Showing papers on "Flexible electronics published in 2011"

Inkjet printing of single-crystal films

Abstract: Printing electronic devices using semiconducting 'ink' is seen as a promising route to cheap, large-area and flexible electronics, but the performance of such devices suffers from the relatively poor crystallinity of the printed material. Hiromi Minemawari and colleagues have developed an inkjet-based printing technique involving controlled mixing on a surface of two solutions — the semiconductor (C8-BTBT) in its solvent and a liquid in which the semiconductor is insoluble. The products of this antisolvent crystallization technique are thin semiconductor films with exceptionally high and uniform crystallinity. The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science1. Whether based on inorganic2,3,4,5 or organic6,7,8 materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has recently been focused on developing simple ways of producing electronic devices by means of printing technologies. ‘Printed electronics’ is being explored for the manufacture of large-area and flexible electronic devices by the patterned application of functional inks containing soluble or dispersed semiconducting materials9,10,11. However, because of the strong self-organizing tendency of the deposited materials12,13, the production of semiconducting thin films of high crystallinity (indispensable for realizing high carrier mobility) may be incompatible with conventional printing processes. Here we develop a method that combines the technique of antisolvent crystallization14 with inkjet printing to produce organic semiconducting thin films of high crystallinity. Specifically, we show that mixing fine droplets of an antisolvent and a solution of an active semiconducting component within a confined area on an amorphous substrate can trigger the controlled formation of exceptionally uniform single-crystal or polycrystalline thin films that grow at the liquid–air interfaces. Using this approach, we have printed single crystals of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) (ref. 15), yielding thin-film transistors with average carrier mobilities as high as 16.4 cm2 V−1 s−1. This printing technique constitutes a major step towards the use of high-performance single-crystal semiconductor devices for large-area and flexible electronics applications.

Pen‐on‐Paper Flexible Electronics

Abstract: Figure 1 . a) Optical image of a rollerball pen loaded with a conductive silver ink. The background shows conductive text written on Xerox paper. b and c) SEM images of the side and top views of the rollerball pen. d) Optical image of the rollerball pen tip, captured during writing a conductive silver track on a Xerox paper. Printed electronics constitute an emerging class of materials with potential application in photovoltaics, [ 1 ] transistors, [ 2 , 3 ] displays, [ 4–6 ] batteries, [ 7 ] antennas, [ 8 ] and sensors. [ 9 , 10 ] Recent attention has focused on paper substrates as a low-cost, enabling platform for fl exible, lightweight, and disposable devices. [ 11–13 ]

Flexible energy storage devices based on graphene paper

Abstract: Recently, great interest has been aroused in flexible/bendable electronic equipment such as rollup displays and wearable devices. As flexible energy conversion and energy storage units with high energy and power density represent indispensable components of flexible electronics, they should be carefully considered. However, it is a great challenge to fabricate flexible/bendable power sources. This is mainly due to the lack of reliable materials that combine both electronically superior conductivity and mechanical flexibility, which also possess high stability in electrochemical environments. In this work, we report a new approach to flexible energy devices. We suggest the use of a flexible electrode based on free-standing graphene paper, to be applied in lithium rechargeable batteries. This is the first report in which graphene paper is adopted as a key element applied in a flexible lithium rechargeable battery. Moreover graphene paper is a functional material, which does not only act as a conducting agent, but also as a current collector. The unique combination of its outstanding properties such as high mechanical strength, large surface area, and superior electrical conductivity make graphene paper, a promising base material for flexible energy storage devices. In essence, we discover that the graphene based flexible electrode exhibits significantly improved performances in electrochemical properties, such as in energy density and power density. Moreover graphene paper has better life cycle compared to non-flexible conventional electrode architecture. Accordingly, we believe that our findings will contribute to the full realization of flexible lithium rechargeable batteries used in bendable electronic equipments.

