB (12–18 GHz) shielding efficiency due to the existence of the metallic Ag NWs network. In addition, successful operation of Hanji‐based interconnectors, thin film heaters, and touch panels demonstrates that the Hanji‐based electronic paper window can be used as a device‐integrated paper window in traditional Hanok or oriental traditional houses. [ABSTRACT FROM AUTHOR]

Paper‐based analytical devices as a low‐cost and point‐of‐care sensing platform have attracted widespread research interest. However, the device fabrication and signal readout remain a challenge for their real‐world applications. Herein, a technically simple paper‐based sensor is developed by taking advantage of the easily accessible paper and the plasmonic property of gold nanomaterials. The sensing mechanism relies on the iodide‐mediated surface etching of gold nanostars that induces a color change from blue to red of the paper strip. The versatility of the paper substrate in size, shape, and materials allows for the facile immobilization of gold nanostars by a simple immersing method, which is easy to operate and free from specialized skills and equipment. In addition, the readout of the paper strip can be conveniently visualized by the naked eye or through a smartphone. This paper‐based sensor advantages in low cost, light weight, easy handling, and disposability that holds great promise as a point‐of‐care detection platform in resource‐constrained settings. [ABSTRACT FROM AUTHOR]

Commercial polypropylene (PP) and polyethylene (PE) films are widely used as separators for lithium‐ion batteries (LIBs). However, owing to the poor thermal stability of PP and PE films, current LIBs suffer from serious safety risks in their practical applications. As an effective path, the design of novel high‐safety composite separators can significantly overcome the safety issues of LIBs. Herein, a universal and cost‐effective strategy is developed to fabricate highly‐thermal‐stable separators via coating natural halloysite nanotubes (HNTs) on both sides of commercial papers or waste newspaper. The resulted separators show superior properties, including thermal stability, heat conduction, wettability, and electrolyte uptake. Compared with commercial PP separators, both HNTs coated A4 paper and waste newspaper composite separators enable better cycling and rate performance for Li/LiFePO4 cells. Even after burning in fire or treating under 180 °C, the composite separators still present a normal structure, and the assembled cell can perform as regular. Furthermore, the nail penetration test of pouch cells illustrates that such separator significantly prevents thermal runaway of LIBs. The inexpensive and environmentally friendly materials with a facile coating process provide a highly‐thermal‐stable separator for commercial LIBs. [ABSTRACT FROM AUTHOR]

Ultrathin devices are rapidly developing for skin‐compatible medical applications and wearable electronics. Powering skin‐interfaced electronics requires thin and lightweight energy storage devices, where solution‐processing enables scalable fabrication. To attain such devices, a sequential deposition is employed to achieve all spray‐coated symmetric microsupercapacitors (μSCs) on ultrathin parylene C substrates, where both electrode and gel electrolyte are based on the cheap and abundant biopolymer, cellulose. The optimized spraying procedure allows an overall device thickness of ≈11 µm to be obtained with a 40% active material volume fraction and a resulting volumetric capacitance of 7 F cm−3. Long‐term operation capability (90% of capacitance retention after 104 cycles) and mechanical robustness are achieved (1000 cycles, capacitance retention of 98%) under extreme bending (rolling) conditions. Finite element analysis is utilized to simulate stresses and strains in real‐sized μSCs under different bending conditions. Moreover, an organic electrochromic display is printed and powered with two serially connected μ‐SCs as an example of a wearable, skin‐integrated, fully organic electronic application. [ABSTRACT FROM AUTHOR]

Single‐use paper‐based wearable devices are receiving increasing attention as a novel platform for disposable, inexpensive, noninvasive, and real‐time sweat monitoring. The bidirectional liquid transport nature of paper is the most critical barrier to effectively controlling sweat samples for reliable and accurate sweat analysis. Excessive or additionally released sweat significantly interferes with analysis when mixed with old sweat. Moreover, bio‐receptors pre‐loaded in the sensing areas can backflow and move to another sensing region generating a cross‐talk issue. This work enables effective sweat sampling and delivery in paper by facilitating unidirectional sweat transport from the skin to the sensing reservoir. The design and fabrication of a single‐layered paper membrane to achieve Janus‐type properties, which only allow moisture to flow in one direction is introduced. When the hydrophobic side of the Janus paper is placed on the skin, sweat is unidirectionally self‐pumped from the hydrophobic side to the hydrophilic sensing areas, but not the reverse. The fabrication takes two steps including easy automatic and scalable printing of hydrophobic micropatterns on paper and simple heating of the printed paper for the wax penetration. Quantitative colorimetric assessment of pH, chloride, sodium, and glucose in sweat is simultaneously performed without cross‐talk between the sensing regions. [ABSTRACT FROM AUTHOR]

Human–machine interaction will be revolutionarily different in the future Internet of Things (IoT) environments. Many displays will be adopted onto electronic devices to enhance human–device communication, even under a very bright sunlight ambience. Thus, power consumption and sunlight visibility are important attributes for this application. Electrophoretic displays (EPDs) have the inherent advantages of ultra‐low power consumption and high sunlight visibility, which are perfectly suitable for IoT applications. The low power consumption resulted from the balance of viscosity, gravity, and other complicated forces involved in the electrophoretic dispersion. This force balance is generally termed "bistability," meaning the particle‐packing can be stable without external power at black and white image states. However, good bistability implies a slow image updating rate, significantly degrades users' experience. In this work, a 3D network structure that undergoes disruption and reorganization with the particles' movement is utilized in the electrophoretic ink dispersion. Dynamic viscosity modulation enables the bistable and fast‐response dual‐working modes. The newly developed design can increase the response speed of EPDs by a factor of 2.38, simultaneously maintaining the bistability. The electronic ink with this reversible network provides a promising solution for the future video‐rate e‐paper displays. [ABSTRACT FROM AUTHOR]

