Search

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]

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]

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]

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]

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]

Macroscopic graphene paper is fabricated by an electrospray deposition approach, and the microstructure can be controlled from highly porous to highly compact geometries by varying deposition parameters including graphene colloid concentration and deposition rate. Free-standing graphene films can be separated from substrates via a simple water exfoliation method in which the surface properties of graphene films and substrates control film exfoliation. Specifically, water exfoliation can be achieved when the contact angle of substrates is 64° or below. Thermal and electrical conductivities of the macroscopic graphene paper upon thermal annealing are measured, enabling the establishment of the process-microstructure-property correlation beneficial for further development and property manipulation of graphene-based materials. [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]

Cellulose nanopapers have been shown to maintain high optical transparency after high temperature heating at 150 °C. High temperature heating to around 150 °C is inevitable in electronic device processing. If a polyethylene terephthalate film is held at 150 °C for tens of minutes, cyclic oligomers migrate to the film surface, causing surface roughness that decreases the film transparency. However, because cellulose nanofibers have high thermal stability, the transparent nanopapers maintained their smooth surfaces and high optical transparency, even after heating to 150 °C for tens of minutes. These findings indicate the suitability of cellulose nanofiber papers for continuous roll-to-roll processing. [ABSTRACT FROM AUTHOR]

We have fabricated bottom-gate amorphous (α-) indium-gallium-zinc-oxide (InGaZnO4) thin film transistors (TFTs) on both paper and glass substrates at low processing temperature (≤100 °C). As a water and solvent barrier layer, cyclotene (BCB 3022–35 from Dow Chemical) was spin-coated on the entire paper substrate. TFTs on the paper substrates exhibited saturation mobility (μsat) of 1.2 cm2 V-1 s-1, threshold voltage (VTH) of 1.9 V, subthreshold gate-voltage swing (S) of 0.65 V decade-1, and drain current on-to-off ratio (ION/IOFF) of ∼104. These values were only slightly inferior to those obtained from devices on glass substrates (μsat∼2.1 cm2 V-1 s-1, VTH∼0 V, S∼0.74 V decade-1, and ION/IOFF=105–106). The uneven surface of the paper sheet led to relatively poor contact resistance between source-drain electrodes and channel layer. The ability to achieve InGaZnO TFTs on cyclotene-coated paper substrates demonstrates the enormous potential for applications such as low-cost and large area electronics. [ABSTRACT FROM AUTHOR]

Tunable piezoresistive sensors based on a drawing on paper with different grades of pencils are proposed. While an external mechanical strain is applied to U-shape resistors prepared by pencil drawings on paper, an increase in the gauge factor with an increase in the graphite resistance is found. The result is attributed to the tunneling effect between neighboring graphite during the drawing process, further suggesting that different-grade pencil drawings can tune the piezoresistive properties. Through many cycles of repeatedly applied and released force, the output voltage for an HB pencil was found to be more sensitive than that for a 9B pencil. [ABSTRACT FROM AUTHOR]

Coincidentally, our group just developed terahertz quantum cascade lasers (THz QCLs) based on resonant phonon scheme, and that APL paper[1] was my natural choice for the centennial book. We decided to celebrate the APL 60th birthday, in print, by inviting our editors to reflect on their experience as editors and APL authors. 82, 1015 (2003).10.1063/1.1554479 2 B. S. Williams, S. Kumar, H. Callebaut, Q. Hu, and J. L. Reno, " Terahertz quantum cascade laser at 100 m using metal waveguide for mode confinement", Appl. Phys. Deputy Editor, David Long Price APL's 60th Anniversary gives me the occasion to reflect on its 50th Anniversary, when I also had the privilege to be a member of APL's editorial team and to realize what a difference 10 years makes. [Extracted from the article]

