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We developed a surfactant-free spray coating process to coat commercial cellulose-based paper with carbon nanotubes (CNTs) and prepared paper-CNTs current collectors for Li-ion batteries (LIBs). The paper-CNTs were used as current collectors for replacing conventional aluminum foil. Li-ion batteries assembled using paper-CNTs were coated with LiFePO4 as the active material and used as cathodes with Li as the anode, and the assembled LIBs showed a high energy density of 460 Wh kg−1 at a power density of 250 W kg−1. These electrodes were stable even at a current density as high as 600 mA g−1, and showed cycling stability for ~450 cycles at 150 mAh g−1. Furthermore, paper-CNTs based electrodes showed ~17% improvement in areal capacity compared to commercial aluminum-based electrodes suggesting that paper-CNTs can readily displace Al foils as current collectors.

The high demand for flexible electroconductive elements, such as organic coatings, is associated with the development of IoT devices, wearable health monitoring devices, and similar devices. To meet cost and environmental standards, the ideal coating should use the richness of nature, be biodegradable, and be water soluble to avoid the use of harmful organic solvents. All of these criteria are met by the composite coating consisting of sodium lignosulfonate (SLS) and multiwall carbon nanotubes (MWCNTs). Furthermore, the SLS/CNT coating on paper substrates is highly electroconductive, hydrophobic, and resistant to annealing, high humidity, bending, and scratching. The electrical conductivity of the SLS/CNT coating varies depending on the substrate used, but it is highly conductive and resistant on all substrates tested. Most importantly, due to the use of abundant and mass produced and cheap materials, the price of a coating containing 77 wt% SLS and 23 wt% CNT, with a sheet resistance of 113 Ω/sq is estimated to be around 2.05 EUR/m2. This coating can be especially beneficial for large-scale applications, such as heating films. [Display omitted] • SLS is an affordable and readily available stabilizer for CNT dispersion in water. • SLS/CNT creates a highly conductive coating on cellulose substrates. • The SLS/CNT coating on paper has potential applications as cost-effective sensors or heaters. • The conductivity of the coating is influenced by the properties of the substrate. [ABSTRACT FROM AUTHOR]

Airflow sensor is a crucial component for monitoring environmental airflow conditions in many engineering fields, especially in the field of aerospace engineering. However, conventional airflow sensors have been suffering from issues such as complexity and bulk in structures, high cost in fabrication and maintenance, and low stability and durability. In this work, we developed a facile direct-writing method for fabricating a low-cost piezoresistive element aiming at high-performance airflow sensing, in which a commercial pen was utilized to drop solutions of single-walled carbon nanotubes onto tissue paper to form a piezoresistive sensing element. The encapsulated piezoresistive element was tested for electromechanical properties under two loading modes: one loading mode is the so-called pressure mode in which the piezoresistive element is pressed by a normal pressure, and another mode is the so-called bending mode in which the piezoresistive element is bended as a cantilever beam. Unlike many other developed airflow sensors among which the sensing elements are normally employed as cantilever beams for facing winds, we designed a fin structure to be incorporated with the piezoresistive element for airflow sensing; the main function of the fin is to face winds instead of the piezoresistive element, and subsequently transfer and enlarge the airflow pressure to the piezoresistive element for the normal pressure loading mode. With this design, the piezoresistive element can also be protected by avoiding experiencing large strains and direct contact with external airflows so that the stability and durability of the sensor can be maintained. Moreover, we experimentally found that the performance parameters of the airflow sensor could be effectively tuned by varying the size of the fin structure. When the fin sizes of the airflow sensors were 20 mm, 30 mm, and 40 mm, the detection limits and sensitivities of the fabricated airflow sensors were measured as 8.2 m/s, 6.2 m/s, 3.2 m/s, 0.0121 (m/s)−2, 0.01657 (m/s)−2, and 0.02264 (m/s)−2, respectively. Therefore, the design of the fin structure could pave an easy way for adjusting the sensor performance without changing the sensor itself toward different application scenarios.

We propose a unique soft actuator—a paper actuator—based on carbon-nanotube-composite paper (CNT-composite paper), which is a composite of carbon nanotubes (CNTs) and paper. CNT-composite paper has highly efficient properties because of the contained CNTs, such as high electrical conductivity and semiconducting properties. We are considering using CNT-composite paper for various devices. In this study, we successfully developed a paper actuator. We determined the structure of the paper actuator by referencing that of bucky-gel actuators. The actuator operates using the force generated by the movement of ions. In addition to making the paper actuator, we also attempted to improve its performance, using pressure as an index and an electronic scale to measure the pressure. We investigated the optimal dispersant for use in paper actuators, expecting the residual dispersant on the CNT-composite paper to affect the performance differently depending on the type of dispersant. Referring to research on bucky-gel actuators, we also found that the addition of carbon powder to the electrode layers is effective in improving the pressure for paper actuators. We believe that the paper actuator could be used in various situations due to its ease of processing.