Intrinsically Stretchable Polymer Light‐Emitting Devices Using Carbon Nanotube‐Polymer Composite Electrodes

Abstract: IO N Stretchable electronics are evolving from a conceptual curiosity into an important branch of modern electronics. Such devices can be potentially useful for a wide range of applications including wearable electronics, “smart skins”, and minimally invasive biomedical devices. [ 1–10 ] Conventional inorganic electronic devices are brittle and certain fl exibility may be obtained by using ultrathin layers of the inorganic materials. Buckled device confi gurations have been reported to introduce stretchability in integrated devices consisting of rigid functional components, however they lack intrinsic stretchability. [ 3 , 7 ] Here we report the fabrication of polymer light-emitting devices using single-walled carbon nanotube (SWNT)-polymer composite electrodes as both the electronand hole-injection electrodes. The devices are metal-free and can be linearly stretched up to 45% strain. This represents a proof-of-concept, highly stretchable semiconductor device wherein every part of the device is intrinsically stretchable. Stretchable devices reported so far generally employ a soft rubbery polymer to embed or bond active electronic components that are rigid. [ 1–3 ] Buckled interconnects can be made using prestrained poly(dimethylsiloxane) (PDMS) with evaporated metallic fi lms. [ 11 ] Rogers et al. also reported buckled active devices using prestrained PDMS; [ 12 , 13 ] the buckled interconnects or devices can be elongated until the vertical displacement has all been converted into planar strain, and after that the rigid components prevent further elongation. Someya et al. reported an elastic conductor formed by coating PDMS substrates with a composite consisting of carbon nanotubes, an ionic liquid salt, and a fl uorinated copolymer. [ 14–16 ] These elastic conductors have been used to wire various rigid active devices including organic light-emitting diodes (OLEDs) and sensors. [ 15 , 16 ] The interconnected devices can be made stretchable wherein the deformation occurs essentially at the elastic interconnects. The recent advancement in polymer electronics opens up new opportunities to achieve intrinsically stretchable devices. Compared with their inorganic counterparts, conjugated polymers are much more compliant. When fabricated on fl exible substrates such as polyethylene terephthlate (PET) or metal foils, highly bendable polymer devices have been demonstrated with fl exed radii as small as several millimeters. [ 17–19 ] Nonetheless,

Substrates for flexible electronics: A practical investigation on the electrical, film flexibility, optical, temperature, and solvent resistance properties

Abstract: Designing and developing flexible electronics requires a thorough investigation of the substrates available for the fabrication of devices. Here, we present a practical study on a variety of significant substrates: polyethylene terephthalate (PET), its heat-stabilized (HS) derivative, HS-PET, and polyethylene naphthalate (PEN) plastic insulating films; indium tin oxide (ITO)-coated ITO/PEN and ITO/PET transparent conducting films; rigid ITO/glass and FTO/glass substrates; stainless steel and titanium foils. We put the substrates through a range of tests these actually undergo during device fabrication to determine their optical, mechanical flexibility (under different types of tensile and compressive stress bending with and without a PEDOT:PSS conducting polymer layer), solvent resistance, stability to temperature treatment (conductivity and deformation), and to UV irradiation. We highlight issues and propose solutions to improve substrate response. The results and thresholds extracted reveal limitations and windows of opportunity useful for the designer of flexible optoelectronics in determining manufacturing processes and the final applications under everyday operation.

Silver Nanowire‐Polymer Composite Electrodes for Efficient Polymer Solar Cells

Abstract: IO N Polymer solar cells are under intensive investigation for renewable energy due to the perceived advantages of large area fabrication at low cost. [ 1 , 2 ] The performance of polymer solar cells has been advanced progressively over the past few years with the current state-of-the-art power conversion effi ciency (PCE) approaching that of amorphous silicon. [ 3–7 ] Further progress in PCE is expected as new materials are continuously being innovated and improved processes and device architectures are introduced. [ 8–12 ] Meanwhile, a great amount of effort has been exerted to realize the perceived low fabrication cost. [ 13 ]

High-Performance Integrated ZnO Nanowire UV Sensors on Rigid and Flexible Substrates

