Printed Carbon Nanotube Research Articles

Printed Carbon Nanotubes on Polymer Films for Active Origami

We describe a facile fabrication of solid-state actuators by coating common polymer films with a layer of carbon nanotubes. The composite material actuators are multifunctional energy transducers and were powered by heat, light, or electricity. The maximum observed force produced by an actuator was 60 times its own weight. Actuators were also demonstrated to bend more than 90°. The actuators were repeatedly activated for nearly 50,000 cycles without significant loss of performance for a sub-hertz actuator and 1,000,000 cycles in the case of a 30 Hz actuator. The utility of these devices was demonstrated by creating a walking robot.

Inkjet printed carbon nanotube networks: the influence of drop spacing and drying on electrical properties

We have measured the electrical resistance of inkjet printed multiwall carbon nanotube networks and found that it depends strongly on the temperature of the substrate during the printing process, with both the resistance and its anisotropy decreasing as temperature increases. A parallel investigation of the surface morphology of the printed networks found long raised ridges running parallel to the printing direction, with the height of the ridges decreasing with increasing substrate temperature. Both these observations are shown to be associated with segregation of the nanotubes during drying (coffee staining) and that this segregation is suppressed at higher substrate temperatures, with the lowest resistance values and anisotropy found with a substrate temperature of 70 °C. Network conductance was found to increase with increasing layer thickness and similar results are obtained through a reduction in drop spacing or by printing multiple layers.

Fully Printed Separated Carbon Nanotube Thin Film Transistor Circuits and Its Application in Organic Light Emitting Diode Control

The advantages of printed electronics and semiconducting 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.

Influence of surface chemistry on inkjet printed carbon nanotube films

Carbon nanotube ink chemistry and the proper formulation are crucial for direct-write printing of nanotubes. Moreover, the correct surface chemistry of the self-assembled monolayers that assist the direct deposition of carbon nanotubes onto the substrate is equally important to preserve orientation of the printed carbon nanotubes. We report that the successful formulation of two single walled carbon nanotube (SWNT) inks yields a consistent, homogenous printing pattern possessing the requisite viscosities needed for flow through the microcapillary nozzles of the inkjet printer with fairly modest drying times. The addition of an aqueous sodium silicate allows for a reliable method for forming a uniform carbon nanotube network deposited directly onto unfunctionalized surfaces such as glass or quartz via inkjet deposition. Furthermore, this sodium silicate ingredient helps preserve applied orientation to the printed SWNT solution. Sheet resistivity of this carbon nanotube ink formula printed on quartz decreases as a function of passes and is independent of the substrate. SWNTs were successfully patterned on Au. This amine-based surface chemistry dramatically helps improve the isolation stabilization of the printed SWNTs as seen in the atomic force microscopy (AFM) image. Lastly, using our optimized SWNT ink formula and waveform parameters in the Fuji materials printer, we are able to directly write/print SWNTs into 2D patterns. Dried ink pattern expose and help orient roped carbon nanotubes that are suspended in ordered arrays across the cracks.

High sensitivity carbon nanotube based electrochemiluminescence sensor array

Ink jet printed carbon nanotube forest arrays capable of detecting picomolar concentrations of immunoglobulin G (IgG) using electrochemiluminescence (ECL) are described. Patterned arrays of vertically aligned single walled carbon nanotube (SWCNT) forests were printed on indium tin oxide (ITO) electrodes. Capture anti-IgG antibodies were then coupled through peptide bond formation to acidic functional groups on the vertical nanotubes. IgG immunoassays were performed using silica nano particles (Si NP) functionalized with the ECL luminophore [Ru(bpy)2PICH2]2+], and IgG labelled G1.5 acid terminated PAMAM dendrimers. PAMAM is poly(amido amine), bpy is 2,2′-bipyridyl and PICH2 is (2-(4-carboxyphenyl)imidazo[4,5-f][1,10]phenanthroline). The carboxyl terminal of [Ru(bpy)2PICH2]2+ (fluorescence lifetime≈682±5ns) dye was covalently coupled to amine groups on the 800nm diameter silica spheres in order to produce significant ECL enhancement in the presence of sodium oxalate as co-reactant in PBS at pH 7.2). Significantly, this SWCNT-based sensor array shows a wide linear dynamic range for IgG coated spheres (106 to 1012 spheres) corresponding to IgG concentrations between 20 pM and 300nM. A detection limit of 1.1±0.1pM IgG is obtained under optimal conditions.