Inspired by the excellent mechanical reinforcement effect of carbon nanotubes (CNTs) and the strong interactions between metal ions and graphene oxide (GO), ultra-robust, and high-toughness GO papers were fabricated via the synergistic reinforcement of CNTs and copper ions (Cu2+). The freestanding and flexible CNT/GO nanocomposite papers with a layered structure were readily fabricated by the vacuum-assisted filtration. After being cross-linked by a trace amount of copper ions (Cu2+), the tensile strength, elastic modulus and toughness of the modified GO papers increase 409.7%, 81.5% and 188.2%, respectively, when compared with the pure GO papers. It is revealed by scanning electron microscope and in situ Raman spectroscopy analysis that the CNTs and Cu2+ hindered the interlayer slippage between the GO sheets and promoted the stress transfer during the tensile loading. Considering the tunable and versatile properties of this hybrid carbon nanomaterial, this study will open an avenue for integrating rGO or GO papers to various applications. Image 1 [ABSTRACT FROM AUTHOR]

A 3-dimensional carbonized multi-walled carbon nanotube (MWCNT) paper was used as the host of nano-tin oxide (SnO2) for lithium-ion batteries (LIBs). The cellulose fibers were fully mixed with MWCNTs in water. Then, the paper was obtained via vacuum filtration. Carbonization was carried out in a vacuum furnace at 1460°C. SnO2 slurry was coated on the carbonized MWCNT paper (CMP). Scanning electron microscopy (SEM) was utilized to observe the anode electrode. The images of SEM indicated that the nano-SnO2 was embedded into the holes of the porous CMP collector. This contributed the increase of contact interface area of the nano-SnO2 and the collector and the significantly reduced interface resistance. Electrochemical tests showed that the initial discharge capacity reached 1745 mAh g−1 with a coulumbic efficiency (CE) of 70.39% at a current density of 50 mA g−1. The composite electrode still maintained a reversible capacity of 753 mAh g−1 with a CE of 98% at a current density of 200 mA g−1 after 100 cycles. These marvelous composite electrodes exhibited a promising future for the next generation of LIBs. [ABSTRACT FROM AUTHOR]

Abstract: A simple and scalable method to fabricate a yarn‐type supercapacitor with a large specific capacitance without the aid of traditional pseudocapacitive electrode materials such as conducting polymers and metal oxides is reported. The yarn‐type supercapacitors are made from twisting reduced graphene oxide (rGO) or/and single‐walled carbon nanotubes (SWNTs)‐coated Korean traditional paper (KTP). The yarn‐type paper supercapacitor displays surprisingly enhanced electrochemical capacitance values, showing synergistic effect between rGO and SWNTs (500 times larger than performance of yarn‐type rGO‐coated paper supercapacitors). Coating rGO or/and SWNTs on KTP gives good morphology to the composite film, in which porosity increases and mean pore diameter decreases. The yarn‐type rGO/SWNT paper supercapacitor shows good mechanical strength, high flexibility, excellent electrochemical performance, and long‐life operation. The yarn‐type supercapacitor has an excellent electrochemical performance with a specific capacitance of 366 F g−1 at scan rate of 25 mV s−1 and high stability without any degradation in electrical performance up to 10 000 charge–discharge cycles. The average capacitance of rGO/SWNT@KTP yarn‐type supercapacitors is seven times higher than that of sheet‐type supercapacitors at scan rate of 500 mV s−1. The lighting of a red light‐emitting diode (LED) is demonstrated by the yarn‐type paper supercapacitor without connecting supercapacitors in series. [ABSTRACT FROM AUTHOR]

ABSTRACT: Conventional cellulosic paper, rendered electro‐conductive, may hold considerable promise for diversified applications in such areas as electro‐magnetic interference shielding and energy storage. Here, an electro‐conductive cellulosic paper was prepared by surface application of multi‐walled carbon nanotubes (MWCNTs)/polyaniline (PANI) nanocomposites onto a conventional base paper. MWCNTs/PANI nanocomposites were prepared by in situ polymerization of aniline with different contents of MWCNTs and used as electro‐conductive filler for the fabrication of electro‐conductive surface‐coated paper. The achieved MWCNTs/PANI nanocomposites exhibited a core‐shell structure, as evidenced by TEM. Effects of feeding ratios of MWCNTs on the rheological behavior of nanocomposite coatings, as well as the mechanical properties and electrical conductivity of surface‐coated paper were studied. Results revealed that the rheological behavior of the nanocomposite coatings showed strong dependence on the MWCNTs content. Moreover, both the electro‐conductivity and mechanical properties of surface‐coated paper were improved as a function of surface application of MWCNTs/PANI nanocomposites, particularly, in presence of an optimum content of MWCNTs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46329. [ABSTRACT FROM AUTHOR]

