Y.H. Cho

Development of microfluidic device for electrical/physical characterization of single cell

A novel device with microchannels for flowing cells and twin microcantilever arrays for measuring the electrical impedance of a single cell is proposed. The fabrication process is demonstrated and the twin microcantilever arrays have been successfully fabricated. In our research, we measured the electrical impedance for normal and abnormal red blood cell over the frequency range from 1 Hz to 10 MHz. From the electrical impedance experiment of normal and abnormal red blood cell, it was examined that the electrical impedance between normal and abnormal red blood cells was significantly different in magnitude and phase shift. In this paper, we show that the normal cell can be taken apart from the abnormal cell by electrical impedance measurement. Therefore, it is expected that the applicability of this technology can be used in cellular studies such as cell sorting, counting or membrane biophysical characterization.

Fabrication of silicon dioxide submicron channels without nanolithography for single biomolecule detection.

We successfully fabricated nanochannel arrays with silicon dioxide (SiO(2)) surfaces for single biomolecule detection. The SiO(2) nanochannel fabrication is based on the combination of anisotropic etching by potassium hydroxide (KOH) solution, local oxidation of silicon (LOCOS) and plasma etching of silicon. This fabrication technique is easily controllable and is a simple and practical solution for low-cost and high-throughput fabrication of nanofluidic channels. Thus, this technique enables the generation of nanochannels with various nanoscale dimensions without using nanolithography.

Simple fabrication of Si nanowire and its biological application

A novel, relatively simple and cost effective method is reported to fabricate suspended silicon nanowires. This method allows for the production of suspended silicon nanowires using anisotropic wet etching and thermal oxidation of single crystalline silicon. The dimensions of the silicon nanowires fabricated with the proposed method are evaluated. The vibration properties of the nanowires obtained by heterodyne laser doppler interferometer show the potential of being nanomechanical sensors.

Fabrication and Characterization of Thermally Actuated Bimorph Probe for Living Cell Measurements with Experimental and Numerical Analysis

This paper deals with a novel structure for single-cell characterization which makes use of bimorph micro thermal actuators combined with electrical sensor device and integrated microfluidic channel. The goal for this device is to capture and characterize individual biocell. Quantitative and qualitative characteristics of bimorph thermal actuator were analyzed with finite element analysis methods. Furthermore, optimization for the dimension of cantilevers and integrated parallel probe systems with microfluidic channels is able to be realized through the virtual simulation for actuation and the practical fabrication of prototype of probes. The experimental value of probe deflection was in accordance with the simulated one.

MEMS-based biochip for the characterization of single red blood cell

We introduce a novel biosensor device for various biocell measurements by singular cell level with parallel analysis and high throughput. This paper deals with the details of its fabrication, including device packaging, and the practical measurement of red blood cells using a twin microcantilever type sensor array. Based on a simple measurement of the electrical impedance of a living single red blood cell and its suspension, an important set of data, which can be used to describe living matter, could be obtained.

Si-based micro probe card with sharp knife-edged tips combined metal deposition

This paper presents the micro-machined cantilever type MEMS probe card with a special shape of tips in single crystal silicon. The probe cantilevers including the sharp tip are formed with anisotropic KOH etching and LOCOS, and the tips are deposited with Cr, Au, and W. This probe can endure enough force because both of tip and cantilever are entirely fabricated by single crystal silicon, and the specific shape of sharp probe tip was fabricated to break the oxidized surface of the IC chip. This probe is also expected to have a long life-time and enough tip hardness since the end of tip is coated with hard metal of tungsten (W). A novel process for the micro machined probe card with a sharp tip formation is developed and the micro probe arrays with 40 /spl mu/m in pitch are also realized.

A Silicon-Based Single-Cell Electroporation Microchip for Gene Transfer

In our contribution, we present the fabrication of electroporation microchip in detail. The practical experiments of single-cell electroporation with our fabricated microchip will be carried out. Electroporation test efficiency and cell viability tests will be provided. This device enables to reduce the size of samples and thus the use of small amount of reagents. It may also permit to avoid cell separation (transfected cells versus non transfected cells) encountered when traditional bulk electroporation is held

Characterization of single red blood cell using twin microcantilever type sensor array

We have introduced a new biosensor device for red blood cell measurement by singular cell level with parallel analysis and high throughput. This paper deals with the practical measurement of red blood cells as well as the details on its fabrication, including device packaging. Based on a simple measurement of the electrical impedance of a living single red blood cell and its suspension, an important set of data, which can be used to describe living matter, could be obtained. It was confirmed that the electrical impedance between normal and abnormal red blood cells was significantly different in magnitude and phase shift.

High-Throughput Single-Cell Electroporation Microchip with Three Dimensional Si Microelectrodes for Gene Transfection

We present details on fabrication of electroporation microchip, practical experiments of single-cell electroporation with our fabricated microchip. Also, the continuous electroporation for the continuous flow of cells is used for high-throughput electroporation. The delivery efficiency and cell viability tests are provided and the successful GFP transfection into cells is also evaluated with a fluorescent microscope after electroporation.

Nanochannels for Manipulation of DNA Molecule using Various Fabrication Molecule

In this report, several fabrication techniques for the formation of various nanochannels (with SiO₂, Si, or Quartz) are introduced. Moreover, simple fabrication technique for generating SiO₂ nanochannels without nanolithography is presented. By using different nanochannels, the degree of stretching DNA molecule will be evaluated. Finally, we introduce a nanometer scale fluidic channel with electrodes on the sidewall of it, to detect and analyze single DNA molecule. The cross sectional shape of the nanotrench is V-groove, which was implemented by thermal oxidation. Electrodes were deposited through both sidewalls of nanotrench and the sealing of channel was done by covering thin polydimethiysiloxane (PDMS) polymer sheet.