High-Performance Semiconducting Nanotube Inks: Progress and Prospects

While the potential for high mobility printed semiconducting nanotube inks has been clear for over a decade, a myriad of scientific and technological issues has prevented commercialization and practical use. One of the most challenging scientific problems has been to understand the relationship between the pristine, individual nanotube mobility (known to be in the 10,000 cm(2)/V·s range) and the as-deposited random network mobility (recently demonstrated in the 100 cm(2)/V·s range). An additional significant scientific hurdle has been to understand, manage, and ultimately eliminate the effects of metallic nanotubes on the network performance, specifically the on/off ratio. Additional scientific progress is important in understanding the dependence of nanotube length, diameter, and density on device performance. Finally, the development of ink formulations that are of practical use in manufacturing is of paramount importance, especially with regard to drying time and uniformity, and ultimately, the issue of scalability and cost must be addressed. Many of these issues have recently been investigated from a phenomenological point of view, and a comprehensive understanding is beginning to emerge. In this paper, we present an overview of solution-based printed carbon nanotube devices and discuss long-term technology prospects. While significant technical challenges still remain, it is clear that the prospects for the use of nanotube ink in a myriad of systems is feasible given their unmatched mobility and compatibility with heterogeneous integration into a variety of applications in printed and flexible electronics.

Activation-free printed carbon nanotube field emitters

When a carbon nanotube paste is formulated based on highly functional hyperbranched polymerssuch as dipentaerythritol hexaacrylate, the volume shrinkage during thermal curing buildsup internal stress that generates microcrack patterns on the printed surface. The nanotubesexposed in the cracks emit electrons successfully at such an extremely low electric field as0.5 V µm − 1, and reach25.5 mA cm − 2 of currentdensity at 2 Vµm − 1 from an optimized paste concerning mainly the size and spatial uniformity of the crack. Inaddition to the superior field emission properties with low manufacturing cost, thisactivation-free technology can provide a minimized nanohazard in the device fabricationprocess, compared to those conventional activation technologies developing seriousnanoflakes by using destructive methods.

Experimental Fabrication of Small Flat-Panel Field Emission Lamp with Printed Carbon Nanotubes as Field Emitters

With effective screen-printing technique, the flat-panel field emission lamp (FPFEL) based on carbon nanotube as cold cathode material was fabricated. The prepared CNT paste was printed on the cathode glass plate to form the field emitter and sealed into the device vacuum room of FPFEL. For improving the display image uniformity, the discrete anode indium tin oxide (ITO) zones method was adopted, and the anode voltage could be applied through the silver anode connecting line for the different anode ITO zones. The anode insulation wall was fabricated to support the anode glass plate, which the deforming of anode glass plate would be avoided. The emission image for the small vacuum-sealed FPFEL with printed carbon nanotube as field emitters was presented. The fully-sealed FPFEL possessed high luminance brightness and better field emission uniformity.

Fabrication and Optimization of Printed Carbon Nanotube Field Emitters for Flat-Panel Display Device

Screen-printing process was adopted to prepare the carbon nanotube cathode. For improving the field emission performance of cold-cathode material, the optimized carbon nanotube cathode fabrication structure was given, and the detailed manufacture process was also described. The photoetched cathode indium-tin-oxide (ITO) stripes including the narrow bar ITO connecting line was fabricated to form the cathode electrodes. The annular silver conducting layer was adopted between the cathode ITO stripes and the carbon nanotube field emitters. The whole display device was packaged by means of glass frit, and vacuum-sealed through the exhaust tube. The fabricated field emission display could display some dot matrix number and characters, which possessed better field emission performance, higher display brightness and good field emission uniformity.