Abstract: Due to the large surface area-to-volume ratio and high quality crystal structure, single nanowire (NW)-based UV sensors exhibit very high on/off ratios between photoresponse current and dark current. Practical applications require a large-scale and low-cost integration, compatibility to flexible electronics, as well as reasonably high photoresponse current that can be detected without high-precision measurement systems. In this paper, NW-based UV sensors were fabricated in large-scale by integrating multiple NWs connected in parallel via the contact printing method. Linear scaling of the photoresponse current with the number of NWs is demonstrated. Integrated ZnO NW UV sensors were fabricated on rigid glass and flexible polyester (PET) substrates at the macroscopic scale. The flexible and rigid sensors performed comparably, exhibiting on/off current ratios approximately three orders of magnitude higher than sensors made from polycrystalline ZnO thin films. Under UV irradiance of 4.5 mW cm−2 and 3 V bias, photoresponse currents and on/off current ratios for the rigid and flexible UV sensors reached 12.22 mA and 82 000, and 14.1 mA and 120 000, respectively. This result suggests that lateral integration of semiconductor NWs is an effective approach to large-scale fabrication of flexible NW sensors that inherit the merits of single-NW-based systems with unaffected performance compared to using rigid substrate.

Organic electrochemical transistors integrated in flexible microfluidic systems and used for label-free DNA sensing.

Abstract: enzyme sensors, [ 9 ] DNA sensors, [ 10 ] dopamine sensor, [ 11 ] and cell-based biosensors. [ 12 ] A transistor-based sensor is the combination of a sensor and an amplifi er since a small potential change at an interface can induce a substantial variation of the channel current. [ 16–18 ] Therefore such devices are highly sensitive and potentially low cost. More importantly, OECT can be easily miniaturized and fabricated on fl exible substrates, which is essential for some applications in living systems. OECTs have been integrated in microfl uidic channels and used as ion sensors and enzyme sensors. [ 5 , 6 , 9 ] As for fl exible devices, OECTs were fabricated on fi bers and showed excellent transistor performance. [ 19 , 20 ] However, the application of the fi ber-supported devices in biosensors is limited by solid electrolytes used in the devices. Therefore, we study the OECT integrated in a fl exible microfl uidic system and explore its applications in biosensors, such as DNA sensors. Nucleic acid diagnostics has attracted much interest due to its great scientifi c and economic importance, and it has signifi cant applications in gene expression monitoring, viral and bacterial identifi cation, biowarfare and bioterrorism agents detecting, and clinical medicine. [ 21 ] Besides the traditional technique that is based on the confocal fl uorescence microscope, several different label-free technologies have been developed for the analysis of DNA microarrays, including atomic force microscopy, [ 22 ] electrochemical detection, [ 23 ] surface vibration spectroscopy, [ 24 ] scanning Kelvin probe microscopy (SKPM), [ 25 ]

Flexible memristive memory array on plastic substrates.

Abstract: The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has recently increased due to their advantages over present rigid electronic systems. Flexible memory is an essential part of electronic systems for data processing, storage, and communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. This paper describes the development of NOR type flexible resistive random access memory (RRAM) with a one transistor–one memristor structure (1T-1M). By integration of a high-performance single crystal silicon transistor with a titanium oxide based memristor, random access to memory cells on flexible substrates was achieved without any electrical interference from adjacent cells. The work presented here can provide a new appr...

Highly flexible printed alkaline batteries based on mesh embedded electrodes

Abstract: A flexible battery and a method to form the flexible battery include forming an anode by embedding an anode type electro-active material within a mesh material and associating an anode current collector with the anode. Similarly a cathode is formed by embedding a cathode type electro-active material within a mesh material and a cathode current collector is associated with the cathode. An electrolyte is located between the anode and cathode, and the arrangement is sealed.