This study is an investigation for an inexpensive, simple and sensitive biosensor to detect prostate cancer using bioactivated-multi wall carbon nanotubes (MWCNTs, diameter of 20 nm, length of 5 µm) and a micro-pore filter paper (pore size of 0.45 µm). For the immunoassay of prostate specific antigen (PSA), which is a biomarker of prostate cancer, MWCNTs were activated with PSA antibody (monoclonal antibody of the prostate specific antigen) by using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide sodium salt (NHSS). The activated MWCNTs were deposited on the micro-pore filter paper to use as a biosensor. The prepared biosensor can assay from 0 to 500 ng/mL of PSA level within 2 h with the detection limit of 1.18 ng/mL by the measurement of resistance change. The resistance change was caused by site selective interaction between PSA and PSA-antigen with an inexpensive bench top digital multimeter (5 1/2 digits). The detection range and sensitivity of the prepared sensor are good enough to diagnose the early stage of prostate cancer (> 4 ng/mL of PSA). This paper-based biosensor is about 20 times cheaper (fabricated biosensor price: 2.4 $) and over 10 times faster than enzyme-linked immunosorbent assay (ELISA), which is a general method for the detection of a specific protein in the modernized hospitals. Furthermore, the maximum detection limit is about 50 times higher than ELISA. [ABSTRACT FROM AUTHOR]

Nanostructured composites built with microporous cellulose fibers and carbon nanotubes (CNTs) have potential impacts in the fields of energy storage, sensors, and flexible electronics. Few results have been shown for high mechanoelectrical sensitivity of CNT‐paper composite because of numerous current paths in the network. Here, CNT‐paper‐based nanostructured composite sensors whose sensitivities are generated by controlled tensile fracture of the composite are presented. Under uniaxial load, the cellulose fibers in the paper experience straightening, stiffening, and fracture. The cellulose fibers originally parallel to the tension are fractured while those inclined and perpendicular to the tension are reorganized to form crossbar junctions in the vicinity of a crack. The cross junctions exhibit resistive and capacitive sensitivity to the out‐of‐plane force by the compression of the junctions. Such piezoresistive and piezocapacitive sensitivities are characterized and evaluated for human behavior monitoring. [ABSTRACT FROM AUTHOR]

Cotton wool, cotton textile, tissue paper and printing paper, all potential waste cellulosic materials, were directly converted to sorbitol using a Ru/CNT catalyst in the presence of H 2 and using only water as solvent, without any acids. Conversions up to 38% were attained for the raw substrates, with sorbitol yields below 10%. Ball-milling of the materials disrupted their crystallinity, allowing reaching 100% conversion of cotton wool, cotton textile and tissue paper after 4 h, with sorbitol yields around 50%. Mix-milling these materials with the catalyst greatly enhanced their conversion rate, and the materials were efficiently converted to sorbitol with a yield around 50% in 2 h. However, ball- and mix-milled printing paper presented a conversion of only 50% after 5 h, with sorbitol yields of 7%. Amounts of sorbitol of 0.525, 0.511 and 0.559 g could be obtained from 1 g of cotton wool, cotton textile and tissue paper, respectively. [ABSTRACT FROM AUTHOR]

Recently, actuating materials based on carbon nanotubes or graphene have been widely studied. However, present carbon-based actuating materials are mostly driven by a single stimulus (humidity, light, electricity, etc.), respectively, which means that the application conditions are limited. Here, a new kind of multiresponsive actuating material which can be driven by humidity, light, and electricity is proposed, so it can be used in various conditions. The fabrication is based on the simplest pencil-on-paper method, in which the pencil and paper are both low-cost and easily obtained daily materials. The actuation effect is more remarkable due to a dual-mode actuation mechanism, which leads to an ultralarge actuation (bending curvature up to 2.6 cm−1). Elaborately designed, the actuator can further exhibit a bidirectional bending actuation, which is a significant improvement compared with previous reported thermal actuators. What is more, a colorful biomimetic flower and a smart curtain are also fabricated, fully utilizing the printable characteristic of the paper and multiresponsive characteristic of the actuator. It is assumed that the newly designed actuating material has great potential in the fields of lab-on-paper devices, artificial muscles, robotics, biomimics, and smart household materials. [ABSTRACT FROM AUTHOR]

