Fiber swelling to improve cycle performance of paper-based separator for lithium-ion batteries application

It is well established that paper-based separators display short-circuit risk in lithium-ion batteries due to their intrinsic micron-sized pores.In this research,we have adjusted pore structure of paper by fiber swelling in liquid electrolyte.Specifically,the paper-based separator is prepared by propionylated sisal fibers through a wet papermaking process.Scanning electron microscope(SEM)and multi-range X-ray nano-computed tomography(CT)images display strong swelling of modified fibers after electrolyte absorption,which can effectively decrease the pore size of separator.Due to the high electrolyte uptake(817 wt%),paper-based separator exhibits ionic conductivity of 2.93 mS cm^(-1).^(7)Li solid-state NMR spectroscopy and Gaussian simulation reveal that the formation of local high Li^(+)ion concentration in the separator and its low absorption energy with Li^(+) ion(62.2 kcal mol^(-1))is conducive to the ionic transportation.In particular,the assembled Li/separator/LiFePO_(4) cell displays wide electrochemical stability window(5.2 V)and excellent cycle performance(capacity retention of 96.6%after 100 cycles at 0.5C)due to the reduced side reactions as well as enhanced electrolyte absorption and retention capacity by propionylation.Our proposed strategy will provide a novel perspective to design high-performance biobased separators to boost the development of clean and sustainable energy economy.

In Situ Directional Polymerization of Poly(1,3-dioxolane)Solid Electrolyte Induced by Cellulose Paper-Based Composite Separator for Lithium Metal Batteries

In traditional in situ polymerization preparation for solid-state electrolytes,initiators are directly added to the liquid precursor.In this article,a novel cellulose paper-based composite separator is fabricated,which employs alumina as the inorganic reinforcing material and is loaded with polymerization initiator aluminum trifluoromethanesulfonate.Based upon this,a separator-induced in situ directional polymerization technique is demonstrated,and the extra addition of initiators into liquid precursors is no longer required.The polymerization starts from the surface and interior of the separator and extends outward with the gradually dissolving of initiators into the precursor.Compared with its traditional counterpart,the separator-induced poly(1,3-dioxolane)electrolyte shows improved interfacial contact as well as appropriately mitigated polymerization rate,which are conducive to practical applications.Electrochemical measurement results show that the prepared poly(1,3-dioxolane)solid electrolyte possesses an oxidation potential up to 4.4 V and a high Li+transference number of 0.72.After 1000 cycles at 2 C rate(340 mA g^(−1)),the assembled Li||LiFePO_(4)solid battery possesses a 106.8 mAh g^(−1)discharge capacity retention and 83.5%capacity retention ratio,with high average Coulombic efficiency of 99.5%achieved.Our work may provide new ideas for the design and application of in situ polymerization technique for solid electrolytes and solid batteries.

A MXene-functionalized paper-based electrochemical immunosensor for label-free detection of cardiac troponin I

Convenient,rapid,and accurate detection of cardiac troponin I(cTnI)is crucial in early diagnosis of acute myocardial infarction(AMI).A paper-based electrochemical immunosensor is a promising choice in this field,because of the flexibility,porosity,and cost-efficacy of the paper.However,paper is poor in electronic conductivity and surface functionality.Herein,we report a paper-based electrochemical immunosensor for the label-free detection of cTnI with the working electrode modified by MXene(Ti_(3)C_(2))nanosheets.In order to immobilize the bio-receptor(anti-cTnI)on the MXene-modified working electrode,the MXene nanosheets were functionalized by aminosilane,and the functionalized MXene was immobilized onto the surface of the working electrode through Nafion.The large surface area of the MXene nanosheets facilitates the immobilization of antibodies,and the excellent conductivity facilitates the electron transfer between the electrochemical species and the underlying electrode surface.As a result,the paper-based immunosensor could detect cTnI within a wide range of 5-100 ng/mL with a detection limit of 0.58 ng/mL.The immunosensor also shows outstanding selectivity and good repeatability.Our MXene-modified paper-based electrochemical immunosensor enables fast and sensitive detection of cTnI,which may be used in real-time and cost-efficient monitoring of AMI diseases in clinics.