Complementary Metal Oxide Semiconductor Technology With and On Paper

Abstract: One of today’s challenges in electronics is to produce portable, fl exible, low cost, and easily recyclable products, [ 1 ] such as paper [ 2 ] since they do not require the high process temperatures used in crystalline silicon (c-Si) technologies. In addition, the devices should have low power energy consumption to allow densely packed integrated circuits for a plethora of applications such as computer memory chips, digital logic and microprocessors, to (linear) analogue circuits, among others, to fuel the next-generation microelectronics revolution for information and communication technologies. [ 3 ] For illustrative purposes, we consider a temporary register as an example. In a static circuit the contents of the register remain fi xed until new information arrives to be stored and remains active unless the power goes out or the computer is turned off. In a dynamic circuit, the contents of the register leak away and must be periodically refreshed. The advantage of dynamic circuits is that they do not draw current between refreshing; the disadvantage is that refreshing requires additional circuitry including clocks to synchronize the refresh cycle with the operation of the register. [ 3 , 4 ]

Transparent lithium-ion batteries

Abstract: Transparent devices have recently attracted substantial attention. Various applications have been demonstrated, including displays, touch screens, and solar cells; however, transparent batteries, a key component in fully integrated transparent devices, have not yet been reported. As battery electrode materials are not transparent and have to be thick enough to store energy, the traditional approach of using thin films for transparent devices is not suitable. Here we demonstrate a grid-structured electrode to solve this dilemma, which is fabricated by a microfluidics-assisted method. The feature dimension in the electrode is below the resolution limit of human eyes, and, thus, the electrode appears transparent. Moreover, by aligning multiple electrodes together, the amount of energy stored increases readily without sacrificing the transparency. This results in a battery with energy density of 10 Wh/L at a transparency of 60%. The device is also flexible, further broadening their potential applications. The transparent device configuration also allows in situ Raman study of fundamental electrochemical reactions in batteries.

Pseudo-CMOS: A Design Style for Low-Cost and Robust Flexible Electronics

Abstract: Thin-film transistors (TFTs) are a key element of flexible electronics implemented on low-cost substrates. Most TFT technologies, however, have only monotype-either n- or p-type-devices. In this paper, we propose a novel design style Pseudo-CMOS for flexible electronics that uses only monotype single-VT TFTs but has comparable performance with the complementary-type or dual-VT designs. The manufacturing cost and complexity can therefore be significantly reduced, whereas the circuit yield and reliability are enhanced with built-in postfabrication tunability. Digital cells are fabricated in two different TFT technologies, i.e., p-type self-assembled-monolayer-organic TFTs and n-type metal-oxide InGaZnO TFTs, to validate the proposed Pseudo-CMOS design style. To the best of our knowledge, this is the first design solution that has been experimentally proven to achieve superior performance for both types of TFT technologies.

Organic electronics on banknotes.

Abstract: Organic transistors and circuits are fabricated directly on the surface of banknotes. The transistors operate with voltages of 3 V and have a field-effect mobility of about 0.2 cm2 V−1s−1. For an array of 100 transistors a yield of 92% is obtained.

Air/Liquid‐Pressure and Heartbeat‐Driven Flexible Fiber Nanogenerators as a Micro/Nano‐Power Source or Diagnostic Sensor

Abstract: We present a new approach for fabricating flexible fiber nanogenerators (FNGs) that can be used for smart shirts, flexible electronics, and medical applications. These FNGs are based on carbon fibers that are covered cylindrically by textured zinc oxide (ZnO) thin films. Once subjected to uni-compression by applying a pressure, the cylindrical ZnO thin film is under a compressive strain, resulting in a macroscopic piezopotential across its inner and exterior surfaces owing to the textured structure of the film, which is the driving force for generating an electric current in the external load. Using such a structure, an output peak voltage of 3.2 V and average current density of 0.15 μA cm(-2) are demonstrated. The FNGs rely on air pressure, so that it can work in a non-contact mode in cases of rotating tires, flowing air/liquid, and even in blood vessels. Pressure-driven FNGs added to a syringe show potential to harvest energy in blood vessels, gas pipes, and oil pipes, as long as there is a fluctuation in pressure (or turbulence). Heart-pulse driven FNGs can serve as ultrasensitive sensors for monitoring the behavior of the human heart, which may possibly be applied to medical diagnostics as sensors and measurement tools.

