Chin-Sung Park

Bacteria concentration using a membrane type insulator-based dielectrophoresis in a plastic chip

We report an insulator‐based (or, electrodeless) dielectrophoresis utilizing microfabricated plastic membranes. The membranes with honeycomb‐type pores have been fabricated by patterning the SU‐8 layer on a substrate which was pretreated with self‐assembled monolayer of octadecyltrichlorosilane for the easy release. The fabricated membrane was positioned between two electrodes and alternating current field was applied for the particle trap experiments. The particle could be trapped due to the dielectrophoresis force generated by the non‐uniformities of the electric fields applied through the membranes with pores. Simulations using CFD‐ACE+(CFD Research, Huntsville, Alabama) suggested that the dielectrophoresis force is stronger in the edge of the pores where the field gradient is highest. The bacteria could be captured on the near edge of the pores when the electric field was turned on and the trapped bacteria could be released when the field was turned off with the release efficiency of more than 93±7%. The maximal trapping efficiency of 66±7% was obtained under the electric fields (E=128 V/mm and f=300 kHz) when the dilute bacteria solution (Escherichia coli: 9.3×103 cell/mL, 0.5 mS/m) flowed with a flow rate of 100 μL/min.

A world-to-chip microfluidic interconnection technology with dual functions of sample injection and sealing for a multichamber micro PCR chip

This paper presents a practical world-to-chip microfluidic interconnection technology with dual functions of sample injection and sealing for a multichamber Micro PCR (Polymerase Chain Reaction) chip. After sample injection and sealing, leakage test is conducted by elevating the temperature up to 100 /spl deg/C for 30 min. No leakage flows are found during the test for 10 cartridges. In conclusion, we have introduced a simple and cheap microfluidic interconnection technology for both sample injection and sealing, which provides a zero dead volume, a zero leakage flow, and biochemical compatibility. Also, this world-to-chip interconnection technology enables one or more operators to interface between the micro world and real world easily by using conventional pipettes.

Fabrication of 3-Dimensional Structure of Metal Oxide Semiconductor Field Effect Transistor Embodied in the Convex Corner of the Silicon Micro-Fluidic Channel

As micro-fluidic systems and biochemical detection systems are scaled to smaller dimensions, the realization of small and portable biochemical detection systems has become increasingly important. In this paper, we propose a 3-dimensional structure of a metal oxide semiconductor field-effect transistor(3-D MOSFET) using tetramethyl ammonium hydroxide (TMAH) anisotropic etching, which is a suitable device for combining with a micro-fluidic system. After fabricating a trapezoidal micro-fluidic channel, the 3-D MOSFET embodied in the convex corner of the micro-fluidic channel was fabricated. The length of the gate is about 20 µm and the width is about 9 µm. The depth and top width of the trapezoidal micro-fluidic channel are about 8 µm and 60 µm, respectively. The measured drain saturation current of the 3-D MOSFET was about -22 µA at VGS=-5 V and VDS=-5 V, and the device characteristics exhibit a typical MOSFET behavior. Moreover, a gold layer was used for the MOSFETs gate metal to detect charged biochemical samples using the affinity between gold and thiol.