Facile Fabrication of Cellulosic Paper-based Composites with Temperature-controlled Hydrophobicity and Excellent Mechanical Strength

In this paper,we presented a novel strategy to employ a plantderived carbohydrate polymer,i.e.,cellulose,to prepare a hydrophobic composite.Cellulose was used as a scaffold,and ethylene-propylene side by side(ES)fiber was thermally melted and then coated on the cellulose surface to achieve hydrophobicity.Experimental results revealed that the thermocoating ES fibers greatly increased the water contact angle of the cellulose scaffold from 25°to 153°while simultaneously enhanced the wet tensile strength of the composite approximately 6.7-fold(drying temperature of 170℃)compared with the pure cellulose paper.In particular,compared with other related research,the prepared cellulose-based composite possessed excellent hydrophobicity and superior mechanical strength,which introduces a new chemical engineering approach to prepare hydrophobic cellulose-based functional materials.

Determination of inhibitory activity of Salvia miltiorrhiza extracts on xanthine oxidase with a paper-based analytical device

A novel paper-based analytical device(PAD)was prepared and applied to determine the xanthine oxidase(XOD)inhibitory activity of Salvia miltiorrhiza extracts(SME).First,polycaprolactone was 3D printed on filter paper and heated to form hydrophobic barriers.Then the modified paper was cut according to the specific design.Necessary reagents including XOD for the colorimetric assay were immobilized on two separate pieces of paper.By simply adding phosphate buffer,the reaction was performed on the double-layer PAD.Quantitative results were obtained by analyzing the color intensity with the specialized device system(consisting of a smartphone,a detection box and sandwich plates).The 3Dprinted detection box was small,with a size of 9.0 cm×7.0 cm×11.5 cm.Color component G performed well in terms of linearity and detection limits and thus was identified as the index.The reaction conditions were optimized using a definitive screening design.Moreover,a 10%glycerol solution was found to be a suitable stabilizer.When the stabilizer was added,the activity of XOD could be maintained for at least 15 days under 4℃ or-20℃ storage conditions.The inhibitory activity of SME was investigated and compared to that of allopurinol.The results obtained with the PAD showed agreement with those obtained with the microplate method.In conclusion,the proposed PAD method is simple,accurate and has a potential for point-of-care testing.It also holds promise for use in rapid quality testing of medicinal herbs,intermediate products,and preparations of traditional Chinese medicines.

Fabrication of paper-based devices for in vitro tissue modeling

Paper devices have recently attracted considerable attention as a class of cost-effective cell culture substrates for various biomedical applications.The paper biomaterial can be used to partially mimic the in vivo cell microenvironments mainly due to its natural three-dimensional characteristic.The paper-based devices provide precise control over their structures as well as cell distributions,allowing recapitulation of certain interactions between the cells and the extracellular matrix.These features have shown great potential for the development of normal and diseased human tissue models.In this review,we discuss the fabrication of paper-based devices for in vitro tissue modeling,as well as the applications of these devices toward drug screening and personalized medicine.It is believed that paper as a biomaterial will play an essential role in the field of tissue model engineering due to its unique performances,such as good biocompatibility,eco-friendliness,cost-effectiveness,and amenability to various biodesign and manufacturing needs.

Highly Improved Microstructure and Properties of Poly(p-phenylene terephthalamide) Paper-based Materials via Hot Calendering Process

In this study,the effect of hot calendering process on the microstructure and properties of poly(p-phenylene terephthalamide)(PPTA) paper-based materials was investigated.The microstructures of the fracture surface,crystalline structure,and single fiber strength of the PPTA paperbased materials as well as the different bonding behaviors between the PPTA fibers and PPTA fibrids obtained before and after the hot calendering process were examined.The results indicated that a high linear pressure would result in a limited improvement of the strength owing to the unimproved paper structure.The optimal values of tensile index and dielectric strength of 56.6 N·m/g and 27.6 kV/mm,respectively,could only be achieved with a synergistic effects of hot calendering temperature and linear pressure(240℃ and 110 k N/m,respectively).This result suggested it was possible to achieve a significant reinforcement and improvement in the interfacial bonding of functional PPTA paper-based materials,and avoid the formation of unexpected pleats and cracks in PPTA paper-based materials during the hot calendering process.

