An analysis of electrode patterns in capacitive touch screen panels

In the design of capacitive touch-screen panels, electrodes are patterned to improve touch sensitivity. In this paper, we analyze the relationship between electrode patterns and touch sensitivity. An approach is presented where simulations are used to measure the sensitivity of touch-screen panels based on capacitance changes for various electrode patterns. Touch sensitivity increases when the touch object is positioned in close proximity to fringing electric fields generated by the patterned electrodes. Three new electrode patterns are proposed to maximize field fringing in order to increase touch sensitivity by purely electrode patterning means. Simulations showed an increased touch sensitivity of up to 5.4%, as compared with the more conventional interlocking diamonds pattern. Here, we also report empirical findings for fabricated touch-screen panels. © 2005-2012 IEEE.

A graphene-based large area surface-conduction electron emission display

The fabrication and functionality of a 21 cm graphene-based transverse electron emission display panel is presented. A screen-printed triode edge electron emission geometry has been developed based on chemical vapor deposited (CVD) graphene supported on vertically aligned carbon nanotubes (CNT) necessary to minimize electrostatic shielding induced by the proximal bulk substrate. Integrated ZnO tetrapod electron scatterers have been shown to increase the emission efficiency by more than 90%. Simulated electron trajectories validate the observed emission characteristics with driving voltages less than 60 V. Fabricated display panels have shown real-time video capabilities that are hysteresis free (<0.2%), have extremely stable lifetimes (<3% variation over 10 h continuous operation) in addition to rapid temporal responses (<1 ms). © 2013 Elsevier Ltd. All rights reserved.

Graphene SOI CMOS sensors for detection of PPB levels of NO2 in air

There is considerable demand for sensors that are capable of detecting ultra-low concentrations (sub-PPM) of toxic gases in air. Of particular interest are NO2 and CO that are exhaust products of internal combustion engines. Electrochemical (EC) sensors are widely used to detect these gases and offer the advantages of low power, good selectivity and temporal stability. However, EC sensors are large (1 cm3), hand-made and thus expensive ($25). Consequently, they are unsuitable for the low-cost automotive market that demands units for less than $10. One alternative technology is SnO2 or WO3 resistive gas sensors that are fabricated in volume today using screen-printed films on alumina substrates and operate at 400°C. Unfortunately, they suffer from several disadvantages: power consumption is high 200 mW; reproducibility of the sensing element is poor; and cross-sensitivity is high. © 2013 IEEE.

Field emission characteristics of contact printed graphene fins.

Carbon nanostructures have been much sought after for cold-cathode field emission applications. Herein a printing technique is reported to controllably nanostructure chemical vapor deposited graphene into vertically standing fins. The method allows for the creation of regular arrays of bilayer graphene fins, with sharp ridges that, when printed onto gold electrodes, afford a new type of field emission electron source geometry. The approach affords tunable morphologies and excellent long term and cyclic stabilities.

Effect of process parameters on the morphology and nanostructure of roll-to-roll printed P3HT:PCBM thin films for organic photovoltaics

Roll-to-roll (R2R) gravure exhibits significant advantages such as high precision and throughput for the printing of photoactive and conductive materials and the fabrication of flexible organic electronics such as organic photovoltaics (OPVs). Since the photoactive layer is the core of the OPV, it is important to investigate and finally control the process parameters and mechanisms that define the film morphology in a R2R process. The scope of this work is to study the effect of the R2R gravure printing and drying process on the nanomorphology and nanostructure of the photoactive P3HT:PCBM thin films printed on PEDOT:PSS electrodes towards the fabrication of indium tin oxide (ITO)-free flexible OPVs. In order to achieve this, P3HT:PCBM blends of different concentration were R2R printed under various speeds on the PEDOT:PSS layers. Due to the limited drying time during the rolling, an amount of solvent remains in the P3HT:PCBM films and the slow-drying process takes place which leads to the vertical and lateral phase separation, according to the Spectroscopic Ellipsometry and Atomic Force Microscopy analysis. The enhanced slow-drying leads to stronger phase separation, larger P3HT crystallites according to the Grazing Incidence X-Ray Diffraction data and to weaker mechanical response as it was shown by the nanoindentation creep. However, in the surface of the films the P3HT crystallization is controlled by the impinged hot air during the drying, where the more the drying time the larger the surface P3HT crystallites. The integration of the printed P3HT:PCBM and PEDOT:PSS layers in an OPV device underlined the feasibility of fabricating ITO-free flexible OPVs by R2R gravure processes. © 2013 Elsevier B.V.

Characterization of a liquid crystal microlens array using multiwalled carbon nanotube electrodes.

Reconfigurable liquid crystal microlenses employing arrays of multiwalled carbon nanotubes (MWNTs) have been designed and fabricated. The cells consist of arrays of 2 microm high MWNTs grown by plasma-enhanced chemical vapor deposition on silicon with a top electrode of indium tin oxide coated glass positioned 20 microm above the silicon and the gap filled with the nematic liquid crystal BLO48. Simulations have found that, while its nematic liquid crystal aligns with MWNTs within a distance of 10nm, this distance is greatly enhanced by the application of an external electric field. Polarized light experiments show that light is focused with focal lengths ranging from approximately 7 microm to 12 microm.

Self-aligned electrodes for suspended carbon nanotube structures

We report on a study into electrode fabrication for the gate control of carbon nanotubes partially suspended above an oxidised silicon substrate. A fabrication technique has been developed that allows self-aligned side-gate electrodes to be placed with respect to an individual nanotube with a spacing of less than 10 nm. The suspended multi-walled carbon nanotube (MWCNT) is used as an evaporation mask during metal deposition. The metal forms an island on the nanotube, with increasing width as the metal is deposited, forming a wedge shape, so that even thick deposited layers yield islands that remain separated from the metal deposited on the substrate due to shadowing of the evaporation. The island can be removed during lift-off to leave a set of self-aligned electrodes on the substrate. Results show that Cr yields self-aligned side gates with around 90% effectiveness. © 2003 Elsevier Science B.V. All rights reserved.

Self-aligned split gate electrodes fabricated on suspended carbon nanotubes

We describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems.

Self-aligned split gate electrodes fabricated on suspended carbon nanotubes

We describe the fabrication of self-aligned split gate electrodes on suspended multiwalled carbon nanotube structures. A suspended multiwalled carbon nanotube structure was used as an evaporation mask for the deposition of metal electrodes resulting in the formation of discontinuous wire deposition. The metal deposits on the nanotubes are removed with lift-off due to the poor adhesion of metal to the nanotube surface. Using Al sacrificial layers, it was possible to fabricate self-aligned contact electrodes and control electrodes nanometers from the suspended carbon nanotubes with a single lithography step. It was also shown that the fabrication technique may also be used to form nano-gaped contact electrodes. The technique should prove useful for the fabrication of nano-electromechanical systems. © 2003 Materials Research Society.