A versatile method for the preparation of efficient and reusable nanocatalysts involving the painting of a commercial filter paper with a Pd@CNT (CNT=carbon nanotubes) ink was herein explored. The resulting paper-based material provided excellent results in the semihydrogenation of alkynes and alkynols and could be recycled at least five times without loss of activity or selectivity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Water based conductive carbon nanotube ink is synthesized. [•] Direct writing on paper is demonstrated with off-the-shelf nib of fountain pen. [•] Dual sided and multilayered paper circuit boards are demonstrated with the pen. [•] Excellent robustness against bending, folding, crumpling are confirmed. [Copyright &y& Elsevier]

Abstract: Progress of carbon nanotube (CNT) research and development in terms of published papers and patents is reported. Developments concerning CNT structures, synthesis, and major parameters, in terms of the published documents are surveyed. Publication growth of CNTs and related fields are analyzed for the period of 2000–2010. From the explored search term, “carbon nanotubes”, the total number of papers containing the CNT concept is 52,224, and for patents is 5,746, with a patent/paper ratio of 0.11. For CNT research in the given period, an annual increase of 8.09% for paper and 8.68% for patents are resulted. Published papers for CNT, CVD and CCVD synthesis parameters for the period of 2000–2010 are compared. In other research, publications for CNT laser synthesis, for the period of 2000–2010, are reviewed. Publications for major laser parameters in CNT synthesis for the period of 2000–2010 are described. The role of language of the published references for CNT research for the period of 2000–2010 is also investigated. Published papers/patents in English, Japanese, Chinese, Russian, German, French, Polish, and Spanish languages are compared. As expected, the number of paper/patent publications in English dominates other languages. [Copyright &y& Elsevier]

Abstract: In this work, we demonstrated a novel paper-based mediator-less and compartment-less biofuel cell (BFC) with small size (1.5cm×1.5cm). Ionic liquid functionalized carbon nanotubes (CNTs-IL) nanocomposite was used as support for both stably confining the anodic biocatalyst (i.e., NAD+-dependent glucose dehydrogenase, GDH) for glucose electrooxidation and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., bilirubin oxidase, BOD) for O2 electroreduction. Such BFC provided a simple approach to fabricate low-cost and portable power devices on small-size paper, which can harvest energy from a wide range of commercial beverages containing glucose (e.g., Nescafe instant coffee, Maidong vitamin water, Watermelon fresh juice, and Minute Maid grape juice). These made the low-cost paper-based biodevice potential for broad energy applications. [Copyright &y& Elsevier]

Abstract: Paper supports were used to develop a simple, inexpensive, fast and sensitive electrochemical immunosensor for the analysis of antibiotic residues in milk samples, where single-walled carbon nanotubes (SWNTs) and a simple dip–dry coating method were employed to prepare the highly sensitive biosensor. Well-dispersed SWNTs were impregnated with an antibody against neomycin to obtain a composite coating solution, followed by dipping the filtration paper in the solution to fabricate the sensitive biosensor which had high electrical conductivity. Based on the impedance change in the entire paper supported biosensor with increased concentrations of neomycin, the limit detection of the optimized method was 0.04ngmL−1 and a linear detection range from 0.2 to 125ngmL−1, well below the European Union regulations for neomycin in this matrix. This paper supported biosensor was applied to determine neomycin in milk samples after a simple sample treatment, with spiked recoveries which ranged from 93.25 to 110.47%. A variety of antibiotic residues in milk samples could be determined following similar sensor preparation. [Copyright &y& Elsevier]

Paper, invented more than 2,000 years ago and widely used today in our everyday lives, is explored in this study as a platform for energy-storage devices by integration with 1D nanomaterials. Here, we show that commercially available paper can be made highly conductive with a sheet resistance as low as 1 ohm per square (π/sq) by using simple solution processes to achieve conformal coating of single-walled carbon nanotube (CNT) and silver nanowire films. Compared with plastics, paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30-47 Watt-hour/kilogram (Wh/kg). a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved. In addition, this conductive paper can be used as an excellent lightweight current collector in lithium-ion batteries to replace the existing metallic counterparts. This work suggests that our conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract: This study explores the possibility of converting a self-supporting, randomly aligned, low impedance multi-wall carbon nanotube (MWCNT) paper into a resistive temperature measurement unit working at ambient pressure in air in the 25–70°C range. Thermosensitization was achieved by decorating the surface of the films with pyroelectric CsNO3 or LiNbO3 crystals. Assuming a linear temperature response, temperature coefficient of resistance values of −0.158%°C−1 and −0.246%°C−1 were calculated for CsNO3 and LiNbO3 doped films, respectively. The corresponding temperature measurement accuracies (2.2°C and 3.0°C) are acceptable for some applications but the precision of the temperature measurement needs to be improved. [Copyright &y& Elsevier]