Paper‐based photodetectors have emerged as reliable candidates for wearable electronics due to their low‐cost, degradability and excellent bending properties. However, the application of quantum dots (QDs) to paper‐based devices remains a challenge due to the low carrier mobility. In this work, lead sulfide (PbS) QDs are successfully applied to paper‐based devices by constructing the amorphous indium gallium zinc oxide (a‐IGZO)/PbS QDs‐EDT heterojunction to enhance the photoconductive gain of the QDs film. The effect of different paper substrates are investigated on device performance and demonstrate that the heterojunction is not suitable for the fiber‐like paper substrate. Heterojunction devices based on Senyan paper and glass paper exhibit stable detection performance with detectivity of 1.71 × 1010 and 3.19 × 1011 Jones, respectively. Benefit from the unique micro‐morphology, the Senyan paper‐based device exhibits excellent bending resistance and remained stable after 1000 bends. [ABSTRACT FROM AUTHOR]

Electrode architectures significantly influence the electrochemical performance, flexibility, and applications of lithium‐ion batteries (LiBs). However, the conventional bar coating for fabricating electrodes limits the addition of customized architecture or patterns. In this study, as a novel approach, patterns are integrated into electrodes through large‐scale roll‐to‐roll (R2R) flexographic printing. Additionally, flexible, recyclable, and biodegradable paper are innovatively used as a printing substrate during printing LiBs manufacturing, which exhibited superior printability. Moreover, the paper is modified with a thin‐layer Al2O3 to function as the separator in the printed LiB. The Al2O3‐coated paper enables an admirable wettability for printing, excellent mechanical properties for high‐speed R2R manufacturing, and outstanding thermal stability for the safe and stable operation of LiBs. The assembled paper cells exhibit nearly 100% discharge capacity retention after 1000 cycles at 3 C and outstanding rate performance. This work inspires future large‐scale microbatteries manufacturing integrated with high‐resolution architecture designs. [ABSTRACT FROM AUTHOR]

Paper flowers are frequently, for example as indoor decorations and in wedding bouquets. But these traditional paper flowers can only maintain static conditions, greatly affecting their sensory effects, vividness, and appreciation. The design of novel paper flowers with dynamic shape deformation could effectively broaden the application of paper flowers. Here, inspired by Chinese calligraphy, a novel polyvinyl butyral (PVB)/carbon/cellulose composite (PCC) magic paper with a sandwiched structure is prepared. The hygroscopicity difference between hydrophobic PVB and hydrophilic cellulose layer endows the PCC paper with humidity responsiveness, and the maximum bending angle is up to 91.4° upon exposure to humidity environment. Carbon in the interlayer with strong light–heat conversion capacity could further accelerate water desorption and deformation speed, resulting in highly sensitive light responsiveness. The recovery time of PCC paper from maximum bending to the original flat state is shorter than 1 s. The PCC paper has good flexibility and processability, which can be cut and assembled into flowers with different shapes, and these unique magic flowers could freely bloom and furl upon external stimulus. All these results indicate that PCC paper has great potential in the production of magic props, artworks, and intelligent household decorations fields. [ABSTRACT FROM AUTHOR]

Soft robotics driven by origami can fundamentally advance robotic functionalities by significantly improving continuum, compliance, and configurability. Here, a new field is proposed, "paper robotics," which is based on moisture‐responsive self‐folding of paper substrates into functional 3D machines using origami‐inspired techniques. By properly designing a hydrophobic wax layer and a hygro‐expandable hydrophilic layer, printed bilayer paper will fold automatically into desired shapes through anisotropic swelling that occurs when water is sprayed on the structure. The bilayer actuators can be readily fabricated on paper by the asymmetrical penetration of wax that is printed on both sides of the paper. The patterned paper automatically folds when water is added and unfolds as the water evaporates. The structure can perform various mechanical functions, including gripping and biomimetic locomotion. One of the practical applications, a kirigami paper robotic finger as an electrical switch, is also demonstrated. The functional mechanism based on the swelling and shrinking properties of paper is modeled and critical parameters for the design of the bilayer actuation are thoroughly characterized. This work will be a starting point for paper robotics and open new avenues to merge soft robotics and origami techniques. [ABSTRACT FROM AUTHOR]

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

Nucleic acid amplification testing (NAAT) is the gold standard for infectious disease diagnostics. Currently NAATs are mainly limited to centralized laboratories, while paper‐based antigen tests are used for rapid home‐based diagnostics. DNA extraction, the initial sample preparation step in NAATs, remains a bottleneck that hinders its development toward home‐based kits. This step requires the use of compounds detrimental to the enzymes in downstream DNA amplification. Here, this work overcomes this bottleneck by immobilizing the enzyme achromopeptidase (ACP) on nitrocellulose, to both store and enable the separation of the enzymes from the other steps. This work provides proof‐of‐concept that immobilized ACP is effective at lysis and release of amplifiable DNA from gram‐positive Staphylococcus epidermidis and enables the use of the lysate directly for DNA amplification, without the need for heat deactivation of the enzyme. This sample preparation method requires only incubation at 37 °C and mild agitation, which allows to implement it with fully disposable and affordable equipment. Consequently, this work enables to combine the paper‐based DNA extraction method with the isothermal recombinase polymerase amplification (RPA) followed by lateral flow detection to demonstrate a sample‐to‐answer NAAT packaged as an instrument free self‐test kit expanding the capabilities of home‐testing beyond antigen tests. [ABSTRACT FROM AUTHOR]

