Plastic Microfluidic Devices for Bio/Chemical Analysis
Prof. Chonghun Han
Department of Chemistry, Pohang University of Science and Technology
2002. 11. 21
Microfluidic devices are finding increasing application in bio/chemical analysis. Conventionally, microfluidic devices are fabricated by etching in glass and silicon. Soft-lithographic methods of fabricating microfluidic devices in poly(dimethylsiloxane) (PDMS) provide rapid prototyping and replica molding, which enable the devices to be fabricate under benchtop conditions and have greater accessibility to analytical chemists. Recently we have developed several PDMS microfluidic devices for bio/chemical analysis. (a) A precolumn-derivatization/separation microchip with enhanced mixing attain the optimized efficiency of diffusive mixing by using the reactions between OPA and biogenic amines. (b) A separation device with an absorption detector, where a light collimating system consisting of optical fibers, a microlens, and slits are integrated. In conventional on-column absorbance detection, the short optical path length available in small microchannels limits the detection sensitivity. A Z-shaped flow detection cell is the usual method of choice, to attain enhanced detectability. In most microchip applications, light is delivered to and collected from the Z-shaped flow cell by using a pair of optical fibers. However, divergence of light from the excitation fiber becomes serious as the path length of the flow cell increases, which degrades the linearity in calibration. We have integrated a micro-collimating system in a separation chip and improved the linearity greatly. (c) A rapid, membrane-less cleanup chip for electrospray ionization (ESI) mass spectrometry of protein samples, where a multiphase laminar flow is employed to accomplish rapid desalting by diffusion. We have demonstrated that in both off- and on-line modes, about 1-second diffusion-based cleanup of horse heart myoglobin with 500 mM NaCl gives an ESI mass spectrum as good as obtained after 2-hour dialysis. (d) A microchip for analyzing both Cr(VI) and Cr(III), where reduction of Cr(VI) to Cr(III) and chemiluminescence generation for quantifying Cr(III) are taking place on the same chip. And (e) a squeezing pump for microfluidic chips, where rolling back and forth of squeezers on reservoirs in a PDMS chip suck in and deliver individual fluids quantitatively. When this squeezing pump is employed for delivering and controlling fluids in a microchip, any external tubing connections are not needed and the whole system can be greatly simplified.
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Last update: Nov. 21, 2002