Jeong Hee Shin

Psychological tactile sensor structure based on piezoelectric nanowire cell arrays

To produce artificial psychological feeling, especially ‘pain’, an electrical structure that mimics human skin has been studied. Touch by a sharp and a blunt object induces different deformations of the skin of human fingers. In order to imitate this phenomenon, a skin-mimicking device employing piezoelectric nanowire sensor arrays is used to generate an electrical ‘pain’ signal with signal processing when a pen cap presses the device. The electrical ‘pain’ signal is expected to enhance the protection mechanism of an android robot or mobile phone against harsh environments.

Structural Solution to Enhance the Sensitivity of a Self-Powered Pressure Sensor for an Artificial Tactile System

Structural design factors of sensor units have been studied in order to enhance the sensitivity of pressure sensors based on utilizing a piezoelectric material for an artificial tactile sensor. In this study, we have primarily demonstrated the effect of a square pattern array design in a pressure sensor using ZnO nanowires. Nanowires grown on the edge of cells can be bent easily because of growth direction, density control, and buckling effect. Since smaller square pattern arrays induce a higher circumference to cell area ratio, if one sensor unit consists of many micro-level square pattern arrays, the design enhances the piezoelectric efficiency and the sensitivity. As a result, 20

Zinc oxide nanowire-based pressure and temperature sensor

\mu {\mathrm { m}}\times 20\,\,\mu {\mathrm { m}}

High Growth Yield of Single Multiwall Carbon Nanotube With Different Length Effect

cell arrays showed three times higher pressure sensitivity than

Metal-insulator-metal tunneling diode using vertical metal cylinder structure

250~\mu {\mathrm { m}}\times 250\,\,\mu {\mathrm { m}}

Geometric effect in a vertical stack-up metal-insulator-metal tunnel diode

cell array structures at a pressure range from 4 kPa to 14 kPa. The induced piezoelectric voltage with the same pressure level also increased drastically. Therefore, the square pattern array design is more appropriate for a high-sensitive pressure sensor than a simple one-body cell design for tactile systems, and it has the advantage of better power efficiency, which is also important for artificial tactile systems. This suggested cell array design can be applied to various systems using piezoelectric nanowires.

Development of a virtual metrology method using plasma harmonics analysis

Tactile sensors have been received with tremendous attention and developed rapidly for the last few decades. There have been various technologies and transduction methods to innovate the tactile sensor; however, the ability of tactile sensors has left much to be desired. For example, a resistive and a capacitive type sensor, most widely used techniques for touch screen technology and tactile sensor have a limit of detecting temperature. In this study, Zinc Oxide (ZnO) nanowire-based tactile sensors which can detect both the pressure and temperature is demonstrated when the sensor is under pressure or heat. Pressure or temperature sensitivity from dynamic tactile sensing is also discussed from the results.

Electrical Broad Tuning of Plasmonic Color Filter Employing an Asymmetric-Lattice Nanohole Array of Metasurface Controlled by Polarization Rotator

Vertically aligned single multiwalled carbon nanotube (MWCNT) is quite an interesting nanostructure due to its high probability of nanodevice realization with an ultrahigh integration density. Although ~200 nm catalyst diameter size and plasma-enhanced chemical vapor deposition (PECVD) method have been known as key parameters to grow a single MWCNT, the details and the phenomenon of below 200 nm catalyst size have not been studied or published well. Here, we report the details of catalyst size effect below 200 nm. One-hundred-nanometer diameter Ni catalyst on SiO2 layer shows 95% yield of single MWCNT growth. Surface roughness of substrate makes a large deviation in the yield and the critical catalyst size for single MWCNT. The various catalyst sizes result in the different growth rate of carbon nanotube (CNT) at the same growth condition. The change of diffusion surface area induces such a difference. From the results, single MWCNTs with various lengths are successfully grown on the same substrate by a one-step growth process.

Ultrafast metal-insulator-multi-wall carbon nanotube tunneling diode employing asymmetrical structure effect

Metal-Insulator-Metal(MIM) tunneling diodes have been studied to enhance the efficiency of rectifying. To improve the electrical characteristics of the device, the structural geometry and the material effect of MIM diodes have been studied. Metal cylinder structure which has nano-scale geometry induced asymmetrical tunneling probability compare with flat metal electrode and it resulted in increased the rectifying efficiency. In addition, the optimization of material selection has been done to increase the efficiency more.

Micro-size antenna structure with vertical nanowires for wireless power transmission and communication.

The geometric effect was investigated in a vertically designed metal-insulator-metal (MIM) tunnel diode for which a narrow tunneling distance can be controlled easily and reliably, with the goal of enhancing rectifying efficiency, based on the angle of a pointed shape electrode and various thicknesses of insulator material. Although MIM tunneling diodes can provide ultra- high working speeds (>THz), the very low contrast ratio between forward and reverse currents results in poor rectifying efficiency. An asymmetric geometry design with two metal electrodes can be an effective approach for enhancing the contrast ratio between the tunneling currents. Using a sharp electrode with a pointed shape, it was determined that the rectifying efficiency and tunneling probability could be increased impressively depending on the angle of the pointed shape of the electrode. Moreover, the selection of insulation material was also important for improving efficiency. Although the band gap of Al2O3 is larger than that of Hf...