A flow chemiluminescence paper-based microfuidic device for detection of chromium(Ⅲ)in water

In this work,a solely gravity and capillary force-driven flow chemiluminescence(GCF-CL)paper-based microfuidic device has been proved for the first time as a new platforn for inex-pensive,usable,mini mally instrumented dynamic chemiluninescence(CL)detection of chromium(Ⅲ)[Cr(Ⅲ)],where an appropriate angle of inclination between the loading and detection zones on the paper produces a rapid flow of CL prompt solution through the paper charnel.For this study,we use a cost-effective paper device that is manufactured by a simple wax screen-printing method,while the signal generated from the Cr(Ⅲ)-catalyzed oxidation of luminol by H_(2)O_(2) is recorded by a low-cost and luggable CCD camera.A series of GCF-CL affecting factors have been evaluated carefully.At optimal conditions,two linear relationships between GCF-CL intensities and the logarithms of Cr(Ⅲ)concentrations are obtained in the concentration mnges of 0.025-35 mg/L and 50-500 mg/L separately,with the detection limit of 0.0245mg/L for a les than 30s assay,and relative standard deviations(RSDs)of 38%,4.5%and 2.3%for 0.75,5 and 50 mg/L of Cr(Ⅲ)(n=8).The above results indicate that the GCF-CL paper-based microfluidic device possesses a receivable sensitivity,dynamic range,storage stability and reproducibility.Finally,the developed GCF-CL is utilized for Cr(Ⅲ)detection in real water samples.

Literature Review of the Use of Zinc and Zinc Compounds in Paper-Based Microfluidic Devices

Zinc and its compounds, alloys and composites play an important role in the modern day world and find application in almost every aspect that can improve the quality of our lives. This ranges from supplements and pharmaceuticals that are meant to improve our health and wellbeing to additives meant to guard or reduce corrosion in metals. However, over the past several years, a new area of technology has been garnering a great deal of attention and has made use of zinc and its compounds. This is with reference to paper-based microfluidic technology that offers several advantages and that keeps expanding in the amount of applications it covers. In this paper, a review is offered for the applications that have used zinc or zinc compounds in paper-based microfluidic devices.

Flexible Paper-Based Li-ion Batteries: A Review

Lithium-ion (Li-ion) batteries have been fabricated in various ways to improve flexibility. Flexibility could be enhanced via active materials, separators, electrodes, and electrolytes, which could then be integrated to form flexible electronic devices with promising electrochemical properties compared to traditional non-flexible Li-ion batteries. Recent progress towards flexible Li- ion batteries fabrication, materials, and their electrochemical properties are investigated in this review. Additionally, recent developments in electronic devices utilizing flexible batteries and their future applications are explored. Portable and wearable electronics, as the primary beneficiaries of the flexible, rechargeable, and high-performance Li-ion batteries, are examined. In the end, various applications and challenges of flexible batteries in healthcare and various energy storage systems, considering practical implementation, are argued.

Paper-based biosensors based on multiple recognition modes for visual detection of microbially contaminated food

Microbially contaminated food can cause serious health hazards and economic losses,therefore sensitive,rapid,and highly specific visual detection is called for.Traditional detection of microorganisms is complex and time-consuming,which cannot meet current testing demands.The emergence of paper-based biosensors provided an effective method for efficient and visual detection of microorganisms,due to its high speed,all-in-one device,low cost,and convenience.This review focused on 5 biomarkers,namely nucleic acids,proteins,lipopolysaccharides.metabolites,and the whole microorganism of microorganisms.Besides,the recognition methods were summed up in 5 forms,including immunological recognition,aptamer recognition,nucleic acid amplification-mediated recognition.DNAzyme recognition and clustered regularly interspaced short palindromic repeats mediated recognition.In addition,we summarized the applications of paper-based biosensors in the detection of microorganisms thoroughly.Through the exploration of different biomarkers,identification methods,and applications,we hope to provide a reference for the development of paper-based biosensors and their application in safeguarding the food chain.

A paper-based microfluidic biosensor integrating zinc oxide nanowires for electrochemical glucose detection

This paper reports an electrochemical microfluidic paper-based analytical device(EμPAD)for glucose detection,featuring a highly sensitive working electrode(WE)decorated with zinc oxide nanowires(ZnO NWs).In addition to the common features ofμPADs,such as their low costs,high portability/disposability,and ease of operation,the reported EμPAD has three further advantages.(i)It provides higher sensitivity and a lower limit of detection(LOD)than previously reportedμPADs because of the high surface-to-volume ratio and high enzyme-capturing efficiency of the ZnO NWs.(ii)It does not need any light-sensitive electron mediator(as is usually required in enzymatic glucose sensing),which leads to enhanced biosensing stability.(iii)The ZnO NWs are directly synthesized on the paper substrate via low-temperature hydrothermal growth,representing a simple,low-cost,consistent,and mass-producible process.To achieve superior analytical performance,the on-chip stored enzyme(glucose oxidase)dose and the assay incubation time are tuned.More importantly,the critical design parameters of the EμPAD,including the WE area and the ZnO-NW growth level,are adjusted to yield tunable ranges for the assay sensitivity and LOD.The highest sensitivity that we have achieved is 8.24μA·mM^(−1)·cm^(−2),with a corresponding LOD of 59.5μM.By choosing the right combination of design parameters,we constructed EμPADs that cover the range of clinically relevant glucose concentrations(0−15 mM)and fully calibrated these devices using spiked phosphate-buffered saline and human serum.We believe that the reported approach for integrating ZnO NWs on EμPADs could be well utilized in many other designs of EμPADs and provides a facile and inexpensive paradigm for further enhancing the device performance.