Paper has attracted considerable interest as a promising pressure‐sensing element owing to its foldability/bendability and deformability due to its high porosity. However, paper‐based tactile sensors reported hitherto cannot achieve high sensitivity and a wide sensing range simultaneously. In this study, a resistive tactile sensor using carbon nanotube‐ and silver nanoparticle‐printed mulberry paper as a pressure‐sensing element and electrodes, respectively, is developed. The rough surface and high inner porosity of mulberry paper induce a significant change in the contact area when a multilayer‐stacked structure is used, resulting in increased sensitivity to pressure. Moreover, the enhanced mechanical robustness of mulberry paper originating from the highly bonded network of long and thick fibers affords a wide pressure‐sensing range. The sensor exhibits a high sensitivity exceeding 1 kPa−1 in an applied pressure range of 0.05–900 kPa; this achievement has not been reported among paper‐based tactile sensors. Furthermore, the sensor exhibits a fast response/relaxation time, low detection limit, high resolution, high durability, and high flexibility. The advantages of the sensor afford several applications, including a crosstalk‐free pressure sensor array, a three‐axis pressure sensor, and wearable devices for measuring signals from a user. [ABSTRACT FROM AUTHOR]

Paper‐based microfluidics emerges as an innovative platform for constructing miniaturized electrochemical devices, which mainly benefit from the spontaneous capillary action of paper. Nevertheless, the capillary‐driven flow dynamics on paper are determined exclusively by the intrinsic properties of paper and fluidics, thus lacking the controllability that conventional pump‐based microfluidics can provide. Herein, an approach to regulating the capillary flow on paper is introduced by conjugating the outlets of microfluidic channels with a photothermal module for water evaporation. The capillary flow rate on paper can be handily regulated from 4 to 37 µL min−1 under controllable illumination conditions. As a proof‐of‐concept, prototypical paper‐based microfluidic fuel cells integrated with the photothermal module are constructed. Their peak power density can be boosted from 0.3 up to 2.1 mW cm−2 under the simulated sunlight irradiation. The influence of capillary flow rate on the fuel cell performance is further validated using multiphysics simulations. The present work not only provides a practically feasible method to boost the performance of paper‐based microfluidic fuel cells using solar energy, but also opens a new avenue for modulating the performance of paper‐based microfluidics, which has long been a challenge in this field. [ABSTRACT FROM AUTHOR]

Inkjet printing (IJP) is the most widespread direct‐write technique in paper electronics. However, this technique cannot be used for printing devices on untreated regular paper, since its low‐viscosity nanoinks leak through the cellulose fibers. Thus, a planarization coating is frequently used as a barrier, even though this makes substrates more expensive and less eco‐friendly. Alternatively, high solid content screen printing (SP) inks could allow printing on regular paper due to their high viscosity and large particle size; however, they cannot be printed through IJP. Another digital technique is then required: laser‐induced forward transfer (LIFT). This work aims at proving the feasibility of LIFT for printing devices on regular paper. The main transfer parameters are systematically varied to obtain uniform Ag‐SP interconnects, whose performance is improved by a multiple‐printing approach. It results in low resistances with much better performance than those typical of IJP. After optimizing the functionality of the printed lines, a proof‐of‐concept consisting of a radio‐frequency inductor is provided. The characterization of the device shows a substantially higher performance than that of the same device printed with IJP ink in similar conditions, which proves the potential of LIFT for digitally fabricating devices on regular paper. [ABSTRACT FROM AUTHOR]

Wax printing is one of the most widely used techniques to print hydrophobic barriers on hydrophilic microfluidic paper‐based analytical devices (µPADs) based on its simplicity, speed, and low cost, allowing large‐scale production. Nonetheless, its function is just passive, without any action on fluids. Thus, this work proposes multifunctional hydrophobic composites based on conductive graphene nanoplatelets (GNPs) integrated into the wax matrix to allow a dual role of barrier and heater, the latter being required in a large variety of temperature‐sensitive reactions and microfluidic applications. The effect of GNP weight content on the physicochemical properties of the wax, printed wax, and generated heating are evaluated. Wax prints with mechanical stability and adequate impregnation through the paper are obtained after post‐thermal curing. With respect to the functional response, controlled temperatures ranging from room temperature to ≈107 °C can be achieved after just 10 s. Two proofs of concept are presented involving thermochromic inks, specific printed systems designs, and low‐power batteries. The benefits of µPADs allied to the increased functionality and performance of the developed waxes, hold great promise to meet the requirements for a next generation of versatile, effective, and accurate µPADs for an increasing number of applications. [ABSTRACT FROM AUTHOR]