Towards All‐Soft Matter Circuits: Prototypes of Quasi‐Liquid Devices with Memristor Characteristics

Abstract: IO N We present a new class of electrically functional devices composed entirely of soft, liquid-based materials that display memristor-like characteristics. A memristor, or a “memory resistor”, is an electronic device that changes its resistive state depending on the current or voltage history through the device. Memristors may become the core of next generation memory devices because of their low energy consumption and high data density and performance. [ 1–3 ] Since the concept of memristors was theorized in 1971, [ 4 ] resistive switching memories have been fabricated from a variety of materials operating on magnetic, [ 5 ] thermal, [ 6 ] photonic, [ 7 ] electronic and ionic mechanisms. [ 3 , 8 , 9 ] Conventional memristive devices typically include metalinsulator-metal (M-I-M) junctions composed of rigid stacks of fi lms fabricated by multiple vacuum-deposition steps, often at high temperature. The most common “insulator” materials in M-I-M memristor junctions are inorganic metal oxides such as TiO 2 [ 10 ] and NiO. [ 11 ] Conducting pathways can form by current through such layers. Solid electrolytes between metal electrodes can also be used to create resistance switches (e.g., Ag/ Ag 2 S/Pt), in which conductive metal fi laments that bridge the two electrodes can be formed or annihilated on demand. [ 3 , 9 ] Memristive circuits composed of organic materials have some advantages over conventional metal oxides due to their ease of processing, light weight, and low cost. A variety of organic materials such as homogeneous polymers, small-molecule or nanoparticle doped polymers, and organic donor-acceptor complexes have been evaluated as components in memory switching devices. [ 12 ] We report new controllably bi-stable memristor-like devices fabricated entirely from liquid-based materials. These soft and fl exible devices are built from liquid metal and hydrogels that are used routinely in laboratories for hosting biological molecules and supporting cell growth. Hydrogels are soft, moldable and bio-compatible media similar to biological systems with high ion mobility due to the high water content ( > 90% water). [ 13 , 14 ] The ionic properties of the gels can be tuned by inclusion of polyelectrolytes that are immobilized via entanglement within the gel network. Hydrogels doped with polyelectrolytes have been utilized for fabricating electronic devices such as diodes and photovoltaic cells. [ 13 , 15 , 16 ] The electrodes of these devices, however, are rigid metals such as platinum and

Highly Transparent, Flexible, and Thermally Stable Superhydrophobic ORMOSIL Aerogel Thin Films

Abstract: We report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or post-treatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers.

Fully printed separated carbon nanotube thin film transistor circuits and its application in organic light emitting diode control.

Abstract: The advantages of printed electronics and semi- conducting single-walled carbon nanotubes (SWCNTs) are combined for the first time for display electronics. Conductive silver ink and 98% semiconductive SWCNT solutions are used to print back-gated thin film transistors with high mobility, high on/off ratio, and high current carrying capacity. In addition, with printed polyethylenimine with LiClO4 as the gating material, fully printed top-gated devices have been made to work as excellent current switches for organic light emitting diodes (OLEDs). An OLED driving circuit composed of two top-gated fully printed transistors has been fabricated, and the successful control over external OLED is demonstrated. Our work demonstrates the significant potential of using printed carbon nanotube electronics for display backplane applications.

Thiocyanate-Capped PbS Nanocubes: Ambipolar Transport Enables Quantum Dot Based Circuits on a Flexible Substrate

Abstract: We report the use of thiocyanate as a ligand for lead sulfide (PbS) nanocubes for high-performance, thin-film electronics. PbS nanocubes, self-assembled into thin films and capped with the thiocyanate, exhibit ambipolar characteristics in field-effect transistors. The nearly balanced, high mobilities for electrons and holes enable the fabrication of CMOS-like inverters with promising gains of ∼22 from a single semiconductor material. The mild chemical treatment and low-temperature processing conditions are compatible with plastic substrates, allowing the realization of flexible, nonsintered quantum dot circuits.

Transparent flexible organic transistors based on monolayer graphene electrodes on plastic.

