Simple and Rapid Fabrication of PDMS Microfluidic Devices Compatible with FTIR Microspectroscopy

A simple and rapid fabrication method of IR transparent poly(dimethylsiloxane) (PDMS) microfluidic devices is presented. Spin coating of PDMS pre-polymer was employed to attain a thin PDMS microchannel layer, allowing for transmission IR microspectroscopy. Key advantages of this approach include simplicity, low fabrication cost, reliability and rapid production time. PDMS microfluidic devices manufactured using this approach were successfully used to demonstrate transmission IR microscopic measurements of on-chip dilution of NaN3 using water. A linear relationship between peak area (centered at ca. 2050 cm−1) of azide and the concentration estimated from the ratio of the flow rates of two inlets was observed in the range from 15 to 150 mM. The kinetics of the reduction of hexacyanoferrate(III) ([Fe(CN)6]3−) by ascorbic acid (AA) was also analyzed. We observed that the peak at ca. 2115 cm−1 (hexacyanoferrate(III)) was decreasing, while the peak at ca. 2040 cm−1 (hexacyanoferrate(II)) was increasing as the reaction was in progress. From the systematic analysis by changing the concentrations of hexacyanoferrate(III) and AA, we evaluated that the reaction order with respect to each substance was 1st order.