Jang-Kyoo Shin

Biologically Inspired Saliency Map Model for Bottom-up Visual Attention

In this paper, we propose a new saliency map model to find a selective attention region in a static color image for human-like fast scene analysis. We consider the roles of cells in our visual receptor for edge detection and cone opponency, and also reflect the roles of the lateral geniculate nucleus to find a symmetrical property of an interesting object such as shape and pattern. Also, independent component analysis (ICA) is used to find a filter that can generate a salient region from feature maps constructed by edge, color opponency and symmetry information, which models the role of redundancy reduction in the visual cortex. Computer experimental results show that the proposed model successfully generates the plausible sequence of salient region.

Field Effect Transistor-based Bimolecular Sensor Employing a Pt Reference Electrode for the Detection of Deoxyribonucleic Acid Sequence

We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investigated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The gate potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.

Fabrication and Characteristics of a Field Effect Transistor-Type Charge Sensor for Detecting Deoxyribonucleic Acid Sequence

We have fabricated an field effect transistor (FET)-type deoxyribonucleic acid (DNA) charge sensor which can detect the DNA sequence by sensing the variation of drain current due to DNA hybridization and investigated its electrical characteristics. It is fabricated as a PMOSFET-type because the DNA probe has a negative charge. Au which has a chemical affinity with thiol was used as the gate metal in order to immobilize DNA. The operating principle is very similar to that of MOSFET. The gate potential is determined by the electric charge possessed by the DNA. The variation of the drain current with time was measured. The drain current increased when thiol DNA and target DNA were injected into the solution, because of the field effect due to the electrical charge of DNA molecules. Therefore it is confirmed that the DNA sequence can be detected by measuring the variation of the drain current due to the variation of DNA charge and it is concluded that the proposed FET-type DNA charge sensor might be useful for the implementation of the DNA chip.

Quantum-wired MOSFET photodetector fabricated by conventional photolithography on SOI substrate

NMOSFETs with a sub-30 nm-wide silicon quantum wire were fabricated and its electrical and optical characteristics were investigated. The silicon quantum wire was obtained by conventional photolithography with the help of anisotropic wet etching and reactive ion etching on a silicon-on-insulator substrate. Step-like conductance versus gate voltage, which is an evidence of one-dimensional electron motion, has been observed even at temperatures below 173 K. A maximum photo-responsivity of the quantum MOSFET was larger than 1/spl times/10/sup 2/ A/W at a wavelength of 632.8 nm. These features make this transistor feasible for applications to highly sensitive photodetectors.

A novel retina chip with simple wiring for edge extraction

A novel silicon retina chip based on the information processing in the vertebrate retina was designed and fabricated. The chip has a novel wiring structure in which all pixels are connected through the channel of MOS transistors, which simplifies a wiring structure compared with conventional resistive networks. The proposed structure minimizes the pixel area and certainly increases a fill factor since each pixel consists of only two photodiodes and three MOS transistors. Experimental results showed that the chip could extracted the edge of input images successfully. Furthermore, it was shown that the chip could operate over a wide range of light intensities by adjusting its spatial resolution.

Low cost implementation of filterless class D audio amplifier with constant switching frequency

A new and simple configuration of filterless class D audio amplifier is proposed in this paper. The proposed filterless class D audio amplifier provides the advantages of both low total system cost and generation of synchronized 3-level pulse-width modulated (PWM) output. Moreover, as a result of hysteresis window variation, a close to constant switching frequency of PWM output is obtained. The proposed filterless class D audio amplifier is verified by the PSpice simulation and prototype circuit experiment

Fabrication of circular-type microchannel using photoresist reflow and isotropic etching for microfluidic devices

In this study, we fabricated circular channels using photoresist reflow and isotropic etching. A silicon substrate, using Si3N4 as a mask, was selectively etched using the hydrofluoric acid, nitric acid, acetic acid (HNA) etching system for fabricating the bottom hemisphere of the channels. Photoresist reflow was used to make the top of the channels round. Then Si3N4 was deposited on the reflowed photoresist. Since the deposited Si3N4 was approximately 6000 A thick, it was possible to observe the inside of the channel. We expect to apply such circular channels to simple bio-systems and microfluidic devices in which optical detection is required.

K+-ion sensing using surface plasmon resonance by NIR light source

A surface plasmon resonance (SPR) sensor, which detects K + ion using gold thin film, was constructed at different incident wavelengths, 670 and 830 nm. The properties of gold thin film and wavelength are very important factors in exciting surface plasmon resonance. We investigated the SPR phenomenon at different incident wavelengths when the surface plasmon resonated with evanescent waves. The resonance angle changed about 4.4 ◦ as the light source changed from 670 to 830 nm wavelengths in pure water. The sensor chip that is coated with a sensing membrane was tested at each wavelength. We found no resonance point at the 670 nm wavelength because the sensing film was too thick when the K + ion concentration was varied from 10 −8 to 1 M. As the light source was changed to the 830 nm wavelength, we could detect the resonance point even though the film was thick. Therefore, we could detect surface plasmon resonance phenomena at the longer incident wavelength and the smaller resonance angle. We could detect the K + ion concentration from 10 −8 to

Highly and Variably Sensitive Complementary Metal Oxide Semiconductor Active Pixel Sensor Using P-Channel Metal Oxide Semiconductor Field Effect Transistor-Type Photodetector with Transfer Gate

In this paper, a new sensor using a p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector with a transfer gate has been designed and fabricated by a 0.35 µm standard complementary metal oxide semiconductor (CMOS) process. The photodetector is composed of a floating gate connected to an n-well and a transfer gate. The transfer gate controls photocurrent flow by controlling the barrier for holes in the PMOSFET-type photodetector. The designed photodetector has similar IDS–VDS characteristics to a conventional PMOSFET when the incident light power instead of the gate voltage is varied. A unit pixel that uses this photodetector consists of a PMOSFET-type photodetector with a transfer gate and four n-channel metal oxide semiconductor field effect transistors (NMOSFETs). Its area is 7.2 ×8.1 µm2. It is confirmed that this photodetector, with a high and variable level of sensitivity, could be applied to an image acquisition system at a low illumination level.

Design and fabrication of a micro electro mechanical systems-based electrolytic tilt sensor

An electrolytic tilt sensor has been designed and fabricated using micro electro mechanical systems (MEMS) technique. The anisotropic KOH etching is used to form a deep Si cavity where conductive electrolyte solution is filled in. Au/NiCr electrodes are simultaneously deposited and patterned using e-beam evaporator with an aligned shadow mask, which is fabricated by through-wafer via etching on a 400-µm-thick Si wafer. A composite electrolyte of 4.8 µL in the volume is filled in the anisotropically-etched cavity that has a volume of 7.3 µL. The electrolyte solution is comprised of variable amount of KCl and a mixture of deionized (DI) water, ethanol and methanol (50, 25, and 25 vol %, respectively). When the electrolyte is injected into the cavity, a cover glass is bonded to seal the electrolyte solution. The fabricated electrolytic tilt sensor is excited by an alternating current to prevent electrolysis in the electrolyte-filled cavity and measured by Wheatstone bridge setup that reads the variation of resistance with respect to an incoming inclination. The measured output characteristic of the MEMS-based electrolytic tilt sensor is as good as that of a conventional electrolytic tilt sensor. Moreover, MEMS-based sensor prevails in its small size, low cost and possible mass production.