We present a simple x-ray phase imaging method that utilizes the sample-induced distortion of a high contrast random intensity pattern to quantitatively retrieve the two-dimensional phase map at the exit surface of a coherently illuminated sample. This reference pattern is created by placing a sheet of sandpaper in the x-ray beam, with the sample-induced distortion observed after propagation to the detector, a meter downstream. Correlation analysis comparing a single 'sample and sandpaper' image to a reference 'sandpaper only' image produces two sensitive differential phase contrast images, giving the sample phase gradient in vertical and horizontal directions. These images are then integrated to recover the projected phase depth of the sample. The simple experimental set-up, retention of flux, and the need for only a single sample image per reconstruction suggest that this method is of value in imaging a range of dynamic processes at both synchrotron and laboratory x-ray sources. [ABSTRACT FROM AUTHOR]

Oxide-based thin-film transistors (TFTs) with in-plane gate structure are self-assembled on paper substrates at room temperature by using only one nickel shadow mask. Indium-tin-oxide (ITO) channel and ITO electrodes (gate, source, and drain) can be deposited simultaneously without precise photolithography and alignment process. The equivalent field-effect mobility, subthreshold swing, and on/off ratio of such paper TFTs are estimated to be 22.4 cm2/V s, 192 mV/decade, and 8×105, respectively. A model based on two capacitors in series is proposed to further understand the operation mechanism. [ABSTRACT FROM AUTHOR]

Organic materials have attracted considerable attention for thermoelectric (TE) applications. Given their potential as wearable power generators, there is an urgent need to develop organic TE materials that possess superior electronic properties as well as excellent mechanical and environmental stability. Here, we develop paper-based TE materials using the poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS), graphene nanoplatelets (GNPs), and a starch-based biopolymer as a binder for GNPs. The device fabrication consists of spraying the biopolymer/GNP ink onto the cellulose paper followed by spraying the PEDOT:PSS solution. Further enhancement of TE properties was obtained by adding an ionic liquid (IL), bis(trifluoromethane)sulfonimide lithium salt to the PEDOT:PSS solution. Upon addition of the IL, the electrical conductivity of as-fabricated PEDOT:PSS films increased nearly two orders of magnitude. The electrical conductivity increases with GNPs' content due to formation of an effective electrical percolation network. Interestingly, incorporating GNPs simultaneously improves the Seebeck coefficient. Raman measurements suggest that the concurrent enhancement of the Seebeck coefficient and electrical conductivity might be related to the chemical bonding between the conducting polymer chains and the filler. In addition, these composites display remarkable flexibility at various bending angles and environmental stability without losing their original conductivity after three months of exposure to ambient conditions. [ABSTRACT FROM AUTHOR]

Field emission studies of bucky paper of multiwalled carbon nanotubes (MWNTs), prepared after microwave (MW) assisted acid functionalization are reported along with a comparison with that of “as-grown” sample. MW treated bucky papers reveal an interesting linear field emission behavior in Fowler–Nordheim plot. The field emission currents at preset value are found to be remarkably stable over a period of more than 3 h sustaining current densities of 4.9 mA/cm2 and 8.5 mA/cm2 for “as-grown” and functionalized sample, respectively. The enhancement in the field emission due to functionalization has been discussed in terms of tip opening and defect induced charge transport caused by intershell and intertubular interaction. [ABSTRACT FROM AUTHOR]

The authors report extremely low electron field emission thresholds from acid oxidized multiwall carbon nanotubes deposited on paper substrates by dip coating in an aqueous nanotube ink. Using paper substrates of differing surface roughness, field emission threshold fields ranging from 0.8 to 11.6 V/μm were observed, varying in an approximate inverse linear log relationship with the surface roughness of the underlying paper substrate. This study shows how field emission from supported nanotube films can be tailored via the morphology of the scaffold substrate, and how these composite electrodes can be straightforwardly fabricated on cheap, flexible substrates. [ABSTRACT FROM AUTHOR]

