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A lightweight wideband honeycomb absorber is theoretically and experimentally investigated. The proposed absorber is constructed of aramid paper, which contains carbon fibers to absorb partially the incident electromagnetic wave. Graded silver paste circuits are also printed on aramid paper to improve the impedance matching properties and, thus, achieve wideband absorption performance. An absorber sample was fabricated and measured to verify the design strategies. The designed absorber has a fractional absorption bandwidth of 133% from 3.6–18 GHz, with a thickness of 0.19λL at the lowest frequency. The total weight of the absorber is 18.2 g, with a density of 28.4 kg/ m 3 . [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) capable of efficiently harvesting various mechanical energies from the environment are an effective way to solve the energy supply problem of wearable electronic devices. A series of flexible and lightweight TENGs with different surface morphologies of "dots"–"lines"–"honeycombs" hierarchical micro-structures are developed using low-cost and easily accessible background paper as a substrate. Polydimethylsiloxane films with dots–lines–honeycombs hierarchical micro-structures are prepared by the spin coating to obtain larger contact areas and, thus, enhance the triboelectric effect. Under the same test conditions, the honeycombs TENG (H-TENG) with complex surface morphology has the largest output performance with an open-circuit voltage of 55 V and a short-circuit current of 2.7 μA, which is 2.1 and 2.5 times that of the flat TENG, respectively. By combining with nylon gloves, the H-TENG can harvest the mechanical energy during hand movement and realize sensing of hand movement patterns through the difference of electrical signals. In addition, this device can power the liquid crystal display screen through a rectifier circuit and capacitor. This simple and efficient TENG device shows great potential in the wearable field. [ABSTRACT FROM AUTHOR]

Writing with ink on a paper and the rapid diagnostics of diseases using paper cartridge, despite their remarkable diversities from application perspective, both involve the motion of a liquid from a source on a porous hydrophilic substrate. Here we bring out a generalization in the pertinent dynamics by appealing to the concerned ensemble-averaged transport with reference to the underlying molecular picture. Our results reveal that notwithstanding the associated complexities and diversities, the resultant liquid transport characteristics on a paper matrix, in a wide variety of applications, resemble universal diffusive dynamics. Agreement with experimental results from diversified applications is generic and validates our unified theory. [ABSTRACT FROM AUTHOR]

The goal of this work is to investigate the porosity of old paper with foxings. Initially, paper samples are characterized using the conventional absorption and Fourier transform infrared spectroscopies. Optoacoustic method based on laser excitation of short ultrasound transients is used for porosity measurements. The paper porosity is calculated using the theory of two-component mixture with the experimentally determined sound speeds in paper samples saturated with liquids. An increase in the porosity in foxing stains on paper in comparison with the foxing-free fragments is clearly demonstrated. [ABSTRACT FROM AUTHOR]

Rapid and even spreading of complex fluids over a large area on substrates like paper is required for chemical and biological sensing applications. Non-Newtonian flow behavior and the presence of multi-phase components pose a significant challenge to uniform flow in porous media. Specifically in the case of blood, for biosensing applications, fast spread on a large area is required to avoid coagulation and non-uniform component spread. In this work, we have developed a filter paper-based device to resolve this spreading challenge. We sandwich the filter paper between a matrix of nanofibrous membrane backed by polyethylene terephthalate (PET) sheets, forming a multi-scale porous network: one within the filter paper and the other between the PET sheet and the filter paper. By doing so, we decrease the overall resistance to flow while maintaining the same capillary suction pressure to obtain a quick, uniform spread of dyed liquids, milk solutions, and whole blood. The device design and concepts used here can be used in paper microfluidic applications and to develop devices for dried blood spot analysis, which utilize this fast flow while maintaining even spreading over a large area. [ABSTRACT FROM AUTHOR]

Paper-based microfluidics and sensors have attracted great attention. Although a large number of paper-based devices have been developed, surprisingly there are only a few studies investigating paper actuators. To fulfill the requirements for the integration of both sensors and actuators into paper, this work presents an unprecedented platform which utilizes ferromagnetic particles for actuation and graphite for motion monitoring. The use of the integrated mechanical sensing element eliminates the reliance on image processing for motion detection and also allows real-time measurements of the dynamic response in paper-based actuators. The proposed platform can also be quickly fabricated using a simple process, indicating its potential for controllable paper-based lab on chip. [ABSTRACT FROM AUTHOR]