Real‐time and continuous monitoring of ultraviolet (UV) radiation in daily activity is critical in diverse fields ranging from personal fitness, cosmetics, to medical aspects. Here, a wearable UV monitoring patch that can be easily fixed/removed at desired locations and provide real‐time and continuous UVA levels in daily life is developed. The wearable patch consists of a highly sensitive, flexible graphene sensor for UVA measurement and a multifunctional fabric patch integrated with commercial electronic components for signal processing, wireless transmission. To achieve a high sensitive UVA sensor with high flexibility and long‐term stability, porous reduced graphene oxide (pRGO) papers are fabricated by simple solvent evaporation followed by thermochemical reduction. The flexible UVA sensors based on pRGO papers feature a high UVA photoresponsivity of 125 mA W−1, which is comparable to that of a commercial silicon‐based UV sensor. Furthermore, the polydimethylsiloxane‐encapsulated pRGO (PDMS‐pRGO) sensors exhibit stable UVA photoresponse characteristics that is maintained under severe conditions, such as a large number of bending cycles, thermal heating, and high humidity. The use of wearable patches that enable real‐time, wireless monitoring of personal UVA levels in various practical applications are demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: Paper electronics is considered very environmentally friendly, but effective recyclability of metallic circuits on paper still needs more improvement. Therefore, liquid metal (Galinstan) circuits based on the reversible conversion from particles to wires are fabricated on paper using mechanical methods, i.e., mechanical sintering and sonication. Line‐width of liquid metal (LM) circuit is kept in the range of 10 µm to ≥0.5 mm by controlling the sintering force. The results demonstrate that LM circuits exhibit high electrical stability during deformation, as resistance changes only ≤4% after the passage of 10 000 folding cycles. Meanwhile, LM particles spread on paper's porous structures, have enhanced the thermal diffusivity of paper and make paper electronics work in a facile temperature when integrated with high density units. More importantly, the reborn circuits exhibit almost identical electrical stability under deformation and thermal characteristic with pristine ones, thus making LM circuits environmentally friendly during their whole life span. [ABSTRACT FROM AUTHOR]

In recent years, paper has become an essential substrate material for developing different types of sensors, from wearable devices to single‐use test strips and biosensors. In parallel, a polymer‐based toolbox has emerged in order to add additional functions to these paper‐based analytical devices. In this article, examples are compiled from the recent literature showing microfluidic systems based on printing impermeable polymer barriers with different methods as well as the implementation of electrochemical, fluorescent, and colorimetric polymer‐based transducers in paper‐based analytical platforms. Externally actuated or dissolvable polymer valves and reservoirs, analyte concentrators, and separation devices, as well as polymer‐based recognition elements (molecularly imprinted polymers) printed on paper substrates are also reviewed. The search has revealed a plethora of possibilities for developing complex lab‐on‐chip devices implementing different polymer‐based components in them. The ability of patterning these polymers with common printing methods that do not require specialized facilities paves the way for mass producing this kind of advanced paper‐based analytical device. [ABSTRACT FROM AUTHOR]

Printed electronics answers to the emerging trend of using truly inexpensive and easily accessible techniques to design and fabricate low‐cost and recyclable flexible electronic components. Nevertheless, printing of inorganic semiconductor materials arises some barriers for flexible electronics, as they usually may require high annealing temperatures to enhance their electronic performances, which are not compatible with paper. Here, the formulation of a water‐based, screen‐printable ink loaded with zinc oxide nanoparticles that does not require any sintering process is reported. The ink is used to create the channel in fully printed electrolyte‐gated transistors on paper, gated by a cellulose‐based ionic conductive sticker. The high conformability of the electrolyte‐sticker mitigates the effect of the surface roughness of the channel, yielding transistors that operate under low voltage (<2.5 V) with a current modulation above 104 and μSat ≈ 22 cm2 V−1 s−1. These devices operate even under moderate outward bending conditions. The screen‐printed transistors are readily integrated in "universal" logic gates (NOR and NAND) by using ubiquitous calligraphy accessories for patterning of conductive paths and graphitic load resistances. This demonstrates the manufacturing of reliable and recyclable cellulose‐based iontronic circuits with low power consumption, paving the way to a new era of sustainable "green" electronics. [ABSTRACT FROM AUTHOR]

Flexible strain sensors are indispensable components providing repeatable electronic signals responding to mechanical deformations. Nevertheless, there is a stringent demand for flexible sensors to maintain normal performance in daily use and even in harsh conditions, such as high humidity and high temperature. Herein, inspired by scorpions, a highly sensitive flexible strain sensor based on ceramic fiber paper (CFP) with superhydrophobic and high‐temperature‐resistant properties is developed by a combination of mechanical cutting and spray coating method, which minimizes performance degradation commonly seen in polymer‐based and textile‐based sensors under harsh conditions. The prepared strain sensor exhibits high sensitivity (gauge factor ≈1254), low detection limit (0.078%), fast response time (108 ms), and notable stability (over 10 000 cycles). The ultra‐high sensitivity originates from the existence of the micro‐scale cracks. To further improve stability of the device in some harsh conditions, superhydrophobic and heat‐resisting coatings consisting of SiO2 aerogels and SiO2 nanoparticles are introduced onto the surface of CFP. Owing to the synergistic effect of the high‐temperature resistance of ceramics fibers and the coatings, the device operates normally at temperature up to 220 °C with a water contact angle of 159°, showing great promises for harsh conditions, especially in the industrial and aerospace fields. [ABSTRACT FROM AUTHOR]