The patterned electron field emission of printed carbon nanotube films by image transfer technology

The patterned electron field emission of printed carbon nanotube (PCNT) films using image transfer technology is reported. If we transfer an image to the surface of PCNT films, such as using a stamp, the emission image of PCNT films will be the transferred pattern. Based on many experiments, we are convinced that the essential feature of pattern emission from PCNT films by image transfer technology is the great emission enhancement of the image transferred area and the reduced emission from the raw area. According to the results from field emission scanning electron microcopy (FESEM), we suggest that the connecting CNT bundles protruding from the substrate result in the emission enhancement of the image transferred area. At the same time, the emission current increase causes the external and internal voltage drop to increase which results in a decrease in the emission from the untreated area. Using image transfer technology, a well-resolved emission image of PCNT films could easily be obtained without any post-treatment.

Improved emission uniformity and stability of printed carbon nanotubes in electrolyte

In this paper, we studied the effect of NaCl electrolyte as a surface treatment on improving the uniformity and stability of field emission of screen-printed carbon nanotubes (CNTs). A short period of the electrolyte treatment of CNT films remarkably increase emission uniformity and stability. Furthermore, the field emission characteristics of screen-printed carbon nanotubes (CNTs) such as low turn-on field, high emission current density and strong adhesion of the CNT film on the substrate were also reinforced after post-treated. SEM, TEM and Raman spectrum study revealed that uniformity and stability of field emission is enhanced by two factors. Firstly, the electrolyte treatment appeared to render the CNT surfaces more actively by exposing more CNTs form the CNT paste, which dominates initial uniformity and stability of field emission. Secondly, the number of opened CNTs and defects CNTs of CNT film were increased by electrical current energy.

The influence of organophilic clay on field electron emission uniformity and lifetime of screen printed carbon nanotube film

The effect of adding clay, modified by a silane coupling agent, into the carbon nanotube (CNT) paste on the field electron emission and a lifetime of screen printed CNT film was studied. The composition of organophilic clay and CNTs was characterized by a combination of X-ray diffraction, and scanning electron microscopy. The incorporation of clay improved the dispersivity, adhesiveness, and conductive networking of paste, therewith enhancing the field emission's uniformity and stability. The improvement of this gas barrier on the CNT film by clay loading prevents emission degradation.

WITHDRAWN: Improved emission uniformity and stability of printed carbon nanotubes in electrolyte

WITHDRAWN: Improved emission uniformity and stability of printed carbon nanotubes in electrolyte

Enhanced field emission from printed CNTs by hard hairbrush and electrolytic treatment in NaCl solution

The effects of hard hairbrush and electrolytic treatment on field emission characteristics of the printed carbon nanotubes (CNTs) cathode films were investigated. Significant improvement in emission current density, emission stability and uniformity were achieved for the hard hairbrush- and electrolytic-treated CNTs films. The improved field emission characteristics of CNTs film can be attributed to the CNT surface more actively by removing organic material cover on the CNTs, which dominates initial characteristics of field emission. Besides, the generation of a high density of structural defects and lower resistance contact CNT to the substrate after treatment are all helpful for improving the field emission characteristics of the treated CNTs. It is suggested that hard hairbrush and electrolytic treatment may be a key technology for the commercialization of CNT field emission display.

Uniform and stable field emission from printed carbon nanotubes through oxygen trimming

When carbon nanotube field emitters are operated, a few highly protruded ones generate most of the emission currents that cause spatial nonuniformity and fast decay in lifetime behavior. We present a cost-effective means to solve this problem using selective oxidation on those nanotubes emitting higher currents, which is assisted by Joule heating generated during field emission. Our simple technique is potentially useful for the field emission devices such as display, backlight, x-ray tube, and others using multiple carbon nanotube emitters.

