| Microfluidic chip technology is the current development of micro total analysis systems forward and it has been one of development hot spots. Polymer microfluidic chips have the advantages of easy processing, integration, mass production and low cost. Thermoplastic polymer microfluidic chips draw more extensive attention in recent years. Fabrication of micro-channels and the bonding of chips are key techniques. For fabrication of microfluidic chips. However, solvent bonding is a simple and rapid method of sealing chips at room temperature.In this paper, a new method for solvent bonding thermoplastic polymers poly(methyl methacrylate)(PMMA) microfluidic chips using ethyl acetate solvent was developed at room temperature. The channel structure of a microchip was replicated by hot embossing using a silicon master. Ethyl acetate and acetonitrile were selected since they can partly dissolve PMMA material. In order to control the amount of reacted solvent, a porous material was first introduced into the solvent bonding processing of microchips. In the experiment, we have investigated the effects of the solvent contact time, bonding temperature, pressure and the bonding time on the bonding quality. Comparing the toxicity and the bonding quality of chips, ethyl acetate was selected as bonding solvent. At room temperature, PMMA microchips were bonded with solvent under optimum experimental conditions.CCD and SEM images of microchannels and its cross section in the microfluidic chips were taken to show the effectiveness of the procedure. The microchannels imprinted by silicon master in the substrate were81.4μm in top width,166.1μm in bottom width and54.4μm in depth. The average microchannels (n=5) bonded with ethyl acetate were77.5μm in top width,161.8μm in bottom width and53.5μm in depth. Less than1μm difference in depth was checked with1.7%of the relative deformation and0.94%of RSD in depth (n=5) after solvent bonding. CCD and SEM images of the cross section of microchannels were taken to show the effectiveness of solvent bonding with less distortion. The average tensile stress of1.95MPa was higher than the0.55MPa reported by a literature. Higher tensile stress was measured to show the high bonding intensity for the chips using solvent bonding. The performance of the PMMA microfluidic chips was demonstrated in16electrophoretic separations of Cy5with a fluorescence intense precision of1.7%RSD, a migration time precision of2.0%RSD and an efficiency of1.6×105plates/m. PMMA microfluidic chips bonded with ethyl acetate can be applied to capillary electrophoresis. The simple solvent bonding based on solvent control by porous materials at room temperature was developed with high bonding intensity and less distortion. The method can be applied to fabricate small batches of PMMA microfluidic chips with low cost for research purposes in common chemical labs. |
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