Abstract: There has been much interest in graphene-based electronic devices because graphene provides excellent electrical, optical, and mechanical properties. [ 1 ] In this sense, organic electronic devices using graphene electrodes have attracted considerable attention, and several reports have described the use of graphene source/drain electrodes in organic fi eld-effect transistors (OFETs). [ 2 ] One of the ultimate goals in the fabrication of OFETs using graphene electrodes lies in the fabrication of fl exible and transparent organic transistors, assembled on plastics substrates, that maintain their high performance under ambient conditions. However, no reports have described the fabrication of organic transistors assembled on plastic substrates because the synthesis of either graphene or reduced graphene oxide requires high-temperature fabrication processes. Another important goal in the context of fabricating organic electronic devices with graphene electrodes lies in the fabrication of highly transparent graphene electrodes that cover large areas. Graphene transmittance decreases linearly as the number of layers increases in n-layer graphene. [ 3 ] Thus, the use of monolayer graphene is necessary to achieve high transparency in graphene electrodes, provided that the conductivity of the graphene is suffi cient for device electrode applications. Another merit of monolayer graphene is its extremely low thickness (3–4 Å). Source/drain electrodes in staggered bottomcontact FET structures should be thin to ensure step coverage of the active layer during sequential transistor fabrication. [ 4 ] For this reason, one-atom-thick monolayer graphene provides ideal source/drain electrodes for effi cient charge injection. Recently, several groups succeeded in fabricating high-quality/largearea graphene with preferential monolayer thickness using a

Bending Fatigue Study of Sputtered ITO on Flexible Substrate

Abstract: Recently, there has been a tremendous rise in production of portable electronic devices. To produce flexible devices, flexible substrates should replace conventional glass substrates. Indium-tin-oxide (ITO) is the preferred transparent conducting layer used in the display technology. Although ITO has excellent sheet resistance and very good optical properties, ITO can crack at very low tensile strains which might cause failure in the conductive layer because of the unusual structure of a very thin film of brittle ceramic material applied to a polymer substrate. Therefore, the mechanics of ITO on flexible substrates has been thoroughly considered in the design and manufacturing of flexible devices. In a typical roll-to-roll manufacturing process, many challenges exist during the travel of the coated web over the rollers which produce bending stresses that might cause failure even if the stresses are below the yield strength of the material. Therefore, the high cycle bending fatigue of ITO thin films on flexible substrates is of a significant importance. In this work, high cycle bending fatigue experiments were conducted on ITO coated PET substrate. The effect of bending diameter, bending frequency, and sample width on the change in electrical resistance was investigated. High magnification images were obtained to observe crack initiation and propagating in the ITO layer. The goal of this work is to establish a baseline for a comprehensive reliability study of ITO thin films on flexible substrate. It was found that bending diameters as well as the number of bending cycles have a great influence on the electrical conductivity of the ITO layer.

Transparent Flexible Circuits Based on Amorphous-Indium–Gallium–Zinc–Oxide Thin-Film Transistors

Abstract: Circuits implemented with high-performance amorphous-indium-gallium-zinc-oxide thin-film transistors (TFTs) are realized on polyimide/polyethylene-terephthalate plastic substrates. The TFTs on plastic exhibit a saturation mobility of 19 cm2/V·s and a gate voltage swing of ~0.14 V/dec. For an input of 20 V, an 11-stage ring oscillator operates at 94.8 kHz with a propagation delay time of 0.48 μs. A shift register, consisting of ten TFTs and one capacitor, operates well with good bias stability. AC driving of pull-down TFTs gives the gate driver an improved lifetime of over ten years.

Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics

Abstract: In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO3 mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 × 10 −8 –8.76 × 10 −8 � m after thermal treatment at 160 ◦ C for 30 min, which was about five times that of bulk silver (1.586 × 10 −8 � m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices. S Online supplementary data available from stacks.iop.org/Nano/22/425601/mmedia (Some figures in this article are in colour only in the electronic version)

All-Inkjet-Printed Organic Thin-Film Transistor Inverter on Flexible Plastic Substrate

Abstract: We report an all-inkjet-printed inverter using two p-type organic thin-film transistors (OTFTs) on a flexible plastic substrate. Metal-organic precursor-type silver ink, poly-4-vinylphenol solution, and 6,13-bis (triisopropylsilylethynyl)-pentacene solution were used to print gate and source/drain electrodes, gate-dielectric layer, and active semiconductor layer, respectively. By optimizing fabrication conditions, we obtained OTFTs with a mobility of 0.02 cm2/V·s, an on/off ratio of 104, and a threshold voltage of -1.2 V, and inverters with good switching performance showing a gain of 7.8 at a supply voltage of VDD = -40 V .