Flexible supercapacitor with all components monolithically integrated into an on-chip paper substrate demonstrates excellent electrochemical and mechanical performance. Supercapacitors are drawn with a conductive ink of nitrogen-doped carbon nanotube and graphene ink, which has been prepared without assistance of surfactant. The engineering strategy is intrinsically scalable toward flexible paper devices. [Display omitted] • A surfactant-free ink of nitrogen-doped carbon nanotubes and graphene is prepared. • The electrodes are integrated onto a paper in mirror image. • The resultant supercapacitor presents a high volumetric capacitance of 0.45 F cm−3. • The strategy is intrinsically scalable toward flexible supercapacitors. We demonstrate a facile strategy to fabricate flexible paper-based supercapacitors, in which all the components are integrated onto a paper with poly (vinyl alcohol)/H 3 PO 4 as the gel electrolyte. The electrodes are drawn on both sides of the paper in a mirror image with a surfactant-free ink of nitrogen-doped carbon nanotubes and graphene. The resultant supercapacitors present a high volumetric capacitance of 0.45 F cm−3 and an energy density of 40.0 μWh cm−3. Moreover, this strategy is intrinsically scalable toward flexible energy devices while maintaining their electrochemical and mechanical performance. [ABSTRACT FROM AUTHOR]

Airflow sensor is a crucial component for monitoring environmental airflow conditions in many engineering fields, especially in the field of aerospace engineering. However, conventional airflow sensors have been suffering from issues such as complexity and bulk in structures, high cost in fabrication and maintenance, and low stability and durability. In this work, we developed a facile direct-writing method for fabricating a low-cost piezoresistive element aiming at high-performance airflow sensing, in which a commercial pen was utilized to drop solutions of single-walled carbon nanotubes onto tissue paper to form a piezoresistive sensing element. The encapsulated piezoresistive element was tested for electromechanical properties under two loading modes: one loading mode is the so-called pressure mode in which the piezoresistive element is pressed by a normal pressure, and another mode is the so-called bending mode in which the piezoresistive element is bended as a cantilever beam. Unlike many other developed airflow sensors among which the sensing elements are normally employed as cantilever beams for facing winds, we designed a fin structure to be incorporated with the piezoresistive element for airflow sensing; the main function of the fin is to face winds instead of the piezoresistive element, and subsequently transfer and enlarge the airflow pressure to the piezoresistive element for the normal pressure loading mode. With this design, the piezoresistive element can also be protected by avoiding experiencing large strains and direct contact with external airflows so that the stability and durability of the sensor can be maintained. Moreover, we experimentally found that the performance parameters of the airflow sensor could be effectively tuned by varying the size of the fin structure. When the fin sizes of the airflow sensors were 20 mm, 30 mm, and 40 mm, the detection limits and sensitivities of the fabricated airflow sensors were measured as 8.2 m/s, 6.2 m/s, 3.2 m/s, 0.0121 (m/s)−2, 0.01657 (m/s)−2, and 0.02264 (m/s)−2, respectively. Therefore, the design of the fin structure could pave an easy way for adjusting the sensor performance without changing the sensor itself toward different application scenarios. [ABSTRACT FROM AUTHOR]

We propose a unique soft actuator—a paper actuator—based on carbon-nanotube-composite paper (CNT-composite paper), which is a composite of carbon nanotubes (CNTs) and paper. CNT-composite paper has highly efficient properties because of the contained CNTs, such as high electrical conductivity and semiconducting properties. We are considering using CNT-composite paper for various devices. In this study, we successfully developed a paper actuator. We determined the structure of the paper actuator by referencing that of bucky-gel actuators. The actuator operates using the force generated by the movement of ions. In addition to making the paper actuator, we also attempted to improve its performance, using pressure as an index and an electronic scale to measure the pressure. We investigated the optimal dispersant for use in paper actuators, expecting the residual dispersant on the CNT-composite paper to affect the performance differently depending on the type of dispersant. Referring to research on bucky-gel actuators, we also found that the addition of carbon powder to the electrode layers is effective in improving the pressure for paper actuators. We believe that the paper actuator could be used in various situations due to its ease of processing. [ABSTRACT FROM AUTHOR]