We report results of studies relating to the fabrication of a flexible, disposable, and label free biosensing platform for detection of the cancer biomarker (carcinoembryonic antigen, CEA). Polyaniline (PANI) has been electrochemically deposited over gold sputtered paper (Au@paper) for covalent immobilization of monoclonal carcinoembryonic antibodies (anti-CEA). The bovine serum albumin (BSA) has been used for blocking nonspecific binding sites at the anti-CEA conjugated PANI/Au@Paper. The PANI/Au@Paper, anti-CEA/PANI/Au@Paper, and BSA/anti-CEA/ PANI/Au@Paper platforms have been characterized using scanning electron microscopy, X-ray diffraction, Fourier transmission infrared spectroscopy, chronoamperometry, and electrochemical impedance techniques. The results of the electrochemical response studies indicate that this BSA/ anti-CEA/PANI/Au@paper electrode has sensitivity of 13.9 µA ng–1 ml cm2, shelf life of 22 days, and can be used to estimate CEA in the range of 2–20 ng ml–1. This paper sensor has been validated by detection of CEA in serum samples of cancer patients via immunoassay technique. [ABSTRACT FROM AUTHOR]

A kind of continuous flexible paper substrate thin film transistors (TFTs) of the ratio of a controllable length to width nickel (Ni) two-dimensionally connected metal-organic frameworks, Ni-TCNQ (TCNQ = 7, 7, 8, 8-tetracyanoquinodimethane), has been prepared skillfully by using all ink-jet printing Ni(NO3)2·6H2O and the TCNQ hydrothermal interface in situ reaction method. The structure analysis of Ni-TCNQ on copper electrodes was revealed by combining transmission electron microscope and powder x-ray diffraction techniques, indicating that it has a lamellar and porous structure. The morphology and structure of the transistor channel are stacked up by nanosheets of 2D lattice of [Ni(C12H4N4)2]n, which is further verified by scanning electron microscope, FT-IR, and x-ray photoelectron spectroscopy. I–V characteristics show that electrical behaviors of the p-type junctionless TFT are fabricated at room temperature. [ABSTRACT FROM AUTHOR]

When a liquid droplet is placed on a sufficiently hot surface, it will be levitated by the vapor cushion between the droplet and the hot surface due to the Leidenfrost effect. Such Leidenfrost-based levitation can greatly reduce friction and thus offers a promising approach for low-friction devices. In this work, we demonstrated a self-propelled rotational Leidenfrost rotor made of wet paper with asymmetric mass distribution. The rotor has shown the capability of reaching angular velocities of more than 30 rad/s and prolonged the rotation duration through refueling with water. We experimentally investigated the influence of mass repartition and substrate heating temperature on the rotation behavior of the rotor. It was found that both the initial acceleration and the maximum angular velocity increase with the increasing mass ratio of the connector over the evaporator within the rotor and the substrate heating temperature. A theoretical model was proposed to simulate the trend, and the simulated results are in good agreement with the experimental results. The paper-based Leidenfrost rotor provides an alternative way to utilize the Leidenfrost effect for exploring self-propelled movement and relevant applications such as surface cleaning and rotary heat engines. [ABSTRACT FROM AUTHOR]

We report a flexible paper transistor made with regenerated cellulose and covalently bonded multiwalled carbon nanotube (RC-MWCNT). MWCNT bonded to cellulose chains can act as electron channel paths in dielectric cellulose layers. It is found that the covalent bonding between cellulose and MWCNT can be modulated by reaction time and temperature. The RC-MWCNT paper transistor shows that the leakage current and the on/off ratio are strongly associated with the concentration of MWCNTs. The estimated electron mobility of RC-MWCNT paper is comparable to other organic transistor materials. The RC-MWCNT paper transistor has a potential for flexible electronic paper. [ABSTRACT FROM AUTHOR]

Presently, we contemplate the merger of paper and electronics in different forms. There is a great desire to further explore this twinning of the information displaying features of printed papers and electronic inks. Here, we report a full-color paperboard display technology comprised of thermochromic and static inks combined with a patterned heater foil. Black and full-color thermochromic ink dots were screen-printed adjacent to, and on top of, static ink dots using a zero-angle mesh and template pattern orientation. As the heater is turned on and off, the display alter its content in between two predefined four-color pictures. [ABSTRACT FROM AUTHOR]

