Fabrication of PDMS-Based Nitrite Sensors Using Teflon AF Coating Microchannels

This study shows a novel polydimethylsiloxane (PDMS) nitrite sensor using liquid-core waveguide techniques. A 6 cm straight and Teflon AF 1601S coated PDMS microchannel (600 mum width and depth) replicated from a SU-8 master and sealed with a glass slide with the same coating. This formed a low index of refraction channel in which a high index aqueous solution was flowed. Light generated by a fiber-coupled tungsten halogen lamp propagated by total internal reflection to the end of the channel where the light was detected using a palm-size CCD array spectrometer. The result shows a dramatic difference between channels with and without a Teflon coating. The absorbance response of this sensor varies linearly with concentration and adheres to Beer´s law. Moreover, calculations of absorbance using this sensor are in excellent agreement with a commercial spectrometer. This innovative technique provides a potentially low-cost and high efficient approach to fill the inspection technology gap between in situ and laboratory analyses. It is believed that the novel PDMS-based nitrite sensor is expected to give an impact to the aqueous inspection and to create a highly value-added technology in optical test and measurement industry.