Recent Advances and Applications in Paper-Based Devices for Point-of-Care Testing

Point-of-care testing(POCT),as a portable and user-friendly technology,can obtain accurate test results immediately at the sampling point.Nowadays,microfluidic paper-based analysis devices(μPads)have attracted the eye of the public and accelerated the development of POCT.A variety of detection methods are combined withμPads to realize precise,rapid and sensitive POCT.This article mainly introduced the development of electrochemistry and optical detection methods onμPads for POCT and their applications on disease analysis,environmental monitoring and food control in the past 5 years.Finally,the challenges and future development prospects ofμPads for POCT were discussed.

Screen printing fabricating patterned and customized full paper-based energy storage devices with excellent photothermal,self-healing,high energy density and good electromagnetic shielding performances

Supercapacitors are favored by researchers because of their high power density,especially with the acceleration of people’s life rhythm.However,their energy density,especially from the point of view of the whole energy storage device,is far lower than that of commercial batteries.In this work,a kind of customizable full paper-based supercapacitor device with excellent self-healing ability is fabricated by simple and low-cost screen printing,electropolymerization and dip coating methods.The resultant separatorfree supercapacitor device exhibits both ultrahigh gravimetric and areal specific energy(power)densities of 39 Wh kg^(-1)(69 k W kg^(-1))and 692μWh cm^(-2)(236 m W cm^(-2)),achieving excellent supercapacitor performance.Notably,the addition of vitrimers endows the whole device with outstanding self-healing properties,which is helpful for enhancing the adaptability of the device to the environment.In addition,this kind of paper-based device also displays good photothermal and electromagnetic shielding performances.These striking features make paper matrix composites attractive in the fields of supercapacitors,medical photothermal treatment and electromagnetic shielding.

Flexible and disposable paper-based gas sensor using reduced graphene oxide/chitosan composite

Nitrogen dioxide(NO_(2))is a representative toxicant in air pollution that mostly arises from the exhaust gas released by automobiles.It is related to various respiratory diseases such as pneumonia and sudden infant death syndrome.Additionally,because the toxicity of nitrogen dioxide is high in overpopulated areas(i.e.,a capital or metropolis),the development of simple,practical,and facile sensors is highly needed.This work presents a flexible and disposable paper-based NO_(2)sensor based on a reduced graphene oxide/chitosan(r GO/CS)composite.The synthesized r GO/CS composite can be easily flexed and deformed into various shapes,which are attributed to chitosan molecules that function as a dispersion and reduction agent and support material.In addition,this composite can be attached to paper owing to its adhesive property;hence it can be utilized in versatile applications in a disposable manner.By analyzing the conductive change of the r GO/CS composite when it reacts with NO_(2),we can detect nitrogen dioxide in a concentration range of 0–100 ppm with a detection limit of 1 ppm.Moreover,we performed NO_(2)detection in the exhaust gas released by automobiles using the r GO/CS composite for practical application.The results indicated that the r GO/CS composite has the potential to be used in feasible gas sensing as a facile and disposable sensor under various conditions.

Double-folding paper-based generator for mechanical energy harvesting

Paper-based generators are essential elements for building all paper-based systems. To obtain robust paper-based generators with outstanding high power outputs, this paper introduced a new type of double- folding paper-based generator by folding two paper components together. The output performance levels of the double-folding generator were twice higher than that of the single-folding and parallel-plate generators. A peak power of-3.24 mW was achieved under a stimulating frequency of 3 Hz. Furthermore, 47 light-emitting diodes （LEDs） were lit directly by a double-folding paper-based generator assembled to the crack of a door that opens and closes. This finding indicated the potential applications of the double-folding generator in the production of door ornaments or for security in places where doors frequently open and close.