Printing electronics has led to application areas which were formerly impossible with conventional electronic processes. Solutions are used as inks on top of large areas at room temperatures, allowing the production of fully flexible circuitry. Commonly, research in these inks have focused on organic and metal-oxide ink materials due to their printability, while these materials lack in the electronic performance when compared to silicon electronics. Silicon electronics, on the other hand, has only recently found their way in solution processes. Printing of cyclopentasilane as the silicon ink has been conducted and devices with far superior electric performance have been made when compared to other ink materials. A thermal annealing step of this material, however, was necessary, which prevented its usage on inexpensive substrates with a limited thermal budget. In this work, we introduce a method that allows polycrystalline silicon (poly-Si) production directly from the same liquid silicon ink using excimer laser irradiation. In this way, poly-Si could be formed directly on top of paper even with a single laser pulse. Using this method, poly-Si transistors were created at a maximum temperature of only 150 °C. This method allows silicon device formation on inexpensive, temperature sensitive substrates such as polyethylene terephthalate, polyethylene naphthalate or paper, which leads to applications that require low-cost but high-speed electronics. [ABSTRACT FROM AUTHOR]

We report the preparation of large-area graphite papers with thicknesses from 100 µm to more than 1 mm, by the reduction and graphitization of graphite oxide at elevated temperatures. The papers can be produced on a size of 20 x 20 cm² and have a low mass density. X-ray diffraction and Raman characterization show that the stacking of graphitic layers in the papers follows the Bernal stacking, and X-ray photoelectron spectroscopy indicates a carbon purity of above 98 at. % in the papers. The graphite papers have an electrical conductivity of 2533-4996 S/m and a thermal conductivity of 42-149W/mK, depending on the thickness. When a power input of above 10W is applied on the paper with a thickness of 98 µm, incandescence is observed, corresponding to a temperature of higher than 1000 °C, which is increased with the input power. [ABSTRACT FROM AUTHOR]

Due to their high thermal conductivity, stability, light weight, and low cost, graphite products are widely used as thermally conductive materials in current electronic devices and are promising materials for future flexible electronics. However, the intrinsic high rough surface of graphite severely impedes the fabrication of thermal transistors based on graphite products. On the other hand, most of the flexible thermal transistors reported to date are based on polymer substrates, whose thermal conductivities are extremely low for thermal sensing. To address these issues herein, a flexible commercial graphite paper with high thermal conductivity was used as both the substrate and the back gate of thermal transistors. Fluorinated polyimide was also synthesized as a high performance dielectric material and was skillfully blade-coated on a flexible graphite paper to reduce the surface roughness. As a result, the as-fabricated flexible device exhibits extremely low hysteresis, wide operating temperature range (20–100 °C), high stability, and temperature sensing performance. Moreover, the as-fabricated pentacene device reached the mobility of 0.146 cm2 V−1 s−1, which is highly competitive among the reported flexible organic thermal transistors. Such thermal transistors are promising for integration in current electronic devices and promote the diversity of the flexible transistor substrates. [ABSTRACT FROM AUTHOR]

Three-color electrowetting (EW) reflective display devices have been achieved using a vertical stack structure with colored oils. Fundamental properties (interface tension and geometry) of the EW process were investigated. Arrays of ∼1000–2000 pixels were constructed with pixel sizes of 200×600 and 300×900 μm2. Each color layer can be switched independently. Open (oil-free) area fraction of ∼80% in each cell is achieved at ∼10–12 V. Switch-on times range from 5 to 15 ms, suitable for video content display. These characteristics demonstrate that the EW vertical structure has the potential to produce attractive video-speed color reflective electronic paper devices. [ABSTRACT FROM AUTHOR]

We report carbon nanotube thin film-based supercapacitors fabricated with printing methods, where electrodes and separators are integrated into single sheets of commercial paper. Carbon nanotube films are easily printed with Meyer rod coating or ink-jet printing onto a paper substrate due to the excellent ink absorption of paper. A specific capacity of 33 F/g at a high specific power of 250 000 W/kg is achieved with an organic electrolyte. Such a lightweight paper-based supercapacitor could be used to power paper electronics such as transistors or displays. [ABSTRACT FROM AUTHOR]

