Woo Sung Cho

Carbon Nanotube-Based Triode Field Emission Lamps Using Metal Meshes With Spacers

We fabricated a carbon nanotube (CNT)-based triode field emission flat lamp with a gated emitter structure, which is composed of a metal grid with a spacer as a gate, a cathode electrode layer, and a CNT layer. The metal mesh was designed with trenches and numerous holes to make a gap between gate and cathode electrodes and to provide electrons with a highly efficient passage. We observed that this metal mesh decreased the vibration and leakage current owing to high electric field generated from anode. As a result, the uniformity and stability of this field emission lamp was improved

Flexible Tactile Sensor Fabricated using Polymer Membrane

We present the fabrication process and the characteristics of a flexible tactile sensor by silicon micromachining, polymer processing and packaging technologies. The fabrication process for the tactile sensor was composed of in the fabrication of sensor chips and their packaging on the flexible printed circuit board (FPCB). The variation rate of resistance was about 4.6%/N when normal force was applied. This sensor can be used to sense touch, pressure, and slip because the signals are is are determined by the variations of resistance of the metal strain gauge for normal and shear force in tactile sensor.

Fabrication and field emission properties of spray-deposited RNA-carbon nanotube films

Carbon nanotubes (CNTs) were effectively dispersed and functionalized by being wrapped with RNA. The RNA-CNT hybrids attached strongly to an indium tin oxide (ITO) glass substrate and formed a uniform film, making it possible to use field emitters for field emission applications. An electron field emission cathode was fabricated with a spray method using these RNA-CNT hybrids. Well-defined RNA-CNT patterns were obtained on the ITO glass substrate. The cathode showed a uniform emission pattern across the entire surface and also exhibited a high current density. The RNA-CNT hybrids compared favorably to other factionalized CNTs for use in the spray method.

Technology development of silicon based CMOS tactile senor for robotics applications

This paper describes the design, manufacture and measure of tactile sensor with piezoresistive detection of deflection. The tactile sensor array was constructed with a fully integrated complementary metal oxide semiconductor (CMOS) fabrication process and bulk micromachining for the sensing structures. Electrical connections were made between the flexible printed circuit boards (FPCB) and the sensor array module using an anisotropic conductive film (ACF) bonding. The individual sensor element has been shown to demonstrate linear responses to applied normal stress (117 mV/N). Therefore, this approach could yield a highly sensitive tactile sensor array for use in dexterous robotic applications.

MEMS-Based Fabrication of Multi-Walled Carbon Nanotube pH Sensor

In this paper, We presents experimental results that demonstrate the pH sensing capability of MW-CNTs. High-density, well-aligned carbon nanotubes, which are MW-CNTs and vertically aligned on a large area of substrate, has been synthesized. The absorption of different range of pH buffer solution in the MW-CNTs changes the conductivity of the MW-CNTs at room temperature. A MEMS-based fabrication process was developed to fabricate a device where MWCNTs based sensing material was precisely assembled pattern.

Improved surface morphologies of printed carbon nanotubes by heat treatment and their field emission properties

Abstract This paper presents heating process for obtaining standing carbon nanotube emitters to improve field‐emission properties from the screen‐printed multiwalled carbon nanotube (MWCNT) films. In an atmosphere with optimum combination of nitrogen and air for heat treatment of CNT films, the CNT emitters can be made to protrude from the surface. This allows for high emission current and the formation of very uniform emission sites without special surface treatment. The morphological change of the CNT film by this technique has eliminated additional processing steps, such as surface treatment which may result in secondary contamination and damage to the film. Despite its simplicity the process provides high reproducibility in emission current density which makes the films suitable for practical applications.

Improved field emission by liquid elastomer modification of screen-printed CNT film morphology

Abstract The effect of improvement on the surface morphology of screen‐printed carbon nanotube (CNT) films was studied by using the optically clear poly‐dimethylsiloxane (PDMS) elastomer for surface treatment. After the PDMS activation treatment was applied to the diode‐type CNT cathode, the entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field‐emission characteristics over the as‐deposited CNT film. Also, the cathode film morphology of a top gated triode‐type structure can be treated by using the proposed surface treatment technique, which is a low‐cost process, simple process. The relative uniform emission image showed high brightness with a high anode current. This result shows the possibility of using this technique for surface treatment of large‐size field emission displays (FEDs) in the future.

P-40: Field Emission Properties of 4.5 inch Triode Type Flat Lamp using the Screen Printing Method

A triode type flat lamp (4.5-in.) using screen printed carbon nanotube emitters was fabricated. The spacer of about 200um between the cathode and gate electrode with a metal mesh was placed by the simple screen printing technique, which does not correspond with method of the past. The buried CNTs were exposed on the surface by the electric field condition without other mechanical surface treatments. A high brightness of 10100 cd / m2 with relatively homogenous emission sites was obtained at the voltage of gate and anode of D.C. bias 280 V and 3KV, respectively. The turn-on voltage was 180 V and the anode current of 5 mA was extracted at the gate voltage of 275 V. Through accurate alignment of the gate holes and the CNT dots, the gate leakage current was significantly decreased including emitted electrons focusing effect.

Field emission enhancement by electric field activation in screen-printed carbon Nanotube film

Abstract By applying a critical field treatment instead of the conventional surface treatments such as soft rubber roller, ion beam irradiation, adhesive taping, and laser irradiation, electron emission properties of screen‐printed carbon nanotubes (CNTs) were enhanced and investigated based on the emission current‐voltage characteristics through scanning electron microscopy. After nanotube emitters were activated at the applied electric‐field of 2.5 V/um, the electron emission current density with good uniform emission sites reached the value of 2.13 mA/cm2, which is 400 times higher than that of the untreated sample, and the turn‐on voltage decreased markedly from 700 to 460 V. In addition, enhancement of the alignment of CNTs to the vertical direction was observed.