Facile and Low-Cost Fabrication of a Thread/Paper-Based Wearable System for Simultaneous Detection of Lactate and pH in Human Sweat

Wearable devices have received tremendous interests in human sweat analysis in the past few years.However,the widely used polymeric substrates and the layer-by-layer stacking structures greatly influence the cost-efficiency,conformability and breathability of the devices,further hindering their practical applications.Herein,we report a facile and low-cost strategy for the fabrication of a skin-friendly thread/paper-based wearable system consisting of a sweat reservoir and a multi-sensing component for simultaneous in situ analysis of sweat pH and lactate.In the system,hydrophilic silk thread serves as the micro-channel to guide the liquid flow.Filter papers were functionalized to prepare colorimetric sensors for lactate and pH.The smartphone-based quantitative analysis shows that the sensors are sensitive and reliable.Although pH may interfere the lactate detection,the pH detected simultaneously could be employed to correct the measured data for the achievement of a precise lactate level.After being integrated with a hydrophobic arm guard,the system was successfully used for the on-body measurement of pH and lactate in the sweats secreted from the volunteers.This low-cost,easy-to-fabricate,light-weight and flexible thread/paper-based microfluidic sensing device may hold great potentials as a wearable system in human sweat analysis and point-of-care diagnostics.

Paper-Based Electrochemical Biosensors for Point-of-Care Testing of Neurotransmitters

Abstract Neurotransmitters are important biological molecules related to several nervous system diseases(NSDs).Point-of-care test-ing(POCT)of neurotransmitters is of great importance in preclinical research and early diagnosis of NSDs.Among various POCT platforms,paper-based electrochemical biosensors have achieved great advances in detection of neurotransmitters,thus taking a significant role in POCT of neurotransmitters nowadays.This review gives an overview of the recent advances of paper-based electrochemical biosensors for POCT of neurotransmitters.We first introduce the types of neurotransmitters and biological sample sources mainly used for neurotransmitter detection.Second,we review the components and the traditional fabrication technologies for paper-based electrochemical POCT biosensors,and then the functional modification methods of biosensor surfaces and three-dimensional fabrication methods for further enhancement of their detection performance.Then,we list examples of paper-based electrochemical biosensors used for detecting different neurotransmitters in biologi-cal samples.Last,we give a conclusion and promising development direction of paper-based electrochemical biosensors for neurotransmitters detection.The purpose of this review is to introduce the paper-based electrochemical biosensors as an emerging technology for POCT of neurotransmitters,offering a reference for readers and researchers for early diagnosis of NSDs using POCT technologies.

Paper-based all-solid-state flexible asymmetric micro-supercapacitors fabricated by a simple pencil drawing methodology

Flexible micro-scale energy storage devices as the key component to power the flexible miniaturized electronic devices are attracting extensive attention. In this study, interdigitated asymmetric all-solidstate flexible micro-supercapacitors（MSCs） were fabricated by a simple pencil drawing process followed by electrodepositing MnO_2 on one of the as-drawn graphite electrode as anode and the other as cathode.The as-prepared electrodes showed high areal specific capacitance of 220 μF/cm^2 at 2.5 μA/cm^2. The energy density and the corresponding power density of the resultant asymmetrical flexible MSCs were up to 110 μWh/cm^2 and 1.2 μW/cm^2, respectively. Furthermore, excellent cycling performance（91% retention of capacity after 1000 cycles） was achieved. The resultant devices also exhibited good electrochemical stability under bending conditions, demonstrating superior flexibility. This study provides a simple yet efficient methodology for designing and fabricating flexible supercapacitors applicable for portable and wearable electronics.

A Smartphone-assisted Paper-based Analytical Device for Fluorescence Assay of Hg2+

Rapid,efficiency and portable detection systems in low-resource settings with limited laboratory equipment and technical expertise are urgently needed.Herein,an integrated platform composed of a paper-based analytical device and a smartphone detection system for Hg^2+ onsite testing was developed.Nitrogen-doped carbon dots(N-CDs)were synthesized by a simple hydrothermal method using citric acid as the carbon source and ethanediamine as the nitrogen source,which gave out bright blue fluorescence under the excitation at 350 nm UV light and the absolute fluorescence quantum yield was 17.1%.The fluorescence of the prepared N-CDs can be effectively quenched by Hg^2+.In addition,an external attachment of smartphone for illumination and external light interference was designed to trace the fluorescence signals,and a software application of Android system with simple operation program was developed to perform snapshot and image processing.The smartphone-assisted detection system was combined with the N-CDs decorated paper chip to achieve the sensitive detection of Hg^2+ in water samples.This integrated method for reliable sensing of Hg^2+ shows a good linear detection range of 10–800μmol/L(R2=0.9595)with detection limit of 1.07×10^?8 mol/L.