Paper‐based electronics are emerging as a new class of technology with broad areas of application. Despite several efforts to fabricate new types of flexible electronic devices by screen printing of conductive paste, many of them are often nonbiodegradable, toxic, and expensive, limiting their practical use in bioresorbable paper‐based electronics. To address this need, a highly conductive and biodegradable bimodal conductive paste is developed using cost‐effective zinc‐based micro and nanoparticles with a facile low‐temperature sintering process compatible with paper substrates. The two‐step sintering process involves the removal of the insulating zinc oxide layer by spray coating acetic acid followed by a heat press sintering process to ensure the formation of highly packed and continuous metallic traces. The required conditions for the heat press sintering process are systematically studied using electrical, optical, and mechanical characterization techniques. The results of these investigations revealed an ultra‐packed microstructure with high electrical conductivity (0.5 × 105 S m−1) and low oxide content that is obtained with a heat press sintering setting of 220 °C for 60 s. Finally, as a proof of concept, the conductive paste with an optimized sintering process is used to fabricate a wearable wireless heater for remote‐controlled release of therapeutics. The controlled delivery of the system is validated in the practical and on‐demand delivery of antibiotics for eradicating commonly found bacteria such as Staphylococcus aureus in dermal wound infections. The biocompatibility of all the materials and manufacturing process is validated by NIH/3T3 fibroblast cells via MTT assay and live/dead staining. [ABSTRACT FROM AUTHOR]

Paper‐based thermoelectric generators are a promising and economical alternative to expensive organic conductors that are normally preferred for flexible generators. In the present work, graphite pencil traces on regular Xerox paper are successfully employed to constitute a thermoelectric generator. In conjunction with polyethylenimine polymer, the graphite traces act as both the p‐type and n‐type thermoelectric "legs," of a graphite‐based thermoelectric generator. The fabrication method is facile and requires no conducting paste or silver paste to connect individual thermoelectric legs. A test module containing five pairs of p‐n legs is fabricated on paper to test its performance. The device produces a thermoelectric voltage of 9.2 mV, generating an output power of 1.75 nW at a temperature difference of ≈60 K. The present work demonstrates that ordinary pencil on paper may be used as the foundation for a cheap, flexible, easily disposable, and environmentally friendly thermoelectric generator. [ABSTRACT FROM AUTHOR]

Ocean research currently relies heavily on bulky bioelectronic tags and sensory telemetry networks for data collection. Therefore, in this study, a compact and flexible waterproof bioelectronic tag with a kirigami (paper cutting)‐based design for underwater conductivity, temperature, depth, and strain sensing is designed and evaluated. Unlike invasive bioelectronic tags, the kirigami bioelectronic tag can be attached to robotic fish or aquatic animals without harming the host. The kirigami‐based design facilitates excellent stretchability and reduces stress within the sensor, thus inhibiting crosstalk induced by movement during multimodal sensing. A working bioelectronic tag is fabricated and tested. Notably, the performance of the kirigami sensors shows very little degradation even after >1000 stretching cycles. Specifically, the multimodal bioelectronic tag demonstrates a wide working pressure range of 0–5.0 MPa, and the kirigami design effectively suppresses signal coupling. The kirigami‐based bioelectronic tag is applied to a robotic dolphin and underwater environmental parameters and detailed movement parameters, such as swing angle, swing frequency, and typical gestures are detected simultaneously with high sensitivity and accuracy. Therefore, the device can be applied to a broad range of applications in various fields such as behavioral biology, ocean informatics, and underwater robotics. [ABSTRACT FROM AUTHOR]

Paper electronics are expected to be a game‐changer in next‐generation flexible electronics that could replace conventional plastic electronics. Paper electronics are disposable and cost‐effective, two distinct advantages for the development of broadly accessible devices, but their poor performance has limited their practical implementation so far. Here, a high‐sensitivity, high‐performance, paper‐based, wearable ammonia sensor comprising composite poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and iron(III) compounds is reported. The sensor achieves 10‐times smaller size than the conventional sensor on Kapton film and high tolerance for humidity without losing practical sensor response. The utility of the device is demonstrated for wearable ammonia sensing in a facial mask and a nasal filter; wireless monitoring of food spoilage; and wireless monitoring of the ammonia level in a diaper. The approach of this study may open the door to advanced healthcare based on ubiquitous wearable sensing. [ABSTRACT FROM AUTHOR]

Porous graphene (PG) devices fabricated in situ from polyimide (PI) adhered onto paper substrates provide a cost‐effective and recycling‐friendly alternative to re‐engineer paper for liquid‐based power sources and sensors. However, paper is generally damaged due to heating during the fabrication of PG devices. Here integrated graphene‐paper electronics with exceptional thermal control through the proposed thermally localized laser graphitization (LLG) process is demonstrated, employing optimized ultrafast laser writing. LLG enables in situ fabrication of localized porous graphene (LPG) devices (>1775 K) on 65 µm thick PI tape adhered to paper without heating above 348 K. Laser parameters for LLG are predicted using an analytical temperature model and validated experimentally. The LLG is demonstrated by fabricating liquid electrolyte LPG micro‐supercapacitors and humidity sensors on liquid susceptible paper. It is envisaged that the scientific concepts proposed and demonstrated here will expedite the development of low‐cost, scalable, and chemically robust LPG devices on thermally sensitive substrates. [ABSTRACT FROM AUTHOR]