Prospects for Nanowire-Doped Polycrystalline Graphene Films for Ultratransparent, Highly Conductive Electrodes

Abstract: Traditional transparent conducting materials such as ITO are expensive, brittle, and inflexible. Although alternatives like networks of carbon nanotubes, polycrystalline graphene, and metallic nanowires have been pro- posed, the transparency-conductivity trade-off of these materials makes them inappropriate for broad range of applications. In this paper, we show that the conductivity of polycrystalline graphene is limited by high resistance grain boundaries. We demonstrate that a composite based on polycrystalline graphene and as ubpercolating network of metallic nanowires offers as imple and effective route to reduced resistance while maintaining high transmittance. This new approach of "percolation-doping by nanowires" has the potential to beat the transparency- conductivity constraints of existing materials and may be suitable for broad applications in photovoltaics, flexible electronics, and displays.

One selector-one resistor (1S1R) crossbar array for high-density flexible memory applications

Abstract: Lack of a suitable selection device to suppress sneak current has impeded the development of 4F2 crossbar memory array utilizing stable and scalable bipolar resistive-switching. We report a high-performance nonlinear bipolar selector realized by a simple Ni/TiO 2 /Ni MIM structure with a high current density of 105 A/cm2, and a Ni/TiO 2 /Ni/HfO 2 /Pt vertically stacked 1S1R cell capable of gigabit memory implementation. Furthermore, the demonstration of 1S1R array fabricated completely at room temperature on a plastic substrate highlights the promise of future extremely low-cost flexible nonvolatile memory.

Ultra-transparent, flexible single-walled carbon nanotube non-volatile memory device with an oxygen-decorated graphene electrode.

Abstract: The next-generation electronic systems are expected to be light and portable for applications in wearable computers, fl exible displays, fl exible integrated circuit (IC)cards, fl exible potable solar cells, and artifi cial bodies. Flexibility and transparency are the key ingredients for these next generation electronic systems. Several studies have been executed to realize transparency and fl exibility using carbon nanotubes, [ 1–8 ] inorganics, [ 9–11 ] and organics [ 12–16 ] in transistors and memory devices. Most studies have focused on the transistor, in which fl exibility, stretchability, and transparency have been realized to some degree. [ 1–14 ]

Development of a Flexible SU-8/PDMS-Based Antenna

Abstract: In this letter, a flexible SU-8/PDMS-based antenna has been demonstrated, not only targeting the wearable computing, but also fitting well in the RF system-on-package (RF SOP) applications. The characteristics of the proposed antenna fabricated on a flexible polymer substrate (SU-8/PDMS) with different bending angles have been successfully measured and characterized for the first time. The measured results have shown fairly good agreement with the simulation results. The measured bandwidth and maximum gain are 3% from 6.2 to 6.4 GHz and 2.17 dBi, respectively, when the antenna is flat. Moreover, related antenna fabrication process provides a practical approach to realize the flexible antenna for the portable wireless electronics applications.

Fabrication of paper-based conductive patterns for flexible electronics by direct-writing

Abstract: A kind of conductive pen was designed, prepared with nano-silver colloid as the conductive ink and gel-ink pen as the writing implement, and used to draw conductive patterns on paper substrate by direct-writing for flexible electronics. Silver nanoink (20 wt%) was characterized using field emission transmission electron microscopy (FETEM), size distribution analyser (SDA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and selected-area electron diffraction (SAED). Paper-based conductive patterns were investigated by a surface profilometer, a 4-point probe, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. It can be found that silver nanoparticles have a small size, about 2.1 ± 0.5 nm in diameter with monodispersity, and the melting point sharply decreased to 105 °C. A conductive line drawn on weighing paper not only had good mechanical/electrical fatigue properties, but also low resistivity. Especially, when the sintering condition is 200 °C for 60 min, the resistivity can be down to 6.8 μΩ cm, 4.25 times the bulk resistivity. In addition, the reparation of conductive patterns and application in a practical circuit were also studied.