This paper presents a flexible solid-state supercapacitor of high energy density. The electrodes of the supercapacitor are made of porous and absorbent cotton paper coated with single-wall carbon nanotubes. To ensure all solid-state configuration, a solid-state polymer-based electrolyte (poly (vinyl alcohol)/phosphoric acid) is used. The as-fabricated supercapacitor can be charged to over 3 V. It has high specific capacitance and high energy density of 115.8301 F/g carbon and 48.8587 Wh/kg carbon. Its performance is comparable to that of commercial supercapacitors, which need to utilize liquid electrolytes. Flexible solid-state supercapacitors offer several significant advantages for use in hybrid electric vehicles. [ABSTRACT FROM AUTHOR]

Extensive work has been done in order to determine the bulk elastic modulus of isotropic samples from force curves acquired with atomic force microscopy. However, new challenges are encountered given the development of new materials constructed of one-dimensional anisotropic building blocks, such as carbon nanostructured paper. In the present work, we establish a reliable framework to correlate the elastic modulus values obtained by amplitude modulation atomic force microscope force curves, a nanoscopic technique, with that determined by traditional macroscopic tensile testing. In order to do so, several techniques involving image processing, statistical analysis, and simulations are used to find the appropriate path to understand how macroscopic properties arise from anisotropic nanoscale components, and ultimately, being able to calculate the value of bulk elastic modulus. [ABSTRACT FROM AUTHOR]

In-situ sputtering ZnO films on graphene oxide (GO) paper are used to fabricate graphene based ZnO films. Crystal structure and surface chemical states are investigated. Results indicated that GO paper can be effectively deoxygenated by in-situ sputtering ZnO on them without adding any reducing agent. Based on the principle of radio frequency magnetron sputtering, we propose that during magnetron sputtering process, plasma streams contain large numbers of electrons. These electrons not only collide with argon atoms to produce secondary electrons but also they are accelerated to bombard the substrates (GO paper) resulting in effective deoxygenation of oxygen-containing functional groups. In-situ sputtering ZnO films on GO paper provide an approach to design graphene-semiconductor nanocomposites. [ABSTRACT FROM AUTHOR]

We present a method for improving the thermal stability of insulation paper cellulose. A polysiloxane was grafted to the hydroxyl group connected to the C6 atom in the cellulose chain. The effects of the mass fraction of polysiloxane on the mechanical properties and glass-transition temperatures of model cellulose samples modified by polysiloxane grafting were investigated using molecular dynamics simulations. The results show that for four models, with polysiloxane mass fractions of 0%, 3.3%, 6.5%, and 12.2%, the best chain performance was achieved using a mass fraction of 6.5%. The glass-transition temperature of the modified cellulose with a 6.5% mass fraction of polysiloxane was 48K higher than that of unmodified cellulose, which shows that modification improved the thermal stability of the cellulose. [ABSTRACT FROM AUTHOR]

We report the rapid prototyping of passive electrical components (resistors and capacitors) on plain paper by an additive and parallel technology consisting of supersonic cluster beam deposition (SCBD) coupled with shadow mask printing. Cluster-assembled films have a growth mechanism substantially different from that of atom-assembled ones providing the possibility of a fine tuning of their electrical conduction properties around the percolative conduction threshold. Exploiting the precise control on cluster beam intensity and shape typical of SCBD, we produced, in a one-step process, batches of resistors with resistance values spanning a range of two orders of magnitude. Parallel plate capacitors with paper as the dielectric medium were also produced with capacitance in the range of tens of picofarads. Compared to standard deposition technologies, SCBD allows for a very efficient use of raw materials and the rapid production of components with different shape and dimensions while controlling independently the electrical characteristics. Discrete electrical components produced by SCBD are very robust against deformation and bending, and they can be easily assembled to build circuits with desired characteristics. The availability of large batches of these components enables the rapid and cheap prototyping and integration of electrical components on paper as building blocks of more complex systems. [ABSTRACT FROM AUTHOR]