Improvement of electron field emission from carbon nanotubes by Ar neutral beam treatment

To improve the field emission properties of screen printed carbon nanotube (CNT) films, an Ar neutral beam was used as one of the surface treatment techniques and the CNT field emission characteristics after the treatment were compared with those after Ar ion beam treatment. The Ar neutral beam treatment enhanced the field emission properties of the CNTs and by decreasing the turn-on field and by increasing emission sites. When the field emission properties were measured after the treatment for 10 s with an energy of 100 eV, the turn-on field decreased from 1.7 to 0.9 V/μm while that after the ion beam treatment increased from 1.7 to 2.8 V/μm showing damage of exposed CNTs due to the intensive bombardment by the positive ions in the beam. The neutral beam treatment appeared to expose more CNT field emitters from the CNT paste without cutting or severely damaging the already exposed long CNT emitters because there were no charged particles in the beam.

Electron translocation and field emission in printed CNT film by high-temperature sintering and post-treatment

The main problem of printed carbon nanotube film (CNTF) is that emitters do not have distributed uniformity. CNT was buried in leftover binding materials, which needs to be removed by fitted sintering and post-treatment. A new paste for printed CNTF was developed. Tunneling coefficients of leftover potential barrier were calculated respectively by the numerical method. The electrons translocation results through potential barrier between CNTs in calculated CNTF were tested by an experiment. A novel post-treatment, including high-temperature sintering and mechanical shearing and blowing, was performed to evidently improve the electron translocation and field emission current density of CNTF. Excellent emission prosperities were exhibited: stable current density, distributed uniformity emitters and long lifetime. The treatment of high-temperature sintering and mechanical shearing and blowing, may be an important prerequisite for future field emission display.

Effects of microwave plasma treatment on the field emission properties of printed carbon nanotubes/Ag nano-particles films

The effects of Ar microwave plasma treatment on field emission properties of the printed carbon nanotubes (CNTs) cathode films using Ag nano-particles as binder were investigated. The field emission J– E characteristics were measured at varied plasma treatment time. Significant improvement in emission current density, emission stability and uniformity were achieved for the Ar treated CNTs films, even though the plasma treatment increased the turn on electric field slightly. High-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy revealed the microstructural changes of CNTs after the plasma treatment. The improved field emission properties of CNTs film can be attributed to the generation of a high density of structural defects after treatment, which increased greatly the possible emission active sites. Besides, the formation of the sharpened and open-ended CNTs tips is all helpful for improving the field emission properties of the treated CNTs.

Simulation studies of self-focusing carbon nanotube field emitter

It has been shown that carbon nanotubes exhibit good electron field emission properties, therefore have potential application in field emission displays as electron field emitters. In this study, the authors propose a new coplanar printed carbon nanotube (CNT) field emitter design that possesses symmetrical self-focusing properties without adding a focusing gate. A cylindrical gate electrode is located at the center and surrounded by the cathode. CNT paste can be applied to the cathode surface near or on the corner. A two-dimensional, particle-in-cell computer simulation code MAGIC was used to investigate the field emission characteristics of this new type of field emitter. Simulations were carried out for different gate voltages to investigate the effects on the emission current and beam divergence. Typical simulation parameters are anode voltage of 1000V, cathode voltage of 0V, and an anode-cathode distance of 95μm. It was found that there is an optimum gate voltage that gives the best focusing effect. The optimum gate voltages are different for different CNT paste locations. For CNT paste located on the round corner, with a radius of curvature of 0.5μm, an optimum negative gate voltage of about −15V is needed to push the overfocused emitted electrons to a focused spot having a current-weighted beam radius of 2.1μm. For a ring of CNT paste with 1μm width located on the flat surface next to the corner of the cathode, it would require an optimum gate voltage of about 45V to attract the emitted electrons to fall on a single spot on the anode having a current-weighted beam radius of 1.6μm. The electron emission can be turned off on individual emitter by applying a large negative gate voltage. This study shows the proposed simple field emitter design can produce well-focused electron beams for high resolution display applications.

Improving the emission characteristics of a carbon nanotube cathode in an aging process

Aging of the field emission performance of the printed carbon nanotubes (CNTs) cathode is studied. A continuous increase of the field emission current as well as the density of field emission sites under a constant voltage is observed. It is revealed that the resistant heating may play an important role in the activation of the potential emitters during the aging process. A technique of activating the printed CNT cathode with an aging process is suggested. F– N curves before and after the aging processes are analyzed and it is revealed that the effective emission area increases during the aging process.