Laser‐induced graphene (LIG) produced by irradiation of paper (paper‐LIG)holds substantial promise for flexible devices. This article presents paper‐LIG humidity and temperature sensors fabricated by single‐step irradiation of common filter paper with a pulsed UV laser (355 nm). The influence of the process parameters on the conversion of cellulose fibers into LIG is discussed based on the resulting morphology, structure, conductivity, and chemical composition, revealing a distinct barrier to transformation and a propagation behavior not seen under CO2 laser irradiation. The obtained material is constituted by a porous, electrically conductive network of fibers. The paper‐LIG relative humidity (RH) and temperature sensors with sensitivities of up to 1.3 × 10−3%RH−1 and ‐ 2.8 × 10−3 °C−1, respectively, are examined in terms of their linearity, reproducibility, and response time. A detailed discussion on the response mechanism is presented in the context of literature, pointing towards the absorption of water molecules in the interlayer spacing of graphene as the main reason for the increase in resistance with RH. Additionally, a contribution from variable range hopping along the ab plane of graphene at high RH is suggested. These results demonstrate the potential of paper‐LIG for low‐cost, sustainable, and environmentally friendly sensing. [ABSTRACT FROM AUTHOR]

Paper‐based analytical devices, or μPADs, have proven to be valuable bioanalytical tools for a broad range of applications. New methods for μPAD fabrication are needed, however, to facilitate their mass production at a competitive cost. To address this need, the use of a boronic acid‐containing siloxane polymer (BorSilOx) has been reported for patterning hydrophobic barriers for μPADs. This material functions by covalently binding to hydroxyl groups in the paper substrate. It is compatible with inkjet printing or roll‐to‐roll (stamping) processes, as demonstrated here using three different deposition methods. BorSilOx is able to render a broad range of cellulosic materials (from paper towels to wood) hydrophobic, with contact angle measurements demonstrating superhydrophobicity in many cases.The utility of the polymer in μPADs via assays for pH and glucose is further demonstrated. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) experimental platforms are frequently utilized in the teaching of chemical experiments because of its high level of interest, lifelike effect, and safe and dependable advantages. However, users are unable to operate genuine experimental equipment on the present VR experimental platform, and these systems are unable to precisely assess and manage users' operation intentions. In light of the aforementioned concerns, this paper develops a smart glove with cognitive capabilities, which is composed of a variety of simple commercial sensors and binocular cameras. The smart glove can be applied to the virtual‐reality fusion chemical experiment platform established in this paper. Additionally, a navigation interaction algorithm based on multimodal intention understanding is also proposed in this study (hereinafter referred to as NIAMIU algorithm). The smart glove can accurately and efficiently obtain the user's operation intention through the algorithm. The experiment showcased that the smart glove detailed in this paper is capable of precisely determining the position of users' hands in space and guiding and rectifying the user's interactive behavior. Meanwhile, users may converse with the smart glove in an unsupervised setting and conclude the experiment by following the directions supplied by the smart glove. In comparison to a conventional data glove, the smart glove designed in this paper considerably augments the accuracy and efficiency of human‐computer interaction. [ABSTRACT FROM AUTHOR]

The high‐efficiency conversion of water drop mechanical energy into electrical energy has always been an urgent issue in the development and utilization of raindrop energy. In this work, a novel drum‐like triboelectric nanogenerator (D‐TENG) with robust self‐cleaning superhydrophobic features is developed to harvest water drop energy. An elastic superhydrophobic cellulose paper is created by spray‐coating nanofumed silica dispersed in a thermoplastic elastomer solution, followed by treatment with triethoxy‐1H,1H,2H,2H‐tridecafluoro‐n‐octylsilane. When raindrops hit the D‐TENG surface, the superhydrophobic cellulose paper will vibrate and periodic contact and separation with polytetrafluoroethylene will occur to generate electricity. The results demonstrate that when a 6 mm water drop falls from a height of 2.5 m and hits the D‐TENG, the generated voltage output can reach a peak of 21.6 V and charge transfer of 10 nC. The output power of the D‐TENG can reach 16 µW per droplet, which is more than 13.3 times that generated from the previous TENGs based on the electrostatic induction of water droplets. These results indicate that the superhydrophobic cellulose paper‐based D‐TENG is potentially a strong candidate for harvesting energy from raindrops, thereby making it a promising sustainable energy source for next‐generation electronics. [ABSTRACT FROM AUTHOR]

There is a need to develop inexpensive, lightweight, and flexible high‐performance triboelectric nanogenerators (TENGs) from renewable resources. Here, a multifunctional cellulose filter paper (CFP)‐based TENG consisting of dielectric Ti0.8O2 nanosheets (Ti0.8O2 NSs) and conducting Ag nanoparticles (Ag NPs) is prepared by a simple dip coating method. The incorporation of dielectric Ti0.8O2 NSs onto the CFP significantly improves charge generation, while the inclusion of Ag NPs provides an electrically conductive path for charge transportation. The presence of these fillers can be deduced from XRD, SEM, EDS, X‐ray photoelectron spectroscopy, and Raman spectroscopy. Their distribution is visualized in 3D by synchrotron radiation X‐ray tomography. The present CFP‐based TENG provides an output voltage and current density of ≈42 V and ≈1 µA cm−2, respectively with the power density of ≈25 µW cm−2. It is capable of lighting up 40 light‐emitting diode bulbs and charging a 0.22 µF capacitor to 8 V in only 5 s. The developed TENG is also capable of detecting simple human motions, i.e., finger tapping, finger rubbing, and foot trampling. This work offers a facile design of low cost yet efficient paper‐based TENG by dual modification with multifunctional nanomaterials, and also demonstrates its use as a feasible power source that not only drives small electronics, but also scavenges energy from human actions. [ABSTRACT FROM AUTHOR]