Solution-derived poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) piezoelectric thin films on cellulose paper substrates were prepared as flexible power generators for wearable device applications. Optimization of appropriate annealing and cooling sequences of the co-polymer films resulted in the formation of dense and uniform microstructures exhibiting a well-developed b-phase. A maximum open-circuit voltage of 1.5V was generated from the periodic bending and releasing of the paper power generator at approximately 1 Hz. To demonstrate the wearable applications, P(VDF-TrFE) piezoelectric film-based paper power generators were directly attached on the back of a human hand, and they generated a maximum output open-circuit voltage of 0.4V at low bending frequencies of 0.25 Hz. Good open-circuit voltage performance at low frequencies makes P(VDF-TrFE) piezoelectric thin films on paper substrates a strong candidate for future selfpowered wearable devices. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) are promising materials as active channels for flexible transistors owing to their excellent electrical and mechanical properties. However, flexible SWCNT transistors have never been realized on paper substrates, which are widely used, inexpensive, and recyclable. In this study, we fabricated SWCNT thin-film transistors on photo paper substrates. The devices exhibited a high on/off current ratio of more than 106 and a field-effect mobility of approximately 3cm²/V·s. The proof-of-concept demonstration indicates that SWCNT transistors on flexible paper substrates could be applied as low-cost and recyclable flexible electronics. [ABSTRACT FROM AUTHOR]

The pencil-drawn sensor is expected to enable a simple, low-cost, and reproducible paper-based sensor platform for widely deployed wireless environmental monitoring of NO2. Herein, we demonstrated a rapid prototyping of chemiresistor-type NO2 sensor by mechanical abrasion of an 8B pencil to form a stripe of uniform graphitic coating on printed silver interdigitated electrodes (IDEs). The Ag IDEs not only offer a low resistance but also provide the assembly of Ag nanoparticles into exfoliated graphene sheets for the paper-based NO2 gas sensors in order to realise much higher sensitivity and better reproducibility comparing with pencil-drawn sensors directly on weighing paper. [ABSTRACT FROM AUTHOR]

Perpendicular magnetic anisotropy was observed in Pt/Co/Pt trilayers prepared on three kinds of paper substrates with conspicuous difference of roughness by sputtering. Anomalous Hall effect exhibits well magnetic transport properties for partial samples. The trends of Hall resistivity over longitudinal resistivity (ρAH/ρxx) versus qxx are bending instead of a traditional linear relationship for thick single-layer Co films. Further, study reveals that this behavior strongly depends on ratios among contributions from the skew scattering induced by residual resistance and phonons, the side jump and the intrinsic parts in anomalous Hall effect. A 3D map of correlation coefficients (R) of ρAH/ρxx and qxx shows the ratios locate at a critical and ultra-narrow area for our trilayers. This study may throw new light on the understanding of anomalous Hall effect as well as lead to an economical and practical method to fabricate Hall devices on flexible substrates. [ABSTRACT FROM AUTHOR]

The thermal conductivities of graphene oxide paper (GOP) and the alkaline earth metal ions (Mg2+, Ca2+) modified analogues, prepared by a facile vacuum filtration method, were measured by a laser flash method. The thermal conductivities of GOP, Mg-modified GOP, and Ca-modified GOP are 3.91 W/(m × K), 32.05 W/(m × K), and 61.38 W/(m × K), respectively, which indicate the modification of GOP with metal ions has resulted in significant enhancement in thermal conduction properties compared with unmodified GOP. The crosslink between graphene oxide sheet and metal ions, the neat stacking of graphene oxide sheets in modified GOP, together with the intercalation of metal ions into the gallery spaces between the graphene oxide sheet basal planes, result in a decrease of thermal resistance of the boundary and an increase of contact surface, thus increases the thermal conductivity of modified graphene oxide paper. [ABSTRACT FROM AUTHOR]

We report on the fabrication and the electrical properties of amorphous (α-)InGaZnO4 thin-film transistors deposited on cellulose paper by sputtering at room temperature. The 150-μm-thick paper was used as both a gate dielectric and a substrate for device structural support. The transistors on paper were patterned by lithography and operated in enhancement mode with a threshold voltage of 3.75 V, and exhibited saturation mobility, subthreshold gate-voltage swing, and drain current on-to-off ratio of ∼35 cm2 V-1 s-1, 2.4 V decade-1, and ∼104, respectively. These results verify that simple cellulose paper is a good gate dielectric as well as a low-cost substrate for flexible electronic devices such as paper-based displays. [ABSTRACT FROM AUTHOR]