Fabrication And In Situ Raman Spectroscopy Detection Of Glass Microfluidic Chips

Microfluidic chip is an interdisciplinary field. As the dimension sharply reduced to sub-millimeter or even micrometer, physicochemical phenomena of microfluidic such as diffusion, surface tension and viscosity become much more important than that of macrofluidic, and then dominate many performances. In this thesis, wet etching and electroforming were employed in microfluidic chip fabrication, and confocal Raman spectroscopy was used to monitor the interdiffusion and reaction of liquids at the controlled microfluidic interface. The main work and results are summarized as follow:1. Set up and optimized the manufacture of smooth PDMS replicas. The procedure of silicon wet etching was optimized by increasing the concentration of TMAH etching solution and prebaking the silicon pieces prior to wet etching. The silicon mold with surface roughness (Ra) at only 2nm was achieved. The parameters of nickle electroforming were also optimized to achieve highly smooth nickle mold, through employing a initial cathodic current density of 0.5A/dm2 and increasing gradually to 1.5A/dm2.2. Developed a rapid fabrication approach of glass chip which was suit for Raman detection. The enamel or Cr / Au / enamel film were used as sacrificial layer, then the development of pattern was carried out by CO2 laser before wet etching. The effect of CO2 laser power, etching solution and sacrificial layer was evaluated.3. Improved the sample injection interface, and leakage was then avoided even under a high velocity upon 120μL/min; Optimized the experimental parameters of PDMS bonding by oxygen plasma, then the PDMS/PDMS and PDMS/glass chip were bonded irreversibly4. Raman microscopy was used to monitor the enzyme catalyzed reaction of benzidine and p-Toluidin, which was carried out at the stable water/organic interface provided by the microfluidic chip. The results showed that the different product from benzidine could be observed at various position in the chip, which didn't happen in beaker or p-Toluidin system. This might be caused by the different ranked orientation of the two molecules at the the water/organic interface.5. Diffusion behavior between KSCN solution and aniline was studied quantitatively through local concentrations scanning with the confocal Raman microscope. A stable interface of two miscible liquids (water/red ink) was achieved in a wide range of flow rates in the microchannel, and the effect of flow rate was well evaluated.6. Developed a new approach to fabricate Ag SERS-active substrate within microfluidic chip by electrochemical oxidation-reduction-cycle (ORC) roughening. The self-made SERS dectection system for microfluidic chip was used to monitor the formation of imine in situ, and the enhanced signal obtained was more than 7000cps.