Paper‐based advanced functional materials have become the focus of intense research in recent years. Particularly, magnetic papers show strong potential for applications in a wide range of 4.0 technologies including communication, magnetic sensing, electromagnetic filtering, magnetic‐based health care tools, point‐of‐care microfluidic devices, and security. In situ and lumen‐loading, the main methods to prepare magnetoactive papers, have problems such as the rigorous reaction conditions, hard control of deposition location, decreased tensile strength, poor retention of magnetic nanoparticles, or the obligation to perform the magnetic impregnation during the papermaking process, that hinder their applicability. Those issues are addressed in the present work, in which ≈20 nm Fe3O4 nanoparticles are hydrothermally synthesized and later incorporated in a wax‐based home‐made cartridge and nanoimpregnated into paper by a thermal process leading to a magnetic paper with improved stress and strain at rupture and Young's modulus, 30 MPa, 4.5%, and 2 GPa, respectively, when compared to neat paper, 15 MPa, 3.5%, and ≈1 GPa, respectively. Additionally, the reported magnetic impregnation method provides the paper with a 0.2 emu g–1 magnetic saturation, allowing it to work as a bending actuator with a bending of 12 mm at an applied magnetic field of 105 mT. [ABSTRACT FROM AUTHOR]

Cancer is one of the leading causes of death worldwide producing an estimated cost of $161.2 billion in the US in 2017 only. Early detection of cancer can not only reduce cancer mortality rates but also dramatically reduce healthcare costs given that the 17 million new cancer cases in 2018 are estimated to grow 27.5 million new cases by 2040. Analytical devices based upon paper substrates can provide effective, rapid, and extremely low‐cost alternatives for early cancer detection compared to existing testing methods. However, low concentrations of biomarkers in body fluids as well as the possible association of any given biomarker with multiple diseases remains one of the greatest challenges to widespread adoption of these paper‐based devices. Fortunately, recent advances have opened the possibility of detecting multiple biomarkers within the same device, which can be predictive of a patient's condition with unprecedented cost‐effectiveness. Accordingly, this review highlights the recent advancements in paper‐based analytical devices with a multiplexing focus. The primary areas of interest include lateral flow assay and microfluidic paper‐based assay formats, signal amplification approaches to enhance the sensitivity for a specific cancer type, along with current challenges and future outlook for the detection of multiple cancer biomarkers. [ABSTRACT FROM AUTHOR]

The present work reports on the handwriting of electronic circuits on paper based on the deposition of an inorganic oxide semiconductor, exploiting the pen‐on‐paper (PoP) approach. The method relies on the use of a parallel metal plate pen, well known from calligraphy applications, which permits controlled deposition of a continuous zinc oxide (ZnO) dual‐phase layer on conventional printing paper. The hand‐drawn ZnO film exhibits a continuous and uniform surface with a thickness of roughly 1.5 µm, allowing the application as active layer for UV sensors and field effect transistors on paper. Photocurrent generated from the UV radiation reaches values up to 3.4 mA cm−2 with switching times on the order of few seconds. The final written paper transistors, where paper plays simultaneously the role of substrate and dielectric, reaches On/Off current ratios (IOn/IOff) of about two orders of magnitude and field effect mobility close to 5 × 10−3 cm2 V−1 s−1. As a final proof‐of‐concept a common source amplifier showing clear inverting characteristics is fabricated using a PoP written driving ZnO‐based transistor and a pencil‐drawn track as the load resistance. [ABSTRACT FROM AUTHOR]

Stretchable devices significantly expand the scope of applications such as flexible displays and wearable devices/sensors. To enable stretchable wearable electronics, methods for connecting unit devices and developing circuits are required. Previously, research was performed to manufacture circuits with 3D structures or patterns that remain intact when the flexible and stretchable substrates are deformed. A method for drawing a circuit directly on a substrate with a conductive ink pen is proposed, although it is limited by the surface properties of the substrate. Most existing transparent papers are not sufficiently stretchable for flexible and wearable electronics applications. Therefore, a polydimethylsiloxane–cellulose nanocrystals (PDMS–CNC) composite paper is developed that is both highly flexible and stretchable, while maintaining a high transmittance. The versatility of the composite paper is demonstrated as a suitable substrate for flexible devices by patterning with a conductive ink pen. The PDMS–CNC composite paper has an excellent transmittance of ≈70%, and can withstand over 800% tensile strain. The patterned circuits have only minor increase in resistance after a 50% deformation and recovery. The composite paper is a suitable technology for fabricating electrical components and devices for the Internet of Things and wearable and flexible electronics applications. [ABSTRACT FROM AUTHOR]

Organic photovoltaic (OPV) modules, which are attractive for large‐volume high‐throughput production, can become more environmentally sustainable with eco‐friendly flexible substrates such as paper. This article reports fabrication and performance of 108 cm2 active area 12 by 12 cm OPV, built on 15 by 15 cm paper substrates. Active area power conversion efficiency (PCE) values up to 2.38 and 4.23% respectively for poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) (PTB7):PCBM blend heterojunction photoactive layer modules under AM1.5G spectrum one sun (100 mW cm−2) intensity illumination are demonstrated. Due to better spectrum matching, for 1000 lux cool‐white light emitting diode (LED) illumination, the power density demonstrated is up to 12 µW cm−2 for these modules, which is comparable to 13 µW cm−2 from a (standard illumination PCE 15%) silicon PV device for the same illumination. These results make OPV on environment friendly paper substrate, an attractive option for practical applications. [ABSTRACT FROM AUTHOR]