We have fabricated organic thin-film transistors and ring oscillators on paper and on flexible polyetherether ketone film using small-molecule hydrocarbon pentacene as the semiconductor and solution-processed polyvinylphenol as the gate dielectric. Transistors on paper have a carrier mobility of 0.2 cm2/V s and an on/off current ratio of 106, similar to devices on polyetherether ketone. A signal propagation delay of 22 μs per stage was measured for pentacene ring oscillators on polyetherether ketone film, and a signal delay of 12 ms was obtained for ring oscillators on paper. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Lateral orientation and aggregation of the graphene sheets limited field enhancement of graphene paper (GP). To improve the field enhancement of GP, argon plasma treatment was induced to destroy the aggregation and cause formation of surface protrusions. After Ar plasma treatment, turn-on field and threshold field of GP were reduced from 2.3 V/μm to 1.6 V/μm and 4.4 V/μm to 3.0 V/μm, respectively. The enhancement was attributed to the protrusions. Scanning electron microscopy and hydrophobicity had been used to prove the morphology change after plasma treatment. [ABSTRACT FROM AUTHOR]

Battery drivable low-voltage SnO2-based paper thin-film transistors with a near-zero threshold voltage (Vth=0.06 V) gated by microporous SiO2 dielectric with electric-double-layer (EDL) effect are fabricated at room temperature. The operating voltage is found to be as low as 1.5 V due to the huge gate specific capacitance (1.34 μF/cm2 at 40 Hz) related to EDL formation. The subthreshold gate voltage swing and current on/off ratio is found to be 82 mV/decade and 2.0×105, respectively. The electron field-effect mobility is estimated to be 47.3 cm2/V s based on the measured gate specific capacitance at 40 Hz. [ABSTRACT FROM AUTHOR]

We report the architecture and the performances of a memory based on a single field-effect transistor built on paper able to write-erase and read. The device is composed of natural multilayer cellulose fibers that simultaneously act as structural support and gate dielectric; active and passive multicomponent amorphous oxides that work as the channel and gate electrode layers, respectively, complemented by the use of patterned metal layers as source/drain electrodes. The devices exhibit a large counterclockwise hysteresis associated with the memory effect, with a turn-on voltage shift between 1 and -14.5 V, on/off ratio and saturation mobilities of about 104 and 40 cm2 V-1 s-1, respectively, and estimated charge retention times above 14 000 h. [ABSTRACT FROM AUTHOR]

The cellulose-liquid biphasic dielectric composite serves as the irreplaceable main electrical insulating structure in the power industry, owing to its peculiar high dielectric breakdown strength compared to that of monophasic cellulose paper or insulating liquid. Although this advanced electrical characteristic is utilized worldwide, its physical–chemical nature remains unclear, which greatly restricts the design and improvement of next generation electrical insulating composites. Herein, the interfacial charge behaviors in cellulose-liquid composites are investigated, and the results indicate that the majority of charge carriers in insulating liquid are electrostatically adsorbed at the nano-scale interface, forming interfacial charge traps, leading to 17.66 times increased deep trap density, which suppress further charge migration under high voltages, and consequently lead to the ∼400% improved dielectric breakdown strength compared to that of cellulose paper and insulating liquid. By controlling the interfacial trap characteristics with insulating liquids of strong electron withdrawing ability, the resistivity and breakdown strength of cellulose-liquid composites are further improved. [ABSTRACT FROM AUTHOR]

The realization of multi-level storage of chalcogenide phase change materials (C-PCMs) has been proved to be an effective way to achieve high-density data storage. However, Ge2Sb2Te5 (GST), as one of the most representative C-PCMs, has poor performance in multi-level storage. In this paper, a bi-layer composite structure GST–nAg was proposed and prepared by magnetron sputtering accompanied by thermal annealing. Microstructure and multi-level optical properties of GST–nAg were investigated using x-ray diffraction, scanning electron microscopy, variable angle spectroscopic ellipsometry, Raman spectrometer, micro-area reflectivity testing system, etc. The results showed that the formation of the Ag nanoparticles layer changed the heat distribution and heat transmission in the GST layer when irradiated by a nanosecond pulsed laser. By changing the laser fluence, the microstructure of the GST layer could be adjusted and ten crystal states with different optical reflectivity were obtained. In addition, the introduction of Ag nanoparticles reduced the compressive stress among the Ge/Sb–Te tetrahedral structure and grain size, which benefits to the formation and stable existence of more crystal states. Finally, an optical irradiation device based on GST–nAg was built and the storage density of this optical irradiation device was increased about three times. This paper provides a way to realize multi-level optical storage. [ABSTRACT FROM AUTHOR]

