Inlaid Microfluidics: A Novel Approach to Optical Measurements on Lab-on-Chip Devices
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A novel type of microfluidic optical cell is presented here that inlays black poly(methyl methacrylate) (PMMA) into a clear PMMA substrate to realize an isolated optical channel with microlitre volumes. Optical measurements are frequently performed on microfluidic devices, offering effective, quick, and robust chemical analysis capabilities on small sample volumes. However, sophisticated coordination of light through a small cross-section is needed, often requiring collimating and beam-steering optics. Detailed here is the fabrication process to realize optical cells based on a simple hybrid-material approach. A z-shape microchannel structure crosses a clear-black interface at both ends of the cell, thereby creating integral optical windows that permit light coupling into a microchannel completely embedded in black PMMA. The novel cell design is characterized using typical colourimetric measurements for nitrite, nitrate, phosphate, and rhodamine B with agreement to the literature. Finally, the inlaid cell design is integrated into an automated lab-on-chip nitrite sensor.