Detecting hydrogen peroxide (H2O2) as the side product of enzymatic reactions is of great interest in food and medical applications. Despite the advances in this field, the majority of reported H2O2 sensors are bulky, expensive, limited to only one phase detection (either gas or liquid), and require multistep fabrications. This article aims to address some of these limitations by presenting a 3D printable paper‐based sensor made from poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) decorated with horseradish peroxidase, an enzyme able to interact with H2O2. Unlike most electrochemical PEDOT:PSS‐based H2O2 sensors with voltametric or potentiometric mechanisms, the sensing mechanism in this technology is impedimetric, significantly simplifying the fabrication process. Here, the resistance of sensors proportionally changes with H2O2 concentration upon exposure to liquid or gas with a linear trend within the range of 61.3 × 10−9 and 61.3 × 10−6m H2O2. The observed correlation between the resistance and H2O2 concentration is highly dependent on the level of integrated enzyme, suggesting the direct contribution of horseradish peroxidase in the co‐redoxing of PEDOT:PSS in the presence of H2O2. Raman and UV–vis spectroscopies also confirm the structural change of PEDOT in the presence of H2O2 which is facilitated by the enzyme. [ABSTRACT FROM AUTHOR]

For the first time, the plasma‐assisted inkjet printing of metal‐organic decomposition (MOD) inks is demonstrated to provide an easily up‐scalable method toward the deposition of highly conductive silver features on paper. Atmospheric plasma sintering methods provide a fast and effective alternative to thermal treatment. This high‐speed, room‐temperature approach ensures the immediate conversion of the MOD inks after printing and thus overcomes wetting issues typically encountered in porous substrates—a mechanical solution to a chemical problem. [ABSTRACT FROM AUTHOR]

Nondestructive testing (NDT) is crucial technology for authenticity identification of paper‐based artworks. Emerging optical spectroscopy is an important technique of NDT at present, by which high‐bightness light, electron beams, and rays could cause permanent damage to different types of paper‐based artworks. Here, using only NDT technology, triboelectric closed‐loop sensing system (TE‐CLSS) is developed by contact electrification effect. It is composed of a stethoscope‐like triboelectric nanogenerator (SL‐TENG) and matched closed‐loop feedback circuit (CLFC), that is capable of active sensing in a similar way to a stethoscope when it makes slight contact with the surface of object. The results report that the ΔV accuracy of TE‐CLSS could achieve 0.01 V, with relative error of measurement within 3%, and average response time of 0.205 s. Furthermore, it could sense the area change of the test material layers that accurately reach millimeter level, by which different grayscale values, colored inks, and oil paintings are successfully identified. This work gives a new insight into the future NDT technologies suitable for the identification of cultural relics. [ABSTRACT FROM AUTHOR]

Abstract: Paper‐based electronics (papertronics) are recently considered as one of the most exciting device platforms because of their flexibility, sustainability, eco‐friendliness, and low cost as well as their excellent mechanical, dielectrical, and fluidic properties. Now, innovative structure engineering techniques can manipulate diameters of the cellulose fibers of paper, smoothing the roughness and controlling the transparency for numerous device applications. Novel functionalization techniques of paper with organic, inorganic, and biological entities enable many engineering possibilities, revolutionizing papertronics for the next generation of electronics. Among those techniques for new functionalities, integrating electric bacteria into paper has attracted considerable interest as a new energy technique for papertronics. Paper has unique synergistic characteristics including a porous and hydrophilic environment for bacterial viability, a high surface area for bacterial accumulation, and sustainability even in resource‐limited settings. In this work, comprehensive analytical and experimental approaches to provide a novel but realistic and accessible power source from bacteria loaded into paper are pursued. This report provides new approaches to revolutionarily activate the biobattery and significantly improve its shelf life. Furthermore, for the first time the practical efficacy of the explored technique is ensured, generating on‐demand energy even in resource‐limited environments. [ABSTRACT FROM AUTHOR]

The world in the 21st century is confronted with multifaceted challenges against rapid climate change and continuous ecological disturbances caused by revolutionary socio‐economic developments, accelerated expansion of disposable electronic gadgets, and growing dependence on unrecyclable raw materials, among others. The ever‐increasing consumer demand for electronic devices is significantly contributing to the world's fastest‐growing waste stream, known as electronic waste (e‐waste), which is becoming an environmental threat at an alarming rate due to its toxic legacy. The ever‐shortening lifespan of smart technologies has created a "tsunami of e‐waste," as the United Nations has characterized it, with 50 million tons accumulated each year, of which only 20% undergo formal e‐recycling. Therefore, the challenge of optimizing the current resources management models with an aim of improving the manufacturing processes and lifecycles of electronic devices, as well as building a circular economy, has become significantly prominent. Paper/cellulose, which covers a wide range of essential needs in everyday scenarios (from packaging to writing utilities), constitutes promising candidates for the effective achievement of a circular economy. Particularly, cellulose is revealed as an advantageous material for electronic applications because of its abundant availability, which contributes to its cost‐effectiveness, straightforward fabrication process, and high recyclability and reproducibility. [ABSTRACT FROM AUTHOR]