Electro-osmosis is the preferred transport mechanism in microfluidic systems. The electro-osmotic mobility in an aqueous solution is essentially independent of the microchannel size. However, in low-permittivity solvents, the screening effect is absent and the mobility is found to grow with the capillary radius according to our analytical theory and electro-osmotic flow experiments. Our results show that regardless of low surface charge density, electro-osmosis always occurs for long enough microchannels. Therefore, electro-osmosis provides a method for determining extremely low surface charge density associated with low-permittivity media. The implication in the response time of electronic paper is given as well. [ABSTRACT FROM AUTHOR]

Electrofluidic display pixels are demonstrated with zero-power grayscale operation for 3 months and with >70% reflectance. The color of the pixel is changed as electrowetting moves the pigment dispersion between a top and bottom channel. When voltage is removed, a near zero Laplace pressure and a hysteresis pressure of 0.11 kN/m2 stabilizes the position. For 450 μm pixels, an electromechanical pressure of 1.4 kN/m2 moves the pigment dispersion at a speed of ∼2650 μm/s. The predicted switching speed for ∼150 μm pixels is consistent with video rate operation (20 ms). The geometrically sophisticated pixel structure is fabricated with only simple photolithography and wet chemical processing. [ABSTRACT FROM AUTHOR]

Here we report a highly sensitive single-axis membrane-type paper accelerometer. The accelerometer is consisted of a suspended parallel-plate sensing capacitor prepared by cost-effective nano ink printing technologies on a flexible paper substrate. The proof mass and suspension bridge structures of the accelerometer are designed based on the simulation results for the optimization of sensitivity. Vertical acceleration sensitivity of the optimized design with long ellipse-shaped bridges and round-shaped proof mass can reach 20 fF/g at z-axis acceleration of 1-10 g. [ABSTRACT FROM AUTHOR]

We also welcome our new Advisory Board member Professor Susan Coppersmith from the University of New South Wales, an expert in silicon and silicon/germanium quantum dot technology. Sartison, S. Seyfferle, S. Kolatscheket al., " Single-photon light-emitting diodes based on preselected quantum dots using a deterministic lithography technique", Appl. Phys. 11 S. A. Studenikin, L. Gaudreau, K. Kataokaet al., " Enhancement-mode two-channel triple quantum dot from an undoped Si/Si0.8Ge0.2 quantum well hetero-structure", Appl. Phys. 14 X. Mi, J. V. Cady, D. M. Zajac, J. Stehliket al., " Circuit quantum electrodynamics architecture for gate-defined quantum dots in silicon", Appl. Phys. [Extracted from the article]

The lifetime of deep-ultraviolet light-emitting diodes (LEDs) is still limited by a number of factors, which are mainly related to semiconductor defects, and still need to be clarified. This paper improves the understanding of UV LED degradation, by presenting an analysis based on combined deep-level transient spectroscopy (C-DLTS), electro-optical characterization, and simulations, carried out before and during a constant current stress test. The original results of this paper are (i) C-DLTS measurements allowed us to identify three traps, two associated with Mg-related defects, also detected in the unaged device, and one related to point defects that were generated by the ageing procedure. (ii) Based on these results and on TCAD simulations, we explain the variation in the forward I–V by the degradation of the p-contact, due to Mg passivation. (iii) On the other hand, optical degradation is ascribed to an increase in defectiveness of the active region and surrounding areas, which led to a decrease in injection efficiency, to an increase in non-radiative recombination, and to an increase in trap-assisted tunneling processes. [ABSTRACT FROM AUTHOR]